the nainital-cape survey

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A&A 590, A116 (2016) DOI: 10.1051/0004-6361/201527242 c ESO 2016 Astronomy & Astrophysics The Nainital-Cape Survey IV. A search for pulsational variability in 108 chemically peculiar stars ? S. Joshi 1 , P. Martinez 2, 3 , S. Chowdhury 4 , N. K. Chakradhari 5 , Y. C. Joshi 1 , P. van Heerden 3 , T. Medupe 6 , Y. B. Kumar 7 , and R. B. Kuhn 3 1 Aryabhatta Research Institute of Observational Sciences, Manora peak, 263129 Nainital, India e-mail: [email protected] 2 SpaceLab, Department of Electrical Engineering, University of Cape Town, Private Bag X3, 7701 Rondebosch, South Africa 3 South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa 4 Department of Physics, Christ University, Hosur Road, 560029 Bangalore, Karnataka, India 5 School of Studies in Physics and Astrophysics, Pt Ravishankar Shukla University, 492 010 Raipur, India 6 Department of Physics, University of the North-West, Private Bag X2046, 2735 Mmabatho, South Africa 7 National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, PR China Received 25 August 2015 / Accepted 7 March 2016 ABSTRACT Context. The Nainital-Cape Survey is a dedicated ongoing survey program to search for and study pulsational variability in chemically peculiar (CP) stars to understand their internal structure and evolution. Aims. The main aims of this survey are to find new pulsating Ap and Am stars in the northern and southern hemisphere and to perform asteroseismic studies of these new pulsators. Methods. The survey is conducted using high-speed photometry. The candidate stars were selected on the basis of having Strömgren photometric indices similar to those of known pulsating CP stars. Results. Over the last decade a total of 337 candidate pulsating CP stars were observed for the Nainital-Cape Survey, making it one of the longest ground-based surveys for pulsation in CP stars in terms of time span and sample size. The previous papers of this series presented seven new pulsating variables and 229 null results. In this paper we present the light curves, frequency spectra and various astrophysical parameters of the 108 additional CP stars observed since the last reported results. We also tabulated the basic physical parameters of the known roAp stars. As a part of establishing the detection limits in the Nainital-Cape Survey, we investigated the scintillation noise level at the two observing sites used in this survey, Sutherland and Nainital, by comparing the combined frequency spectra stars observed from each location. Our analysis shows that both the sites permit the detection of variations of the order of 0.6 milli-magnitude (mmag) in the frequency range 1–4 mHz, Sutherland is on average marginally better. Key words. asteroseismology – methods: observational – surveys – stars: chemically peculiar – stars: oscillations 1. Introduction A chemically peculiar (CP) star can be distinguished from a chemically normal star by its spectrum, where anomalies can be seen on a visual inspection of low-dispersion spectra. The opti- cal spectra of the CP stars exhibit normal hydrogen lines com- bined with enhanced silicon, metal, and or rare-earth lines and weak calcium lines. The chemical peculiarities in these stars re- sult from the diusion process (Michaud 1970; Michaud et al. 1981; Babel 1992; Richer et al. 2000). Chemical elements with many lines near flux maximum, such as iron peak and rare earth elements, are brought up to the surface by the dominance of ra- diation pressure over gravity in the radiative envelopes of these stars, causing an apparent overabundance of such elements. The elements with few lines near the flux maximum settle gravita- tionally and appear to be underabundant. Slow rotation is thus a basic condition to operate the diusion process in CP stars. The CP stars are found on the main-sequence between spectral ? The dataset is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A116 types B2 and F5, from the zero-age main-sequence (ZAMS) to the terminal-age main-sequence (TAMS), and have masses rang- ing from 1.5 to about 7 M . Based on their spectroscopic characteristics, Preston (1974) divided the CP stars into the following groups: Am/Fm (CP1), Ap/Bp (CP2), Hg-Mn (CP3), He weak and He strong (CP4) stars. Renson & Manfroid (2009) compiled an up-to-date catalog of 8205 CP stars. A subset of Ap and Am stars shows photomet- ric variability with periods ranging from a few minutes to a few hours, and are the focus of the Nainital-Cape Survey. The Am/Fm stars are relatively cool stars of spectral type F5-A8, with temperatures ranging from 6500 K to 10 000 K. The spectra of these stars exhibit an underabundance (weak lines) of Ca or Sc (or of both elements) and overabundance (strong lines) of Sr, Eu and other rare-earth elements. Some of the mem- bers of this group show δ Sct-type pulsational variability (Joshi et al. 2003, 2006, 2009; Smalley et al. 2011; Catanzaro & Ripepi 2014; Hou et al. 2015). The Am stars rotate slower than chem- ically normal A-type stars and the frequency of binarity among these stars is much higher than among normal stars of the same mass (Abt & Golson 1962; Abt & Snowden 1973). It is well un- derstood that these stars do not exhibit strong global magnetic Article published by EDP Sciences A116, page 1 of 36

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Page 1: The Nainital-Cape Survey

A&A 590, A116 (2016)DOI: 10.1051/0004-6361/201527242c© ESO 2016

Astronomy&Astrophysics

The Nainital-Cape Survey

IV. A search for pulsational variability in 108 chemically peculiar stars?

S. Joshi1, P. Martinez2, 3, S. Chowdhury4, N. K. Chakradhari5, Y. C. Joshi1, P. van Heerden3,T. Medupe6, Y. B. Kumar7, and R. B. Kuhn3

1 Aryabhatta Research Institute of Observational Sciences, Manora peak, 263129 Nainital, Indiae-mail: [email protected]

2 SpaceLab, Department of Electrical Engineering, University of Cape Town, Private Bag X3, 7701 Rondebosch, South Africa3 South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa4 Department of Physics, Christ University, Hosur Road, 560029 Bangalore, Karnataka, India5 School of Studies in Physics and Astrophysics, Pt Ravishankar Shukla University, 492 010 Raipur, India6 Department of Physics, University of the North-West, Private Bag X2046, 2735 Mmabatho, South Africa7 National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, PR China

Received 25 August 2015 / Accepted 7 March 2016

ABSTRACT

Context. The Nainital-Cape Survey is a dedicated ongoing survey program to search for and study pulsational variability in chemicallypeculiar (CP) stars to understand their internal structure and evolution.Aims. The main aims of this survey are to find new pulsating Ap and Am stars in the northern and southern hemisphere and to performasteroseismic studies of these new pulsators.Methods. The survey is conducted using high-speed photometry. The candidate stars were selected on the basis of having Strömgrenphotometric indices similar to those of known pulsating CP stars.Results. Over the last decade a total of 337 candidate pulsating CP stars were observed for the Nainital-Cape Survey, making it oneof the longest ground-based surveys for pulsation in CP stars in terms of time span and sample size. The previous papers of this seriespresented seven new pulsating variables and 229 null results. In this paper we present the light curves, frequency spectra and variousastrophysical parameters of the 108 additional CP stars observed since the last reported results. We also tabulated the basic physicalparameters of the known roAp stars. As a part of establishing the detection limits in the Nainital-Cape Survey, we investigated thescintillation noise level at the two observing sites used in this survey, Sutherland and Nainital, by comparing the combined frequencyspectra stars observed from each location. Our analysis shows that both the sites permit the detection of variations of the order of0.6 milli-magnitude (mmag) in the frequency range 1–4 mHz, Sutherland is on average marginally better.

Key words. asteroseismology – methods: observational – surveys – stars: chemically peculiar – stars: oscillations

1. Introduction

A chemically peculiar (CP) star can be distinguished from achemically normal star by its spectrum, where anomalies can beseen on a visual inspection of low-dispersion spectra. The opti-cal spectra of the CP stars exhibit normal hydrogen lines com-bined with enhanced silicon, metal, and or rare-earth lines andweak calcium lines. The chemical peculiarities in these stars re-sult from the diffusion process (Michaud 1970; Michaud et al.1981; Babel 1992; Richer et al. 2000). Chemical elements withmany lines near flux maximum, such as iron peak and rare earthelements, are brought up to the surface by the dominance of ra-diation pressure over gravity in the radiative envelopes of thesestars, causing an apparent overabundance of such elements. Theelements with few lines near the flux maximum settle gravita-tionally and appear to be underabundant. Slow rotation is thusa basic condition to operate the diffusion process in CP stars.The CP stars are found on the main-sequence between spectral

? The dataset is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A116

types B2 and F5, from the zero-age main-sequence (ZAMS) tothe terminal-age main-sequence (TAMS), and have masses rang-ing from 1.5 to about 7 M�.

Based on their spectroscopic characteristics, Preston (1974)divided the CP stars into the following groups: Am/Fm (CP1),Ap/Bp (CP2), Hg-Mn (CP3), He weak and He strong (CP4)stars. Renson & Manfroid (2009) compiled an up-to-date catalogof 8205 CP stars. A subset of Ap and Am stars shows photomet-ric variability with periods ranging from a few minutes to a fewhours, and are the focus of the Nainital-Cape Survey.

The Am/Fm stars are relatively cool stars of spectral typeF5-A8, with temperatures ranging from 6500 K to 10 000 K. Thespectra of these stars exhibit an underabundance (weak lines)of Ca or Sc (or of both elements) and overabundance (stronglines) of Sr, Eu and other rare-earth elements. Some of the mem-bers of this group show δ Sct-type pulsational variability (Joshiet al. 2003, 2006, 2009; Smalley et al. 2011; Catanzaro & Ripepi2014; Hou et al. 2015). The Am stars rotate slower than chem-ically normal A-type stars and the frequency of binarity amongthese stars is much higher than among normal stars of the samemass (Abt & Golson 1962; Abt & Snowden 1973). It is well un-derstood that these stars do not exhibit strong global magnetic

Article published by EDP Sciences A116, page 1 of 36

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fields, however based on the observations from Kepler spacemission, Balona et al. (2015) found flares in two Am stars, whichstrongly suggests that at least some Am stars possess significantmagnetic fields.

The Ap/Bp stars have effective temperatures in the rangeof 6400 K to 15 000 K. These stars exhibit the most conspicu-ous chemical anomalies of all the CP stars: enhanced lines ofsome elements, particularly Si, Cr, Sr, Mn, Fe, Eu, Gd, andCe (overabundant by up to a factor of 106), and weak lines oflight elements (underabundant by a factor of 10−2). The Ap starsshow low rotation velocities with ve sin i usually not exceeding100 km s−1. These stars have strong global magnetic fields withan intensity ranging from hundreds of Gauss to tens of kilogauss.

The coolest subgroup of Ap stars (6400 K ≤ Teff ≤ 8700 K)located near the main-sequence (MS) part of the classical insta-bility strip, are known as roAp stars. Since the discovery of firstroAp star HD 101065 (Kurtz 1978), 61 other members of thisclass have been discovered (Smalley et al. 2015). The roAp starsshow pulsational variability in both the broad photometric bandsand in narrow spectral lines. These pulsations are character-ized as high-overtone, low-degree p-modes with typical periodsbetween 5.6 min and 23.6 min and photometric amplitudes rang-ing from a few micro-magnitudes (µmag) up to tens of milli-magnitudes (mmag) and radial velocity (RV) amplitudes rang-ing from a few m s−1 to km s−1. The roAp stars possess strongmagnetic fields with typical strengths of a few kG to tens ofkG (Hubrig et al. 2012) with overabundances of some rare earthelements that can exceed the solar value by 106 (Ryabchikovaet al. 2004). To date, there have been no roAp stars found inclose binary systems though a few Ap stars are in close bina-ries. The roAp stars are among the more challenging MS starsto model owing to their pulsations in the combined presence ofa strong global magnetic field together with element segregationand stratification, but at the same time they can be considered asstellar atomic physics laboratory.

The pulsation frequency spectrum of some of the roAp starsshows frequency multiplets with spacings corresponding to thefrequency of rotation of the star. This phenomenon can be ex-plained using the oblique pulsator model (Kurtz 1982), in whichthe pulsation axis is aligned with the axis of the magnetic field,which is assumed to be roughly a dipole inclined with respect tothe axis of rotation. As a star rotates, the observed aspect of thepulsation changes, leading to amplitude modulation and, in somecases, phase modulation. The driving mechanism of the pulsa-tions in roAp stars is thought to be the classical κ-mechanism op-erating in the partial hydrogen ionization zone (Balmforth et al.2001). Cunha & Gough (2001) suggested an alternative excita-tion mechanism for roAp stars where pulsation is driven by theturbulent pressure in the convection zone.

Some roAp stars have highly stable pulsation frequen-cies and amplitudes, even on timescales of years whileother roAp stars show frequency and amplitude variations ontimescales as short as hours (Medupe et al. 2015). Whether thisis a result of driving and damping, mode coupling or some in-stability is not known. It is important to know where in the roApinstability strip the stable and unstable pulsators lie.

The Kepler mission, launched in 2009 with the aim to detectand characterize Earth-sized planets in the habitable zone, hasrevolutionized our ability to detect and study very low-amplitudelight variations of the order of a few µ-mag in rather faint stars(Koch et al. 2010). The Kepler mission has enabled the discoveryof five roAp stars, all which have pulsation amplitudes muchbelow the detection limits of ground-based photometry.

While initially roAp stars were discovered and studied withphotometric methods, time-resolved spectroscopy has allowedthe study of wider physical aspects of the pulsating stellar atmo-sphere. The rapid radial velocity variations of spectral lines ofcertain chemical elements allow us to sample the velocity fieldin the stellar atmosphere as a function of atmospheric depth. Ofthe 61 known roAp stars, about a quarter of them were discov-ered using spectroscopic methods. A combination of simultane-ous spectroscopy and photometry constitutes the most sophis-ticated asteroseismic data set for any roAp star. The observedphase lag between the variations in luminosity and in RV is animportant parameter for modeling the stellar structure.

Similar to other pulsating stars, the roAp stars are also ex-cellent asteroseismic candidates through which one can comparethe observed frequency spectrum to the asymptotic pulsation the-ory and then obtain information about the spherical harmonicdegrees of the pulsation modes, the distortion of the modes fromnormal modes, atmospheric structures, evolutionary status andthe geometry of the magnetic field. Using such information onecan derive the various physical parameters such as rotation peri-ods, temperatures, luminosities, radii and their masses (see Joshi& Joshi 2015 for a recent review on asteroseismology of pulsat-ing stars). Although the extent of the roAp phenomenon has beenfairly well delineated in photometric and spectroscopic terms,there is as yet no known combination of these (and other) ob-servable parameters that can be used as a predictors of pulsationin any given Ap star. In other words, one can have two Ap starsthat are apparently similar in all observable parameters, whereone is a pulsating roAp star and the other has no detectable pul-sations and is a so-called “noAp” star.

The Nainital-Cape Survey was initiated in 1999 bythe Aryabhatta Research Institute of Observational Sciences(ARIES) at Manora Peak, Nainital, India, and the South AfricanAstronomical Observatory (SAAO) in Sutherland to search forpulsations in CP stars. The goals of the survey were: (i) to in-crease the number of known pulsating CP stars; (ii) to determinethe observational limits of the roAp phenomenon; and (iii) tobroaden the number and distribution (in parameter space) of es-tablished constant (noAp) stars, so as to shed some light on whatdistinguishes the pulsating from the apparently constant CP starsof similar spectral type and other observable physical parame-ters. This is the only survey of its kind that was conducted fromboth the northern and southern hemisphere. The first three pa-pers of this survey described the scope and methods of the sur-vey and reported the discovery of pulsations in several CP stars(Martinez et al. 2001; Paper I, Joshi et al. 2006; Paper II, Joshiet al. 2009: Paper III). The present paper is the fourth in this se-ries and presents the null results obtained for 108 stars observedduring the period of 2006 to 2009.

Similar to other papers of this series, the present paper is alsobased on photoelectric photometry of the sample stars and is or-ganized as follows: the target selection, observations and datareduction procedures are described in Sect. 2, followed by thefrequency analysis of the time series photometric data in Sect. 3.In Sect. 4, the observational limits for the detection of light vari-ations at the ARIES and SAAO sites are discussed. The starsclassified as null results and their basic astrophysical parametersare given in Sect. 5. In Sect. 6, we provide the basic physicalparameters of all the currently known roAp stars. In this section,we also compare the evolutionary status of the known roAp starsto the sample of stars observed under the Nainital-Cape Survey.The statistics of several surveys to search for new roAp stars arediscussed in Sect. 8. Finally, we outline the conclusions drawnfrom our study in Sect. 9.

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2. Target selection, observations and data reduction

2.1. Selection criteria

Following the target selection strategy of Martinez et al. (1991),the primary source of candidates for the Nainital-Cape Surveywas the subset of CP stars with Strömgren photometric indicessimilar to those of the known roAp stars. In this range, we alsofound many Am stars and included them in the list of targets.Apart from the sources of target mentioned in Martinez et al.(1991), we also included Ap/Am stars from Renson et al. (1991)and magnetic stars from Bychkov et al. (2003).

On the basis of the Strömgren photometric indices of knownroAp stars (see Table A.1), we revised the range of indices thatencompass the roAp phenomenon:

0.082 ≤ b − y ≤ 0.4310.178 ≤ m1 ≤ 0.387−0.204 ≤ δm1 ≤ 0.012

0.002 ≤ c1 ≤ 0.870−0.370 ≤ δc1 ≤ 0.031

2.64 ≤ β ≤ 2.88

where b− y is the color index and β measures the strength of theHβ line, which is indicator of temperature for stars in the spec-tral range from around A3 to F2. The m1 and c1 indices indicateenhanced metallicity and increased line blanketing, respectively.The parameters δm1 and δc1 measure the blanketing differenceand Balmer discontinuity relative to the ZAMS for a given β,respectively. Indices in the ranges given above are not an unam-biguous indicator of roAp pulsation, although they serve to nar-row down the field of candidates to the most promising subset.It is interesting to note that, whereas previously the roAp phe-nomenon seemed to be confined to the temperature range of theδ Scuti instability strip, it now appears that the roAp instabil-ity strip has a considerably cooler red edge, well into the F-typestars (see Fig. 2). As can be seen by the paucity of cooler starstested for pulsation, this is an area for future work, to establishmore firmly the cool edge of the roAp instability strip.

2.2. Photometric observations

For many roAp stars, the pulsational photometric variationshave amplitudes less than 20 mmag. The detection of such low-amplitude variations demands high-precision photometric obser-vations that can be attained with fast photometers mounted onsmall telescopes at observing sites such as ARIES Nainital inIndia and SAAO Sutherland South Africa. The ARIES obser-vations presented in this paper were acquired using the ARIEShigh-speed photoelectric photometer (Ashoka et al. 2001) at-tached to the 1.04-m Sampurnanand telescope at ARIES. TheSAAO observations were acquired using the Modular Photome-ter attached to the 0.5-m telescope and the University of CapeTown Photometer attached to the 0.75-m and 1.0-m telescopesat the Sutherland site of SAAO.

Each star was observed in high-speed photometric mode withcontinuous 10-sec integrations through a Johnson B filter. Theobservations were acquired in a single-channel mode (i.e. no si-multaneous comparison star observations), with occasional in-terruptions to measure the sky background, depending on thephase and position of the moon. To minimize the effects of see-ing fluctuations and tracking errors, we selected a photometricaperture of 30′′. Each target was observed continuously for 1–3 h at a time. Since the amplitudes of the rapid photometric os-cillations in roAp stars exhibit modulation due to rotation and

interference among frequencies of different pulsation modes, anull detection for pulsation may be obtained simply owing to acoincidence of the timing of the observations. Hence, each can-didate was observed several times.

2.3. Data reduction

The data reduction process began with a visual inspection of thelight curve to identify and remove obviously bad data points,followed by correction for coincidence counting losses, sub-traction of the interpolated sky background, and correction forthe mean atmospheric extinction. After applying these correc-tions, the time of the midpoint of the each observation was con-verted into a heliocentric Julian date (HJD) with an accuracy of10−5 day (∼1 s). The reduced data comprise a time-series of HJDand ∆B magnitude with respect to the mean of the light curve.

3. Frequency analysis

A fast algorithm (Kurtz 1985) based on the Deeming discreteFourier transform (DFT) for unequally spaced data (Deeming1975) was used to calculate the Fourier transformation. The lightcurves were also inspected visually for evidence of δSct oscilla-tions with periods of a few tens of minutes and longer. On thesetimescales, single-channel photometric data are affected by skytransparency variations and it is not always possible to distin-guish between oscillations in the star and variations in sky trans-parency. This is where the comparison of data of the same staracquired under different conditions on different nights is helpfulfor confirming the tentative detection of coherent oscillations ina given light curve.

After visual inspection of the light curves to search for indi-cations of δSct pulsations in a given light curve on timescaleslonger than about half an hour, we removed the sky transparencyvariations from the DFT data to reduce the overall noise levelto approximately the scintillation noise. This is practicable forsingle-channel data because, on good photometric nights, theroAp oscillation frequencies are generally well resolved from thesky transparency variations. To remove the effect of sky trans-parency variations, the DFT data were prewhitened to removesignals with frequencies in the range 0–0.9 mHz, which is thefrequency range commonly affected by sky transparency varia-tions in single-channel photometric data. These frequencies wereremoved until the noise level in the DFT of the residuals approx-imated a white noise spectrum. Depending on the stability of thephotometric transparency of a given night, it was generally pos-sible to correct for the effects of sky transparency by removing 3to 5 frequencies in the above mentioned frequency range.

The first and second panels of Fig. A.1 show the light curvesof the candidate stars filtered for low frequency sky transparencyvariations. The third and fourth panels show the prewhitened am-plitude spectra of the sample stars filtered for low-frequency skytransparency variations.

4. Noise level characterization

The detection limit for photometric variability depends upon theatmospheric noise, which consists of scintillation noise and skytransparency variations, and the photon noise. For the brighter(∼10 mag) stars, the atmospheric scintillation noise dominatesover the photon noise and is one of the fundamental factors lim-iting the precision of ground based photometry. In order to char-acterize the two observing sites used in the Nainital-Cape Survey

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and to put constraints on the detection limits for low amplitudevariability, we estimated the observational and the theoreticalscintillation noise values for both the sites.

Given the altitude and diameter of the telescope, and the ob-servational exposure time and airmass, one can find the contri-bution of scintillation noise in photometric measurements usingthe Young approximation (Young 1967, 1974). Using this scal-ing relation, it is possible to compare the level of scintillationnoise at different observatory sites. Although the precise amountof scintillation changes from night to night, the Young’s scalingrelation appears to hold very well for telescope apertures up to4 m, and for different sites (Kjeldsen & Frandsen 1991; Gilliland& Brown 1992; Gilliland et al. 1993). However, recent studies byKornilov et al. (2012) and Osborn et. al (2015) showed that thisequation tends to underestimate the median scintillation noiseat several major observatories around the world. Osborn et. al.(2015) presented a modified form of the Young approximation(Eq. (1)) that uses empirical correction coefficients to give morereliable estimates of the scintillation noise at a range of astro-nomical sites:

σ2Y = 10 × 10−6C2

Y D−4/3t−1(cos γ)−3 exp (−2hobs/H), (1)

where CY is the empirical coefficient, D is the diameter of thetelescope, t is the exposure time of the observation, γ is thezenith distance, hobs is the altitude of the observatory and Hthe scale height of the atmospheric turbulence, which is gener-ally accepted to be approximately 8000 m. All parameters arein standard SI units. The empirical coefficients CY for the ma-jor observatories around the world are listed by Osborne et al.(2015).

The theoretical values of scintillation noise for Sutherlandand Nainital were estimated using Eq. (1). The scintillation noisein terms of amplitude was obtained by taking the square rootof σY . However, we have to scale the theoretical value to com-pare the two sites with different telescope diameters. Therefore,the theoretical scintillation noise for SAAO (50 cm telescope)was scaled to the aperture of the ARIES telescope (104 cm)using the same relation. The input parameters used to estimatethe theoretical scintillation noise are: height (ARIES: 1958-m,SAAO: 1798 m), sec(Z) (airmass): 1, CY : 1.5, integration time:10 sect. The estimated scintillation values of ARIES (D: 104 cm)and SAAO (D: 50 cm) are 0.0338 mmag and 0.0433 mmag, re-spectively. The scaled value of the scintillation noise for SAAO(scaled to 104 cm) is 0.0340 mmag. Figure 1 shows the theoreti-cal noise levels for the ARIES and SAAO sites (both scaled andunscaled).

Since the observations in the Nainital-Cape Survey were car-ried out over many nights and in a variety of atmospheric con-ditions, the noise levels in the Fourier spectra of the individuallight curves are expected to be higher than the theoretical scin-tillation values for each site, and they are also not expected tobe white noise. We first transformed the time-series data of starsobserved from ARIES during 2006–2009 and from SAAO dur-ing 2006–2007 into their individual periodograms to estimatethe observational values of the noise in our amplitude spectra asa function of frequency. We then combined all the periodogramsfrom each site into a single pseudo-periodogram and fitted anacspline function to obtain the average estimated noise profileas a function of frequency. These observational noise curves areshown in Fig. 1 in solid blue for ARIES and dot-dashed red forSAAO. These noise profiles provide a useful first check of thesignificance of possible oscillation frequencies identified in theFourier spectra in Fig. 3 of this paper.

Fig. 1. Noise characteristics at the ARIES site at Nainital and SAAOSutherland site. The acspline-fitted curve of ARIES and SAAO ampli-tude spectra are shown in solid blue and dot-dashed red curves, respec-tively. The theoretical scintillation noise levels of ARIES and SAAO areshown with blue long-dashed and red small-dashed horizontal lines, re-spectively, and the scintillation noise level of SAAO (scaled to 104 cmdiameter) is also shown with a green dotted horizontal line.

More than half of the known roAp stars were discovered pho-tometrically from SAAO. One of the basic reasons behind this isthat the Sutherland site has stable and good sky transparency, fa-cilitating a closer match to scintillation noise than at many otherobserving sites used in other roAp surveys. However, in the lastten years that we have been running the Nainital-Cape Survey,we have noticed a gradual increase in sky brightness and at-mospheric noise owing to enhanced human activities around theARIES and Sutherland observatories. It can be inferred from thescaling relation (Eq. (1)) that the combined atmospheric noisecan be minimized by installing bigger telescopes at a good ob-serving site where one can find stable photometric sky conditions(Young 1967). A new 1.3 m optical telescope is now operationalat a new astronomical site of ARIES observatory known as Dev-asthal (longitude: 79◦40′57′′ E, latitude : 29◦22′26′′ N, altitude:2420-m). In addition, a new 3.6 m telescope has been recentlyinstalled at the Devasthal site and is likely to be operational by2016. The theoretical scintillation noise estimated for this tele-scope is 0.0217 mmag making the telescope very efficient for de-tecting tiny amplitude variations. The 0.5-m telescope of SAAOis also soon to be replaced with a 1.0-m robotic telescope. Theseupcoming observing facilities equipped with modern state-of-the-art instruments at ARIES and SAAO will be the next step toboost the Nainital-Cape Survey and other projects aimed at thedetection of sub-mmag light variations.

5. New null results from the Nainital-Cape Survey

We report the non-detections of pulsation in 108 CP stars.The first and second panels of Fig. A.1 depict the light curvesof the candidate stars observed from ARIES and SAAO. Theprewhitened frequency spectra of the respective time-series areplotted in the third and fourth columns. The name of the star,

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duration of observations in hours and the heliocentric Juliandates are denoted in each panel.

Here it is worth recalling that roAp stars show amplitudemodulation due to rotation and beating between multiple pulsa-tion frequencies. Therefore, the nondetection of light variationsmay be due to fact that the observations are acquired at a timewhen the pulsations are below the detection limit of the survey.For example, Joshi et al. (2006) classified HD 25515 as a nullresult and then subsequently, after further observations, classi-fied it as a δ Scuti-type pulsating variable (Joshi et al. 2009).Hence, a nulldetection of pulsations does not mean that the staris nonvariable, but rather that its light output was not detectedto vary during the particular interval of the observations. Thisdemonstrates the necessity for repeated observations of the can-didate stars. These null results are also an important contribu-tion toward understanding the distinction between pulsating andnonpulsating CP stars that are otherwise similar in all other ob-servational respects (Murphy et al. 2015). As mentioned above,a by-product of these null results is an observational character-ization of a particular observing site for data acquired on manynights over a wide range of observing conditions.

6. Comparison of known roAp stars with the nullresults

At the time the Nainital-Cape Survey began, only 23 roAp starswere known. Therefore, our knowledge of the extent of theroAp phenomenon at that time was used to define the targetselection and observing strategy. Since then, the number ofknown roAp stars has more than doubled, and currently standsat 61 confirmed members of this class. The compilation of thevarious physical parameters of the known roAp stars are impor-tant to study the roAp and noAp (“non-roAp”) phenomena inAp stars. Tables A.1 and A.2 list the astrophysical parameters ofthe known roAp stars extracted from the available sources in theliterature. For each star Table A.1 lists, the table entry number,the HD number of roAp star, their popular name, spectral type,Strömgren indices b−y, m1, c1, β, δm1, δc1, effective temperatureTeff , and reference(s) from which the data were taken. Table A.2lists the table entry number, HD or HR catalog number and othername(s) of the roAp star, visual magnitude mv, parallax π, dis-tance d, absolute magnitude Mv, luminosity parameter log

(L?L�

),

pulsational period corresponding to the highest amplitude, fre-quency separation ∆µ, maximum photometric amplitude varia-tion Amax, maximum radial velocity variation RVmax, rotationalperiod Prot, surface gravity log g, mass M?, radius R?, meanlongitudinal magnetic field, and the projected rotational velocityv sin i. Where no data is available in the data archives or in theliterature for a given parameter, this is denoted with a “-” symbolin the relevant column. It is instructive to compare the coverageof the Nainital-Cape Survey with the currently established extentof the roAp phenomenon. Therefore, the catalog of the basic pa-rameters of the known roAp stars can be used for the statisticalanalysis of roAp and noAp phenomena in Ap stars located in thesame part of the H-R diagram.

7. Evolutionary states of the studied samples

To establish the evolutionary status of the sample null resultstars, we first established their luminosities and effective temper-atures, which then allowed us to compare them with the knownroAp stars. The absolute magnitudes and luminosities of the

candidate stars observed in the Nainital-Cape Survey were de-termined based on the data taken from the Hipparcos catalog(van Leeuwen 2007). The photometric Teff is calculated fromthe Strömgren β indices using the grids of Moon & Dworet-sky (1985) that give a typical error of about 200 K. The variousastrophysical parameters of the stars observed in the Nainital-Cape Survey are listed in Table A.3. These parameters are ei-ther taken from the Simbad database or calculated using thestandard relations (Cox 1999). For each star, this Table lists theHD number, right ascension α2000, declination δ2000, visual mag-nitude mv, spectral type, parallax π, Strömgren indices b− y, m1,c1, β, δm1, δc1, effective temperature Teff , luminosity parame-ter log

(L?L�

), duration of the observations ∆t, heliocentric Julian

dates (HJD:2 450 000+) and year of observations (2000+) whenthe star was observed. The Strömgren indices δm1 and δc1 arecalculated using the calibration of Crawford (1975, 1979).

The absolute magnitude Mv in the V-band was determinedusing the standard relation (Cox 1999),

Mv = mv + 5 + 5 log π − Av, (2)

where π is trigonometric parallax measured in arcsec, the in-terstellar extinction in the V band is AV = RV E(B − V) =3.1E(B − V). The reddening parameter E(B − V) is obtained bytaking the difference of the observed colour (taken from the Sim-bad data base) and intrinsic colour (estimated from Cox 1999).

The stellar luminosity was calculated using the relation

logLL�

= −MV + BC − Mbol,�

2.5, (3)

where we adopted the solar bolometric magnitude Mbol,� =4.74 mag (Cox 1999), and used the standard bolometric correc-tion BC from Flower (1996). Taking all of the contributions tothe Mv and L?

L�error budgets into account, we find a typical un-

certainty of 20–25% for both parameters.The null objects shown in Fig. 2 include all the objects from

Papers I–IV (this paper) of the Nainital-Cape Survey. The posi-tions of known roAp stars and the newly discovered δ-Scuti typevariables in our survey are also shown. The evolutionary tracksfor stellar masses ranging from 1.5 to 3.0 M� (Christensen-Dalsgaard 1993) are overplotted. The position of the blue (left)and red (right) edges of the instability strip are shown withtwo oblique lines (Turcotte et al. 2000). Figure 2 clearly showsthat most of the sample stars are located within the instabilitystrip. For reasons given above, we may expect that some of thestars listed as null results in this paper may well turn out to bevariables in near future. However, with each subsequent non-detection of pulsations, the constraint on nonvariability will bestrengthened and they are established as “noAp” stars, thus help-ing to shed light on the other observational characteristics thatallow us to distinguish between pulsating and constant CP stars,which is one of the long-term goals of the Nainital-Cape Survey.

8. Ground-based surveys on pulsationin chemically peculiar stars

In the past, several surveys have been conducted around theglobe to search for roAp stars with different instrumental setupsindependently in both the northern and southern hemisphere.Such surveys required much telescope time, hence the photo-metric surveys were performed on 1 m class telescopes, where itwas possible to secure ample telescope time. Spectroscopic sur-veys became more popular in recent years because of improved

A116, page 5 of 36

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A&A 590, A116 (2016)

Fig. 2. Positions of the null results (filled triangle) and δ-Scuti typevariables discovered under the Nainital-Cape Survey (filled square). Forcomparison, positions of known roAp stars are also shown (open star).The solid lines show theoretical evolutionary tracks from the ZAMS(Christensen-Dalsgaard 1993). The dashed lines indicate the red andblue edges of the instability strip.

sensitivity of the high-resolution spectroscopic instruments usedto search for low amplitude oscillations in roAp candidates. Themajor drawback of this technique remains the small amount ofobserving time available on large telescopes. In this section, weprovide a short description of the various surveys conducted forpulsation in CP stars.

8.1. Cape survey

Following the discovery of first roAp star HD 101065 in 1978,only 14 stars were known prior to 1990. A systematic surveyof roAp stars in the southern hemisphere was initiated by DonKurtz and Peter Martinez at SAAO with two objectives: firstto increase the number of members of this class and, second,to study the relationship between the roAp stars and the otherpulsating stars located at the same region of the H-R diagram.The observations for this survey were acquired with the pho-toelectric photometers attached to the 0.5-m and 1.0-m tele-scopes at Sutherland. Under the Cape survey 134 Southern ApSrCrEu stars were checked for the pulsational variability and 12new roAp stars were discovered (Martinez et al. 1991; Martinez& Kurtz 1994a, 1994b).

8.2. Nainital-Cape survey

The detection of the small amplitude light variations needs alot of observational expertise. As mentioned above most of theroAp stars known prior to 2000 were discovered under the Capesurvey, where the SAAO astronomers gained a lot of observa-tional experience. However, this meant that most of the knownroAp stars were southern objects. The Nainital-Cape Survey wasinitiated in 1999 as a collaboration between South African andIndian astronomers to increase the number of known roAp starsin the northern sky. This survey was started in 1999 and lastedfor ten years making it the most extensive survey for pulsation

in CP stars, where a total of of 337 Ap and Am stars weremonitored. Although only one new roAp star, HD 12098, wasdiscovered under this survey but the milli-magnitude level lightvariations with periods similar to those of the δ-Scuti stars wasdicovered in seven Am stars. This survey is thus unique in asense that both the Ap and Am stars were included in the sam-ples, hence there were plenty of chances to discover pulsationsin CP1 and CP2 stars. The null results of this survey have beenpublished in Martinez et al. (2001), Joshi et al. (2006, 2009) andin the present paper. The archive of well established null resultsis useful to delineate the extent of the roAp phenomenon and alsoto shed light on the distinction between roAp and noAp stars.

8.3. Lowell-Wisconsin survey

Between 1985 to 1991, Nelson & Kreidl (1993) conducted a sur-vey of pulsation in 120 northern Ap stars of spectral range B8–F4. Although these authors did not report the discovery of anynew roAp stars from their survey, their main finding was the ab-sence of pulsation in the spectral range B8–A5, indicating thatroAp-like oscillations are likely to be confined to the cooler pe-culiar stars.

8.4. The Hvar survey

A photometric survey was initiated in 2011 to search for newnorthern roAp stars at the Hvar observatory (Paunzen et al.2012, 2015). For this survey, a CCD based photometer attachedto the 1.0 m Austrian-Croatian telescope was used for the ob-servations of candidate stars. Under this survey, 80 candidateroAp stars were examined for a total duration of 100 h. Differen-tial CCD photometry was performed to detect the light variationsin the sample Ap stars. The authors have not reported any posi-tive detections and have presented the frequency spectra and thebasic parameters of the null results they observed.

8.5. Other minor photometric surveys

In addition to the above surveys, a number of smaller photo-metric surveys have also been conducted independently in thenorthern and southern hemisphere by Dorokhova & Dorokhov(1998), Kurtz (1982), Matthews et al. (1988), Heller & Kramer(1990), Schutt (1991), Belmonte (1989), Hildebrandt (1992),and Handler & Paunzen (1999). Though these surveys aresmall in terms of sample size and number of newly discoveredroAp stars, they have helped to define candidate selection criteriafor other roAp surveys.

8.6. Spectroscopic surveys

Spectroscopy of high spectral and temporal resolution usinglarge telescopes permits the detailed study of line profile vari-ations (Hatzes & Mkrtichian 2005). After the discovery of sig-nificant RV pulsational variations in some known roAp stars(Kanaan & Hatzes 1998), in the last ten years candidateroAp stars have been monitored with time resolved high res-olution spectroscopic observations by several observers. Theseobservations revealed that the highest RV amplitudes are ob-served in the spectral lines of the rare earth elements, while spec-tral lines of the other elements show weak or undetectable os-cillations. Using spectroscopic techniques, about 15 roAp starshave been discovered (Kochukhov 2006; Kochukhov et al. 2008,2009, 2013; Alentive et al. 2012; Elkin et al. 2005a; 2005b;Kurtz et al. 2006).

A116, page 6 of 36

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S. Joshi et al.: The Nainital-Cape Survey. IV.

9. Conclusions

In this paper, we presented the light curves and frequency spectraof the 108 candidate stars observed in the Nainital-Cape Survey.Analyses of the photometry acquired at Sutherland and Naini-tal indicate that we have achieved a detection level of about0.6 mmag in the frequency range 1–5 mHz in the Nainital-CapeSurvey. Using the standard relations and data extracted from theliterature we presented the various astrophysical parameters ofthe null results. We also compiled the basic physical parame-ters of the known roAp stars. On comparing the positions of theknown roAp stars to the observed sample stars in the H-R dia-gram, we infer that the boundary of the roAp phenomenon ex-tends beyond the cool edge of the classical instability strip.

Acknowledgements. This work was carried out under the Indo-South AfricaScience and Technology Cooperation INT/SAFR/P-3(3)2009) and NRFgrant UID69828 funded by Departments of Science and Technology of the In-dian and South African Governments. S.C. acknowledges support under theIndo-Russian grant INT/RFBR/P-118 through which he received a stipend toperform this work. We acknowledge use of SIMBAD, NASA’s ADS and ESA’sHipparcos database.

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A&A 590, A116 (2016)

App

endi

xA

Tabl

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833

8000

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8250

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5516

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211

0.62

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4265

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0.25

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325

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979

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9249

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0.30

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615

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000

2.81

275

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21.

HD

9623

711

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0109

A4S

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233

0.26

10.

704

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54–0

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2.82

478

0011

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HD

9712

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1110

54+

1703

48F3

pSr

Eu(

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6300

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D99

563

1127

17–0

852

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0.17

10.

206

0.74

5–0

.001

–0.0

902.

830

7000

18,1

9,20

24.

HD

1010

65Pr

zbyl

ski’s

star

1137

37–4

643

00C

ontr

over

sial

0.43

10.

387

0.00

2–0

.204

–0.3

702.

641

6800

7,21

,22

25.

HD

1152

2613

1800

–72

5701

A3p

Sr–

––

––

–76

0023

26.

HD

1161

1413

2146

–18

4432

ApS

rCrE

u0.

172

0.22

60.

843

–0.0

160.

008

2.83

676

0024

27.

HD

1190

2713

4120

–28

4660

ApS

rEu(

Cr)

0.25

70.

214

0.55

7–0

.034

–0.0

762.

731

7050

2528

.J1

430

1430

50+

3147

55A

9pSr

Eu

––

––

––

7100

129

.H

D12

2970

1404

49+

0524

51F0

0.26

00.

178

0.54

0–0

.005

–0.0

112.

707

7000

2630

.H

D12

8898

αC

ir14

4230

–64

5830

ApS

rEu(

Cr)

0.15

20.

195

0.76

00.

012

–0.0

772.

831

7500

7,27

,28

31.

HD

1322

0515

0004

–55

0260

A2E

uSrC

r–

––

––

–78

0029

32.

HD

1342

1415

0902

–13

5959

ApS

rEu(

Cr)

0.21

60.

223

0.62

0–0

.029

–0.1

082.

774

7400

30

Not

es.1

.Hol

dsw

orth

etal

.(20

14a)

;2.K

urtz

etal

.(19

96);

3.K

urtz

etal

.(19

94b)

;4.M

artin

ez&

Kur

tz(1

994a

);5.

Gir

ish

etal

.(20

01);

6.Sc

hnei

der

etal

.(19

92);

7.K

urtz

(198

2);8

.Kur

tzet

al.

(200

5b);

9.M

krtic

hian

&H

atze

s(2

005a

);10

.Mat

thew

set

al.(

1987

);11

.Elk

inet

al.(

2011

);12

.Koc

hukh

ovet

al(2

009)

;13.

Kur

tzet

al.(

1997

b);1

4.K

ochu

khov

(200

6);1

5.K

urtz

etal

.(19

97a)

;16

.Kur

tz&

Mar

tinez

(199

4);1

7.E

lkin

etal

.(20

10);

18.D

orok

hova

&D

orok

hov

(199

8);1

9.H

andl

eret

al.(

2006

);20

.Elk

inet

al.(

2005

b);2

1.M

krtic

hian

&H

atze

s(2

005b

)22.

Mar

tinez

&K

urtz

(199

0);2

3.K

ochu

khov

etal

(200

8);2

4.E

lkin

etal

.(20

05a)

;25.

Mar

tinez

etal

.(19

93);

26.H

andl

eret

al.(

2002

);27

.Bal

ona

&L

aney

(200

3);2

8.K

urtz

etal

.(19

94a)

;29.

Koc

hukh

ovet

al.(

2013

);30

.Kre

idl&

Kur

tz(1

986)

;31.

Hat

zes

&M

krtic

hian

(200

4);3

2.K

urtz

etal

.(20

05a)

;33.

Mkr

tichi

anet

al.(

2003

);34

.Kur

tz(1

991)

;35.

Kur

tzet

al.(

2006

);36

.Mar

tinez

etal

.(19

91);

37.K

urtz

etal

.(2

003)

;38.

Kur

tz&

Mar

tinez

(198

7);3

9.H

olds

wor

thet

al.(

2014

b);4

0.H

atze

s&

Mkr

tichi

an(2

005)

;41.

Hel

ler&

Kra

mer

(199

0);4

2.K

urtz

etal

.(20

11);

43.B

alon

aet

al.(

2013

);44

.Ale

ntie

vet

al.

(201

2);4

5.H

olds

wor

th(2

015)

;46.

Kur

tz&

Mar

tinez

(199

5);4

7.B

alon

aet

al.(

2011

);48

.Sm

alle

yet

al.(

2015

);49

.Koc

hukh

ov&

Rya

bchi

kova

(200

1);5

0.M

artin

ezet

al.(

1996

);51

.Mar

tinez

etal

.(19

90);

52.M

artin

ezet

al.(

1998

);53

.Kre

idle

tal.

(199

1);5

4.G

onza

lez

et.a

l(20

08).

A116, page 8 of 36

Page 9: The Nainital-Cape Survey

S. Joshi et al.: The Nainital-Cape Survey. IV.

Tabl

eA

.1.c

ontin

ued.

S.N

.St

arna

me

Oth

erα

2000

δ 200

0Sp

.b-y

m1

c 1δm

1δc

T eff

Ref

.na

me

Type

mag

mag

mag

mag

mag

mag

K33

.H

D13

7909

βC

rB15

2750

+29

0620

F0p

0.14

10.

257

0.74

0–0

.056

0.00

22.

839

7800

3134

.H

D13

7949

33L

ib15

2935

–17

2627

ApS

rEuC

r0.

196

0.31

10.

580

–0.1

05–0

.236

2.81

877

0032

,33,

3435

.H

D14

3487

1601

44–3

054

57A

3SrE

uCr

0.31

10.

262

0.39

3–0

.089

–0.1

692.

706

7000

1736

.H

D14

8593

1629

39–1

435

06A

2Sr

––

––

––

7850

2937

.J1

640

1640

03–0

737

30A

8pSr

Eu

––

––

––

7400

138

.H

D15

0562

1644

11–4

839

18A

/F(p

Eu)

0.30

10.

212

0.65

9–0

.015

–0.0

872.

783

7500

439

.H

D15

1860

1652

59–5

409

46A

2SrE

u0.

327

0.22

10.

538

––

–70

5029

40.

HD

1547

0817

1028

–58

0017

Ap

0.27

70.

256

0.46

4–0

.079

0.01

52.

757

7200

3541

.H

D16

1459

1748

30+

5155

02A

pEuS

rCr

0.24

50.

246

0.67

9–0

.040

–0.1

412.

820

7950

3642

.H

D16

6473

1812

26–3

745

09A

pSrE

uCr

0.20

80.

321

0.51

4–0

.118

–0.2

682.

801

7700

37,3

843

.K

IC00

7582

608

1844

12+

4317

51A

p–

––

––

–87

0039

44.

HD

1762

3210

Aql

1858

47+

1354

24F0

pSrE

u0.

150

0.20

80.

829

–0.0

040.

031

2.80

974

0040

,41

45.

KIC

0101

9592

619

0527

+47

1548

Ap

––

––

––

7400

4246

.K

IC00

8677

585

1906

28+

4450

33A

5p–

––

––

–76

0043

47.

HD

1777

6519

0710

–26

1954

A5S

rEuC

r0.

248

0.26

10.

731

–0.0

54–0

.110

2.83

480

0044

48.

J192

119

2129

+47

1053

F3p

SrE

uCr

––

––

––

6200

4549

.H

D18

5256

1939

20–2

944

34A

pSr(

EuC

r)0.

277

0.18

50.

615

–0.0

04–0

.039

2.73

872

5046

50.

J194

019

4008

–44

2009

F2(p

Cr)

––

––

––

6900

151

.K

IC01

0483

436

1946

29+

4737

50A

p–

––

––

–73

8847

52.

HD

2259

14K

IC00

4768

731

1948

26+

3951

58A

p–

––

––

–77

2648

53.

HD

1902

9020

1356

–78

5242

ApE

uSr

0.28

90.

293

0.46

6–0

.091

–0.3

062.

796

7500

3654

.H

D19

3756

2024

12–5

143

25A

pSrC

rEu

0.18

10.

213

0.76

0–0

.008

–0.0

402.

810

7500

3655

.H

D19

6470

2038

10–1

730

06A

pSrE

u(C

r)0.

211

0.26

30.

650

–0.0

59–0

.144

2.80

778

5036

56.

HD

2016

01γ

Equ

2110

20+

1007

54F0

p0.

147

0.23

80.

760

–0.0

32–0

.058

2.81

976

0049

,50

57.

HD

2039

3221

2604

–29

5548

ApS

rEu

0.17

50.

196

0.74

20.

004

–0.0

202.

791

7200

5158

.H

D21

3637

2233

12–2

002

22A

(pE

uSrC

r)0.

298

0.20

60.

411

–0.0

35–0

.031

2.67

064

0052

59.

HD

2175

2223

0147

–44

5027

Ap(

Si)C

r0.

289

0.22

70.

484

–0.0

56–0

.015

2.69

171

0053

60.

HD

2184

9523

0928

–63

3912

A2p

EuS

r0.

114

0.25

20.

812

–0.0

49–0

.098

2.87

080

0036

61.

HD

2189

9423

1316

–60

3503

A3S

r0.

154

0.19

60.

826

0.00

80.

032

2.80

776

0054

A116, page 9 of 36

Page 10: The Nainital-Cape Survey

A&A 590, A116 (2016)Ta

ble

A.2

.Add

ition

alpa

ram

eter

sfo

rthe

know

nro

Ap

star

s.

S.N

.St

arna

me

mv

πd

MV

log(

L ?/L�)

Ppu

l∆µ

Am

axR

Vm

axP

rot

logg

M?

R?

Mag

.Fie

ldv

sin

im

agm

aspc

mag

min

µH

zm

mag

kms−

1da

ysde

xM�

R�

kGkm

s−1

1.J0

008

10.1

6–

––

–9.

58–

0.76

––

––

––

–2.

HD

6532

8.40

6.14

162.

872.

201.

227.

1047

5.00

1.15

1.94

4.30

––

0.22

303.

HD

9289

9.38

––

2.42

–10

.52

–3.

500.

858.

554.

15–

–0.

6510

.54.

HD

1209

88.

07–

––

–7.

61–

3.00

–5.

464.

201.

701.

701.

4610

5.H

D12

932

10.2

5–

–2.

55–

11.6

1–

4.00

1.40

3.53

4.15

––

1.20

2.50

6.H

D19

918

9.34

4.07

245.

702.

341.

0611

.04

–2.

001.

30–

4.34

––

1.60

3.00

7.H

D24

355

9.65

––

––

6.42

–1.

38–

13.9

5–

––

––

8.H

D24

712

6.00

20.3

249

.21

2.32

0.87

6.13

6810

.00

0.25

12.4

64.

301.

551.

773.

105.

609.

HD

4265

96.

767.

6013

1.58

2.38

1.48

9.70

520.

800.

70–

4.40

2.10

–0.

3919

.00

10.

HD

2580

4810

.52

––

––

8.49

–1.

49–

––

––

––

11.

J065

111

.51

––

––

10.8

8–

0.79

––

––

––

–12

.H

D60

435

8.89

4.41

226.

761.

541.

1411

.90

5216

.00

1.90

7.68

4.40

1.82

–0.

3010

.813

.H

D69

013

9.56

––

––

11.2

2–

–0.

20–

4.50

––

2.90

6.0

14.

HD

7544

57.

129.

3010

8.34

1.96

1.17

9.00

––

0.29

2.08

4.32

1.81

–2.

982

15.

J085

510

.80

––

––

7.30

–1.

40–

3.09

––

––

–16

.H

D80

316

7.78

7.25

137.

932.

261.

117.

40–

2.00

0.32

2.08

4.58

1.70

1.53

0.18

32.0

17.

HD

8336

86.

1714

.16

70.6

22.

471.

0911

.60

–10

.00

3.33

2.85

4.20

1.76

2.00

0.50

33.0

18.

HD

8404

19.

33–

–2.

38–

1560

6.00

0.50

3.69

4.30

––

0.48

25.0

19.

HD

8618

19.

323.

4928

6.53

2.49

1.01

6.20

–4.

60–

––

––

0.40

–20

.H

D92

499

8.89

3.54

282.

481.

631.

0510

.40

––

0.06

6–

4.00

1.68

–8.

153.

321

.H

D96

237

9.43

1.53

653.

59–

1.61

13.8

9–

–0.

10–

4.30

––

2.90

622

.H

D97

127

9.43

––

––

13.5

1–

0.66

––

––

––

–23

.H

D99

563

8.67

3.92

255.

101.

901.

1010

.70

–10

.00

4.9

2.91

4.20

2.03

1.90

0.57

28.0

24.

HD

1010

657.

998.

9311

1.98

2.09

0.91

12.1

668

13.0

01.

033.

944.

201.

521.

982.

304.

025

.H

D11

5226

8.51

6.80

147.

062.

670.

8610

.86

––

1.24

3.30

4.00

1.60

–0.

7527

26.

HD

1161

147.

027.

7112

9.70

1.35

1.32

21.3

0–

–0.

65–

4.10

2.07

–0.

502.

227

.H

D11

9027

10.0

2–

–3.

040.

678.

6352

2.00

0.14

8–

4.40

––

3.10

4.0

28.

J143

011

.56

––

––

6.11

–1.

06–

––

––

––

29.

HD

1229

708.

338.

6711

5.34

2.94

0.82

11.1

868

2.00

1.05

3.88

4.20

1.50

1.80

0.22

4.2

30.

HD

1288

983.

2060

.35

16.5

71.

901.

046.

8250

5.00

0.80

4.48

4.20

1.70

1.90

1.50

13.5

31.

HD

1322

058.

72–

––

–7.

14–

–0.

097

–4.

40–

–5.

209.

5032

.H

D13

4214

7.46

9.74

102.

672.

600.

885.

69–

7.00

0.72

248

4.05

1.60

1.80

2.70

2.6

33.

HD

1379

093.

6829

.17

34.2

81.

171.

4616

.20

––

0.04

18.4

94.

401.

601.

455.

303.

534

.H

D13

7949

6.67

11.2

888

.65

1.88

1.17

8.27

403.

000.

33–

4.30

1.78

2.60

4.70

3.0

35.

HD

1434

879.

42–

––

–9.

63–

–0.

047

–5.

00–

–4.

701.

536

.H

D14

8593

9.13

––

––

10.6

9–

––

–4.

40–

–3.

005.

0037

.J1

640

12.6

7–

––

–9.

48–

3.52

–3.

67–

––

––

38.

HD

1505

629.

82–

–2.

68–

10.8

050

0.80

0.14

–4.

40–

–5.

001.

5

A116, page 10 of 36

Page 11: The Nainital-Cape Survey

S. Joshi et al.: The Nainital-Cape Survey. IV.

Tabl

eA

.2.c

ontin

ued.

S.N

.St

arna

me

mv

πd

MV

log(

L ?/L�)

Ppu

l∆µ

Am

axR

Vm

axP

rot

logg

M?

R?

Mag

.Fie

ldv

sin

im

agm

aspc

mag

min

µH

zm

mag

kms−

1da

ysde

xM�

R�

kGkm

s−1

39.

HD

1518

609.

01–

––

–12

.30

––

–0.

083

4.50

––

2.50

4.5

40.

HD

1547

088.

766.

7514

8.15

2.39

0.73

8.00

––

0.09

5.37

4.11

1.50

1.70

24.5

04.

041

.H

D16

1459

10.3

3–

–2.

47–

12.0

0–

1.30

––

4.38

––

1.76

–42

.H

D16

6473

7.92

––

2.52

1.24

8.80

682.

000.

10–

4.47

1.80

–8.

502.

543

.K

IC00

7582

608

11.2

5–

––

1.21

7.90

–1.

45–

20.4

54.

302.

371.

773.

05–

44.

HD

1762

325.

8912

.76

78.3

72.

551.

3211

.60

510.

600.

54–

4.10

2.00

2.50

1.40

2.7

45.

KIC

0101

9592

610

.66

––

–1.

5017

.14

550.

078

0.17

15.

683.

601.

703.

605

2146

.K

IC00

8677

585

10.1

9–

––

0.80

10.2

837

0.03

3–

4.30

3.90

1.80

2.50

3.20

4.2

47.

HD

1777

659.

15–

––

1.50

23.6

––

0.14

8–

3.80

2.20

–3.

602.

548

.J1

921

12.1

6–

––

–11

.18

–1.

99–

––

––

––

49.

HD

1852

569.

94–

––

–10

.33

–3.

000.

15–

4.30

––

0.71

6.2

50.

J194

013

.02

––

––

8.16

–4.

16–

9.58

––

––

–51

.K

IC01

0483

436

11.4

3–

––

0.84

12.3

2–

0.06

8–

4.30

4.15

1.60

1.61

–20

52.

KIC

0047

6873

19.

17–

––

–23

.4–

0.06

2–

––

––

––

53.

HD

1902

909.

91–

–2.

49–

7.34

402.

000.

504.

034.

54–

–3.

2316

54.

HD

1937

569.

20–

–2.

55–

13.0

0–

0.90

0.74

–4.

29–

–0.

1917

.055

.H

D19

6470

9.72

––

2.52

–10

.80

–0.

70–

–4.

37–

–1.

48–

56.

HD

2016

014.

6827

.55

36.3

02.

491.

1012

.40

303.

000.

58–

4.20

1.74

2.16

3.80

2.5

57.

HD

2039

328.

82–

–2.

65–

5.94

662.

000.

33–

4.30

––

0.26

74.

758

.H

D21

3637

9.61

––

–1.

0311

.50

–1.

500.

36<

253.

601.

60–

0.74

3.5

59.

HD

2175

227.

5211

.36

88.0

32.

770.

8513

.70

584.

000.

128.

554.

201.

491.

861.

702.

760

.H

D21

8495

9.38

––

2.23

–7.

44–

1.00

0.79

–4.

40–

–0.

9116

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.H

D21

8994

8.56

3.55

281.

691.

251.

0614

.20

––

0.09

3–

4.10

––

0.44

05.

2

A116, page 11 of 36

Page 12: The Nainital-Cape Survey

A&A 590, A116 (2016)

Tabl

eA

.3.C

Pst

ars

obse

rved

forp

ulsa

tion

from

AR

IES

and

SAA

Oan

dcl

assi

fied

asnu

llre

sults

inth

issu

rvey

.

S.N

.St

arα

2000

δ 200

0mv

Sp.

πb−y

m1

c 1β

δm1

δc1

T eff

log(

L/L �

)∆

tH

JDY

earo

fH

Dm

agTy

pem

asm

agm

agm

agm

agm

agm

agK

hrO

bser

vatio

n1.

1169

0016

05+

0806

567.

60A

58.

83±

0.69

0.18

70.

240

0.71

62.

772

–0.0

47–0

.008

7455

1.18

0.45

4365

071.

0743

6607

2.14

8600

1918

+59

0820

7.28

B9V

6.32±

0.83

––

––

––

––

2.78

4071

062.

4143

6707

1.91

4375

073.

7343

7607

1.42

4400

072.

1844

0107

3.22

4402

072.

8444

2807

2.09

4429

073.

2837

0032

09+

4342

429.

16A

0p2.

75±

1.08

––

––

––

––

1.42

4459

074.

3321

0036

22+

3338

398.

42A

36.

34±

0.90

––

––

––

––

2.07

4397

075.

6757

0108

53+

4512

277.

70A

0Vp

3.35±

0.91

––

––

––

––

1.35

4427

071.

0144

3107

6.76

7601

1607

–34

0856

8.37

A5p

3.50±

0.74

0.08

50.

280

0.71

52.

830

–0.0

73–0

.120

8008

1.47

1.95

4097

067.

8441

0124

19+

4308

326.

67A

2p4.

88±

0.59

0.02

20.

141

1.14

52.

833

0.06

60.

306

9617

1.97

2.30

4751

088.

8783

0124

00–7

219

287.

82A

p3.

99±

0.44

0.07

20.

199

1.08

6–

––

––

2.89

4077

069.

1109

001

4635

–67

2806

10.7

8A

p–

––

––

––

–1.

1921

2701

3.45

2128

0110

.11

948

0158

51+

5534

547.

85F0

p6.

71±

0.73

0.11

50.

242

0.87

92.

873

–0.0

160.

027

8323

1.50

0.97

4459

0711

.12

211

0200

33+

2753

199.

00A

7V7.

12±

1.97

––

––

––

––

0.69

4399

074.

4244

0107

2.14

4402

0712

.14

433

0221

55+

5714

346.

39A

1Ia

0.79±

0.46

0.46

3–0

.088

0.91

32.

606

––

––

1.98

2238

0113

.15

144

0226

00–1

520

285.

86A

6Vsp

12.9

0.74

0.40

20.

213

0.29

82.

584

––

––

1.86

4085

0614

.15

550

0230

38+

1951

196.

14A

9V15

.14±

0.46

0.15

60.

187

0.83

52.

776

––

––

1.54

4431

0715

.16

145

0235

04–1

717

227.

64A

p4.

33±

0.71

0.02

80.

201

1.05

7–

––

––

1.41

4087

061.

9940

8806

1.92

4089

061.

9240

9006

16.

1703

402

4542

+48

0837

8.63

B8V

+0.

92±

0.90

––

––

––

––

1.68

4427

0717

.17

835

0251

52+

0254

498.

9A

4–

0.16

0.17

0.96

2.84

––

––

0.91

2216

0118

.18

078

0256

32+

5610

418.

30A

0p–

0.08

70.

251

1.07

92.

831

–0.0

440.

243

7947

–0.

9644

5907

19.

1861

002

5418

–73

2710

8.14

Ap

4.69±

0.54

0.11

40.

347

0.61

7–

––

––

2.03

4098

062.

0341

0106

20.

2088

003

1608

–73

3256

7.95

Ap

–0.

094

0.20

81.

030

––

––

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8640

9206

21.

2174

603

3000

–12

2839

9.41

K0/

K1I

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––

1.07

3659

0522

.21

985

0332

25–0

318

488.

3A

1V5.

63±

0.83

0.11

30.

160.

952

2.85

6–

––

–2.

9441

0407

2.27

4108

0723

.22

374

0336

58+

2312

406.

72A

2p7.

65±

0.46

0.06

90.

178

1.09

12.

879

0.02

20.

163

8397

1.70

2.63

4750

08

Not

es.T

heir

phys

ical

para

met

ers

are

liste

d.

A116, page 12 of 36

Page 13: The Nainital-Cape Survey

S. Joshi et al.: The Nainital-Cape Survey. IV.

Tabl

eA

.3.c

ontin

ued.

S.N

.St

arα

2000

δ 200

0mv

Sp.

πb−y

m1

c 1β

δm1

δc1

Teff

log(

L/L �

)∆

tH

JDY

earo

fH

Dm

agTy

pem

asm

agm

agm

agm

agm

agm

agK

hrO

bser

vatio

n24

.22

488

0332

46–6

643

467.

50A

p4.

39±

0.45

––

––

––

––

1.93

4092

0625

.23

207

0342

44–1

842

507.

54A

p4.

83±

0.71

0.10

60.

259

0.85

6–

––

––

1.96

4091

0626

.23

393

0344

29–1

203

318.

30F0

III

4.35±

0.91

0.22

20.

164

0.77

22.

753

0.02

40.

133

7271

1.36

1.96

4094

0627

.24

825

0355

16–3

845

336.

81B

94.

23±

0.33

–0.0

390.

173

1.08

32.

835

0.03

50.

241

9683

1.99

1.34

4077

0628

.25

154

0359

48–0

001

129.

88A

56.

74±

1.41

––

––

––

––

1.21

4397

0729

.25

487

0403

54+

2807

338.

08B

8V4.

82±

0.99

––

––

––

––

0.98

4459

0730

.25

999

0408

18+

3227

367.

51A

p6.

11±

0.85

––

––

––

––

1.15

4815

091.

5248

6909

1.43

4870

0931

.27

463

0416

21–6

056

546.

36A

p7.

92±

0.42

0.02

20.

224

0.89

02.

874

–0.0

23–0

.028

9214

1.61

1.78

4091

0632

.28

430

0427

22–4

011

508.

20A

p2.

52±

0.61

––

––

––

––

1.89

4094

0633

.29

578

0436

31–5

437

168.

51A

p3.

74±

0.61

––

––

––

––

1.93

4095

0634

.31

225

0453

12–2

046

197.

02A

p5.

32±

0.68

0.09

30.

191.

079

––

––

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3340

8806

1.91

4089

061.

3840

9006

35.

3406

005

1203

–49

0337

7.82

B9V

p2.

74±

0.48

––

––

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––

1.91

4095

0636

.34

162

0515

31+

0545

358.

68F0

4.79±

1.13

0.14

80.

186

0.93

52.

834

0.02

70.

153

7982

1.15

1.34

4400

0737

.34

205

0515

06–1

506

019.

32A

p–

0.13

50.

215

0.96

22.

911

––

––

1.60

2288

021.

5922

8902

1.92

2296

022.

1426

8303

2.24

2686

032.

2126

9303

38.

3545

005

2824

+58

4029

8.16

A3

7.42±

0.87

––

––

––

––

1.48

4397

0739

.36

955

0535

04–0

124

069.

58A

2–

0.05

70.

198

0.84

82.

866

0.00

5–0

.054

8270

–1.

0844

2707

40.

3730

805

3653

–17

0059

8.71

A–

––

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4096

0641

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719

0544

20–5

654

587.

50A

p4.

19±

0.45

0.01

10.

206

1.03

8–

––

––

2.19

4095

0642

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817

0550

37+

4400

417.

56A

27.

27±

0.76

0.06

60.

217

0.94

22.

860

–0.0

120.

052

8209

1.50

1.51

4071

0643

.39

082

0550

24+

0457

247.

42B

96.

63±

0.53

–0.0

270.

220

0.88

72.

873

–0.0

19–0

.029

1045

12.

421.

1644

2807

44.

3957

505

5224

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1728

7.83

A0

4.08±

0.70

–0.0

740.

267

0.90

5–

––

––

2.15

4098

0645

.40

277

0551

26–7

028

468.

33A

p4.

45±

0.60

0.04

10.

239

0.90

1–

––

––

1.99

4102

0746

.40

886

0600

28–2

753

188.

21A

00.

83±

0.74

––

––

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––

2.06

4096

0647

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089

0600

51–4

252

146.

57B

9III

p4.

25±

0.29

––

––

––

––

3.03

4092

0648

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511

0604

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629

044.

97A

1V3.

59±

0.31

0.18

60.

030

1.32

32.

775

0.16

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593

9377

3.18

1.99

4103

0749

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786

0608

02+

2117

447.

29F0

9.70±

1.09

0.19

30.

275

0.69

02.

782

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780.

000

7557

2.30

1.11

4101

0650

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326

0609

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717

307.

70A

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66±

0.66

0.00

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231

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901

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749

468.

20A

p1.

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0.13

20.

228

0.94

62.

860

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230.

056

8208

2.35

1.99

4097

0652

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195

0620

42+

0516

427.

54F0

11.2

0.75

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90.

188

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753

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1.96

2285

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36A

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204

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297

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244

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F03.

760.

217

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40.

756

2.74

6–

––

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7819

4301

A116, page 13 of 36

Page 14: The Nainital-Cape Survey

A&A 590, A116 (2016)

Tabl

eA

.3.c

ontin

ued.

S.N

.St

arα

2000

δ 200

0mv

Sp.

πb−y

m1

c 1β

δm1

δc1

Teff

log(

L/L �

)∆

tH

JDY

earo

fH

Dm

agTy

pem

asm

agm

agm

agm

agm

agm

agK

hrO

bser

vatio

n57

.48

953

0646

49+

1646

206.

8F5

10.3

90.

247

0.30

80.

623

2.75

2–

––

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1022

1001

0.91

2305

0258

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496

0700

57+

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139.

83F5

––

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0141

0607

59.

5168

406

5629

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5925

7.94

Ap

3.58±

0.60

0.15

40.

248

0.76

82.

832

––

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2.10

4088

0660

.55

719

0712

16–4

029

565.

31A

3spe

7.93±

0.38

0.01

20.

217

1.03

02.

880

–0.0

170.

100

9101

2.28

2.09

4102

0761

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148

0719

48+

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299.

00F0

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204

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80.

628

2.72

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128

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III

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A116, page 14 of 36

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S. Joshi et al.: The Nainital-Cape Survey. IV.Ta

ble

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A116, page 15 of 36

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A&A 590, A116 (2016)

Time (hours) Frequency (mHz)

Fig. A.1. The light curves (left columns) of the pulsation candidate stars observed from ARIES/SAAO and their corresponding prewhitenedamplitude spectra (right columns). The light curves have been binned to 40-s integrations.

A116, page 16 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 17 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 18 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 19 of 36

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A&A 590, A116 (2016)

Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 20 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 21 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 22 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 23 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 24 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 26 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 28 of 36

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Fig. A.1. continued.

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 30 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 32 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

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Fig. A.1. continued.

A116, page 34 of 36

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Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 35 of 36

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A&A 590, A116 (2016)

Time (hours) Frequency (mHz)

Fig. A.1. continued.

A116, page 36 of 36