university of canterbury people: karen pollard peter cottrell
DESCRIPTION
Coordinated observational campaigns for non-radially pulsating objects at Mt John Observatory (New Zealand). University of Canterbury people: Karen Pollard Peter Cottrell Duncan Wright (PhD, now post-doc at Royal Observatory of Belgium) Florian Maisonneuve (PhD student) - PowerPoint PPT PresentationTRANSCRIPT
Coordinated observational campaigns for non-radially pulsating objects at
Mt John Observatory (New Zealand) University of Canterbury people:
Karen Pollard
Peter Cottrell
Duncan Wright (PhD, now post-doc at Royal Observatory of Belgium)
Florian Maisonneuve (PhD student)
Emily Brunsden (BSc (Hons))
Pam Kilmartin (MJUO observer)
Outline• Mt John University Observatory
– Location– HERCULES
• Asteroseismology Programmes– Spectroscopic observations– Radial velocity measures– Line profile analysis – Specific project: HD49434
• Conclusions
MJUO location• S43°59.2' E170°27.9' and 1031m
above sea level• Mt John is located next to Lake
Tekapo, South Island, New Zealand • Four telescopes on site: two 0.6m,
1.0m McLellan and 1.8m MOA
• Good spectroscopic site (~50%), fair photometric site (~20%)
MJUO location
Mt John University Observatory (MJUO)
Mt John University Observatory (MJUO)
• Instrumentation for asteroseismology:– 1.0 m McLellan telescope– fibre-fed High Efficiency and Resolution Canterbury
University Large Echelle Spectrograph, HERCULES
MJUO 1.0-m telescope
HERCULES• R ~ 40,000 for 100 fibre or
~ 80,000 for 50 fibre • Gives S/N ~ 100 on a 6th mag object
in ~7 min with wavelength coverage from 3800-7500 Å (old CCD 1K x 1K)
• New CCD (2K x 2K) has complete wavelength coverage with similar quantum efficiency
• New fibre scrambler designed and funded. Installation late 2008. Will improve precision. Design also includes the potential to add an Iodine cell for further precision.
Hercules design and stability• Major elements of HERCULES are
fixed to an optical bench inside a cylindrical vacuum tank (4.3 x 1.2 m) where pressure maintained at 1 - 5 torr. The tank is situated in a thermally isolated and insulated room.
• RMS stability of 15 m s-1 over time spans of 4 to 5 years is being achieved.
• This is ideal for high-resolution, time-series asteroseismological studies of reasonably bright stars (V < 8).
Asteroseismology programmes
• In recent years we have initiated and contributed to a number of campaigns to study non-radially pulsating objects: mainly Sct, Dor, Cep stars
Spectroscopic Observations
• Binaries
Spectroscopy - line profileseg Sct star FG Vir
(left) line profile variations (right) grayscale phased
difference from mean
Spectroscopy - line profile variations
(left) Ca I 612.2 nm line profile
(right) Cross correlation profiles
Analysis Tools - Cross correlation
• Cross-correlate an object’s spectrum with a template of delta functions (at correct position and depth of each line) gives a high S/N representative line profile(valid for lines similarly distorted by the pulsation)
Line moments• The periodogram of the first moment (left) shows the periodicities
present in the Scuti star FG Vir, whilst the second moment (right) shows the non-axisymmetric modes (m≠ 0) that are present.
• The line moment technique is useful for Scuti stars where the main line profile variations are line asymmetries.
Specific project: HD 49434
• Ground-based, high-resolution echelle spectra of HD49434 Dor star– CoRot target
HD 49434• MJUO observations 1-18 Feb 2007
– observed by Pollard, Kilmartin– analysed by Emily Brunsden BSc (Hons)
project (with additional data at similar time from SOPHIE and FEROS, supplied by Ennio Poretti)
• Additional MJUO data: (reduced but not analysed)– 2007 Nov1-6, Nov 21 - Dec 02 with
occasional spectra 2007 Dec - 2008 Jan
Data used
• FEROS – Chile
• HERCULES
– New Zealand
• SOPHIE- France
Analysis: Radial velocities
• Auto cross-correlation of non-telluric orders of HERCULES spectra
• Initial results:Δ 6 km s-1 in 16 days
binary?
← 16 Days →
←
6
km
s-1
→
FIGARO and HRSP
• Same overall radial velocity variation
• HRSP has better internal precision
←
6 k
m s
-1
→
← 49 Days →
Collated results• However, no
trend seen in FEROS or SOPHIE data
• Katrien, using single line analysis, finds no trend in HERCULES radial velocities, although larger scatter
Nightly variations
← 3 hours →
← 1
km
s-1
→
Seeing pulsation in spectroscopy
←
90
min
→
1
80
min
blo
cks
Bruntt et al. (2002) This work
Results
• Frequencies of 5, 7 and 11 cycles-per-day
Doradus frequencies
Scuti frequencies
Conclusion
• Binary? Doradus star? Scuti star? • Combination?
• More observations of HD 49434 are needed + analysis of all MJUO data