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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)
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Outline• Mt John University Observatory
– Location– HERCULES
• Asteroseismology Programmes– Spectroscopic observations– Radial velocity measures– Line profile analysis – Specific project: HD49434
• Conclusions
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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%)
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MJUO location
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Mt John University Observatory (MJUO)
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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
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MJUO 1.0-m telescope
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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.
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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).
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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
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Spectroscopic Observations
• Binaries
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Spectroscopy - line profileseg Sct star FG Vir
(left) line profile variations (right) grayscale phased
difference from mean
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Spectroscopy - line profile variations
(left) Ca I 612.2 nm line profile
(right) Cross correlation profiles
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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)
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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.
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Specific project: HD 49434
• Ground-based, high-resolution echelle spectra of HD49434 Dor star– CoRot target
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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
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Data used
• FEROS – Chile
• HERCULES
– New Zealand
• SOPHIE- France
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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
→
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FIGARO and HRSP
• Same overall radial velocity variation
• HRSP has better internal precision
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←
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
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Nightly variations
← 3 hours →
← 1
km
s-1
→
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Seeing pulsation in spectroscopy
←
90
min
→
1
80
min
blo
cks
Bruntt et al. (2002) This work
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Results
• Frequencies of 5, 7 and 11 cycles-per-day
Doradus frequencies
Scuti frequencies
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Conclusion
• Binary? Doradus star? Scuti star? • Combination?
• More observations of HD 49434 are needed + analysis of all MJUO data