university of canterbury people: karen pollard peter cottrell
Post on 15-Jan-2016
Embed Size (px)
DESCRIPTIONCoordinated 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 Presentation
Coordinated observational campaigns for non-radially pulsating objects at Mt John Observatory (New Zealand) University of Canterbury people:Karen PollardPeter CottrellDuncan Wright (PhD, now post-doc at Royal Observatory of Belgium) Florian Maisonneuve (PhD student)Emily Brunsden (BSc (Hons))Pam Kilmartin (MJUO observer)
OutlineMt John University ObservatoryLocationHERCULESAsteroseismology ProgrammesSpectroscopic observationsRadial velocity measuresLine profile analysis Specific project: HD49434 Conclusions
MJUO locationS4359.2' E17027.9' and 1031m above sea levelMt 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%)
Mt John University Observatory (MJUO)
Mt John University Observatory (MJUO)Instrumentation for asteroseismology:1.0 m McLellan telescopefibre-fed High Efficiency and Resolution Canterbury University Large Echelle Spectrograph, HERCULES
MJUO 1.0-m telescope
HERCULESR ~ 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 (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 stabilityMajor 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 programmesIn recent years we have initiated and contributed to a number of campaigns to study non-radially pulsating objects: mainly Sct, Dor, Cep stars
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 correlationCross-correlate an objects 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 momentsThe 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 49434Ground-based, high-resolution echelle spectra of HD49434 Dor starCoRot target
HD 49434MJUO observations 1-18 Feb 2007observed by Pollard, Kilmartinanalysed 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 usedFEROS ChileHERCULES New ZealandSOPHIE- France
Analysis: Radial velocitiesAuto cross-correlation of non-telluric orders of HERCULES spectra Initial results: 6 kms-1 in 16 days binary? 16 Days 6 kms-1
FIGARO and HRSPSame overall radial velocity variation
HRSP has better internal precision
Collated resultsHowever, no trend seen in FEROS or SOPHIE dataKatrien, using single line analysis, finds no trend in HERCULES radial velocities, although larger scatter 6 kms-1 49 Days
Nightly variations 3 hours 1 kms-1
Seeing pulsation in spectroscopy 90 min 180 min blocks Bruntt et al. (2002)This work
ResultsFrequencies of 5, 7 and 11 cycles-per-day Doradus frequencies Scuti frequencies
ConclusionBinary? Doradus star? Scuti star? Combination?
More observations of HD 49434 are needed + analysis of all MJUO data