spectroscopy of pulsations in γ doradus stars
DESCRIPTION
Spectroscopy of pulsations in γ Doradus Stars. Emily Brunsden Department of Physics and Astronomy University of Canterbury [email protected]. Image: http://gong.nso.edu/. Doradus Stars. Pulsating late A to early F stars On or near main sequence - PowerPoint PPT PresentationTRANSCRIPT
Spectroscopy of pulsations in γ Doradus Stars
Emily BrunsdenDepartment of Physics and Astronomy
University of [email protected]
Image: http://gong.nso.edu/
Doradus Stars• Pulsating late A to early
F stars
• On or near main sequence
• Periods of 0.3 - 3 days
• More than 60 confirmed
• Have non-radial g-mode pulsations
Image: J. Christensen-Dalgaard
Motivation for a thesis
• g-modes travel deep in star and inform stellar models- but few have been studied
• Are current mode identification techniques optimal?
• Does the rotation of the star create observable pulsation effects?
Image: http://www.hao.ucar.edu/
The Study of HD135825
• 300 spectra over 18 months
• Not well-studied star
• Low projected rotational velocity
Representative Line Profile
Multi-Periodic Variations
1.31 cycles day-1
0.29 cycles day-1
0.42 cycles day-1
1.88 cycles day-1
Frequency
Pow
er
Modelling all Modes
1.31 cycles day-1
0.29 cycles day-1
0.42 cycles day-1
1.88 cycles day-1
Pow
er
velocity (km/s)
line p
rofile
standard
devia
tion
Modelling all Modes1.31 cycles day-1
0.29 cycles day-1
1.88 cycles day-1
Am
plitude
Am
plitude
Wavelength (velocity space) kms-1
velocity (km/s)
standard
devia
tion
Frequency Order
Frequency (Cycles day-1)
Period
(Hours)
mode
1 1.315 18 (1,1)
2 0.290 83 (2,-2)
3 1.405 17 (4,0)
4 1.883 13 (1,1)
Results for HD 135825
Image: http://www.physics.usyd.edu.au/~bedding/animations/visual.html
γ Doradus
• Class definition- well studied
• 620 spectra over 15 months
• Four frequencies found, agree very well
• Modes consistent with other studies
Frequency (d-1) Mode (l,m)
f1 1.364 (1,1)
f2 1.878 (1,1)
f3 1.471 (2,0)
f4 1.321 (1,1)
HD12901
• Clear pulsations from classification study
• 470 spectra over 31 months at MJUO plus 110 from Chile and USA
• Six frequencies – 2 new
• Five modes- all (1,1)
Frequency (d-1) Mode (l,m)
f1
1.396 (1,1)
f2
1.186 (1,1)
f3
1.681 (1,1)
f4
1.216 (1,1)
f5
1.560 (1,1)
f6
1.245 -
HD49434
• Hybrid γ Doradus/ δ Scuti Star
• CoRoT satellite frequencies (more than 800)
• 660 spectra over five years at MJUO plus 1080 from France, Chile and Spain
• 31 frequencies -almost none seen in photometry
• Two distinct classes of frequency (0.2-2 d-1 and >3 d-1)
HD49434
standard
devia
tion
velocity (km/s)
γ Doradus-like
δ Scuti-like
Major Progress• Three stars with full mode identifications
(previously only ~10)
• Cross-correlation techniques are good for slow-moderate (vsini < 70 km/s ) rotators
• (1,1) modes are common
• Rotation can distort standard deviation profiles
Future Challenges
• Linking observed pulsations to theoretical models– Moving from observed to co-rotating frame
• Hybrid stars & binaries