Spectroscopy of pulsations in γ Doradus Stars

Emily BrunsdenDepartment of Physics and Astronomy

University of Canterburyemily.brunsden@pg.canterbury.ac.nz

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