- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- Spectroscopic variations of the pulsating AP star γ...
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
Spectroscopic variations of the pulsating AP star γ equulei Scott, Sandra L.
Abstract
We investigated the radial velocity (RV) and light variations of the rapidly oscillating Ap (roAp) star γ Equ( HD 201601, HR 8097), with simultaneous (3.6m CFHT) spectroscopic and (UH 0.6m) photometric observations taken over 4 nights in August 1988. Despite lowamplitude detection limits on all nights, convincing RV and light oscillations were seen only on the last night, confirming amplitude modulation and/or mode evolutions noted by previous observers. The RV variations for the last night had a dominant frequency of 1.517 ± 0.01 mHz (P ~ 11.0 minutes) with an amplitude of 418 m s⁻¹, differing significantly from the 1.365 mHz (amplitude ~ 0.001 mag, P ~ 12.2 minutes) photometric frequency of the same night. We attribute the two frequencies to different modes observed almost equator on: the 1.5 mHz frequency to an (l=2, m=0) mode, and the 1.-4 mHz frequency to a dipole (l=1,m=0) mode. The former mode would have high RV amplitude but low photometric amplitude at this orientation, explaining the lack of photometric signal. This is the first time a non-dipole mode has been identified i n a roAp star. Based on our frequency data and those of other investigators plus the mode identifications above, we uniquely determine a fundamental p-mode spacing, Δv[sub o] ~ 60 μHz. Combined with stellar models, this value implies that γ Equ is near the main sequence, resolving an ambiguity about this star which has existed for almost a decade. Our results indicate it is critical that investigators use modes of the same degree l and orientation when determining the RV-to-light ratio (2K/Δm ) if it is to be used as a diagnostic of temperature and pulsational characteristics in roAp, stars.
Item Metadata
Title |
Spectroscopic variations of the pulsating AP star γ equulei
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
1995
|
Description |
We investigated the radial velocity (RV) and light variations of the rapidly oscillating Ap
(roAp) star γ Equ( HD 201601, HR 8097), with simultaneous (3.6m CFHT) spectroscopic
and (UH 0.6m) photometric observations taken over 4 nights in August 1988. Despite lowamplitude
detection limits on all nights, convincing RV and light oscillations were seen only on the last night, confirming amplitude modulation and/or mode evolutions noted by previous observers. The RV variations for the last night had a dominant frequency of 1.517 ± 0.01 mHz (P ~ 11.0 minutes) with an amplitude of 418 m s⁻¹, differing
significantly from the 1.365 mHz (amplitude ~ 0.001 mag, P ~ 12.2 minutes) photometric
frequency of the same night. We attribute the two frequencies to different modes observed
almost equator on: the 1.5 mHz frequency to an (l=2, m=0) mode, and the 1.-4 mHz
frequency to a dipole (l=1,m=0) mode. The former mode would have high RV amplitude
but low photometric amplitude at this orientation, explaining the lack of photometric
signal. This is the first time a non-dipole mode has been identified i n a roAp star.
Based on our frequency data and those of other investigators plus the mode identifications
above, we uniquely determine a fundamental p-mode spacing, Δv[sub o] ~ 60 μHz.
Combined with stellar models, this value implies that γ Equ is near the main sequence,
resolving an ambiguity about this star which has existed for almost a decade.
Our results indicate it is critical that investigators use modes of the same degree l
and orientation when determining the RV-to-light ratio (2K/Δm ) if it is to be used as a
diagnostic of temperature and pulsational characteristics in roAp, stars.
|
Extent |
3392655 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-02-09
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
|
DOI |
10.14288/1.0085634
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
1995-11
|
Campus | |
Scholarly Level |
Graduate
|
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.