1 research outputs found
Time-series Spectroscopy and Photometry of the Pulsating Subdwarf B Star PG 1219+534 (KY UMa)
We present observations and analysis of time-series spectroscopy and
photometry of the pulsating subdwarf B star PG 1219+534 (KY UMa). Subdwarf B
stars are blue horizontal branch stars which have shed most of their hydrogen
envelopes. Pulsating subdwarf B stars allow a probe into this interesting phase
of evolution. Low resolution spectra were obtained at the Nordic Optical
Telescope and Kitt Peak National Observatory, and photometric observations were
obtained at MDM and Baker observatories in 2006. We extracted radial velocity
and equivalent width variations from several Balmer and He I lines in
individual spectra. The pulsation frequencies were separated via phase binning
to detect line-profile variations in Balmer and helium lines, which were
subsequently matched to atmospheric models to infer effective temperature and
gravity changes throughout the pulsation cycle.
From the photometry we recovered the four previously observed frequencies and
detected a new fifth frequency. From the spectra we directly measured radial
velocity and equivalent width variations for the four main frequencies and from
atmospheric models we successfully inferred temperature and gravity changes for
these four frequencies. We compared amplitude ratios and phase differences of
these quantities and searched for outliers which could be identified as
high-degree modes. These are the first such measurements for a "normal"
amplitude pulsating subdwarf B star, indicating that spectroscopic studies can
benefit the majority of pulsating subdwarf B stars.Comment: 9 pages, 13 figures accepted for publication in Astronomy &
Astrophysic