Opening a New Window on AP Star Atmospheres: A T- tau Relation for HR 3831 from Its Limb-darkened Pulsation Amplitudes

Details Opening a New Window on AP Star Atmospheres: A T- tau Relation for HR 3831 from Its Limb-darkened Pulsation Amplitudes Opening a New Window on AP Star Atmospheres: A T- tau Relation for HR 3831 from Its Limb-darkened Pulsation Amplitudes

Mar 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996apj...459..278m&link_type=abstract

Astrophysical Journal v.459, p.278

Astronomy and Astrophysics

Astronomy

14

Stars: Atmospheres, Stars: Individual Bright Star Number: Hr 3831, Stars: Oscillations, Stars: Peculiar

Scientific paper

We demonstrate a new approach for probing the atmospheres of selected chemically peculiar magnetic stars. Using the Cerro Tololo Inter-American Observatory (CTIO) 1.0 and 1.5 m telescopes simultaneously on two nights in 1991, we obtained optical and infrared high-speed photometry of the rapidly oscillating Ap (roAp) star HR 3831 (= HD 83368), which pulsates with a period of 11.8 minutes. Oscillation amplitudes (or upper limits) in each of eight bandpasses were measured by Fourier analysis, revealing the very steep decline in amplitude with increasing wavelength characteristic of roAp stars. Matthews and coworkers have shown that this can be explained by the wavelength dependence of limb darkening and its filtering effect on the integrated amplitude of an (1, m) = (1, 0) nonradial pulsation mode. Since the eigenfrequency spectrum of HR 3831 is dominated by just such a dipole mode, it is possible to infer limb-darkening coefficients fl for its atmosphere from our amplitude measurements. These coefficients are used to derive a source function through the Eddington-Barber relation, which leads to a relation for temperature versus optical depth in the stellar photosphere. Our results show that the T-T_{5000 }curve is much steeper for HR 3831 than for the Sun (at least at the rotational phase when the star's magnetic pole dominates the visible hemisphere). We also calculate the gradient dT/dT as a function of wavelength to compare with the curve expected for H - continuous opacity. This type of diagnostic may become a useful tool for checking the predictions of diffusion theory.

Affiliated with

Also associated with

No associations

Rating

Opening a New Window on AP Star Atmospheres: A T- tau Relation for HR 3831 from Its Limb-darkened Pulsation Amplitudes does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Opening a New Window on AP Star Atmospheres: A T- tau Relation for HR 3831 from Its Limb-darkened Pulsation Amplitudes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Opening a New Window on AP Star Atmospheres: A T- tau Relation for HR 3831 from Its Limb-darkened Pulsation Amplitudes will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1644208