2005ApJ...635.1239Y


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.29CET19:06:11

2005ApJ...635.1239Y - Astrophys. J., 635, 1239-1262 (2005/December-3)

Mode identification from combination frequency amplitudes in ZZ Ceti stars.

YEATES C.M., CLEMENS J.C., THOMPSON S.E. and MULLALLY F.

Abstract (from CDS):

The light curves of variable DA stars are usually multiperiodic and nonsinusoidal, so that their Fourier transforms show peaks at eigenfrequencies of the pulsation modes and at sums and differences of these frequencies. These combination frequencies provide extra information about the pulsations, both physical and geometrical, that is lost unless they are analyzed. Several theories provide a context for this analysis by predicting combination frequency amplitudes. In these theories, the combination frequencies arise from nonlinear mixing of oscillation modes in the outer layers of the white dwarf, so their analysis cannot yield direct information on the global structure of the star as eigenmodes provide. However, their sensitivity to mode geometry does make them a useful tool for identifying the spherical degree of the modes that mix to produce them. In this paper we analyze data from eight hot, low-amplitude DAV white dwarfs and measure the amplitudes of combination frequencies present. By comparing these amplitudes to the predictions of the theory of Goldreich & Wu, we have verified that the theory is crudely consistent with the measurements. We have also investigated to what extent the combination frequencies can be used to measure the spherical degree (ℓ) of the modes that produce them. We find that modes with ℓ>2 are easily identifiable as high ℓ based on their combination frequencies alone. Distinguishing between ℓ=1 and 2 is also possible using harmonics. These results will be useful for conducting seismological analysis of large ensembles of ZZ Ceti stars, such as those being discovered using the Sloan Digital Sky Survey. Because this method relies only on photometry at optical wavelengths, it can be applied to faint stars using 4 m class telescopes.

Abstract Copyright:

Journal keyword(s): stars: individual (GD 66) - stars: individual (GD 244) - Stars: Individual: Alphanumeric: G117-B15A - Stars: Individual: Alphanumeric: G185-32 - stars: individual (L19-2) - Stars: Individual: Alphanumeric: GD 165 - Stars: Individual: Alphanumeric: R548 - Stars: Individual: Alphanumeric: G226-29 - Stars: Oscillations - Stars: Variables: Other - Stars: White Dwarfs

Simbad objects: 10

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Number of rows : 10

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 V* ZZ Cet WD* 01 36 13.6155835488 -11 20 32.631811638   14.328 14.16 14.4   DA4.0 262 0
2 GD 66 WD* 05 20 38.3165475543 +30 48 23.923341864   15.78 15.56     DA4.1 69 1
3 V* RY LMi WD* 09 24 15.2484202569 +35 16 51.400826911   15.72   15.99   DA4 250 0
4 GD 165 WD* 14 24 39.1494933037 +09 17 14.161331419   14.46 14.32 14.6 14.91 DA4.1 150 0
5 V* MY Aps WD* 14 33 07.6357496582 -81 20 14.126849475   13.49 13.35 13.65   DA4.1 124 0
6 GD 358 WD* 16 47 18.3926893312 +32 28 32.865420612 12.511 13.530 13.653 13.752 13.852 DB2 318 0
7 V* DN Dra WD* 16 48 25.6321433630 +59 03 22.663406299   12.34 12.17 12.44   DA4.0 198 0
8 V* PY Vul WD* 19 37 13.7502254298 +27 43 18.736648968   13.14   12.7   DA4.0 117 0
9 GD 244 WD* 22 56 46.1531005640 +12 52 50.310130607   16.0   15.6   DA4.2 40 1
10 V* ZZ Psc WD* 23 28 47.6364608228 +05 14 54.234982405   13.17   13.0   DA4.1 443 0

    Equat.    Gal    SGal    Ecl

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2020.11.29-19:06:11

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