Whole Earth telescope observations of the ZZ Ceti star HL Tau 76
- Author(s)
- Noel Dolez, G Vauclair, Scot J. Kleinman, M Chevreton, Jian Ning Fu, Jan Erik Solheim, J M G Perez, Ana Ulla, L Fraga, Antonio Kanaan, Mike D. Reed, Steven D. Kawaler, M. Sean O'Brien, Travis S. Metcalfe, R. Edward Nather, Divas Sanwal, Eric W. Klumpe, Anjum S. Mukadam, Matt A. Wood, T J Ahrens, Nicole M. Silvestri, Denis J. Sullivan, Tiri Sullivan, Xianjun J. Jiang, Dawei W. Xu, B N Ashoka, Elia M. Leibowitz, P. A. Ibbetson, Eran O. Ofek, D Kilkenny, E G Meistas, D Alisauskas, R Janulis, Romualdas Kalytis, S Zola, J Krzesinski, W Ogloza, Gerald Handler, R Silvotti, S Bernabei
- Abstract
This paper analyses the Whole Earth Telescope observations of HL Tau 76, the first discovered pulsating DA white dwarf. The star was observed during two Whole Earth Telescope campaigns. It was a second priority target during the XCOV13 campaign in 1996 and the first priority one during the XCOV18 campaign in 1999. The 1999 campaign reached 66.5% duty cycle. With a total duration of 18 days, the frequency resolution achieved is 0.68 œHz. With such a frequency resolution, we were able to find as many as 78 significant frequencies in the power spectrum, of which 34 are independent frequencies after removal of all linear combinations. In taking into account other frequencies present during the 1996 WET campaign and those present in earlier data, which do not show up in the 1999 data set, we find a total of 43 independent frequencies. This makes HL Tau 76 the richest ZZ Ceti star in terms of number of observed pulsation modes. We use those pulsation frequencies to determine as much as possible of the internal structure of HL Tau 76. The pulsations in HL Tau 76 cover a wide range of periods between 380 s and 1390 s. We propose an identification for 39 of those 43 frequencies in terms of l = 1 and l = 2 non-radial g-modes split by rotation. We derive an average rotation period of 2.2 days. The period distribution of HL Tau 76 is best reproduced if the star has a moderately "thick" hydrogen mass fraction log qH = -7.0. The results presented in this paper constitute a starting point for a detailed comparison of the observed periods with the periods calculated for models as representative as possible of HL Tau 76. Œ ESO 2006.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- Université Toulouse III Paul Sabatier, Observatoire Midi-Pyrénées, University of Texas, Austin, Université de recherche Paris Sciences et Lettres, Beijing Normal University, University of Oslo, Institute of Astrophysics of the Canary Islands, Enxeñaría Telemática, Universidade Federal de Santa Catarina, Case Western Reserve University, Iowa State University, Yale University, University of Washington, Florida Institute of Technology, Victoria University of Wellington, Chinese Academy of Sciences (CAS), Indian Space Research Organization, Tel Aviv University, California Institute of Technology (Caltech), South African Astronomical Observatory (SAAO), Vilnius University (VU), Pedagogical University of Cracow, Apache Point Observatory, COROT Additional Program Working Group, University of La Laguna
- Journal
- Astronomy & Astrophysics
- Volume
- 446
- Pages
- 237-257
- No. of pages
- 21
- ISSN
- 0004-6361
- DOI
- https://doi.org/10.1051/0004-6361:20053149
- Publication date
- 2006
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103003 Astronomy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/15c32615-7224-4b77-99e5-8c039db7121a