EDP Sciences
Free access
Issue
A&A
Volume 383, Number 1, February III 2002
Page(s) 239 - 243
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20011712


A&A 383, 239-243 (2002)
DOI: 10.1051/0004-6361:20011712

PG 1325+101 and PG 2303+019: Two new large amplitude subdwarf B pulsators

R. Silvotti1, R. Østensen2, 3, U. Heber4, J.-E. Solheim3, S. Dreizler5 and M. Altmann4, 6

1  Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
2  Isaac Newton Group of Telescopes, 37800 Santa Cruz de La Palma, Canary Islands, Spain
    e-mail: roy@ing.iac.es
3  Institutt for Fysikk, Universitetet i Tromsø, 9037 Tromsø, Norway
    e-mail: jan-erik.solheim@phys.uit.no
4  Dr. Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, 96049 Bamberg, Germany
    e-mail: ai03@sternwarte.uni-erlangen.de
5  Institut für Astronomie und Astrophysik, Sand 1, 72076 Tübingen, Germany
    e-mail: dreizler@astro.uni-tuebingen.de
6  Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
    e-mail: maltmann@astro.uni-bonn.de

(Received 6 November 2001 / Accepted 3 December 2001 )

Abstract
We report the detection of short period oscillations in the sdB stars PG 1325+101 ( B=13.8) and PG 2303+019 (alias HS 2303+0152, B=16.0) from time-series photometry made at the Nordic Optical Telescope of a sample of 21 candidates. Both stars are multi-mode pulsators with at least three distinct periods in the range 100-140 s, and relatively large amplitudes up to 2.6 and 1.6% respectively. Moreover PG 1325+101 shows the shortest pulsation period ever registered among sdBV stars, 68.9 s, which corresponds to the first harmonic of the main signal. Following previous temperature and gravity determinations for PG 1325+101 ( $T_{\rm eff}$ = 34 500 K, $\log g=6.1$) and our NLTE model atmosphere analysis for PG 2303+019 ( $T_{\rm eff}$ = 35 200 K, $\log g=5.7$), both stars are well inside the theoretical sdBV instability strip.


Key words: stars: subdwarfs -- stars: oscillations -- stars: individual: PG 1325+101, PG 2303+019

Offprint request: R. Silvotti, silvotti@na.astro.it

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