Period changes in the pulsating extreme helium stars V652 Her and BX Cir

Autor:	F. van Wyk, L. Crause, D. Kilkenny
Rok vydání:	2005
Předmět:	Physics Period (periodic table) chemistry.chemical_element Astronomy Astronomy and Astrophysics Astrophysics Star (graph theory) Ephemeris Stars chemistry Space and Planetary Science Quartic function Chemically peculiar star Maxima Helium
Zdroj:	Monthly Notices of the Royal Astronomical Society. 361:559-564
ISSN:	1365-2966 0035-8711
DOI:	10.1111/j.1365-2966.2005.09188.x
Popis:	Thirty-four new timings of maxima of the radially pulsating extreme helium (EHe) star V652 Her (=BD+13° 3224) obtained during 1996-2004 are reported. The quartic ephemeris (for the pulsation period decrease) is extended and the higher-order terms are defined more accurately. We also report 45 new timings of maxima for the closely similar star BX Cir (= LSS 3184) over the same baseline and present the first evidence that this star also shows a decreasing period. The data obtained thus far can be represented by a quadratic ephemeris - a linearly decreasing period in BX Cir - though the decrease rate (dP/dn ∼ 3.7 x 10 -10 d) is much smaller than in V652 Her.
Databáze:	OpenAIRE
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