Open AccessPeriod changes in the pulsating extreme helium stars V652 Her and BX Cir
Author(s) -
Kilkenny D.,
Crause L. A.,
Van Wyk F.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09188.x
Subject(s) - physics , ephemeris , astrophysics , maxima , helium , star (game theory) , stars , light curve , astronomy , quartic function , atomic physics , satellite , mathematics , performance art , pure mathematics , art history , art
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 (d P /d n ∼ 3.7 × 10 −10 d) is much smaller than in V652 Her.