THE UNUSUAL VARIABLE HOT B SUBDWARF LS IV-14{sup 0}116

Journal Article · Fri Jun 10 00:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/734/1/59· OSTI ID:21576640

Green, E M; Guvenen, B; O'Malley, C J; O'Connell, C J; Baringer, B P; Villareal, A S; Carleton, T M ^[1]; Fontaine, G; Brassard, P ^[2]; Charpinet, S ^[3]

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1. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
2. Departement de Physique, Universite de Montreal, Succ. Centre-Ville, C.P. 6128, Montreal, QC H3C 3J7 (Canada)
3. Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France)

We first present the results of follow-up photometric observations of the He-rich hot B subdwarf LS IV-14{sup 0}116, which confirm the presence of multiperiodic luminosity variations in the light curve of this star. Rather surprisingly, no other follow-up observations of this kind seem to have been published after the initial suggestion in 2005 that LS IV-14{sup 0}116 could be a pulsating star of a new kind. We were able to extract from our data at least six significant periodicities ranging from 1954 s to 5084 s, including the two oscillations uncovered previously. We also present the results of an analysis combining a high signal-to-noise optical spectrum of LS IV-14{sup 0}116 with recently developed non-local thermodynamic equilibrium model atmospheres and synthetic spectra. Our best estimates of the atmospheric parameters of this star are T{sub eff} = 34950 {+-} 250 K, log g = 5.93 {+-} 0.04, and log N(He)/N(H) = -0.62 {+-} 0.03 (formal fitting errors only). These place LS IV-14{sup 0}116 very near the region of maximum instability in the T{sub eff}-log g plane for short-period p-mode pulsators of the hot subdwarf type. If the luminosity variations are indeed due to pulsations, then LS IV-14{sup 0}116 poses a real challenge to current theory: how can such long observed periods (which would have to be associated with medium- to high-order g-modes) be excited at such a high effective temperature and surface gravity, while the short-period p-modes, more typically excited in this domain, are not observed in this particular star?

• OSTI ID: 21576640
• Journal Information: Astrophysical Journal, Vol. 734, Issue 1; Other Information: DOI: 10.1088/0004-637X/734/1/59; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
LUMINOSITY
OSCILLATIONS
PERIODICITY
SPECTRA
STARS
VISIBLE RADIATION
ELECTROMAGNETIC RADIATION
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
VARIATIONS