1. The field high-amplitude SX Phe variable BL Cam: Results from a multisite photometric campaign: II. Evidence of a binary - Possibly triple - System
- Author
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M. Helvaci, M. Blauzek, V. Casanova, J. Michelet, G. Santacana, J. P. Sareyan, L. Kotková, A.-Y. Zhou, Hana Kučáková, S. Fauvaud, I. Scheggia, A. Avdibegovic, J. J. Rives, Petr Zasche, A. Nava-Vega, F. Fumagalli, M. Alvarez, C. Ulusoy, K. Truparová, J. Kliner, P. van Cauteren, B. Yasarsoy, Eric G. Hintz, Raoul Behrend, B. H. Granslo, L. Král, Cahit Yeşilyaprak, J. A. Farrell, S. Bartošíková, M. J. López-González, Patricia Lampens, M. Vilášek, Marek Wolf, F. Van Den Abbeel, G. Klingenberg, K. A. Graham, R. Kocián, I. Ribas, H. Wücher, Raul Michel, M. Fauvaud, John H. Simonetti, F. J. Aceituno, M. P. Nicholson, E. Rodriguez, J.-M. Vugnon, O. Trondal, L. Fox-Machado, Ege Üniversitesi, Observatoire du Bois de Bardon, Groupe européen d’observation stellaire (GEOS), Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Ciencies de l'Espai (ICE), Instituto de Astrofisica de Andalucia, CSIC (IAA), Koninklijke Sterrenwacht van België, Variable Star Section, Norwegian Astronomical Society, Sulphur Flats Observatory, Martin Observatory, Physics Dep., Virginia Polytechnic Institute & State University, Blacksburg, Astronomical Institute, Charles University, National Astronomical Observatoires-CAS, Observatorio Astronómico Nacional, Instituto de Astronomía, Universidad Nacional Autónoma de México, Facultad de Ciencias Químicas e Ingeniería, Universidad Autónoma de Baja California, Societá Astronomica Le pleiadi, Observatoire des Trois Korrigans, Department of Physics and Astronomy, Brigham Young University, Beersel Hills Observatory, Department of Physics, Akdeniz University, Department of Physics, Ataturk University, American Association of Variable Star Observers (AAVSO), Project Eridanus, Observatory and Planetarium of Johann Palisa, Club d'Astronomie Lyon Ampéré [Vaulx-en-Velin] (CALA), Club Eclipse : Club d'Etudes du Ciel, de la Lune, des Instruments, des Planètes, du Soleil et des Etoiles..., Astronomical Institute, Academy of Sciences, Ege University Observatory, Vesqueville Observatory, and Observatoire Astronomique de l'Université de Genève
- Subjects
Physics ,Stars: individual: BL Camelopardalis ,Stars: variables: ? Scuti ,education.field_of_study ,Cepheid variable ,Population ,Brown dwarf ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Stars ,Orbit ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Stars: oscillations ,Binaries: general ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Maxima ,Instability strip ,education ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Stellar evolution ,Solar and Stellar Astrophysics (astro-ph.SR) ,Techniques: photometric - Abstract
Short-period high-amplitude pulsating stars of Population I ($\delta$ Sct stars) and II (SX Phe variables) exist in the lower part of the classical (Cepheid) instability strip. Most of them have very simple pulsational behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is a unique object among them, being an extreme metal-deficient field high-amplitude SX Phe variable with a large number of frequencies. Based on a frequency analysis, a pulsational interpretation was previously given. aims heading (mandatory) We attempt to interpret the long-term behaviour of the residuals that were not taken into account in the previous Observed-Calculated (O-C) short-term analyses. methods heading (mandatory) An investigation of the O-C times has been carried out, using a data set based on the previous published times of light maxima, largely enriched by those obtained during an intensive multisite photometric campaign of BL Cam lasting several months. results heading (mandatory) In addition to a positive (161 $\pm$ 3) x 10$^{-9}$ yr$^{-1}$ secular relative increase in the main pulsation period of BL Cam, we detected in the O-C data short- (144.2 d) and long-term ($\sim$ 3400 d) variations, both incompatible with a scenario of stellar evolution. conclusions heading (mandatory) Interpreted as a light travel-time effect, the short-term O-C variation is indicative of a massive stellar component (0.46 to 1 M$_{\sun}$) with a short period orbit (144.2 d), within a distance of 0.7 AU from the primary. More observations are needed to confirm the long-term O-C variations: if they were also to be caused by a light travel-time effect, they could be interpreted in terms of a third component, in this case probably a brown dwarf star ($\geq$ 0.03 \ M$_{\sun}$), orbiting in $\sim$ 3400 d at a distance of 4.5 AU from the primary., Comment: 7 pages, 5 figures, accepted for publication in A&A
- Published
- 2010
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