stars: early-type; stars: massive; stars: variable: general; stars: Be; X-rays: stars; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - High Energy Astrophysical Phenomena
Abstract :
[en] In the last years, a peculiarity of some Be stars - their association with unusually hard and intense X-ray emission - was shown to extend beyond a mere few cases. In this paper, we continue our search for new cases by performing a limited survey of 18 Be stars using XMM-Newton. The targets were selected either on the basis of a previous X-ray detection (EXOSAT,ROSAT, XMM-slew survey) without spectral information available or because of the presence of a peculiar spectral variability. Only two targets remain undetected in the new observations and three other stars display only faint and soft X-rays. Short-term and/or long- term variations were found in one third of the sample. The spectral characterization of the X-ray brightest 13 stars of the sample led to the discovery of three new γ Cas (HD 44458, HD 45995, and V558 Lyr), bringing the total to 25 known cases, and another γ Cas candidate (HD 120678), bringing the total to two.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Nazé, Yaël ; Université de Liège - ULiège > Groupe d'astrophysique des hautes énergies (GAPHE)
Motch, Christian; Université de Strasbourg, CNRS, Observatoire Astronomique de Strasbourg, 11 rue de l'Université, F-67000 Strasbourg, France
Rauw, Grégor ; Université de Liège - ULiège > Groupe d'astrophysique des hautes énergies (GAPHE)
Kumar, Shami ; Université de Liège - ULiège > AGO > GAPHE
Robrade, Jan; Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany
Lopes de Oliveira, Raimundo; Departamento de Física, Universidade Federal de Sergipe, Av. Marechal Rondon, S/N, 49000-000 São Cristóvão, SE, Brazil ; Observatório Nacional, Rua Gal. José Cristino 77, 20921-400, Rio de Janeiro, RJ, Brazil
Smith, Myron A.; NSF OIR Lab, 950 N Cherry Ave, Tucson, AZ 85721, USA
Torrejón, José M.; Instituto Universitario de Física Aplicada a las Ciencias y las Tecnlogías, Universidad de Alicante, E-03690 Alicante, Spain)
Language :
English
Title :
Three discoveries of γ Cas analogues from dedicated XMM-Newton observations of Be stars
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