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Three discoveries of $\gamma$ Cas analogues from dedicated XMM–Newton observations of Be stars

Abstract : 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 (-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.
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Submitted on : Tuesday, March 10, 2020 - 9:56:45 PM
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Yaël Nazé, Christian Motch, Gregor Rauw, Shami Kumar, Jan Robrade, et al.. Three discoveries of $\gamma$ Cas analogues from dedicated XMM–Newton observations of Be stars. Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2020, 493 (2), pp.2511-2517. ⟨10.1093/mnras/staa457⟩. ⟨hal-02504654⟩



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