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标题：XMM-Newton and TESS observations of the highly variable polar V496 UMa
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作者：Samet Ok ; Axel Schwope
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2022
卷号：662
页码：1-12
DOI：10.1051/0004-6361/202142813
语种：English
出版社：EDP Sciences
摘要：Aims. We studied the temporal and spectral behavior of V496 UMa from the optical to the X-ray regimes. Methods. We used archival XMM-Newton and TESS observations obtained in 2017 and 2019, respectively, to perform a spectral and timing analysis of the highly variable magnetic CV. Results. The light curves of the TESS and XMM-Newton satellites reveal a double-humped pattern modulated with the periodicity of 91.058467 ± 0.00001 min. V496 UMa displays a two-pole accretion geometry in the high accretion state. X-ray spectra from these regions are composed of thermal plasma radiation and soft blackbody components with almost identical temperatures and a total accretion rate of M˙ = 1.4(8) × 10−11 M yr−1 . The X-ray centers of the humps show longitudinal shifts of −18◦ and 4◦ , and shifts around photometric phase zero of −172◦ and −186◦ , for the main hump and second hump, respectively. The long-term ZTF light curves reveal high and low accretions states. Low-state ZTF and SDSS photometric data are consistent with an 0.8 M white dwarf at 10 000 K and a main-sequence donor star with a spectral type of M5.0 at a Gaia determined distance of 758 pc. Conclusions. V496 UMa is a very bright polar in X-rays when it is in the high state. Due to its unusual geometric structure, mass accretion onto the second accretion pole is interrupted occasionally. This discontinuous behavior does not follow a certain pattern in time and has been observed so far only in the high state. The X-ray light curves display clear evidence of an accretion stream at the photometric phase of φ = 0.81, which does not show up in optical light curves. An accurate period was derived using the combined TESS and XMM-Newton data, which differs by 3.8σ from published results.
关键词：novae;cataclysmic variables;binaries: close;X-rays: binaries;stars: individual: V496 UMa;stars: fundamental parameters