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http://hdl.handle.net/20.500.12386/29213
Title: | 2PBC J0658.0-1746: a hard X-ray eclipsing polar in the orbital period gap | Authors: | BERNARDINI, Federico DE MARTINO, Domitilla Mukai, K. Falanga, M. MASETTI, NICOLA |
Issue Date: | 2019 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Number: | 489 | Issue: | 1 | First Page: | 1044 | Abstract: | The hard X-ray source 2PBC J0658.0-1746 was proposed as an eclipsing magnetic cataclysmic variable of the polar type, based on optical follow-ups. We present the first spectral and timing analysis at X-ray energies with XMM-Newton, complemented with archival X-ray, optical, infrared (IR) photometry, and spectroscopy. The X-ray emission shows bright and faint phases and total eclipses recurring every 2.38 h, consistent with optical properties. This firmly identifies 2PBC J0658.0-1746 as an eclipsing polar, the second hard X-ray selected in the orbital period gap. The X-ray orbital modulation changes from cycle-to-cycle and the X-ray flux is strongly variable over the years, implying a non-stationary mass accretion rate both on short and long time-scales. The X-ray eclipses allow to refine the orbital ephemeris with period 0.09913398(4) d, and to constrain the binary inclination 79^{circ}≲ i ≲ 90^{circ} and the mass ratio 0.18< M_2/M_{ WD}< 0.40. A companion mass M<SUB>2</SUB>=0.2-0.25 M_{\odot } with a radius R<SUB>2</SUB>=0.24-0.26 R_{\odot } and spectral type ∼M4, at D=209^{+3}_{-2} pc, is derived. A lower limit to the white dwarf mass of ∼ 0.6 M_{\odot } is obtained from the X-ray spectrum. An upper limit to the magnetic colatitude, β ≲ 50^{circ}, and a shift in azimuth, ψ ∼ 14^{circ}, of the main accreting pole are also estimated. The optical/IR spectral energy distribution shows large excess in the mid-IR due to lower harmonics of cyclotron emission. A high-state mass accretion rate ∼ 0.4-1× 10^{-10} M_{\odot } yr^{-1}, lower than that of cataclysmic variables above the gap and close to that of systems below it, is estimated. With 2PBC J0658.0-1746, the number of hard X-ray-selected polars increases to 13 members, suggesting that they are not as rare as previously believed. | URI: | http://hdl.handle.net/20.500.12386/29213 | URL: | http://arxiv.org/abs/1907.05318v1 https://iopscience.iop.org/article/10.3847/1538-4357/ab2fdf |
ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stz1951 | Bibcode ADS: | 2019MNRAS.489.1044B | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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