2PBC J0658.0-1746: a hard X-ray eclipsing polar in the orbital period gap

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, 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 timescales. The X-ray eclipses allow to refine the orbital ephemeris with period 0.09913398(4) d, and to constrain the binary inclination $79^{\mathrm{o}}\lesssim i\lesssim 90^{\mathrm{o}}$ and the mass ratio 0.18$<{\mathrm{M}}_2/{\mathrm{M}}_{\mathrm{WD}}<$0.40. A companion mass M${}_2=0.2-0.25{\mathrm{M}}_{\odot }$ with a radius R${}_2=0.24-0.26{\mathrm{R}}_{\odot }$ and spectral type $\sim$M4, at D$=209_{-2}^{+3}\mathrm{pc}$, is derived. A lower limit to the white dwarf mass of $\sim 0.6{\mathrm{M}}_{\odot }$ is obtained from the X-ray spectrum. An upper limit to the magnetic colatitude, $\beta \lesssim 50^{\mathrm{o}}$, and a shift in azimuth, $\psi \sim 14^{\mathrm{o}}$, 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 $\sim 0.4-1\times 10^{-10}{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$, 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 thirteen members, suggesting that they are not as rare as previously believed.

arXiv commentAccepted for publication on MNRAS, 11 Pages, 8 Figures, 4 tables

References in corpus (42)

• Gaia Data Release 2. Summary of the contents and survey properties
• On the Absorption of X-rays in the Interstellar Medium
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• The Swift X-ray Telescope
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
• The USNO-B Catalog
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs
• Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
• The Burst Alert Telescope (BAT) on the Swift MIDEX Mission
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Gaia Data Release 2: Photometric content and validation
• The XMM-Newton Optical/UV Monitor Telescope
• Catalogue of cataclysmic binaries, low-mass X-ray binaries and related objects (Seventh edition)
• The Evolution of Cataclysmic Variables as Revealed by their Donor Stars
• The 105 month Swift-BAT all-sky hard X-ray survey
• Magnetic White Dwarfs
• X-ray Emissions from Accreting White Dwarfs: a Review
• Binary Star Origin of High Field Magnetic White Dwarfs
• Effects of Gravity on the Structure of Postshock Accretion Flows in Magnetic Cataclysmic Variables
• The IBIS soft gamma-ray sky after 1000 INTEGRAL orbits
• Population Synthesis of Cataclysmic Variables: I. Inclusion of Detailed Nuclear Evolution
• Far-ultraviolet Spectroscopy of Magnetic Cataclysmic Variables
• The census of cataclysmic variables in the ROSAT Bright Survey
• The energy balance in polars revisited
• CV evolution: AM Her binaries and the period gap
• Constraints on the space density of intermediate polars from the Swift-BAT survey
• Characterization of new hard X-ray Cataclysmic Variables
• One thousand cataclysmic variables from the Catalina Real-time Transient Survey
• X-ray Luminosities of Optically-Selected Cataclysmic Variables and Application to the Galactic Ridge X-ray Emission
• Broad-band characteristics of seven new hard X-ray selected cataclysmic variables
• Optical Studies of 15 Hard X-ray Selected Cataclysmic Binaries
• On the nature of the hard X-ray sources SWIFTJ1907.3-2050, IGRJ12123-5802 and IGRJ19552+0044
• The serendipituous discovery of a short-period eclipsing polar in 2XMMp
• The nature of fifty Palermo Swift-BAT hard X-ray objects through optical spectroscopy
• 2XMMi J225036.9+573154 - a new eclipsing AM Her binary discovered using XMM-Newton
• Irradiated atmospheres of accreting magnetic white dwarfs with an application to the polar AM Herculis
• Swift J2218.4+1925: a new hard X-ray selected Polar observed with XMM-Newton
• The true nature of Swift J0746.3-1608: a possible Intermediate Polar showing accretion state changes
• XMM-Newton observations of the eclipsing polar EP Dra
• IGR J14257-6117, a magnetic accreting white dwarf with a very strong X-ray orbital modulation

Cited by in corpus (10)

• Hard X-ray Cataclysmic Variables
• Galactic Model Parameters and Space Density of Cataclysmic Variables in Gaia Era: New Constraints to Population Models
• Discovery of Two Polars from a Crossmatch of ZTF and the SRG/eFEDS X-ray Catalog
• Identification of 3XMM J000511.8+634018 as a new polar at P(orb)=133.5 min -- is it inside or outside the period gap?
• The period-gap cataclysmic variable CzeV404 Her: A link between SW Sex and SU UMa systems
• Optical and X-ray studies of three polars: RX J0859.1+0537, RX J0749.1-0549, and RX J0649.8-0737
• Broad Observational Perspectives Achieved by the Accreting White Dwarf Sciences in the XMM-Newton and Chandra Eras
• Locating the flickering source in polars
• A persistent bow shock in a diskless magnetised accreting white dwarf
• On the nature of the 2.4 hr-period eclipsing cataclysmic variable W2 in 47 Tuc