Broad-band characteristics of seven new hard X-ray selected cataclysmic variables

Abstract

We present timing and spectral analysis of a sample of seven hard X-ray selected Cataclysmic Variable candidates based on simultaneous X-ray and optical observations collected with XMM-Newton , complemented with Swift/BAT and INTEGRAL/IBIS hard X-ray data and ground-based optical photometry. For six sources, X-ray pulsations are detected for the first time in the range $\sim 296-6098\mathrm{s}$, identifying them as members of the magnetic class. Swift J0927.7-6945, Swift J0958.0-4208, Swift J1701.3-4304, Swift J2113.5+5422, and possibly PBC J0801.2-4625, are Intermediate Polars (IPs), while Swift J0706.8+0325 is a short (1.7 h) orbital period Polar, the 11${}^{\mathrm{th}}$ hard X-ray selected identified so far. X-ray orbital modulation is also observed in Swift J0927.7-6945 (5.2 h) and Swift J2113.5+5422 (4.1 h). Swift J1701.3-4304 is discovered as the longest orbital period (12.8 h) deep eclipsing IP. The spectra of the magnetic systems reveal optically thin multi-temperature emission between 0.2 and 60 keV. Energy dependent spin pulses and the orbital modulation in Swift J0927.7-6945 and Swift J2113.5+5422 are due to intervening local high density absorbing material (${\mathrm{N}}_{\mathrm{H}}\sim 10^{22-23}\mathrm{c}{\mathrm{m}}^{-2}$). In Swift J0958.0-4208 and Swift J1701.3-4304, a soft X-ray blackbody (kT$\sim$50 and $\sim$80 eV) is detected, adding them to the growing group of "soft" IPs. White dwarf masses are determined in the range $\sim 0.58-1.18{\mathrm{M}}_{\odot }$, indicating massive accreting primaries in five of them. Most sources accrete at rates lower than the expected secular value for their orbital period. Formerly proposed as a long-period (9.4 h) novalike CV, Swift J0746.3-1608 shows peculiar spectrum and light curves suggesting either an atypical low-luminosity CV or a low mass X-ray binary.

23 pages, 7 tables, and 6 Figures. Accepted for publications on MNRAS on June 13th, 2017

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• Hard X-ray luminosity functions of cataclysmic variables: Joint Swift/BAT and Gaia data
• Discovery of spin modulated circular polarization from IGR J17014-4306, the remnant of Nova Scorpii 1437 A.D
• DW Cancri in x-rays
• 2PBC J0658.0-1746: a hard X-ray eclipsing polar in the orbital period gap
• The true nature of Swift J0746.3-1608: a possible Intermediate Polar showing accretion state changes
• A Step towards Unveiling the Nature of Three Cataclysmic Variables: LS Cam, V902 Mon, and SWIFT J0746.3-1608
• Discovery of a young pre-intermediate polar
• Chandra, NuSTAR, and Optical Observations of the Cataclysmic Variables IGR J17528-2022 and IGR J20063+3641
• Breaking the degeneracy in magnetic cataclysmic variable X-ray spectral modeling using X-ray light curves
• Optical Studies of Ten Hard X-ray Selected Cataclysmic Binaries
• SRGe J194401.8+284452 -- an X-ray Cataclysmic Variable in the Field of the Gamma-Ray Source 4FGL J1943.9+2841
• Timing analysis of a sample of five cataclysmic variable candidates observed by the XMM-Newton satellite
• Broad Observational Perspectives Achieved by the Accreting White Dwarf Sciences in the XMM-Newton and Chandra Eras
• X-ray emission mechanisms in accreting white dwarfs