IGR J18293-1213 is an eclipsing Cataclysmic Variable

Abstract

Studying the population of faint hard X-ray sources along the plane of the Galaxy is challenging because of high-extinction and crowding, which make the identification of individual sources more difficult. IGR J18293-1213 is part of the population of persistent sources which have been discovered by the INTEGRAL satellite. We report on NuSTAR and Swift/XRT observations of this source, performed on 2015 September 11. We detected three eclipsing intervals in the NuSTAR light curve, allowing us to constrain the duration of these eclipses, $\Delta t=30.8_{-0.0}^{+6.3}$ min, and the orbital period of the system, $T=6.92\pm 0.01$ hr. Even though we only report an upper limit on the amplitude of a putative spin modulation, the orbital period and the hard thermal Bremsstrahlung spectrum of IGR J18293-1213 provide strong evidence that this source is a magnetic Cataclysmic Variable (CV). Our NuSTAR and Swift/XRT joint spectral analysis places strong constraints on the white dwarf mass $M_{\mathrm{wd}}=0.78_{-0.09}^{+0.10}$ M${}_{\odot }$. Assuming that the mass to radius ratio of the companion star $M_{\ast }/R_{\ast }=1$ (solar units) and using $T$, $\Delta t$ and $M_{\mathrm{wd}}$, we derived the mass of the companion star $M_{\ast }=0.82\pm 0.01$ M${}_{\odot }$, the orbital separation of the binary system $a=2.14\pm 0.04$ R${}_{\odot }$, and its orbital inclination compared to the line of sight $i=(72.2_{-0.0}^{+2.4})\pm 1.0^{\circ }$.

8 pages, 5 figures, accepted for publication in MNRAS

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• INTEGRAL/IBIS 17-yr hard X-ray all-sky survey
• New hard X-ray sources discovered in the ongoing INTEGRAL Galactic Plane survey after 14 years of observations
• Broad-band characteristics of seven new hard X-ray selected cataclysmic variables
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• Chandra Observations of the field containing HESS J1616-508
• SRG/ART-XC Galactic Plane Survey near Galactic Longitude $l\simeq 20^{\circ }$: Catalog of Sources
• SRG/ART-XC all-sky X-ray survey: Catalog of sources detected during the first year