Unveiling the short and faint X-ray transient nature of IGR J17419-2802

Abstract

We report new X-ray results from the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), Swift, Chandra, and XMM-Newton observations of the hitherto poorly studied unidentified X-ray transient IGR J17419-2802. We studied in detail the temporal, spectral, and energetic properties of three hard X-ray outbursts detected above 20 keV by INTEGRAL. They are all characterized by an average X-ray luminosity of 3$\times$10$^{35}$~erg~s$^{-1}$ and a constrained duration of a few days. This marks a peculiarly short and faint X-ray transient nature for IGR J17419-2802. From archival unpublished soft X-ray observations, we found that the source spends most of the time undetected at very low X-ray fluxes (down to $<4.7\times10^{-14}$ erg cm $^{-2}$ s$^{-1}$) for a dynamic range >2,000 when in outburst. We provided an accurate arcsecond-sized source error circle. Inside it, we pinpointed the best candidate near-infrared counterpart whose photometric properties are compatible with a late-type spectral nature. Based on our new findings, we suggest that IGR J17419-2802 is a new member of the very faint X-ray transients (VFXTs) class. Detailed investigations of VFXT outbursts above 20 keV are particularly rare. In this respect, our reported INTEGRAL outbursts are among the best studied to date; in particular, their constrained duration of a few days is among the shortest ever measured for a VFXT.