The nature of the X-ray binary IGR J19294+1816 from INTEGRAL, RXTE, and Swift observations

We report the results of a high-energy multi-instrumental campaign with INTEGRAL, RXTE, and Swift of the recently discovered INTEGRAL source IGR J19294+1816. The Swift/XRT data allow us to refine the position of the source to RA(J2000) = 19(h)29(m)55.9(s) Dec(J2000) = +18 degrees 18'38.4 '' (+/- 3.5 ''), which in turn permits us to identify a candidate infrared counterpart. The Swift and RXTE spectra are well fitted with absorbed power laws with hard (Gamma similar to 1) photon indices. During the longest Swift observation, we obtained evidence of absorption in true excess to the Galactic value, which may indicate some intrinsic absorption in this source. We detected a strong (P = 40%) pulsation at 12.43781(+/- 0.00003) s that we interpret as the spin period of a pulsar. All these results, coupled with the possible 117 day orbital period, point to IGR J19294+1816 being an HMXB with a Be companion star. However, while the long-term INTEGRAL/IBIS/ISGRI18-40 keV light curve shows that the source spends most of its time in an undetectable state, we detect occurrences of short (similar to 2000-3000 s) and intense flares that are more typical of supergiant fast X-ray transients. We therefore cannot make firm conclusions on the type of system, and we discuss the possible implications of IGR J19294+1816 being an SFXT.