Unveiling the nature of INTEGRAL objects through optical spectroscopy

Abstract

Within the framework of our program (running since 2004) of identification of hard X-ray INTEGRAL sources through optical spectroscopy, we present the results concerning the nature of 33 high-energy objects. The data were acquired with the use of six telescopes of different sizes and from one on-line archive. The results indicate that the majority of these objects (23 out of 33) are active galactic nuclei (AGNs), whereas 10 are sources in the local Universe with eight of which in the Galaxy and two in the Small Magellanic Cloud (SMC). Among the identified AGNs, 13 are of Type 1 (i.e., with broad emission lines), eight are of Type 2 (with narrow emissions only), and two are X-ray bright, optically normal galaxies with no apparent nuclear activity in the optical. Six of these AGNs lie at high redshift (z > 0.5). Concerning local objects, we found that five of them are Galactic cataclysmic variables, three are high-mass X-ray binaries (two of which lying in the SMC), one is a low-mass X-ray binary, and one is classified as a flare star that is likely of RS CVn type. The main optical properties and inferred physical characteristics of these sources are presented and discussed.

BL Lacertae identifications in a ROSAT-selected sample ofFermiunidentified objects

“…Although this method gives an orderof-magnitude value for the distance of Galactic CVs, our past experience (Masetti et al 2013 and references therein) tells us that these estimates are in general correct to within 50% of the refined value subsequently determined with more precise approaches.…”

BAT AGN Spectroscopic Survey. I. Spectral Measurements, Derived Quantities, and AGN Demographics

“…In only nine cases we use updated galaxy counterparts based on subsequent published studies. These differences are associated with the updated counterparts for SWIFT J1448.7-4009 and SWIFT J1747.7-2253 provided in Masetti et al (2013); SWIFT J0634.7-7445, SWIFT J0654.6+0700, and SWIFT J2157.4-0615 found in Parisi et al (2014); SWIFT J0632.8+6343, SWIFT J0632.8+6343, and SWIFT J1238.6+0928 provided in the updated INTEGRAL catalog of Malizia et al (2016), and finally SWIFT J0350.1-5019; we use the counterpart from Ricci et al (2017) (ESO201-4). Another issue is that some BAT AGN counterparts host dual AGNs (Koss et al 2016b); however, the median value of the ( -L 2 10 keV int ) ratio between the dual AGNs is 11 (Koss et al 2012), so the majority of the emission in the BAT detection is typically coming from a single AGN.…”

“…Other BAT optical spectroscopic studies focused on smaller samples (N=11-75) of newly identified BAT counterparts, such as those from the Palermo BAT catalogs (Parisi et al 2009(Parisi et al , 2014. Yet other studies focused on small samples of AGNs identified with INTEGRAL above 20 keV, with some overlap with the BAT AGNs (e.g., Masetti et al 2013). While these AGN studies made significant advances in counterpart identification, most did not provide measurements of black hole masses and none measured stellar velocity dispersions in obscured sources.…”

IGR J17488–2338: a newly discovered giant radio galaxy

“…In the optical the source has R and B magnitudes of 17.2 and 19, respectively, yielding a lumonosity of 2×10 45 erg s −1 . The source is quite red (R − K = 4.3), possibly due to heavy obscuration along the line of sight related to the source location close to the Galactic plane; indeed Masetti et al (2013) measure 4.9 mag of extinction due to our Galaxy alone.…”

“…the discovery of a new radio galaxy with an active nucleus located behind the Galactic plane. IGR J17488-2338 was then optically classified by Masetti et al (2013) as a Seyfert 1.5 galaxy at z = 0.24. These authors also measured the mass of the source's central black hole using the broad-line velocities; for IGR J17488-2338 the Hβ emission line provides a black hole of 1.3 × 10 9 solar masses.…”