The Ibis Soft Gamma-Ray Sky After 1000 Integral Orbits*

Abstract

We report here an all-sky soft gamma-ray source catalog based on IBIS observations performed during the first 1000 orbits of INTEGRAL. The database for the construction of the source list consists of all good quality data available from launch in 2002 up to the end of 2010. This corresponds to ∼110 Ms of scientific public observations with a concentrated coverage on the Galactic Plane and extragalactic deep exposures. This new catalog includes 939 sources above a 4.5 sigma significance threshold detected in the 17-100 keV energy band, of which 120 represent previously undiscovered soft gamma-ray emitters. The source positions are determined, mean fluxes are provided in two main energy bands, and are reported together with the overall source exposure. Indicative levels of variability are provided, and outburst times and durations are given for transient sources. Comparison is made with previous IBIS catalogs, and those from other similar missions.1 Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries:

First hard X-ray detection and broad-band X-ray study of the unidentified transient AX J1949.8+2534

“…Such detection thresholds are essential to avoid false detections/excesses caused by background noise (e.g. Bird et al 2016). The search was initially performed in the energy band 22-60 keV; this choice takes into account the evolution of the IBIS/ISGRI energy threshold that occurred from revolution number ∼ 900 on.…”

“…The best position is RA=297 • .49 and Dec=25 • .57 with a 90% confidence error circle radius equal to 2 ′ .4. AX J1949.8+2534 is not listed in the latest published IBIS/ISGRI catalog (Bird et al 2016) despite extensive IN-TEGRAL coverage of its sky region (∼ 2 Ms up to revolution n. 1000 considered in Bird et al 2016) and this information can be used to infer an upper limit on its persistent hard X-ray emission. By additionally considering the source exposure from our present dataset (∼ 0.25 Ms), we can infer a 3σ upper limit of ∼ 0.4 mCrab or 3.2×10 −12 erg cm −2 s −1 (20-40 keV) for persistent emission.…”

AX J1910.7+0917: the slowest X-ray pulsar

“…AX J1910.7+0917 is also reported at hard energies (above 20 keV) as a variable HMXB in the IN T EGRAL/IBIS source catalog (Bird et al 2016).…”

Galactic Sources Detected in the NuSTAR Serendipitous Survey

“…The source types that INTEGRAL and Swift/BAT have detected in the largest numbers (Voss & Ajello 2010;Krivonos et al 2012;Bird et al 2016) are active galactic nuclei (AGNs), low-mass X-ray binaries (LMXBs), high-mass X-ray binaries (HMXBs), and cataclysmic variables (CVs). While these accreting black holes, neutron stars, and white dwarfs (WDs) are the most common types, INTEGRAL also detects significant numbers of non-accreting compact objects, including pulsar wind nebulae and magnetars.…”

“…Although the bandpass of NuSTAR is 3-79 keV, the analysis for the serendipitous survey has been carried out in the 3-24 keV band where the source-to-background ratio is higher for most source types. Thus, in energy, the NuSTAR survey is intermediate between surveys and catalogs constructed in the soft X-ray band with ASCA (0.7-10 keV, Sugizaki et al 2001), XMM-Newton (0.2-12 keV, Rosen et al 2016), and the Chandra X-ray Observatory (0.5-7 keV, Evans et al 2010) and at higher energies with Swift/BAT (15-55 keV, Ajello et al 2012) and with INTEGRAL (17-100 keV, Bird et al 2016). In terms of coverage, BAT and INTEGRAL have large fields of view (FOVs), and they have observed the entire sky.…”