Chandra Observations of Eight Sources Discovered by Integral

Mon. Not. R. Astron. Soc.

Rahoui

Krivonos

et al. 2016

Self Cite

IGR J14091-6108 is a Galactic X-ray source known to have an iron emission line, a hard X-ray spectrum, and an optical counterpart. Here, we report on X-ray observations of the source with XMM-Newton and NuSTAR as well as optical spectroscopy with ESO/VLT and NOAO/SOAR. In the X-rays, this provides data with much better statistical quality than the previous observations, and this is the first report of the optical spectrum. Timing analysis of the XMM data shows a very significant detection of 576.3 ± 0.6 s period. The signal has a pulsed fraction of 30 ± 3% in the 0.3-12 keV range and shows a strong drop with energy. The optical spectra show strong emission lines with significant variability in the lines and continuum, indicating that they come from an irradiated accretion disk. Based on these measurements, we identify the source as a magnetic Cataclysmic Variable of Intermediate Polar (IP) type where the white dwarf spin period is 576.3 s. The X-ray spectrum is consistent with the continuum emission mechanism being due to thermal Bremsstrahlung, but partial covering absorption and reflection are also required. In addition, we use the IP mass (IPM) model, which suggests that the white dwarf in this system has a high mass, possibly approaching the Chandrasekhar limit.

Section: Discussionsupporting

confidence: 90%

Section: Optical Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Identifying IGR J14091−6108 as a magnetic CV with a massive white dwarf using X-ray and optical observations

Mon. Not. R. Astron. Soc.

Rahoui

Krivonos

et al. 2016

Self Cite

“…Thus, in most cases, sources are not classified until higher angular resolution X-ray observations are obtained, providing an image to identify extended sources or to improve the source localization, allowing for multi-wavelength counterparts to be found. Large X-ray follow-up programs include the use of the Neil Gehrels Swift Observatory X-ray Telescope (Swift/XRT; Landi et al 2017, and references therein) and the Chandra X-ray Observatory (e.g., Tomsick et al 2006Tomsick et al , 2008Tomsick et al , 2016a. The X-ray localizations enable optical and near-IR spectroscopy (e.g., Chaty et al 2008;Masetti et al 2013;Coleiro et al 2013;Fortin et al 2018), at which point confident source classifications are nearly always obtained.…”

Section: Introductionmentioning

confidence: 99%

Chandra Observations of High-energy X-Ray Sources Discovered by INTEGRAL

Bodaghee

Chaty

et al. 2020

ApJ

Self Cite

The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellite has detected in excess of 1000 sources in the ∼20-100 keV band during its surveys of the sky over the past 17 years. We obtained 5 ks observations of 15 unclassified IGR sources with the Chandra X-ray Observatory in order to localize them, to identify optical/IR counterparts, to measure their soft X-ray spectra, and to classify them. For 10 of the IGR sources, we detect Chandra sources that are likely (or in some cases certain) to be the counterparts. IGR J18007-4146 and IGR J15038-6021 both have Gaia parallax distances, placing them at 2.5 +0.5 −0.4 and 1.1 +1.5 −0.4 kpc, respectively. We tentatively classify both of them as intermediate polar-type Cataclysmic Variables. Also, IGR J17508-3219 is likely to be a Galactic source, but it is unclear if it is a Dwarf Nova or another type of transient. For IGR J17118-3155, we provide a Chandra localization, but it is unclear if the source is Galactic or extragalactic. Based on either near-IR/IR colors or the presence of extended near-IR emission, we classify four sources

“…IGR J18088−2741 was first reported in Krivonos et al (2012), and Tomsick et al (2016b) later identified it as CXOU J180839.8−274131 with Chandra. The fit to its combined Chandra and INTEGRAL spectra with a cut-off power law yields a very hard Γ ≈ −1.5 and E fold ≈ 4.8 keV, whereas the column density is N H < 7 × 10 21 cm −2 .…”

Section: Igr J18088−2741mentioning

confidence: 99%

Identifying fourINTEGRALsources in the Galactic plane via VLT/optical andXMM–Newton/X-ray spectroscopy

Rahoui

Mon. Not. R. Astron. Soc.

Krivonos

2016

Self Cite

We report on FORS2 spectroscopy aiming at the identification of four Galactic Plane sources discovered by INTEGRAL, IGR J18088−2741, IGR J18381−0924, IGR J17164−3803, and IGR J19173+0747, complemented by XMM-Newton spectroscopy for IGR J18381−0924. The presence of broad H i and He i emission lines and a flat Balmer decrement Hα/Hβ show that IGR J18088−2741 is a cataclysmic variable located beyond 8 kpc. For IGR J18381−0924, the detection of red-shifted Hα and O i emission signatures and the absence of narrow forbidden emission lines point towards a low-luminosity Seyfert 1.9 nature at z = 0.031 ± 0.002. Its XMM-Newton spectrum, best-fit by an absorbed Γ = 1.19 ± 0.07 power law combined with a z = 0.026−0.008 red-shifted iron emission feature, is in agreement with this classification. The likely IGR J17164−3803 optical counterpart is an M2III star at 3 to 4 kpc which, based on the X-ray spectrum of the source, is the companion of a white dwarf in an X-ray faint symbiotic system. Finally, we challenge the accepted identification of IGR J19173+0747 as an high mass X-ray binary. Indeed, the USNO optical counterpart is actually a blend of two objects located at the most likely 3 kpc distance, both lying within the error circle of the Swift position. The first is a cataclysmic variable, which we argue is the real nature of IGR J19173+0747. However, we cannot rule out the second one that we identify as an F3V star that, if associated to IGR J19173+0747, likely belongs to a quiescent X-ray binary.