TWO RAPIDLY VARIABLE GALACTIC X-RAY TRANSIENTS OBSERVED WITHCHANDRA,XMM-NEWTON, ANDSUZAKU

Heinke, C. O.; Tomsick, John A.; Yusef‐Zadeh, F.; Grindlay, Jonathan E.

doi:10.1088/0004-637x/701/2/1627

Cited by 23 publications

(29 citation statements)

References 28 publications

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“…It was first discovered during ASCA observations of the GC in 1993 as an eclipsing transient (Kennea & Skinner 1996;Maeda et al 1996). Chandra observations provided precise measurements of its coordinate (17:45:35.64, -29:01:33.90 with a 1 σ coordinate error of 0.32 ′′ ) 1 , which is only 1.45 arcmin from Sgr A ⋆ (Heinke et al 2009). Therefore, it has been intensely observed by many X-ray observatories such as Chandra, XMMNewton, Swift and Suzaku during GC monitoring campaigns (Hyodo et al 2009;Degenaar et al 2012;Ponti et al 2015a).…”

Section: Ax J17456-2901mentioning

confidence: 99%

Probing the interstellar dust towards the Galactic Centre: dust-scattering halo around AX J1745.6−2901

Jin

Ponti

Haberl

et al. 2017

Monthly Notices of the Royal Astronomical Society

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AX J1745.6-2901 is an X-ray binary located at only 1.45 arcmin from Sgr A ⋆ , showcasing a strong X-ray dust scattering halo. We combine Chandra and XMM-Newton observations to study the halo around this X-ray binary. Our study shows two major thick dust layers along the line of sight (LOS) towards AX J1745.6-2901. The LOS position and N H of these two layers depend on the dust grain models with different grain size distribution and abundances. But for all the 19 dust grain models considered, dust Layer-1 is consistently found to be within a fractional distance of 0.11 (mean value: 0.05) to AX J1745.6-2901 and contains only (19-34)% (mean value: 26%) of the total LOS dust. The remaining dust is contained in Layer-2, which is distributed from the Earth up to a mean fractional distance of 0.64. A significant separation between the two layers is found for all the dust grain models, with a mean fractional distance of 0.31. Besides, an extended wing component is discovered in the halo, which implies a higher fraction of dust grains with typical sizes 590Å than considered in current dust grain models. Assuming AX J1745.6-2901 is 8 kpc away, dust Layer-2 would be located in the Galactic disk several kpc away from the Galactic Centre (GC). The dust scattering halo biases the observed spectrum of AX J1745.6-2901 severely in both spectral shape and flux, and also introduces a strong dependence on the size of the instrumental point spread function and the source extraction region. We build Xspec models to account for this spectral bias, which allow us to recover the intrinsic spectrum of AX J1745.6-2901 free from dust scattering opacity. If dust Layer-2 also intervenes along the LOS to Sgr A ⋆ and other nearby GC sources, a significant spectral correction for the dust scattering opacity would be necessary for all these GC sources.

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Section: Ax J17456-2901mentioning

confidence: 99%

Probing the interstellar dust towards the Galactic Centre: dust-scattering halo around AX J1745.6−2901

Jin

Ponti

Haberl

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…in neutron star or black hole HMXBs, symbiotic X-ray binaries (a subclass of LMXBs that contain a neutron star and an M-type giant) or symbiotics in which the accreting object is a white dwarf (e.g. Luna & Sokoloski 2007;Masetti et al 2007;Heinke et al 2009b;Romano et al 2011). In such systems the changing spectral properties are attributed to intrinsic variations in the absorption column density due to the wind of the companion star.…”

Section: Gro J1744-28mentioning

confidence: 99%

A four-yearXMM-Newton/Chandramonitoring campaign of the Galactic centre: analysing the X-ray transients

Degenaar

Wijnands

Cackett

et al. 2012

A&A

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We report on the results of a four-year long X-ray monitoring campaign of the central 1.2 square degrees of our Galaxy, performed with Chandra and XMM-Newton between 2005 and 2008. Our study focuses on the properties of transient X-ray sources that reach 2-10 keV luminosities of L X 10 34 erg s −1 for an assumed distance of 8 kpc. There are 17 known X-ray transients within the field of view of our campaign, eight of which were detected in outburst during our observations: the transient neutron star low-mass X-ray binaries GRS 1741-2853, AX J1745.6-2901, SAX J1747.0-2853, KS 1741-293 (all four are also known X-ray bursters), and GRO J1744-28 (a 2.1 Hz X-ray pulsar), and the unclassified X-ray transients XMM J174457-2850.3, CXOGC J174535.5-290124 and CXOGC J174541.0-290014. We present their X-ray spectra and flux evolution during our campaign, and discuss our results in light of their historic activity. Our main results include the detection of two thermonuclear X-ray bursts from SAX J1747.0-2853 that were separated by an unusually short time interval of 3.8 min. Investigation of the lightcurves of AX J1745.6-2901 revealed one thermonuclear X-ray burst and a ∼1600-s long X-ray eclipse. We found that both XMM J174457-2850.3 and GRO J1744-28 displayed weak X-ray activity above their quiescent levels at L X ∼ 10 33−34 erg s −1 , which is indicative of low-level accretion. We compare this kind of activity with the behaviour of low-luminosity X-ray transients that display 2-10 keV peak luminosities of L X ∼ 10 34 erg s −1 and have never been seen to become brighter. In addition to the eight known X-ray transients, we discovered a previously unknown X-ray source that we designate XMMU J174654.1-291542. This object emits most of its photons above 2 keV and appears to be persistent at a luminosity of L X ∼ 10 34 erg s −1 , although it exhibits strong spectral variability on a time scale of months. Based on its X-ray properties and the possible association with an infrared source, we tentatively classify this object as a cataclysmic variable. No new transients were found during our campaign, reinforcing the conclusion of previous authors that most X-ray transients recurring on a time scale of less than a decade have now been identified near the Galactic centre.

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“…Using FTOOLS xrtcentroid we determine the position to be RA = 17:44:46.26s and DEC = -29:50:56.08 ′′ with positional uncertainty of 9 ′′ , consistent within <2σ with the position of XMMU J174445.5-295044. Given the lack of other X-ray sources nearby (see figure 4 of Heinke et al 2009), the Swift/XRT source is thus certainly the same as XMMU J174445.5-295044.…”

Section: Swift/xrtmentioning

confidence: 99%

“…We reprocessed the Swift/XRT data (using HEASOFT 6.14), extracted a spectrum with XSELECT, and created an effective area file with xrtmkarf. We fit the Swift/XRT spectrum with an absorbed power-law using cstat statistics (Cash 1979) in XSPEC 12.8.1, fixing the photon index to 1.18 (as found in the deepest and most-constrained observation of Heinke et al 2009). We measure NH = 4.5 +7.2 −3.3 ×10 22 cm −2 and an unabsorbed 2-10 keV flux of 8.5 +10.3 −5.0 × 10 −12 erg s −1 cm −2 , the second-highest 2-10 keV flux recorded from XMMU J174445.5-295044.…”

Section: Swift/xrtmentioning

confidence: 99%

“…Heinke et al (2009) also identified a bright near-infrared (NIR) counterpart (2MASS J17444541-2950446) within the 2" XMM error circle. Heinke et al (2009) calculated the probability of a star of this brightness in KS appearing in the X-ray error circle as only 2%, indicating that it is almost certainly the true counterpart. This star appears highly obscured and shows infrared colors typical of late-type stars, which Heinke et al suggested indicates that XMMU J174445.5-295044 is a symbiotic star or symbiotic X-ray binary.…”

Section: Introductionmentioning

confidence: 96%

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Revealing a new symbiotic X-ray binary with Gemini Near-infrared Integral Field Spectrograph

Bahramian

Gladstone

Heinke

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We use K-band spectroscopy of the counterpart to the rapidly variable X-ray transient XMMU J174445.5-295044 to identify it as a new symbiotic X-ray binary. XMMU J174445.5-295044 has shown a hard X-ray spectrum (we verify its association with an Integral/IBIS 18-40 keV detection in 2013 using a short Swift/XRT observation), high and varying N H , and rapid flares on timescales down to minutes, suggesting wind accretion onto a compact star. We observed its near-infrared counterpart using the Near-infrared Integral Field Spectrograph (NIFS) at Gemini-North, and classify the companion as ∼M2 III. We infer a distance of 3.1 +1.8 −1.1 kpc (conservative 1σ errors), and therefore calculate that the observed X-ray luminosity (2-10 keV) has reached to at least 4×10 34 erg s −1 . We therefore conclude that the source is a symbiotic X-ray binary containing a neutron star (or, less likely, black hole) accreting from the wind of a giant.

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TWO RAPIDLY VARIABLE GALACTIC X-RAY TRANSIENTS OBSERVED WITHCHANDRA,XMM-NEWTON, ANDSUZAKU

Cited by 23 publications

References 28 publications

Probing the interstellar dust towards the Galactic Centre: dust-scattering halo around AX J1745.6−2901

Probing the interstellar dust towards the Galactic Centre: dust-scattering halo around AX J1745.6−2901

A four-yearXMM-Newton/Chandramonitoring campaign of the Galactic centre: analysing the X-ray transients

Revealing a new symbiotic X-ray binary with Gemini Near-infrared Integral Field Spectrograph

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