Swift J174540.7−290015: a new accreting binary in the Galactic Centre

Ponti, G.; Jin, Chichuan; Marco, Barbara De; Rea, N.; Rau, A.; Haberl, F.; Zelati, F. Coti; Bozzo, E.; Ferrigno, C.; Bower, Geoffrey C.; Demorest, Paul

doi:10.1093/mnras/stw1382

Cited by 19 publications

(27 citation statements)

References 88 publications

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“…′ from Sgr A ⋆ (SGR J1745-2900, Swift J174540.7-290015 and the foreground component towards AX J1745.6-2901) show neutral absorption column densities consistent with the value of Sgr A ⋆ (Coti- Zelati et al 2015;Ponti et al 2016a;. This suggests that the neutral absorption towards Sgr A ⋆ has an ISM origin.…”

Section: Discussionmentioning

confidence: 58%

A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission

Ponti

George

Scaringi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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119

142

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We present the first fully simultaneous fits to the NIR and X-ray spectral slope (and its evolution) during a very bright flare from Sgr A ⋆ , the supermassive black hole at the Milky Way's center. Our study arises from ambitious multi-wavelength monitoring campaigns with XMMNewton, NuSTAR and SINFONI. The average multi-wavelength spectrum is well reproduced by a broken power-law with Γ N IR = 1.7 ± 0.1 and Γ X = 2.27 ± 0.12. The difference in spectral slopes (∆Γ = 0.57 ± 0.09) strongly supports synchrotron emission with a cooling break. The flare starts first in the NIR with a flat and bright NIR spectrum, while X-ray radiation is detected only after about 10 3 s, when a very steep X-ray spectrum (∆Γ = 1.8 ± 0.4) is observed. These measurements are consistent with synchrotron emission with a cooling break and they suggest that the high energy cut-off in the electron distribution (γ max ) induces an initial cut-off in the optical-UV band that evolves slowly into the X-ray band. The temporal and spectral evolution observed in all bright X-ray flares are also in line with a slow evolution of γ max . We also observe hints for a variation of the cooling break that might be induced by an evolution of the magnetic field (from B ∼ 30 ± 8 G to B ∼ 4.8 ± 1.7 G at the X-ray peak). Such drop of the magnetic field at the flare peak would be expected if the acceleration mechanism is tapping energy from the magnetic field, such as in magnetic reconnection. We conclude that synchrotron emission with a cooling break is a viable process for Sgr A ⋆ 's flaring emission.

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Section: Discussionmentioning

confidence: 58%

A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission

Ponti

George

Scaringi

et al. 2017

Monthly Notices of the Royal Astronomical Society

Self Cite

119

142

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“…There are two X-ray transients whose LOSs are very close to Sgr A ⋆ . Swift J174540.7-290015 was discovered in 2016 at 16 arcsec from Sgr A ⋆ (Reynolds et al 2016), with N H,abs = 1.7 × 10 23 cm −2 (tbnew model and WAM00 abundances, Ponti et al 2016). SGR J1745-2900 is located at 2.4 arcsec from Sgr A ⋆ (Rea et al 2013), with N H,abs = 1.9 × 10 23 cm −2 (tbabs model and WAM00 abundances, Coti- Zelati et al 2015).…”

Section: Dust Distribution In the Gc Directionmentioning

confidence: 99%

“…It has been observed that thousands of point-like X-ray sources and extended sources are sitting in this region (e.g. Wang, Gotthelf & Lang 2002;Muno et al 2003Muno et al , 2005Muno et al , 2009Degenaar et al 2012Degenaar et al , 2015Ponti et al 2015aPonti et al , 2016, including Sgr A ⋆ which is the super-massive black hole (SMBH) closest to Earth (e.g. Genzel, Eisenhauer & Gillessen 2010).…”

Section: Introductionmentioning

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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“…Assuming a Solar mix of abundances, supersolar abundance in the accretion flow of Sgr A* would explain the enhanced emission from argon but not that of iron. This would imply that iron is depleted relative to other metals in the GC region, such as observed in the accretion material of AX J1745.6-2901 (Ponti et al 2016). Figure 5.…”

Section: Comparison Of Gaussian Line Fits To Theoretical Predictionsmentioning

confidence: 98%

The Chandra High-resolution X-Ray Spectrum of Quiescent Emission from Sgr A*

Corrales

Baganoff

Wang

et al. 2020

ApJ

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In quiescence, Sgr A* is surprisingly dim, shining 100,000 times less than expected for its environment. This problem has motivated a host of theoretical models to explain radiatively inefficient accretion flows (RIAFs). The Chandra Galactic Center (GC) X-ray Visionary Program obtained approximately 3 Ms (one month) of Chandra HETG data, offering the only opportunity to examine the quiescent X-ray emission of Sgr A* with high resolution spectroscopy. Utilizing custom background regions and filters for removing overlapping point sources, this work provides the first ever look at stacked HETG spectra of Sgr A*. We model the background datasets with a cubic spline and fit the unbinned Sgr A* spectra with a simple parametric model of a power law plus Gaussian lines under the effects of interstellar extinction. We detect a strong 6.7 keV iron emission line in the HEG spectra and a 3.1 keV emission line in the MEG spectra. In all cases, the line centroids and equivalent widths are consistent with those measured from low-resolution CCD spectra. An examination of the unbinned, stacked HEG±1 spectrum reveals fine structure in the iron line complex. In addition to resolving the resonant and forbidden lines from He-like iron, there are apparent emission features arising with higher statistical significance at lower energy, potentially associated with FeXX-XXIV ions in a ∼ 1 keV plasma arising near the Bondi radius of Sgr A*. With this work, we release the cleaned and stacked Sgr A* and background HETG spectra to the public as a special legacy dataset.

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Swift J174540.7−290015: a new accreting binary in the Galactic Centre

Cited by 19 publications

References 88 publications

A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission

A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission

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

The Chandra High-resolution X-Ray Spectrum of Quiescent Emission from Sgr A*

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