The Chandra Dust-scattering Halo of Galactic Center Transient Swift J174540.7–290015

Corrales, Lía; Mon, Brayden; Haggard, Daryl; Baganoff, F. K.; Garmire, G. P.; Degenaar, N.; Reynolds, M. T.

doi:10.3847/1538-4357/aa68dd

Cited by 14 publications

(16 citation statements)

References 31 publications

(70 reference statements)

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“…The model requires a foreground dust layer in the spiral arms a few kpc away from the GC with N H ∼ 1.7 × 10 23 cm −2 (Jin et al 2018). The column density is consistent with another independent study based on T15 (Corrales et al 2017). The dust model was then constructed for each of the two transients and each source extraction region.…”

Section: Photo-absorption and Dust Scatteringsupporting

confidence: 92%

“…While Corrales et al (2017) studied the dust scattering halo from T15 using the Chandra observations in February 2016, there has been no publication on the two Chandra observations of T37 in July 2016. We investigated the Chandra observations of T37 in July 2016 to characterize its spectral state when the outburst flux was declining.…”

Section: Transient 37 Observationsmentioning

confidence: 99%

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NuSTAR and Chandra Observations of New X-Ray Transients in the Central Parsec of the Galaxy

Mori

Hailey

Mandel

et al. 2019

ApJ

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We report NuSTAR and Chandra observations of two X-ray transients, SWIFT J174540.7−290015 (T15) and SWIFT J174540.2−290037 (T37), which were discovered by the Neil Gehrels Swift Observatory in 2016 within r ∼ 1 pc of Sgr A*. NuSTAR detected bright X-ray outbursts from T15 and T37, likely in the soft and hard states, with 3-79 keV luminosities of 8 × 10 36 and 3 × 10 37 erg s −1 , respectively. No X-ray outbursts have previously been detected from the two transients and our Chandra ACIS analysis puts an upper limit of L X < ∼ 2 × 10 31 erg s −1 on their quiescent 2-8 keV luminosities. No pulsations, significant QPOs, or type I X-ray bursts were detected in the NuSTAR data. While T15 exhibited no significant red noise, the T37 power density spectra are well characterized by three Lorentzian components. The declining variability of T37 above ν ∼ 10 Hz is typical of black hole (BH) transients in the hard state. NuSTAR spectra of both transients exhibit a thermal disk blackbody, X-ray reflection with broadened Fe atomic features, and a continuum component well described by Comptonization models. Their X-ray reflection spectra are most consistent with high BH spin (a * > ∼ 0.9) and large disk density (n e ∼ 10 21 cm −3 ). Based on the best-fit ionization parameters and disk densities, we found that X-ray reflection occurred near the inner disk radius, which was derived from the relativistic broadening and thermal disk component. These X-ray characteristics suggest the outbursting BH-LMXB scenario for both transients and yield the first BH spin measurements from X-ray transients in the central 100 parsec region.

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Section: Photo-absorption and Dust Scatteringsupporting

confidence: 92%

Section: Transient 37 Observationsmentioning

confidence: 99%

NuSTAR and Chandra Observations of New X-Ray Transients in the Central Parsec of the Galaxy

Mori

Hailey

Mandel

et al. 2019

ApJ

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“…The best-fit values of the hydrogen column densities and spectral indexes are similar to the typical values of N H = 14.3×10 22 cm −2 and Γ = 2 determined from the largest X-ray flares of Sgr A* (Porquet et al 2003;Nowak et al 2012). The spectrum of the Chandra observation of SWIFT J174540.7-290015 on 2016 February 13 has been analyzed by Corrales et al (2017). Because of the very high luminosity of the source, the authors extracted the readout streak spectra, which minimizes the contamination by the pile-up and dust-scattering halo.…”

Section: Resultssupporting

confidence: 63%

Continuation of the X-ray monitoring of Sgr A*: the increase in bright flaring rate confirmed

Mossoux

Finociety

Beckers

et al. 2020

A&A

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Context. The supermassive black hole Sagittarius A* (Sgr A*) is located at the dynamical center of the Milky Way. In a recent study of the X-ray flaring activity from Sgr A* using Chandra, XMM-Newton, and Swift observations from 1999 to 2015, it has been argued that the bright flaring rate has increased from 2014 August 31 while the faint flaring rate decreased from around 2013 August. Aims. We tested the persistence of these changes in the flaring rates with new X-ray observations of Sgr A* performed from 2016 to 2018 (total exposure of 1.4 Ms). Methods. We reprocessed the Chandra, XMM-Newton, and Swift observations from 2016 to 2018. We detected 9 flares in the Chandra data and 5 flares in the Swift data that we added to the set of 107 previously detected flares. We computed the intrinsic distribution of flare fluxes and durations corrected for the sensitivity bias using a new method that allowed us to take the error on the flare fluxes and durations into account. From this intrinsic distribution, we determined the average flare detection efficiency for each Chandra, XMM-Newton, and Swift observation. After correcting each observational exposure for this efficiency, we applied the Bayesian blocks algorithm on the concatenated flare arrival times. As in the above-mentioned study, we also searched for a flux and fluence threshold that might lead to a change in flaring rate. We improved the previous method by computing the average flare detection efficiencies for each flux and fluence range. Results. The Bayesian block algorithm did not detect any significant change in flaring rate of the 121 flares. However, we detected an increase by a factor of about three in the flaring rate of the most luminous and most energetic flares that have occurred since 2014 August 30. Conclusions. The X-ray activity of Sgr A* has increased for more than four years. Additional studies about the overall near-infrared and radio behavior of Sgr A* are required to draw strong results on the multiwavelength activity of the black hole.

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“…The majority of the photons are from the bright Sgr A* flares, but also include counts from Sgr A*'s quiescent emission, plus a small contribution from the nearby magnetar. At the position of Sgr A*, the magnetar contributes 3% and 2.5% of the flux, for F1 and F2 respectively (estimated with the raytrace simulation ChaRT/MARX and approximations of the GC dust scattering halo, e.g., Corrales et al 2017;Jin et al 2017, and references therein). We fix the magnetar contribution manually with the model_flux tool.…”

Section: Sgr A* Flarementioning

confidence: 99%

“…The neutral hydrogen column absorption (N H ) is modeled with TBnew, and we use the photoionization cross sections of Verner et al (1996) and the elemental abundances of Wilms et al (2000). Interstellar dust can scatter X-ray photons and is a crucial component in X-ray spectral fitting of Galactic Center sources (Corrales et al 2016;Smith et al 2016;Corrales et al 2017;Jin et al 2017). We apply the dust scattering model fgcdust (Jin et al 2017) developed for AX J1745.6−2901 and tested on X-ray sources in the Galactic Center region by Ponti et al (2017).…”

Section: Spectral Analysismentioning

confidence: 99%

Chandra Spectral and Timing Analysis of Sgr A*'s Brightest X-Ray Flares

Haggard

Nynka

Mon

et al. 2019

ApJ

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We analyze the two brightest Chandra X-ray flares detected from Sagittarius A*, with peak luminosities more than 600× and 245× greater than the quiescent X-ray emission. The brightest flare has a distinctive double-peaked morphology -it lasts 5.7 ksec (∼ 2 hours), with a rapid rise time of 1500 sec and a decay time of 2500 sec. The second flare lasts 3.4 ksec, with rise and decay times of 1700 sec and 1400 sec. These luminous flares are significantly harder than quiescence: the first has a power law spectral index Γ = 2.06 ± 0.14 and the second has Γ = 2.03 ± 0.27, compared to Γ = 3.0 ± 0.2 for the quiescent accretion flow. These spectral indices (as well as the flare hardness ratios) are consistent with previously-detected Sgr A* flares, suggesting that bright and faint flares arise from similar physical processes. Leveraging the brightest flare's long duration and high signal-to-noise, we search for intraflare variability and detect excess X-ray power at a frequency of ν ≈ 3 mHz, but show that it is an instrumental artifact and not of astrophysical origin. We find no other evidence (at the 95% confidence level) for periodic or quasi-periodic variability

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The Chandra Dust-scattering Halo of Galactic Center Transient Swift J174540.7–290015

Cited by 14 publications

References 31 publications

NuSTAR and Chandra Observations of New X-Ray Transients in the Central Parsec of the Galaxy

NuSTAR and Chandra Observations of New X-Ray Transients in the Central Parsec of the Galaxy

Continuation of the X-ray monitoring of Sgr A*: the increase in bright flaring rate confirmed

Chandra Spectral and Timing Analysis of Sgr A*'s Brightest X-Ray Flares

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