Chandra monitoring of the Galactic Centre magnetar SGR J1745−2900 during the initial 3.5 years of outburst decay

Zelati, F. Coti; Rea, N.; Turolla, R.; Pons, José A.; Papitto, A.; Esposito, P.; Israel, G. L.; Campana, S.; Zane, S.; Tiengo, A.; Mignani, Roberto; Mereghetti, S.; Baganoff, F. K.; Haggard, Daryl; Ponti, G.; Torres, D. F.; Borghese, A.; Elfritz, J. G.

doi:10.1093/mnras/stx1700

Cited by 41 publications

(53 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Apart from temperature values of some of the hot spots of SGR 1745-2900, our results contrast with those of Coti Zelati et al (2017) for the same source and data. Firstly, we have taken two and three hot spots, while they assume just a single one.…”

Section: Discussioncontrasting

confidence: 98%

See 1 more Smart Citation

Evidence for a Multipolar Magnetic Field in SGR J1745-2900 from X-Ray Light-curve Analysis

Lima

Coelho

Pereira

et al. 2020

ApJ

View full text Add to dashboard Cite

SGR J1745-2900 was detected from its outburst activity in April 2013 and it was the first soft gamma repeater (SGR) detected near the center of the Galaxy (Sagittarius A * ). We use 3.5-year Chandra X-ray light-curve data to constrain some neutron star (NS) geometric parameters. We assume that the flux modulation comes from hot spots on the stellar surface. Our model includes the NS mass, radius, a maximum of three spots of any size, temperature and positions, and general relativistic effects. We find that the light-curve of SGR J1745-2900 could be described by either two or three hot spots. The ambiguity is due to the small amount of data, but our analysis suggests that one should not disregard the possibility of multi-spots (due to a multipolar magnetic field) in highly magnetized stars. For the case of three hot spots, we find that they should be large and have angular semi-apertures ranging from 16-67 degrees. The large size found for the spots points to a magnetic field with a nontrivial poloidal and toroidal structure (in accordance with magnetohydrodynamics investigations and NICER's recent findings for PSR J0030+0451) and is consistent with the small characteristic age of the star. Finally, we also discuss possible constraints on the mass and radius of SGR J1745-2900 and briefly envisage possible scenarios accounting for the 3.5-year evolution of SGR J1745-290 hot spots.

show abstract

Section: Discussioncontrasting

confidence: 98%

“…Our aim is to find the set of parameters (see Table 1) that best fit the X-ray emission of SGR J1745-2900. We use the light-curve from two epochs: 2013 (D13) and 2016 (D16)presented by Coti Zelati et al (2017). We let the parameters evolve as laid out in Section 3, and this is done independently for each data set.…”

Section: Resultsmentioning

confidence: 99%

Evidence for a Multipolar Magnetic Field in SGR J1745-2900 from X-Ray Light-curve Analysis

Lima

Coelho

Pereira

et al. 2020

ApJ

View full text Add to dashboard Cite

show abstract

“…The flux decay prior to our observations follows a simple exponential function with a characteristic timescale τ = 543 days. Such long decay timescales have been seen in other magnetars (e.g., Scholz et al 2014;Coti Zelati et al 2017;Alford & Halpern 2016). We refer the reader to Y15 for a detailed discussion of the consequences of such long time recoveries.…”

Section: Flux Historymentioning

confidence: 57%

“…The torque then returns to its nominal value on a timescale 1 year . On the other hand, SGR J1745−2900, the Galactic center magnetar that went into outburst in April 2013 (Kennea et al 2013;Mori et al 2013) has shown an increase ofν by a factor of 4.5, and no sign of decrease 3.5 years following the outburst Coti Zelati et al 2017). Last but not least, SGR 1900+14 has also shown strong timing noise following burst-active episodes, e.g., withν increasing by a factor of 5 following its late 1998 major bursting episode and GF (Woods et al 2002;Mereghetti et al 2006).…”

Section: Spectral Analysismentioning

confidence: 99%

The Sleeping Monster: NuSTAR Observations of SGR 1806–20, 11 Years After the Giant Flare

Younes

Baring

Kouveliotou

et al. 2017

ApJ

View full text Add to dashboard Cite

We report the analysis of 5 NuSTAR observations of SGR 1806−20 spread over a year from April 2015 to April 2016, more than 11 years following its Giant Flare (GF) of 2004. The source spin frequency during the NuSTAR observations follows a linear trend with a frequency derivativeν = (−1.25 ± 0.03) × 10 −12 Hz s −1 , implying a surface dipole equatorial magnetic field B ≈ 7.7×10 14 G. Thus, SGR 1806−20 has finally returned to its historical minimum torque level measured between 1993 and 1998. The source showed strong timing noise for at least 12 years starting in 2000, withν increasing one order of magnitude between 2005 and 2011, following its 2004 major bursting episode and GF. SGR 1806−20 has not shown strong transient activity since 2009 and we do not find short bursts in the NuSTAR data. The pulse profile is complex with a pulsed fraction of ∼ 8% with no indication of energy dependence. The NuSTAR spectra are well fit with an absorbed blackbody, kT = 0.62 ± 0.06 keV, plus a power-law, Γ = 1.33 ± 0.03. We find no evidence for variability among the 5 observations, indicating that SGR 1806−20 has reached a persistent and potentially its quiescent X-ray flux level after its 2004 major bursting episode. Extrapolating the NuSTAR model to lower energies, we find that the 0.5-10 keV flux decay follows an exponential form with a characteristic timescale τ = 543 ± 75 days. Interestingly, the NuSTAR flux in this energy range is a factor of ∼ 2 weaker than the long-term average measured between 1993 and 2003, a behavior also exhibited in SGR 1900 + 14. We discuss our findings in the context of the magnetar model.

show abstract

“…To isolate Sgr A*'s quiescence count rate, we must calculate the subset of the magnetar's counts that overlap Sgr A*'s extraction region. We adopt the background region from Coti Zelati et al (2017), i.e., an annulus with an inner radius of 5" and outer radius of 8" (see Figure 1). We extract count rates in the 2-8 keV band from 3 regions located at the same radial distance from the magnetar as Sgr A*, with the same size as Sgr A*'s extraction region (radius of 1.25").…”

Section: Estimation Of the Magnetar's Contaminationmentioning

confidence: 99%

No Sign of G2's Encounter Affecting Sgr A*'s X-Ray Flaring Rate from Chandra Observations

Bouffard

Haggard

Nowak

et al. 2019

ApJ

View full text Add to dashboard Cite

An unusual object, G2, had its pericenter passage around Sgr A*, the 4 × 10 6 M supermassive black hole in the Galactic Centre, in Summer 2014. Several research teams have reported evidence that following G2's pericenter encounter the rate of Sgr A*'s bright X-ray flares increased significantly. Our analysis carefully treats varying flux contamination from a nearby magnetic neutron star and is free from complications induced by using data from multiple X-ray observatories with different spatial resolutions. We test the scenario of an increased bright X-ray flaring rate using a massive dataset from the Chandra X-ray Observatory, the only X-ray instrument that can spatially distinguish between Sgr A* and the nearby Galactic Centre magnetar throughout the full extended period encompassing G2's encounter with Sgr A*. We use X-ray data from the 3 Ms observations of the Chandra X-ray Visionary Program (XVP) in 2012 as well as an additional 1.5 Ms of observations up to 2018. We use detected flares to make distributions of flare properties. Using simulations of X-ray flares accounting for important factors such as the different Chandra instrument modes, we test the null hypothesis on Sgr A*'s bright (or any flare category) X-ray flaring rate around different potential change points. In contrast to previous studies, our results are consistent with the null hypothesis; the same model parameters produce distributions consistent with the observed ones around any plausible change point.

show abstract

Chandra monitoring of the Galactic Centre magnetar SGR J1745−2900 during the initial 3.5 years of outburst decay

Cited by 41 publications

References 52 publications

Evidence for a Multipolar Magnetic Field in SGR J1745-2900 from X-Ray Light-curve Analysis

Evidence for a Multipolar Magnetic Field in SGR J1745-2900 from X-Ray Light-curve Analysis

The Sleeping Monster: NuSTAR Observations of SGR 1806–20, 11 Years After the Giant Flare

No Sign of G2's Encounter Affecting Sgr A*'s X-Ray Flaring Rate from Chandra Observations

Contact Info

Product

Resources

About