2008A&A...488..549P


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.02CET02:42:15

2008A&A...488..549P - Astronomy and Astrophysics, volume 488, 549-557 (2008/9-3)

X-ray hiccups from Sagittarius A* observed by XMM-Newton. The second brightest flare and three moderate flares caught in half a day.

PORQUET D., GROSSO N., PREDEHL P., HASINGER G., YUSEF-ZADEH F., ASCHENBACH B., TRAP G., MELIA F., WARWICK R.S., GOLDWURM A., BELANGER G., TANAKA Y., GENZEL R., DODDS-EDEN K., SAKANO M. and FERRANDO P.

Abstract (from CDS):

Our Galaxy hosts at its dynamical center SgrA*, the closest supermassive black hole. Surprisingly, its luminosity is several orders of magnitude lower than the Eddington luminosity. However, the recent observations of occasional rapid X-ray flares from SgrA* provide constraints on the accretion and radiation mechanisms at work close to its event horizon. Our aim is to investigate the flaring activity of SgrA* and to constrain the physical properties of the X-ray flares. In Spring 2007, we observed SgrA* with XMM-Newton with a total exposure of ∼230 ks. We have performed timing and spectral analysis of the new X-ray flares detected during this campaign. To study the range of flare spectral properties, in a consistent manner, we have also reprocessed, using the same analysis procedure and the latest calibration, archived XMM-Newton data of previously reported rapid flares. The dust scattering was taken into account during the spectral fitting. We also used Chandra archived observations of the quiescent state of SgrA* for comparison. On April 4, 2007, we observed for the first time within a time interval of roughly half a day, an enhanced incidence rate of X-ray flaring, with a bright flare followed by three flares of more moderate amplitude. The former event represents the second brightest X-ray flare from Sgr A* on record with a peak amplitude of about 100 above the quiescent luminosity. This new bright flare exhibits similar light-curve shape (nearly symmetrical), duration (∼3ks) and spectral characteristics to the very bright flare observed in October 3, 2002 by XMM-Newton. The measured spectral parameters of the new bright flare, assuming an absorbed power law model taken into account dust scattering effect, are NH=12.3+2.1–1.8x1022cm–2 and Γ=2.3±0.3 calculated at the 90% confidence level. The spectral parameter fits of the sum of the three following moderate flares, while lower (NH=8.8+4.4–3.2x1022cm–2 and Γ=1.7+0.7–0.6), are compatible within the error bars with those of the bright flares. The column density found, for a power-law model taking into account the dust scattering, during the flares is at least two times higher than the value expected from the (dust) visual extinction toward SgrA* (AV∼25mag), i.e., 4.5x1022cm–2. However, our fitting of the SgrA* quiescent spectra obtained with Chandra, for a power-law model taking into account the dust scattering, shows that an excess of column density is already present during the non-flaring phase. The two brightest X-ray flares observed so far from SgrA* exhibited similar soft spectra.

Abstract Copyright:

Journal keyword(s): Galaxy: center - X-rays: individual: Sgr A* - X-rays: general - radiation mechanisms: general

CDS comments: Table 2 : the two flares are [BGM2005] J174540.08-290028.48 and [BGM2005] J174540.14-290028.40 in SIMBAD, see NAME SGR A.

Simbad objects: 12

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Number of rows : 12

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 2XMM J174502.1-285450 LXB 17 45 02.33 -28 54 49.7           ~ 119 0
2 NAME Sgr A Region reg 17 45 12 -28 48.3           ~ 920 0
3 HD 316223 * 17 45 25.7877637188 -28 56 27.031850990   11.72 10.85 10.64   F 22 0
4 HD 316224 * 17 45 30.0100290067 -29 07 04.309270647   10.59 10.16 10.10   F8 23 0
5 [SKM2002] 27 LXB 17 45 35.65 -29 01 34.0           ~ 160 1
6 NAME Sgr A West HII 17 45 39.4 -29 00 24           ~ 354 0
7 GAL 000.0+00.0 gam 17 45 39.60213 -29 00 22.0000           ~ 11999 0
8 GCIRS 13 Em* 17 45 39.76 -29 00 29.8           ~ 131 0
9 CXOGC J174539.7-290022 Psr 17 45 39.80 -29 00 19.9           ~ 45 1
10 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 3599 3
11 HD 316232 * 17 45 43.6894069145 -29 13 18.040088310 10.61 10.92 10.27 10.25   O9IV 34 0
12 CD-29 13941 * 17 45 43.9184783899 -29 04 56.646385973   11.93 11.72     F8 16 0

    Equat.    Gal    SGal    Ecl

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