DISCOVERY OF A SUPERLUMINAL Fe K ECHO AT THE GALACTIC CENTER: THE GLORIOUS PAST OF Sgr A* PRESERVED BY MOLECULAR CLOUDS

Journal Article · Sat May 01 04:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/714/1/732· OSTI ID:21448858

Ponti, G; Terrier, R; Goldwurm, A; Trap, G ^[1]; Belanger, G ^[2]

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1. APC Universite Paris 7 Denis Diderot, 75205 Paris Cedex 13 (France)
2. ESA/ESAC, P.O. Box 78, 28691 Villanueva de la Canada (Spain)

We present the result of a study of the X-ray emission from the galactic center (GC) molecular clouds (MCs) within 15 arcmin from Sgr A*. We use XMM-Newton data (about 1.2 Ms of observation time) spanning about eight years. The MC spectra show all the features characteristic of reflection: (1) intense Fe K{alpha}, with equivalent width of about 0.7-1 keV, and the associated K{beta} line; (2) flat power-law continuum, and (3) a significant Fe K edge ({tau} {approx} 0.1-0.3). The diffuse low ionization Fe K emission follows the MC distribution, nevertheless not all MC are Fe K emitters. The long baseline monitoring allows the characterization of the temporal evolution of the MC emission. A complex pattern of variations is shown by the different MCs, with some having constant Fe K emission, some increasing, and some decreasing. In particular, we observe an apparent superluminal motion of a light front illuminating a molecular nebula. This might be due to a source outside the MC (such as Sgr A* or a bright and long outburst of a X-ray binary), though it cannot be due to low energy cosmic rays or a source located inside the cloud. We also observe a decrease of the X-ray emission from G0.11-0.11, behavior similar to that of Sgr B2. The line intensities, clouds dimensions, columns densities, and positions with respect to Sgr A* are consistent with being produced by the same Sgr A* flare. The required high luminosity (about 1.5 x 10{sup 39} erg s{sup -1}) can hardly be produced by a binary system, while it is in agreement with a flare of Sgr A* fading about 100 years ago. The low intensity of the Fe K emission coming from the 50 and the 20 km s{sup -1} MC places an upper limit of 10{sup 36} erg s{sup -1} to the mean luminosity of Sgr A* in the last 60-90 years. The Fe K emission and variations from these MC might have been produced by a single flare of Sgr A*.

• OSTI ID: 21448858
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 714; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMIC RADIATION
EMISSION
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
IONIZATION
IONIZING RADIATIONS
LUMINOSITY
NEBULAE
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS