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Title: CHANDRA/HETGS OBSERVATIONS OF THE BRIGHTEST FLARE SEEN FROM Sgr A*

Abstract

Starting in 2012, we began an unprecedented observational program focused on the supermassive black hole in the center of our Galaxy, Sgr A*, utilizing the High Energy Transmission Grating Spectrometer (HETGS) instrument on the Chandra X-Ray Observatory. These observations will allow us to measure the quiescent X-ray spectra of Sgr A* for the first time at both high spatial and spectral resolution. The X-ray emission of Sgr A*, however, is known to flare roughly daily by factors of a few to ten times over quiescent emission levels, with rarer flares extending to factors of greater than 100 times quiescence. Here we report an observation performed on 2012 February 9 wherein we detected what are the highest peak flux and fluence flare ever observed from Sgr A*. The flare, which lasted for 5.6 ks and had a decidedly asymmetric profile with a faster decline than rise, achieved a mean absorbed 2-8 keV flux of (8.5 {+-} 0.9) Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1}. The peak flux was 2.5 times higher, and the total 2-10 keV emission of the event was approximately 10{sup 39} erg. Only one other flare of comparable magnitude, but shorter duration, has been observed in Sgrmore » A* by XMM-Newton in 2002 October. We perform spectral fits of this Chandra-observed flare and compare our results to the two brightest flares ever observed with XMM-Newton. We find good agreement among the fitted spectral slopes ({Gamma} {approx} 2) and X-ray absorbing columns (N {sub H} {approx} 15 Multiplication-Sign 10{sup 22} cm{sup -2}) for all three of these events, resolving prior differences (which are most likely due to the combined effects of pileup and spectral modeling) among Chandra and XMM-Newton observations of Sgr A* flares. We also discuss fits to the quiescent spectra of Sgr A*.« less

Authors:
; ; ;  [1];
  1. Massachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139 (United States)
Publication Date:
OSTI Identifier:
22086415
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ASTRONOMY; ASTROPHYSICS; ASYMMETRY; BLACK HOLES; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; EMISSION SPECTRA; EMISSION SPECTROSCOPY; GALAXIES; KEV RANGE; PHOTON EMISSION; RESOLUTION; STELLAR FLARES; X RADIATION; X-RAY SPECTRA

Citation Formats

Nowak, M. A., Neilsen, J., Baganoff, F. K., Houck, J., E-mail: mnowak@space.mit.edu, E-mail: jneilsen@space.mit.edu, E-mail: fkb@space.mit.edu, and and others. CHANDRA/HETGS OBSERVATIONS OF THE BRIGHTEST FLARE SEEN FROM Sgr A*. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/2/95.
Nowak, M. A., Neilsen, J., Baganoff, F. K., Houck, J., E-mail: mnowak@space.mit.edu, E-mail: jneilsen@space.mit.edu, E-mail: fkb@space.mit.edu, & and others. CHANDRA/HETGS OBSERVATIONS OF THE BRIGHTEST FLARE SEEN FROM Sgr A*. United States. doi:10.1088/0004-637X/759/2/95.
Nowak, M. A., Neilsen, J., Baganoff, F. K., Houck, J., E-mail: mnowak@space.mit.edu, E-mail: jneilsen@space.mit.edu, E-mail: fkb@space.mit.edu, and and others. Sat . "CHANDRA/HETGS OBSERVATIONS OF THE BRIGHTEST FLARE SEEN FROM Sgr A*". United States. doi:10.1088/0004-637X/759/2/95.
@article{osti_22086415,
title = {CHANDRA/HETGS OBSERVATIONS OF THE BRIGHTEST FLARE SEEN FROM Sgr A*},
author = {Nowak, M. A. and Neilsen, J. and Baganoff, F. K. and Houck, J., E-mail: mnowak@space.mit.edu, E-mail: jneilsen@space.mit.edu, E-mail: fkb@space.mit.edu and and others},
abstractNote = {Starting in 2012, we began an unprecedented observational program focused on the supermassive black hole in the center of our Galaxy, Sgr A*, utilizing the High Energy Transmission Grating Spectrometer (HETGS) instrument on the Chandra X-Ray Observatory. These observations will allow us to measure the quiescent X-ray spectra of Sgr A* for the first time at both high spatial and spectral resolution. The X-ray emission of Sgr A*, however, is known to flare roughly daily by factors of a few to ten times over quiescent emission levels, with rarer flares extending to factors of greater than 100 times quiescence. Here we report an observation performed on 2012 February 9 wherein we detected what are the highest peak flux and fluence flare ever observed from Sgr A*. The flare, which lasted for 5.6 ks and had a decidedly asymmetric profile with a faster decline than rise, achieved a mean absorbed 2-8 keV flux of (8.5 {+-} 0.9) Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1}. The peak flux was 2.5 times higher, and the total 2-10 keV emission of the event was approximately 10{sup 39} erg. Only one other flare of comparable magnitude, but shorter duration, has been observed in Sgr A* by XMM-Newton in 2002 October. We perform spectral fits of this Chandra-observed flare and compare our results to the two brightest flares ever observed with XMM-Newton. We find good agreement among the fitted spectral slopes ({Gamma} {approx} 2) and X-ray absorbing columns (N {sub H} {approx} 15 Multiplication-Sign 10{sup 22} cm{sup -2}) for all three of these events, resolving prior differences (which are most likely due to the combined effects of pileup and spectral modeling) among Chandra and XMM-Newton observations of Sgr A* flares. We also discuss fits to the quiescent spectra of Sgr A*.},
doi = {10.1088/0004-637X/759/2/95},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}