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Far Infrared Variability of Sagittarius A^*: 25.5 Hours of Monitoring with Herschel

Stone, Jordan M. and Marrone, D. P. and Dowell, C. D. and Schulz, B. and Heinke, C. O. and Yusef-Zadeh, F. (2016) Far Infrared Variability of Sagittarius A^*: 25.5 Hours of Monitoring with Herschel. Astrophysical Journal, 825 (1). Art. No. 32. ISSN 0004-637X. doi:10.3847/0004-637X/825/1/32.

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Variable emission from Sgr A^*, the luminous counterpart to the super-massive black hole at the center of our Galaxy, arises from the innermost portions of the accretion flow. Better characterization of the variability is important for constraining models of the low-luminosity accretion mode powering Sgr A^*, and could further our ability to use variable emission as a probe of the strong gravitational potential in the vicinity of the 4 x 10^6M_⊙ black hole. We use the Herschel Spectral and Photometric Imaging Receiver (SPIRE) to monitor Sgr A* at wavelengths that are difficult or impossible to observe from the ground. We find highly significant variations at 0.25, 0.35, and 0.5 mm, with temporal structure that is highly correlated across these wavelengths. While the variations correspond to <1% changes in the total intensity in the Herschel beam containing Sgr A^*, comparison to independent, simultaneous observations at 0.85 mm strongly supports the reality of the variations. The lowest point in the light curves, ~0.5 Jy below the time-averaged flux density, places a lower bound on the emission of Sgr A^* at 0.25 mm, the first such constraint on the THz portion of the spectral energy distribution. The variability on few hour timescales in the SPIRE light curves is similar to that seen in historical 1.3 mm data, where the longest time series is available, but the distribution of variations in the sub-mm do not show a tail of large-amplitude variations seen at 1.3 mm. Simultaneous X-ray photometry from XMM-Newton shows no significant variation within our observing period, which may explain the lack of very large submillimeter variations in our data if X-ray and submillimeter flares are correlated.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Stone, Jordan M.0000-0003-0454-3718
Marrone, D. P.0000-0002-2367-1080
Heinke, C. O.0000-0003-3944-6109
Additional Information:© 2016 American Astronomical Society. Received 2015 August 18; revised 2016 May 2; accepted 2016 May 13; published 2016 June 27. This work is based on observations made with Herschel, a European Space Agency Cornerstone Mission with significant participation by NASA. We thank Chi-Kwan Chan, Feryal Özel, and Dimitrios Psaltis for helpful discussions. DPM and JMS acknowledge support from NSF award AST-1207752 and from NASA through award OT1 cdowell 2 issued by JPL/Caltech. COH acknowledges support from an NSERC Discovery Grant and an Alexander von Humboldt Fellowship.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASA/JPL/CaltechOT1 cdowell 2
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
Subject Keywords:accretion, accretion disks; black hole physics; Galaxy: center
Issue or Number:1
Record Number:CaltechAUTHORS:20160930-144349615
Persistent URL:
Official Citation:Jordan M. Stone et al 2016 ApJ 825 32
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70716
Deposited By: Ruth Sustaita
Deposited On:03 Oct 2016 17:06
Last Modified:11 Nov 2021 04:33

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