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1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-variable Emission on Event Horizon Scales

Fish, Vincent L. and Chamberlin, Richard and Lamb, James and Woody, David (2011) 1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-variable Emission on Event Horizon Scales. Astrophysical Journal Letters, 727 (2). Art. No. L36. ISSN 2041-8205.

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Sagittarius A*, the ~4 × 10^6 M_⊙ black hole candidate at the Galactic center, can be studied on Schwarzschild radius scales with (sub)millimeter wavelength very long baseline interferometry (VLBI). We report on 1.3 mm wavelength observations of Sgr A* using a VLBI array consisting of the JCMT on Mauna Kea, the Arizona Radio Observatory’s Submillimeter Telescope on Mt. Graham in Arizona, and two telescopes of the CARMA array at Cedar Flat in California. Both Sgr A* and the quasar calibrator 1924−292 were observed over three consecutive nights, and both sources were clearly detected on all baselines. For the first time, we are able to extract 1.3mmVLBI interferometer phase information on Sgr A* through measurement of closure phase on the triangle of baselines. On the third night of observing, the correlated flux density of Sgr A* on all VLBI baselines increased relative to the first two nights, providing strong evidence for time-variable change on scales of a few Schwarzschild radii. These results suggest that future VLBI observations with greater sensitivity and additional baselines will play a valuable role in determining the structure of emission near the event horizon of Sgr A*.

Item Type:Article
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Fish, Vincent L.0000-0002-7128-9345
Additional Information:© 2011 American Astronomical Society. Received 2010 November 10; accepted 2010 December 20; published 2011 January 10. High-frequency VLBI work at MIT Haystack Observatory is supported by grants from the National Science Foundation (NSF). ARO receives partial support from the NSFATI program. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Funding for ongoing CARMA development and operations is supported by the NSF and the CARMA partner universities. D.E.B. acknowledges support from the NSF Research Experiences for Undergraduates program. Facilities: CARMA (), HHT (), JCMT (), SMA (), CSO ()
Funding AgencyGrant Number
Smithsonian InstitutionUNSPECIFIED
Academia SinicaUNSPECIFIED
Subject Keywords:Galaxy: center; submillimeter: general; techniques: high angular resolution; techniques: interferometric
Issue or Number:2
Classification Code:PACS: 98.35.Jk; 98.70.Dk; 95.85.Bh
Record Number:CaltechAUTHORS:20110314-092259345
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Official Citation:Vincent L. Fish et al. 2011 ApJ 727 L36 doi: 10.1088/2041-8205/727/2/L36
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22841
Deposited By: Tony Diaz
Deposited On:16 Mar 2011 18:34
Last Modified:09 Mar 2020 13:18

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