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ATEL # 2223; Mark A. Gurwell (Harvard-Smithsonian Center for Astrophysics, MA, USA)
on 2 Oct 2009; 17:26 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Mark A. Gurwell (firstname.lastname@example.org)
Subjects: Millimeter, Sub-Millimeter, Request for Observations, AGN, Quasars
The Submillimeter Array (SMA) performs ongoing flux density monitoring of quasars that are typically bright in the mm/submm bands, in order to optimally choose quasars for use as interferometric calibration sources. Through this monitoring effort, we discovered and reported in ATEL #2150 that that the quasar 3C454.3 (J2253+161) was flaring strongly at millimeter wavelengths starting in mid-2009. Flaring activity has also been reported in the IR, optical, and gamma ray bands (see ATEL #2155, ATEL #2182, ATEL #2200, ATEL #2201).
Here we report that at millimeter and submillimeter bands 3C454.3 continues to increase in flux density. In early August the 1.3 mm flux density was around 11 Jy, while the most recent measurements obtained by the SMA (from October 2) now show the flux density to be 26 +/- 1.4 Jy, an increase of a factor of 2.35 in under 60 days, and and increase of nearly a factor of 9 since a minimum near 3 Jy was observed in early April. At this point 3C454.3 has reached essentially the same peak flux density achieved during the 2008 flare (Sept-October 2008). A figure showing SMA measurements of 3C454.3 since early August 2009, can be accessed at the link provided at the bottom of this ATel. Figures of the flux history of 3C454.3 since 2005 are also available at the same location.
Past flares (e.g. 2005, 2007, 2008) have typically proceeded for many weeks, followed by a variably-long period of relatively steady flux density, finally succumbing with a rapid decrease to a background state near 3 Jy. This suggests that 3C454.3 may continue to brighten in the millimeter (and submillimeter) bands in the weeks to come. Given that strong activity is seen across the spectrum from mm to gamma rays, it is our opinion that continued monitoring of the source at all wavelengths is warranted as this flare progresses.
[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 (USA) and the Academia Sinica (Taiwan).]
Submillimeter Array Observations of a 3C454.3 Millimeter-Band Flare