Tuesday, October 13, 2009

Fermi LAT Weekly report No. 70

Covered period: 2009.Sept.28 - 2009.Oct.04

This was a busy week for the Fermi extragalactic sky:

  • Three gamma-ray blazars consistently reached very high fluxes of 4 x 10-6 ph cm-2. These were 3C 454.3, 3C 273 and 4C 21 (PKS 1222+21). The high fluxes of the former two are in line with their recent trends. In the case of 4C 21, the flare is quite remarkable since this is not a usually bright blazar. Unfortunately, the source is too close to the Sun and few observations at other wavelengths are possible.

  • A gamma-ray flare was detected on Sept 29-30 that was positionally consistent with the location of Fermi Bright source 0FGL J1641.4+3939 (Abdo, A. et al. 2009 ApJ, 700, 597). This is an interesting region for Fermi because there are at least 3 possible counterparts: 3C345, NRAO 512 and CLASS J1641+3935. Well-known blazar 3C 345 is the leading counterpart candidate given the localization of the Fermi flare (as described in ATel#2226) and the increased activity observed at other wavelengths (see ATel#2222). Hopefully, the identity of this Fermi source will be revealed based on the MW data obtained during this week.

  • There was a short but significant flare by PKS 1621-253 (see ATel#2231). Its flux on October 4th (1.9 +/- 0.2 x 10-6 ph cm-2 s-1) was about ~17 times higher than the average flux during the first year of Fermi observations. This blazar was detected by EGRET as 3EG J1626-2519 (Hartman, R.C. et al. 1999, ApJS, 123, 79).

  • The following publicly monitored sources were active during the week: S5 0716+714, PKS 0537-441, PKS 0454-234 and Mrk 421 (one or two significant detections during the week with fluxes <~ 10-6 ph cm-2 s-1).

Fluxes are in the unit of photons/cm^2/s above 100 MeV.

Note. All the flux reported above are by the ASP analysis and should be considered preliminary and should not be used for publication, however they are indicative of the flux range and the current status of a source. Source association is done on the basis of source location, considering spatial coincidence only, and it is not indicative of an identification. - Please acknowledge the LAT team if you use information from this report.

For questions and comments please contact:

- L. Reyes (lcreyes[at]uchicago.edu) for generic information related to this week

- source contact persons on this page for individual objects cited above.

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