Alert Notice 430: Photometry requested of Blazar-type Quasars 3C 273 and 3C 279

January 11, 2011: Dr. Kirill Sokolovsky (Max-Planck-Institut fuer Radioastronomie, Bonn) has requested the assistance of AAVSO observers to obtain optical photometry of the blazar-type quasars 3C 273 and 3C 279 during 2011. The observations obtained by AAVSO observers will be combined with multiwavelength observations - from radio to gamma-rays - as well as with very long baseline interferometry with the VLBA to obtain a better picture of what these objects are and how they vary. In particular, Sokolovsky and collaborators hope to find correlations between the spectral energy distributions (SEDs) of these objects and the behavior of the associated relativistic jets at sub-parsec spatial resolution.

Multicolor CCD observations are requested, in any subset of UBVRcIc filters, with priority given to V and R bands. Unfiltered CCD observations, unfortunately, will not be useful due to the complex spectral shape of the quasars in the optical band. The changing color of the objects will prohibit direct comparison of unfiltered measurements obtained with different instruments and will make absolute flux calibration difficult. For these reasons, observations in standard photometric filters are needed.

Time-series are not required and, in fact, would not be an efficient use of observing time, since these objects vary on timescales of around one day at most. Observations made once a week or so will provide adequate coverage. Observers should aim for a signal-to-noise of at least 50 if possible.  

For more details on the campaign and information on blazars, please see the AAVSO webpage on this observing campaign:

This campaign is also referenced on the AAVSO Observing Campaigns page:

Coordinates (J2000) and magnitudes:
3C 273 12:29:06.70 +02:03:08.6  V~12.7
3C 279 12:56:11.17 -05:47:21.5  V~16.1

Dr. Sokolovsky requests observers use the comparison stars on these finding charts:

3C 273

3C 279

Observations should be reported to the AAVSO International Database using the names "3C 273" and "3C 279".

This Alert Notice was compiled by Elizabeth O. Waagen using material provided by Kirill Sokolovsky and Matthew R. Templeton.


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