Call for visual and CCD observations of Markarian 501

(vsnet-alert 833)

Dear VSNET observers,

one of the well known blazars (very violent type of AGN) named Markarian 501 (R.A. = 16:53:52.2, Decl. = 39:45:36 (J2000), V = 14mag) is now very active in TeV gamma-ray, and thus is monitored by EGRET instrument (and presumably COMPTEL and OSSE, too) from April, 9th to April 15th, 1997, in gamma rays.

Because of unique opportunity to get interesting data, optical monitoring of Markarian 501 is welcomed. The object is usually of 13.5 mag, but we assume it may be brighter nowadays. (We don't know the actual state of Mark 501 in visible light.

If you decide to observe, check our site for more info, finding chart and photometric date, or mail to

Clear skies,

|                                                                      |
|                   T  o  m  a  s     R  e  z  e  k                    |
|                                                                      |
|     Astronomical Institute of Czech Academy of Science, Ondrejov     |
|  E-mail:    Web:   |
|  Snail: Tomas Rezek, Astronomicky ustav AV CR, 251 65 Ondrejov, CZ   |

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