Optical follow-up of Mrk 501
ATel #15062; Roberto Nesci (INAF/IAPS)
on 24 Nov 2021; 23:21 UT
Credential Certification: Roberto Nesci (roberto.nesci@inaf.it)
Following the detection of an X-ray flare of Mrk 501 reported in ATel #15059, I observed the source in the R(Cousins) band with the 30cm telescope of the Foligno Observatory (K56) on 2021-11-24T16:44. Comparison stars were taken from Gonzales-Peres et al (2001, AJ 122, 2055), as used by the Tuorla team in their monitoring of this object (e.g. Nilsson et al., 2018, A&A, 620, 185). Aperture photometry was done with IRAF/apphot using a 4" radius. The core of Mrk 501 gave a magnitude R=13.35 +- 0.07. This is fainter than the last public observation of the Tuorla team (R=13.1 on 2021-10-21). The host galaxy gives an appreciable contribution to the observed flux, so it is not easy to compare data taken with different instruments and seeing conditions, however it is apparent that the X-ray flare produced no significant luminosity increase in the R band.
