NIR follow-up of PKS 0454-234

ATel #3722; R. Nesci (University La Sapienza, Roma, Italy)
on 28 Oct 2011; 10:15 UT
Credential Certification: Roberto Nesci (roberto.nesci@uniroma1.it)

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Prompted by the ATel #3703, reporting a high Gamma-ray luminosity around 2011-10-22, we observed the blazar PKS0454-234 with the INAF REM telescope at La Silla, in the JHK bands, on October 24, 25, 26 and 27. Each pointing consists of 5 frames with exposure times of 30s, taken dithering the telescope in five positions and then coadding the 5 frames to produce an equivalent exposure time of 150s. Seven nearby comparison stars were taken from the 2MASS catalogue for calibration: a linear fit between instrumental and nominal magnitudes always gave good results. In the 2MASS catalogue the source magnitudes are J=15.64, H=14.88, K=13.97. The source is rather faint for REM, so the photometric errors are rather large: we report in the following table our results.

Date	J	H	K
2011-10-24	15.1+-0.1	13.8+-0.2	13.4+-0.2
2011-10-25	15.0+-0.1	14.2+-0.2	13.7+-0.2
2011-10-26	15.0+-0.1	13.7+-0.2	13.7+-0.2
2011-10-27	15.0+-0.1	14.1+-0.2	13.4+-0.2

The source is clearly half magnitude brighter than the historical 2MASS values in all three bands and appears to be rather steady at our accuracy level. Further NIR observations would be useful when the high Gamma-ray level will be over. The source is being monitored also at radio frequencies (see ATel #3713). The previous Gamma-ray flare was detected by Fermi (ATel #1898) nearly three years ago.