Near infrared intraday variability of Mrk 421

Abstract

Abstract.We report results from our monitoring of the BL Lac object Mrk 421 in the near-IR J band. The observations, aimed at studying the intraday variability (IDV) of the object, were carried out systematically over an extended (and near-continuous) period of eight nights from the 1.2 m Mount Abu Infrared Telescope, India. There are limited studies for Mrk 421 in the J band for such an extended period. The observation epoch for this study (25 February-5 March 2003) was chosen to significantly overlap other concurrent studies of Mrk 421 in the X-ray/γ-ray regions being conducted using the Rossi X-ray timing explorer (RXTE) and the solar tower atmospheric Cherenkov effect experiment (STACEE). Hence these results could be useful for a multi-wavelength analysis of the variability behavior of Mrk 421. We find that Mrk 421 was quite active during the observed period and showed significant IDV and short term variability. A maximum variation of 0.89 mag is seen over the entirety of the observed period. Flaring activity, with typical brightness variations of ∼0.4, are also seen on several occasions. The extent of the variability observed by us is compared with the results of other similar studies of Mrk 421 in the J band.

Multiband optical variability studies of BL Lacertae

“…Blazars are known to be variable at all accessible time scales over entire electro-magnetic spectra. Magnitude changes of few hundredth to tenths over a time scale of a day is called intraday variability (IDV) or micro-variability (Wagner & Witzel 1995, Rector & Perlman 2003 which help us in probing innermost regions of AGNs; changes from several days to few months are usually known as short time variability (STV); while those taking from several months to many years are usually called long term variability (LTV; Gupta et al 2004), in last two classes blazar variability can usually exceed even ∼ 5 mag.…”

Simultaneous Multi-Wavelength Observations of the TeV Blazar Mrk 421 during February–March, 2003: X-Ray and NIR Correlated Variability

“…Near Infrared data in J band used in the present paper is taken from (Gupta et al 2004). They have done observations from 1.2 meter optical/NIR telescope at Gurushikhar observatory, Mount Abu, India using NICMOS-3 detector and J band filter.…”

“…They have done observations from 1.2 meter optical/NIR telescope at Gurushikhar observatory, Mount Abu, India using NICMOS-3 detector and J band filter. The detail about NIR observations and data reductions is given in (Gupta et al 2004).…”

“…NIR data for three decades, for several blazars including Mrk 421, were given by (Fan & Lin 1999). A much systematic and comprehensive study of this source was done by Gupta et al (2004) in the same period of the campaign for which the present paper is written. In the compiled optical data for long term observations, variation of 4.6 mag was reported by Stein et al (1976) and rapid variability of 1.4 mag in 2.5 hours was reported by Xie et al (1988).…”

Observations of AGNs using PACT

“…Optical data in V-band for year 2001 was taken by WEBT (Whole Earth Blazar Tele- scope) using KVA-telescope on La Palma [7]. For 2003, Near Infra Red data in J-band was taken at Gurushikhar observatory, Mount Abu [8]. Radio data was taken by Metsähovi radio telescope at 22 GHz and 37 GHz [9].…”