Abstract:
We report the result of simultaneous multi-wavelength observations of the TeV
blazar Mrk 421 during February – March 2003. We observed Mrk 421 using the Pachmarhi
Array of Cerenkov Telescopes (PACT) of Tata Institute of Fundamental Research at
Pachmarhi, India. Other simultaneous data were taken from the literature and public data
archives. We have analyzed the high quality X-ray (2–20 keV) observations from the NASA
Rossi X-Ray Timing Explorer (RXTE). We obtained a possible correlated variability between
X-ray and J band (1.25 μ) near infrared (NIR) wavelength. This is the first case of X-ray and
NIR correlated variability in Mrk 421 or any high energy peaked (HBL) blazar. The corre-
lated variability reported here indicates a similar origin for the NIR and X-ray emissions. The
emission is not affected much by the environment of the surrounding medium of the central engine of Mrk 421. The observations are consistent with the shock-in-jet model for the
emissions.
