X-Ray Intraday Variability of the TeV Blazar Markarian 421 with XMM-Newton

Abstract

Highly variable Markarian 421 is a bright high–synchrotron energy peaked blazar showing a wide featureless nonthermal spectrum, making it a good candidate for our study of intraday flux and spectral variations over time. We analyze its X-ray observations over 17 yr, taken with the EPIC-pn instrument, to probe into the intraday variability properties, focusing on the photon energy band of 0.3–10.0 keV, and its soft (0.3–2.0 keV) and hard (2.0–10.0 keV) subbands. To examine the flux variability, fractional variability amplitudes and minimum variability timescales have been calculated. We also probed into the spectral variability by studying the hardness ratio for each observation, the correlation between the two energy bands, using the discrete correlation function, and inspecting the normalized light curves. The parameters obtained from these methods were studied for any correlations or nonrandom trends. From this work, we speculate on the constraints on the possible particle acceleration and emission processes in the jet, for a better understanding of the processes involving turbulent behavior, except for shocks. A positive discrete correlation function between the two subbands indicates the role of the same electron population in the emission of photons in the two bands. A correlation between the parameter of flux variability and the parameters of spectral variation and lags in the subenergy bands provides the constraints to be considered for any modeling of emission processes.

X-Ray Activity Variations and Coronal Abundances of the Star–Planet Interaction Candidate HD 179949

“…There are insufficient counts in the blocks found for the counts of light curves (Section 3.2.1) to allow time-resolved spectroscopy. Instead, we calculate the evolution of hardness ratios over time and evaluate the strength of the evidence for spectral variability (for analyses that highlight how hardness ratios can be useful, see, e.g., Noel et al 2022;Di Stefano et al 2021). Specifically, we compute the color…”

Study of X-Ray Intraday Variability of HBL Blazars Based on Observations Obtained with XMM-Newton

“…Among the 55 HBLs in TeVcat, 19 have been observed by XMM-Newton from its launch until 2022 March. Of these, we excluded four of the sources previously studied by members of the group (e.g Mrk 421; Priyana Noel et al 2022, PKS 2155Bhagwan et al 2014Bhagwan et al , 2016Wani & Gaur 2020;and PG 1533+113;Dhiman et al 2021). We also did not analyze the shorter observations with exposure time less than 10 ks and those longer observations which were affected heavily by background flaring such that the good exposure time was below 10 ks.…”