Study of longterm flux and photon index distributions of blazars using RXTE observations
Abstract
We present a detailed study of flux and index distributions of three blazars [one flatspectrum radio quasar (FSRQ) and two BL Lacertae objects (BL Lacs)] by using 16 yr of Rossi Xray Timing Explorer (RXTE) archival data. The three blazars were chosen such that their flux and index distributions have sufficient number of data points (≥90) with relatively less uncertainty (\overline{σ _err^{2}}/σ ^{2} < 0.2) in light curves. AndersonDarling (AD) test and histogram fitting show that flux distribution of FSRQ 3C 273 is lognormal, while its photon index distribution is Gaussian. This result is consistent with linear Gaussian perturbation in the particle acceleration timescale, which produces lognormal distribution in flux. However, for two BL Lacs, viz. Mrk 501 and Mrk 421, AD test shows that their flux distributions are neither Gaussian nor lognormal, and their index distributions are nonnormal. The histogram fitting of Mrk 501 and Mrk 421 suggests that their flux distributions are more likely to be a bimodal, and their index distributions are double Gaussian. Since, Sinha et al. had shown that Gaussian distribution of index produces a lognormal distribution in flux, double Gaussian distribution of index in Mrk 501 and Mrk 421 indicates that their flux distributions are probably double lognormal. Observation of double lognormal flux distribution with double Gaussian distribution in index reaffirms two flux states hypothesis. Further, the difference observed in the flux distribution of FSRQ (3C 273) and BL Lacs (Mrk 501 and Mrk 421) at Xrays suggests that the lowenergy emitting electrons have a single lognormal flux distribution, while the highenergy ones have a double lognormal flux distribution.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 January 2020
 DOI:
 10.1093/mnras/stz3108
 arXiv:
 arXiv:1910.14352
 Bibcode:
 2020MNRAS.491.1934K
 Keywords:

 acceleration of particles;
 galaxies: active;
 BL Lacertae objects: individual: Mrk 421;
 BL Lacertae objects: individual: Mrk 501;
 quasars: individual: FSRQ 3C 273;
 Xrays: galaxies;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 7 pages, 6 figures, 6 tables. Accepted for publication in MNRAS