Study of long-term 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 flat-spectrum radio quasar (FSRQ) and two BL Lacertae objects (BL Lacs)] by using 16 yr of Rossi X-ray 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 $\left(\overline{\sigma _{\rm err}^{2}}/\sigma ^{2} < 0.2\right)$ in light curves. Anderson–Darling (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 time-scale, 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 non-normal. 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 X-rays suggests that the low-energy emitting electrons have a single lognormal flux distribution, while the high-energy ones have a double lognormal flux distribution.

THE CHARACTERISTIC DIODE PARAMETERS IN Ti/p-InP CONTACTS PREPARED BY DC SPUTTERING AND EVAPORATION PROCESSES OVER A WIDE MEASUREMENT TEMPERATURE

The titanium/[Formula: see text]-indium phosphide (Ti/[Formula: see text]-InP) Schottky diodes (SDs) have been prepared by thermal evaporation and DC magnetron sputtering deposition. Then, their current–voltage ([Formula: see text]–[Formula: see text]) characteristics have been measured in the sample temperature range of 100–400[Formula: see text]K with steps of 20[Formula: see text]K. The characteristic parameters of both Ti/[Formula: see text]-InP SDs have been compared with each other. The barrier height (BH) values of 0.824 and 0.847 at 300[Formula: see text]K have been obtained for the sputtered and the evaporated SDs, respectively. This low BH value for the sputtered SD has been attributed to some defects introduced by the sputtered deposition technique over a limited depth in to the [Formula: see text]-type substrate. The BH of the evaporated and sputtered diodes has decreased with the standard deviations of 58 and 64[Formula: see text]mV obeying to double-Gaussian distribution (GD) in 220–400[Formula: see text]K range, respectively, and it has seen a more sharper reduction for the BHs with the standard deviations of 93 and 106 mV in 100–220[Formula: see text]K range. The Richardson constant values of 89.72 and 53.24[Formula: see text]A(Kcm)[Formula: see text] (in 220–400[Formula: see text]K range) for the evaporated and sputtered samples, respectively, were calculated from the modified ln([Formula: see text]/[Formula: see text]/2[Formula: see text] vs (kT)[Formula: see text] curves by GD of the BHs. The value 53.24[Formula: see text]A(Kcm)[Formula: see text] for the sputtered sample in high temperatures range is almost the same as the known Richardson constant value of 60[Formula: see text]A(Kcm)[Formula: see text] for [Formula: see text]-type InP.