Multi-wavelength study of the short term TeV flaring activity from the blazar Mrk 501 observed in June 2014

• Published in: Advances in space research 2019-01, Vol.63 (1), p.766-778
• Main Authors: Singh, K.K., Bhatt, H., Bhattacharyya, S., Bhatt, N., Tickoo, A.K., Rannot, R.C.
• Format: Article
• Language: English
• Subjects: (Galaxies:) BL Lac objects: individual: Mrk 501; Gamma-rays: general; Methods: data analysis
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/j.asr.2018.08.013

•Multi-wavelength study of TeV flare from Mrk 501 in June 2014 detected by the HESS telescope.•Near simultaneous soft X-ray and TeV emission activities are obtained to be correlated.•Soft X-ray photon spectral index is anti-correlated with the integral flux.•Optical polarization remains constant whereas EVPA changes significantly.•Single zone leptonic synchrotron and SSC model is used to reproduce the X-ray and TeV emission. In this work, we study the short term flaring activity from the high synchrotron peaked blazar Mrk 501 detected by the FACT and H.E.S.S. telescopes in the energy range 2–20 TeV during June 23–24, 2014 (MJD 56831.86–56831.94). We revisit this major TeV flare of the source in the context of near simultaneous multi-wavelength observations of γ–rays in MeV-GeV regime with Fermi-LAT, soft X-rays in 0.3–10 keV range with Swift-XRT, hard X-rays in 10–20 keV and 15–50 keV bands with MAXI and Swift-BAT respectively, UV-Optical with Swift-UVOT and 15 GHz radio with OVRO telescope. We have performed a detailed temporal and spectral analysis of the data from Fermi-LAT, Swift-XRT and Swift-UVOT during the period June 15–30, 2014 (MJD 56823–56838). Near simultaneous archival data available from Swift-BAT, MAXI and OVRO telescope along with the V-band optical polarization measurements from SPOL observatory are also used in the study of giant TeV flare of Mrk 501 detected by the FACT and H.E.S.S. telescopes. No significant change in the multi-wavelength emission from radio to high energy γ–rays during the TeV flaring activity of Mrk 501 is observed except variation in soft X-rays. The varying soft X-ray emission is found to be correlated with the γ–ray emission at TeV energies during the flaring activity of the source. The soft X-ray photon spectral index is observed to be anti-correlated with the integral flux showing harder-when-brighter behavior. An average value of 4.5% for V-band optical polarization is obtained during the above period whereas the corresponding electric vector position angle changes significantly. We have used the minimum variability timescale from the H.E.S.S. observations to estimate the Doppler factor of the emission region which is found to be consistent with the previous studies of the source.