| Author(s) and Co-Author(s) with Affiliation: Kiran Wani(Indian Institute of Astrophysics, Bangalore - 560034, India), C. S. Stalin(Indian Institute of Astrophysics, Bangalore - 560034, India), S. Muneer(Indian Institute of Astrophysics, Bangalore - 560034, India), Athira Bharathan(Department of Physics and Electronics, CHRIST (Deemed to be University), Bangalore - 560029, India), Vivek K. Agrawal(Space Astronomy Group, ISITE Campus, U. R. Rao Satellite Center, ISRO, Bangalore - 560037, India), Koushal Vadodariya(Space Astronomy Group, ISITE Campus, U. R. Rao Satellite Center, ISRO, Bangalore - 560037, India), Radhakrishna Vatedka(Space Astronomy Group, ISITE Campus, U. R. Rao Satellite Center, ISRO, Bangalore - 560037, India) |
| Abstract: Blazars are a subclass of active galactic nuclei (AGN) that host relativistic jets oriented close to our line of sight. Due to Doppler boosting, their emitted flux is often strongly enhanced, and the characteristic timescales of variability are significantly shortened. Understanding X-ray flux variations in blazars is particularly important as they can provide key constraints on the size of the emission region. Moreover, X-ray observations in conjunction with gamma-ray measurements offer valuable insights into the radiative processes operating in sub-parsec scales in AGN. We present the first results from X-ray observations of an AGN obtained with the XSPECT payload onboard XpoSat launched by ISRO on 1 January 2024. The target blazar was monitored with XSPECT over multiple epochs, complemented by contemporaneous observations with Swift-XRT. The primary objective was to validate XSPECT flux measurements against those obtained with Swift. Simultaneous observations with XSPECT and Swift-XRT conducted in August 2025 yielded consistent fluxes in the 0.8–4 keV band, with XSPECT and Swift-XRT reporting values of (1.34 ± 0.031) × 10⁻¹⁰ erg cm⁻² s⁻¹ and (1.38 ± 0.037) × 10⁻¹⁰ erg cm⁻² s⁻¹, respectively. The XSPECT spectrum in this energy range is well described by a power-law model and exhibits a clear harder-when-brighter trend over a week-long monitoring campaign. Broadband spectral energy distribution modeling within leptonic emission scenarios, required the inclusion of an accretion component to account for the observed UV/optical excess. This accretion signature becomes particularly prominent during the source’s low-flux state, emerging distinctly within the otherwise jet-dominated spectrum. These results demonstrate XSPECT’s capability to deliver reliable X-ray flux measurements and highlight its potential for advancing studies of AGN variability and broadband emission. The results of this work will be presented at the meeting. |
