Short-timescale X-ray variability of the blazar 1ES 1959+650 observed with AstroSat/SXT
Abstract
We analyse the AstroSat Soft X-ray Telescope (SXT) observation of the high-synchrotron-peaked blazar 1ES 1959+650 taken on 2023 September 2, which covers 362 ks with about 95 ks of good exposure. We build 0.6-7 keV light curves in six sub-bands, binned at 5830 s (the orbital period) and 1000 s. All sub-bands show excess variance, with fractional variability of 3.7 to 6.5 per cent that increases with energy (∝ E0.32±0.07). The power spectrum of the total band, fitted with a model that includes the window function of the orbital gaps, is a red-noise power law with slope −1.80 (95 per cent range −2.8 to −1.4). A Lomb-Scargle search finds no significant periodicity (global p>0.57) and would have detected, with 90 per cent probability, a sinusoid with an rms amplitude above 1.9 to 3.7 per cent at periods of 3 to 50 ks. The soft (0.6-1.4 keV) and hard (1.9-7 keV) light curves are correlated near zero lag, but only marginally (global p=0.04 and 0.07 for power-spectrum slopes of −1.7 and −2.0), and the lag is −1+6−10 ks, consistent with zero. No pair of sub-bands that includes 0.6-0.8 keV shows a significant correlation or lag, so an energy-dependent lag of a few ks can be neither confirmed nor excluded. The 0.6-7 keV light curve contains one hump with rise and decay times of about 0.4 to 0.6 d, which is only marginally distinguishable from red noise (p≈0.05 to $0.07$). The count rate distribution is consistent with a lognormal distribution, and the hardness ratio does not depend significantly on flux.
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BibTeX
@misc{akbar2026shorttimescale,
title = {{Short-timescale X-ray variability of the blazar 1ES 1959+650 observed with AstroSat/SXT}},
author = {Sikandar Akbar and Zahir Shah},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.27708},
eprint = {2610.27708},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.27708},
}
RIS
TY - UNPB
TI - Short-timescale X-ray variability of the blazar 1ES 1959+650 observed with AstroSat/SXT
AU - Sikandar Akbar
AU - Zahir Shah
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.27708
UR - https://arxiv.org/abs/2610.27708
AB - We analyse the AstroSat Soft X-ray Telescope (SXT) observation of the high-synchrotron-peaked blazar 1ES 1959+650 taken on 2023 September 2, which covers 362 ks with about 95 ks of good exposure. We build 0.6-7 keV light curves in six sub-bands, binned at 5830 s (the orbital period) and 1000 s. All sub-bands show excess variance, with fractional variability of 3.7 to 6.5 per cent that increases with energy (∝ E^0.32±0.07). The power spectrum of the total band, fitted with a model that includes the window function of the orbital gaps, is a red-noise power law with slope −1.80 (95 per cent range −2.8 to −1.4). A Lomb-Scargle search finds no significant periodicity (global p>0.57) and would have detected, with 90 per cent probability, a sinusoid with an rms amplitude above 1.9 to 3.7 per cent at periods of 3 to 50 ks. The soft (0.6-1.4 keV) and hard (1.9-7 keV) light curves are correlated near zero lag, but only marginally (global p=0.04 and 0.07 for power-spectrum slopes of −1.7 and −2.0), and the lag is −1^+6_−10 ks, consistent with zero. No pair of sub-bands that includes 0.6-0.8 keV shows a significant correlation or lag, so an energy-dependent lag of a few ks can be neither confirmed nor excluded. The 0.6-7 keV light curve contains one hump with rise and decay times of about 0.4 to 0.6 d, which is only marginally distinguishable from red noise (p≈0.05 to $0.07$). The count rate distribution is consistent with a lognormal distribution, and the hardness ratio does not depend significantly on flux.
ER -