Optical constraints on intranight variability in TeV HBLs from a two-year Asiago Schmidt monitoring campaign
Abstract
We present a two-year homogeneous optical monitoring campaign of three TeV-emitting high-synchrotron-peaked BL Lac objects, 1ES 1959+650, H 1426+428, and PG 1553+113, carried out with the Asiago Schmidt 67/92 cm telescope. TeV blazars are key targets in high-energy astrophysics, relevant for relativistic jet physics, particle acceleration, multiwavelength variability studies, and, in selected cases, multimessenger programmes. In this context, dense optical monitoring provides a low-energy synchrotron tracer of jet activity over temporal baselines that are difficult to cover continuously with high-energy facilities. The dataset consists of more than 17,000 R- and I-band photometric measurements obtained over 957 source-filter observing sessions between 2024 February 1 and 2026 January 31, for a total monitoring time of about 420 h. We applied a uniform differential-photometry and classical F-test framework based on two independent comparison-star pairs. Robust IDV is detected only in H 1426+428, with 15 out of 43 analysed sessions classified as variable in the R band and 5 out of 40 in the I band. No significant IDV is detected in 1ES 1959+650 or PG 1553+113 within the adopted statistical framework. For H 1426+428, the corresponding duration-weighted duty cycles, computed using only variable sessions with a measured local characteristic timescale, are 28.0% in the R band and 7.0% in the I band. The inferred local extrapolated doubling/halving timescales are of the order of 5-15 min in the observer frame. These results indicate that rapid optical synchrotron variability in TeV HBLs is intermittent and state-dependent. They also show that robotic small- and medium-aperture optical facilities can provide valuable long-term support for high-energy monitoring programmes by supplying dense, uniform, and repeatable optical coverage.
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BibTeX
@misc{impiombato2026optical,
title = {{Optical constraints on intranight variability in TeV HBLs from a two-year Asiago Schmidt monitoring campaign}},
author = {Domenico Impiombato and Giacomo Bonnoli and Elisa Prandini and Luca Zampieri and Irene Albanese},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20065},
eprint = {2610.20065},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20065},
}
RIS
TY - UNPB
TI - Optical constraints on intranight variability in TeV HBLs from a two-year Asiago Schmidt monitoring campaign
AU - Domenico Impiombato
AU - Giacomo Bonnoli
AU - Elisa Prandini
AU - Luca Zampieri
AU - Irene Albanese
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.20065
UR - https://arxiv.org/abs/2610.20065
AB - We present a two-year homogeneous optical monitoring campaign of three TeV-emitting high-synchrotron-peaked BL Lac objects, 1ES 1959+650, H 1426+428, and PG 1553+113, carried out with the Asiago Schmidt 67/92 cm telescope. TeV blazars are key targets in high-energy astrophysics, relevant for relativistic jet physics, particle acceleration, multiwavelength variability studies, and, in selected cases, multimessenger programmes. In this context, dense optical monitoring provides a low-energy synchrotron tracer of jet activity over temporal baselines that are difficult to cover continuously with high-energy facilities. The dataset consists of more than 17,000 R- and I-band photometric measurements obtained over 957 source-filter observing sessions between 2024 February 1 and 2026 January 31, for a total monitoring time of about 420 h. We applied a uniform differential-photometry and classical F-test framework based on two independent comparison-star pairs. Robust IDV is detected only in H 1426+428, with 15 out of 43 analysed sessions classified as variable in the R band and 5 out of 40 in the I band. No significant IDV is detected in 1ES 1959+650 or PG 1553+113 within the adopted statistical framework. For H 1426+428, the corresponding duration-weighted duty cycles, computed using only variable sessions with a measured local characteristic timescale, are 28.0% in the R band and 7.0% in the I band. The inferred local extrapolated doubling/halving timescales are of the order of 5-15 min in the observer frame. These results indicate that rapid optical synchrotron variability in TeV HBLs is intermittent and state-dependent. They also show that robotic small- and medium-aperture optical facilities can provide valuable long-term support for high-energy monitoring programmes by supplying dense, uniform, and repeatable optical coverage.
ER -