Optical Photometric Monitoring of the Blazar OT 355 and Local Standard Stars’ Calibration
OT 355 (4FGL J1734.3 + 3858) is a relatively rarely studied but highly variable, moderate-redshift (z = 0.975) flat-spectrum radio quasar (blazar). With this work, we aim to study its optical variability on different timescales, which can help us to better understand the physical processes in relati...
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| author | R. Bachev Tushar Tripathi Alok C. Gupta A. Kurtenkov Y. Nikolov A. Strigachev S. Boeva G. Latev B. Spassov M. Minev E. Ovcharov W.-X. Yang Yi Liu J.-H. Fan |
| author_facet | R. Bachev Tushar Tripathi Alok C. Gupta A. Kurtenkov Y. Nikolov A. Strigachev S. Boeva G. Latev B. Spassov M. Minev E. Ovcharov W.-X. Yang Yi Liu J.-H. Fan |
| author_sort | R. Bachev |
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| description | OT 355 (4FGL J1734.3 + 3858) is a relatively rarely studied but highly variable, moderate-redshift (z = 0.975) flat-spectrum radio quasar (blazar). With this work, we aim to study its optical variability on different timescales, which can help us to better understand the physical processes in relativistic jets operating in blazar-type active galactic nuclei. OT 355 was observed in four colors (BVRI) during 41 nights between 2017 and 2023 using three 1 and 2 m class telescopes. The object was also monitored on intra-night timescales, for about 100 h in total. In addition, secondary standard stars in the field of OT 355 were calibrated in order to facilitate future photometric studies. We detected significant intra-night and night-to-night variations of up to 0.5 mag. Variability characteristics, color changes, and a possible “rms-flux” relation were studied and discussed. Using simple arguments, we show that a negative “rms-flux” relation should be expected if many independent processes/regions drive the short-term variability via Doppler factor changes, which is not observed in this and other cases. This finding raises arguments for the idea that more complex multiplicative processes are responsible for blazar variability. Studying blazar variability, especially on the shortest possible timescales, can help to estimate the strength and geometry of their magnetic fields, the linear sizes of the emitting regions, and other aspects, which may be of importance for constraining and modeling blazars’ emitting mechanisms. |
| format | Article |
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| institution | Kabale University |
| issn | 2218-1997 |
| language | English |
| publishDate | 2025-05-01 |
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| record_format | Article |
| series | Universe |
| spelling | doaj-art-edd8130aa7c84c12800f9928cd0ad1dd2025-08-20T03:26:56ZengMDPI AGUniverse2218-19972025-05-0111617110.3390/universe11060171Optical Photometric Monitoring of the Blazar OT 355 and Local Standard Stars’ CalibrationR. Bachev0Tushar Tripathi1Alok C. Gupta2A. Kurtenkov3Y. Nikolov4A. Strigachev5S. Boeva6G. Latev7B. Spassov8M. Minev9E. Ovcharov10W.-X. Yang11Yi Liu12J.-H. Fan13Institute of Astronomy and NAO, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, 1784 Sofia, BulgariaAryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263001, IndiaAryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263001, IndiaInstitute of Astronomy and NAO, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, 1784 Sofia, BulgariaInstitute of Astronomy and NAO, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, 1784 Sofia, BulgariaInstitute of Astronomy and NAO, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, 1784 Sofia, BulgariaInstitute of Astronomy and NAO, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, 1784 Sofia, BulgariaInstitute of Astronomy and NAO, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, 1784 Sofia, BulgariaInstitute of Astronomy and NAO, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, 1784 Sofia, BulgariaInstitute of Astronomy and NAO, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, 1784 Sofia, BulgariaDepartment of Astronomy, Faculty of Physics, Sofia University “St. Kliment Ohridski”, 1116 Sofia, BulgariaCenter for Astrophysics, Guangzhou University, Guangzhou 510006, ChinaCenter for Astrophysics, Guangzhou University, Guangzhou 510006, ChinaCenter for Astrophysics, Guangzhou University, Guangzhou 510006, ChinaOT 355 (4FGL J1734.3 + 3858) is a relatively rarely studied but highly variable, moderate-redshift (z = 0.975) flat-spectrum radio quasar (blazar). With this work, we aim to study its optical variability on different timescales, which can help us to better understand the physical processes in relativistic jets operating in blazar-type active galactic nuclei. OT 355 was observed in four colors (BVRI) during 41 nights between 2017 and 2023 using three 1 and 2 m class telescopes. The object was also monitored on intra-night timescales, for about 100 h in total. In addition, secondary standard stars in the field of OT 355 were calibrated in order to facilitate future photometric studies. We detected significant intra-night and night-to-night variations of up to 0.5 mag. Variability characteristics, color changes, and a possible “rms-flux” relation were studied and discussed. Using simple arguments, we show that a negative “rms-flux” relation should be expected if many independent processes/regions drive the short-term variability via Doppler factor changes, which is not observed in this and other cases. This finding raises arguments for the idea that more complex multiplicative processes are responsible for blazar variability. Studying blazar variability, especially on the shortest possible timescales, can help to estimate the strength and geometry of their magnetic fields, the linear sizes of the emitting regions, and other aspects, which may be of importance for constraining and modeling blazars’ emitting mechanisms.https://www.mdpi.com/2218-1997/11/6/171blazarsvariabilityrelativistic jets |
| spellingShingle | R. Bachev Tushar Tripathi Alok C. Gupta A. Kurtenkov Y. Nikolov A. Strigachev S. Boeva G. Latev B. Spassov M. Minev E. Ovcharov W.-X. Yang Yi Liu J.-H. Fan Optical Photometric Monitoring of the Blazar OT 355 and Local Standard Stars’ Calibration Universe blazars variability relativistic jets |
| title | Optical Photometric Monitoring of the Blazar OT 355 and Local Standard Stars’ Calibration |
| title_full | Optical Photometric Monitoring of the Blazar OT 355 and Local Standard Stars’ Calibration |
| title_fullStr | Optical Photometric Monitoring of the Blazar OT 355 and Local Standard Stars’ Calibration |
| title_full_unstemmed | Optical Photometric Monitoring of the Blazar OT 355 and Local Standard Stars’ Calibration |
| title_short | Optical Photometric Monitoring of the Blazar OT 355 and Local Standard Stars’ Calibration |
| title_sort | optical photometric monitoring of the blazar ot 355 and local standard stars calibration |
| topic | blazars variability relativistic jets |
| url | https://www.mdpi.com/2218-1997/11/6/171 |
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