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Mishra, HD, Dai, X, Chen, P, Cheng, JY, Jayasinghe, T, Tucker, MA, Vallely, PJ, Bersier, D, Bose, S, Do, A, Dong, S, Holoien, TW-S, Huber, ME, Kochanek, CS, Liang, E, Payne, AV, Prieto, J, Shappee, BJ, Stanek, KZ, Bhatiani, S , Cox, J, DeFrancesco, C, Shen, Z, Thompson, TA and Wang, J (2021) The Changing-look Blazar B2 1420+32. Astrophysical Journal, 913 (2). ISSN 0004-637X
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Abstract
Blazars are active galactic nuclei with their relativistic jets pointing toward the observer, comprising two major subclasses, flat-spectrum radio quasars (FSRQs) and BL Lac objects. We present multiwavelength photometric and spectroscopic monitoring observations of the blazar B2 1420+32, focusing on its outbursts in 2018-2020. Multiepoch spectra show that the blazar exhibited large-scale spectral variability in both its continuum and line emission, accompanied by dramatic gamma-ray and optical variability by factors of up to 40 and 15, respectively, on week to month timescales. Over the last decade, the gamma-ray and optical fluxes increased by factors of 1500 and 100, respectively. B2 1420+32 was an FSRQ with broad emission lines in 1995. Following a series of flares starting in 2018, it transitioned between BL Lac and FSRQ states multiple times, with the emergence of a strong Fe pseudocontinuum. Two spectra also contain components that can be modeled as single-temperature blackbodies of 12,000 and 5200 K. Such a collection of "changing-look"features has never been observed previously in a blazar. We measure gamma-ray-optical and interband optical lags implying emission-region separations of less than 800 and 130 gravitational radii, respectively. Since most emission-line flux variations, except the Fe continuum, are within a factor of 2-3, the transitions between FSRQ and BL Lac classifications are mainly caused by the continuum variability. The large Fe continuum flux increase suggests the occurrence of dust sublimation releasing more Fe ions in the central engine and an energy transfer from the relativistic jet to subrelativistic emission components.
| Item Type: | Article |
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| Uncontrolled Keywords: | Science & Technology; Physical Sciences; Astronomy & Astrophysics; ACTIVE GALACTIC NUCLEI; BROAD-LINE REGION; BL-LAC OBJECTS; RADIO GALAXIES; EMISSION-LINES; OPTICAL SPECTROSCOPY; DOPPLER FACTORS; ACCRETION DISC; VARIABILITY; TELESCOPE; astro-ph.HE; astro-ph.HE; astro-ph.GA; 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | American Astronomical Society; IOP Publishing |
| SWORD Depositor: | A Symplectic |
| Date Deposited: | 05 May 2022 12:00 |
| Last Modified: | 07 Jun 2022 00:50 |
| DOI or ID number: | 10.3847/1538-4357/abf63d |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/16761 |
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