Abstract
Context. QSO B1420+326 is a blazar classified as a flat-spectrum radio quasar (FSRQ). At the beginning of the year 2020, it was found to be in an enhanced flux state and an extensive multiwavelength campaign allowed us to trace the evolution of the flare. Aims. We search for very high-energy (VHE) gamma-ray emission from QSO B1420+326 during this flaring state. We aim to characterize and model the broadband emission of the source over different phases of the flare. Methods. The source was observed with a number of instruments in radio, near-infrared, optical (including polarimetry and spectroscopy), ultraviolet, X-ray, and gamma-ray bands. We use dedicated optical spectroscopy results to estimate the accretion disk and the dust torus luminosity. We performed spectral energy distribution modeling in the framework of combined synchrotron-self-Compton and external Compton scenario in which the electron energy distribution is partially determined from acceleration and cooling processes. Results. During the enhanced state, the flux of both SED components of QSO B1420+326 drastically increased and the peaks were shifted to higher energies. Follow-up observations with the MAGIC telescopes led to the detection of VHE gamma-ray emission from this source, making it one of only a handful of FSRQs known in this energy range. Modeling allows us to constrain the evolution of the magnetic field and electron energy distribution in the emission region. The gamma-ray flare was accompanied by a rotation of the optical polarization vector during a low -polarization state. Also, a new superluminal radio knot contemporaneously appeared in the radio image of the jet. The optical spectroscopy shows a prominent FeII bump with flux evolving together with the continuum emission and a MgII line with varying equivalent width.
Highlights
QSO B1420+326, known as OQ 334, is a blazar located at redshift of 0.682 (Hewett & Wild 2010)
In the very-high-energy (VHE, 100 GeV) range, despite the detection of over 60 BL Lac objects by Imaging Atmospheric Cherenkov Telescopes (IACTs), only about 8 flat-spectrum radio quasar (FSRQ) are known to emit in this energy range1
For sources located at high redshift (z ∼ 1), the very high-energy (VHE) gamma-ray part of the spectrum is severely absorbed in the pairproduction process on extragalactic background light (EBL; see, e.g., Domínguez et al 2011), hampering the discovery potential in this energy range
Summary
QSO B1420+326, known as OQ 334, is a blazar located at redshift of 0.682 (Hewett & Wild 2010). In the very-high-energy (VHE, 100 GeV) range, despite the detection of over 60 BL Lac objects by Imaging Atmospheric Cherenkov Telescopes (IACTs), only about 8 FSRQs are known to emit in this energy range. FSRQs are known to be extremely variable (see, e.g., Meyer et al 2019), which is another complication in observing these sources with instruments with relatively small fields of view such as IACTs. The VHE gamma-ray flux has been seen to vary by as much as two orders of magnitude (see, e.g., D’Ammando et al 2019; Zacharias et al 2019). As the number of known VHE FSRQs is still very small, it is important to observe those objects to look for common patterns and differences in their emission and to investigate whether or not the same processes are responsible. The observations need to be multiwavelength, contemporaneously covering the broad energy range of the spectrum, which is often difficult to achieve due to fast variability
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
