The detection of the blazar S4 0954+65 at very-high-energy with the MAGIC telescopes during an exceptionally high optical state

Abstract

The very-high-energy (VHE, $\gtrsim 100$ GeV) $\gamma$-ray MAGIC observations of the blazar S4 0954+65, were triggered by an exceptionally high flux state of emission in the optical. This blazar has a disputed redshift of z=0.368 or z$⩾$0.45 and an uncertain classification among blazar subclasses. The exceptional source state described here makes for an excellent opportunity to understand physical processes in the jet of S4 0954+65 and thus contribute to its classification. We investigate the multiwavelength (MWL) light curve and spectral energy distribution (SED) of the S4 0954+65 blazar during an enhanced state in February 2015 and put it in context with possible emission scenarios. We collect photometric data in radio, optical, X-ray, and $\gamma$ ray. We study both the optical polarization and the inner parsec-scale jet behavior with 43 GHz data. Observations with the MAGIC telescopes led to the first detection of S4 0954+65 at VHE. Simultaneous data with Fermi-LAT at high energy $\gamma$ ray\ (HE, 100 MeV < E < 100 GeV) also show a period of increased activity. Imaging at 43 GHz reveals the emergence of a new feature in the radio jet in coincidence with the VHE flare. Simultaneous monitoring of the optical polarization angle reveals a rotation of approximately 100${}^{\circ }$. (...) The broadband spectrum can be modeled with an emission mechanism commonly invoked for flat spectrum radio quasars, i.e. inverse Compton scattering on an external soft photon field from the dust torus, also known as external Compton. The light curve and SED phenomenology is consistent with an interpretation of a blob propagating through a helical structured magnetic field and eventually crossing a standing shock in the jet, a scenario typically applied to flat spectrum radio quasars (FSRQs) and low-frequency peaked BL Lac objects (LBL).

arXiv comment15 pages, 7 figures, submitted to A&A

References in corpus (46)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• Fermi Large Area Telescope Second Source Catalog
• Fermi Large Area Telescope First Source Catalog
• Photometric Calibration of the Swift Ultraviolet/Optical Telescope
• Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Jet Kinematics from Bimonthly Monitoring with the Very Long Baseline Array
• Extragalactic Background Light Inferred from AEGIS Galaxy SED-type Fractions
• Limits and Confidence Intervals in the Presence of Nuisance Parameters
• Modeling the Extragalactic Background Light from Stars and Dust
• Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program
• The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
• The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• Probing the Inner Jet of the Quasar PKS 1510-089 with Multi-waveband Monitoring during Strong Gamma-ray Activity
• CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• 3FHL: The Third Catalog of Hard Fermi-LAT Sources
• The transition between BL Lac objects and Flat Spectrum Radio Quasars
• Synchrotron Self-Compton Analysis of TeV X-ray Selected BL Lacertae Objects
• 2FHL: The Second Catalog of Hard Fermi-LAT Sources
• The First Fermi-LAT Catalog of Sources Above 10 GeV
• Flaring Behavior of the Quasar 3C~454.3 across the Electromagnetic Spectrum
• Gamma-Ray Studies of Blazars: Synchro-Compton Analysis of Flat Spectrum Radio Quasars
• Compton Dominance and the Blazar Sequence
• Results of WEBT, VLBA and RXTE monitoring of 3C 279 during 2006-2007
• RoboPol: The optical polarization of gamma-ray--loud and gamma-ray--quiet blazars
• RoboPol: First season rotations of optical polarization plane in blazars
• Unfolding of differential energy spectra in the MAGIC experiment
• RoboPol: Connection between optical polarization plane rotations and gamma-ray flares in blazars
• MAGIC gamma-ray and multifrequency observations of flat spectrum radio quasar PKS 1510-089 in early 2012
• Synchrotron Polarization in Blazars
• Performance of the MAGIC telescopes under moonlight
• POLAMI: Polarimetric Monitoring of Active Galactic Nuclei at Millimetre Wavelengths. III. Characterisation of total flux density and polarisation variability of relativistic jets
• POLAMI: Polarimetric Monitoring of Active Galactic Nuclei at Millimetre Wavelengths. I. The program, calibration, and calibrators data products
• The First Simultaneous 3.5 and 1.3mm Polarimetric Survey of Active Galactic Nuclei in the Northern Sky
• Constraining blazar distances with combined Fermi and TeV data: an empirical approach
• A 3.5mm Polarimetric Survey of Radio-loud Active Galactic Nuclei
• An innovative blazar classification based on radio jet kinematics
• POLAMI: Polarimetric Monitoring of Active Galactic Nuclei at Millimetre Wavelengths. II. Widespread circular polarisation
• Break in the VHE spectrum of PG 1553+113: new upper limit on its redshift?
• Optical EVPA rotations in blazars: testing a stochastic variability model with RoboPol data
• Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 2015
• The Outburst of the Blazar S40954+658 in March-April 2011
• Black hole masses and Doppler factors of $\gamma$-ray active galactic nuclei
• Empirical multi-wavelength prediction method for very high energy gamma-ray emitting BL Lacs
• A significant hardening and rising shape detected in the MeV/GeV nuFnu spectrum from the recently-discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February
• Gamma Rays From Blazars

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• IXPE Observation of the Low-Synchrotron Peaked Blazar S4 0954+65 During An Optical-X-ray Flare
• Propagation of very-high-energy $\gamma$-rays from distant blazars
• The `blazar sequence' in TeV band
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