Detection of a gamma-ray flare from the high-redshift blazar DA 193

Abstract

High-redshift ($z>2$) blazars are the most powerful members of the blazar family. Yet, only a handful of them have both X-ray and $\gamma$-ray detection, thereby making it difficult to characterize the energetics of the most luminous jets. Here, we report, for the first time, the Fermi-Large Area Telescope detection of the significant $\gamma$-ray emission from the high-redshift blazar DA 193 ($z=2.363$). Its time-averaged $\gamma$-ray spectrum is soft ($\gamma$-ray photon index = $2.9\pm 0.1$) and together with a relatively flat hard X-ray spectrum (14$-$195 keV photon index = $1.5\pm 0.4$), DA 193 presents a case to study a typical high-redshift blazar with inverse Compton peak being located at MeV energies. An intense GeV flare was observed from this object in the first week of 2018 January, a phenomenon rarely observed from high-redshift sources. What makes this event a rare one is the observation of an extremely hard $\gamma$-ray spectrum (photon index = $1.7\pm 0.2$), which is somewhat unexpected since high-redshift blazars typically exhibit a steep falling spectrum at GeV energies. The results of our multi-frequency campaign, including both space- (Fermi, NuSTAR, and Swift) and ground-based (Steward and Nordic Optical Telescope) observatories, are presented and this peculiar $\gamma$-ray flare is studied within the framework of a single-zone leptonic emission scenario.

14 pages, 9 figures, 2 tables, to appear in the Astrophysical Journal

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Cited by in corpus (12)

• Blazars at the Cosmic Dawn
• Multiwavelength Study of High-Redshift Blazars
• NuSTAR perspective on high-redshift MeV blazars
• Modeling the Broadband Emission of 3C 454.3
• Search for high-redshift blazars with Fermi/LAT
• On the Origin of Gamma-ray Flares from Bright Fermi Blazars
• Radio VLBA polarization and multi-band monitoring of the high-redshift quasar S5 0836+710 during a high activity period
• Origin of multiwavelength emission from flaring high redshift blazar PKS 0537-286
• Very-long-baseline interferometry study of the flaring blazar TXS 1508+572 in the early Universe
• A Systematic Search for Spectral Hardening in Blazar Flares with the Fermi-Large Area Telescope
• A numerical study on the role of instabilities on multi-wavelength emission signatures of blazar jets
• Gamma-Ray Absorption By The Cosmic Lyman Continuum From Star-forming Galaxies