Discovery of $\gamma$-ray emission from steep radio spectrum NLS1s

Abstract

Narrow line Seyfert 1 galaxies (NLS1s) usually do not host relativistic jets and the detection of their $\gamma$-ray emissions is rarely reported. Evidences for strong relativistic beaming effect have been found in all $\gamma$-ray NLS1s to date and hence their jets are believed to be closely aligned. In this work we perform a systematic analysis of 7-year {\it Fermi} Large Area Telescope (LAT) data of 18 steep radio spectrum NLS1s (S-NLS1s) and report the {\it first} two detections of $\gamma$-ray emissions in this class, increasing the total number of known $\gamma$-ray NLS1s to 9. A strong and stable $\gamma$-ray signal (over 8$\sigma$) is produced by SDSS J144318.56+472556.7, and a significant $\gamma$-ray emission (4.5$\sigma$) of SDSS J130522.74+511640.2 has been detected in a monthly flare in November 2013. A thorough investigation of their multiwavelength properties from radio to X rays has been performed, finding no significant variability. Along with their spectral energy distributions and the radio morphology, these facts strongly suggest that these two sources harbor mis-aligned and possibly underdeveloped relativistic jets, which provides valuable targets to reveal the formation and evolution of relativistic jets under extreme circumstances.

replacement of arXiv 1510.05584 (named as "Discovery of gamma-ray emission from a steep radio spectrum NLS1 B3 1441+476")

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• Extreme Gaseous Outflows in Radio-Loud Narrow-Line Seyfert 1 Galaxies
• Radio morphology of southern narrow-line Seyfert 1 galaxies with Very Large Array observations
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• Radio jet structures at ~100 parsec and larger scales of the $\gamma$-ray-emitting narrow-line Seyfert 1 galaxy PMN J0948+0022
• Properties of the narrow line Seyfert 1 galaxies revisited
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• Optical Spectroscopy of Four Young Radio Sources