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A comprehensive observational study of the FRB 121102 persistent radio source

Chen, Ge and Ravi, Vikram and Hallinan, Gregg W. (2022) A comprehensive observational study of the FRB 121102 persistent radio source. . (Unpublished)

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FRB 121102 is the first fast radio burst source to be spatially associated with a persistent radio source (QRS121102), the nature of which remains unknown. We present a detailed observational study of QRS121102 and its host galaxy. We constrain the physical size of QRS121102 by measuring its flux-density variability with the VLA in the Ku-band (12 to 18 GHz) and the K-band (18 to 26 GHz). Any such variability would likely be due to Galactic refractive scintillation and would require the source radius to be <10¹¹ cm at the host-galaxy redshift. We found the radio variability to be lower than the scintillation theory predictions for such a small source, leaving open the possibility for non-AGN models for QRS121102. In addition, we roughly estimated the mass of any potential supermassive black hole (SMBH) associated with QRS121102 from the width of the H\alpha emission line using a medium-resolution optical spectrum from the Keck Observatory. The line width gives a velocity dispersion of <30 km/s, indicating a SMBH mass of <10^(4~5) M_⊙. We find the SMBH mass too low for the observed radio luminosity, and X-ray luminosity constraints, if QRS121102 were an AGN. Finally, some dwarf galaxies that host SMBH may be the stripped cores of massive galaxies during the tidal interactions with companion systems. We find no nearby galaxy at the same redshift as the QRS121102 host from low-resolution Keck spectra, or from the PanSTARRS catalog. In conclusion, we find no evidence supporting the hypothesis that the persistent radio source associated with FRB 121102 is an AGN. We instead argue that the inferred size, and the flat radio spectrum, favors a plerion interpretation. We urge continued broadband radio monitoring of QRS121102 to search for long-term evolution, and the detailed evaluation of potential analogs that may provide greater insight into the nature of this class of object.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Chen, Ge0000-0003-2867-4544
Ravi, Vikram0000-0002-7252-5485
Hallinan, Gregg W.0000-0002-7083-4049
Additional Information:The authors thank Dr. Casey J. Law for VLA imaging and visualization tips and the catalog querying code psquery. We also thank Dr. Casey J. Law and Dr. Liam D. Connor for helpful discussions on PRS and the unknown radio emissions in dwarf galaxies. We thank staff members at the CASA help desk, Dillon Dong and Nitika Yadlapalli for CASA tips. This material is based upon work supported by the National Science Foundation under grant No. AST-1836018.
Group:Astronomy Department
Funding AgencyGrant Number
Subject Keywords:High energy astrophysics: Radio bursts - Transient sources: Radio transient sources - Stellar astronomy: Neutron stars
Record Number:CaltechAUTHORS:20220125-215148573
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113107
Deposited By: George Porter
Deposited On:26 Jan 2022 15:25
Last Modified:26 Jan 2022 15:25

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