The Nature of the IMBH Candidate CXO J133815.6+043255: High-frequency Radio Emission
Abstract
The ultraluminous X-ray source CXO J133815.6+043255 is a strong candidate for a bona fide intermediate-mass black hole residing in the outskirts of NGC 5252. We present 22 GHz radio observations of this source obtained serendipitously in an ongoing high-frequency imaging survey of radio-quiet Active Galactic Nuclei (AGNs), and use this new data point to construct the broadband radio spectral energy distribution (SED). We find that the SED exhibits a spectral slope of α = -0.66 ± 0.02, consistent with a steep spectrum from optically thin synchrotron emission from an unresolved jet. We also find that the L R/L X ratio is approximately 10-3, inconsistent with radio-quiet AGN and many ULXs but consistent with low-luminosity AGN and radio-loud quasars. Together, these observations support the conclusion that CXO J133815.6+043255 is an intermediate-mass black hole producing a low-mass analog of radio jets seen in classical quasars.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2023
- DOI:
- arXiv:
- arXiv:2309.00051
- Bibcode:
- 2023ApJ...956....3S
- Keywords:
-
- Black holes;
- Intermediate-mass black holes;
- Active galactic nuclei;
- 162;
- 816;
- 16;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 8 pages, 3 figures, accepted for publication in the Astrophysical Journal