ALMA Confirmation of Millimeter Time Variability in the Gamma-Ray Detected Seyfert Galaxy GRS 1734-292
Abstract
GRS 1734-292 is a radio-quiet galaxy, exhibiting neither intense starburst nor jet activities. However, Fermi-LAT detected this object in the GeV band. The origin of nonthermal activity in this Seyfert galaxy is an intriguing question. We report Atacama Large Millimeter/submillimeter Array observations of GRS 1734-292 at frequencies of 97.5, 145, and 225 GHz. These observations confirmed the millimeter excess within the central ⪅100 pc region and its time variability based on two separate observations conducted 4 days apart. The timescale of variability aligns with the light-crossing time for a compact source smaller than <100 Schwarzschild radius. If we take into account the power-law synchrotron emission originating from the corona (i.e., the hot plasma located above the accretion disk), the millimeter spectrum indicates the coronal magnetic field of ≈10 G and the size of ≈10 Schwarzschild radius. An alternative explanation for this millimeter emission could be synchrotron and free–free emission from disk winds (i.e., fast wide-opening angle outflows from the disk) with the size of ≈10 pc, although it may be difficult to explain the fast variability. Future millimeter observations with higher resolution (<0.″01) will enable the differentiation between these two scenarios. Such observations will provide insights into the acceleration sites of high-energy particles at the core of active galactic nuclei.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2024
- DOI:
- arXiv:
- arXiv:2404.00647
- Bibcode:
- 2024ApJ...965...68M
- Keywords:
-
- Astrophysical black holes;
- Black hole physics;
- Black holes;
- Supermassive black holes;
- Active galactic nuclei;
- Seyfert galaxies;
- Particle astrophysics;
- High energy astrophysics;
- 98;
- 159;
- 162;
- 1663;
- 16;
- 1447;
- 96;
- 739;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 11 pages, 7 figures, APJ accepted