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Title: Very Large Array Multiband Monitoring Observations of M31*

Abstract

The Andromeda galaxy (M31) hosts one of the nearest and most quiescent supermassive black holes, which provides a rare, but promising opportunity for studying the physics of black hole accretion at the lowest state. We have conducted a multifrequency, multi-epoch observing campaign, using the Karl G. Jansky Very Large Array (VLA) in its extended configurations in 2011–2012, to advance our knowledge of the still poorly known radio properties of M31*. For the first time, we detect M31* at 10, 15, and 20 GHz and measure its spectral index, α ≈ −0.45 ± 0.08 (S{sub ν} ∝ ν {sup α}), over the frequency range of 5–20 GHz. The relatively steep spectrum suggests that the observed radio flux is dominated by the optically thin part of a putative jet, which is located at no more than a few thousand Schwarzschild radii from the black hole. On the other hand, our sensitive radio images show little evidence for an extended component, perhaps except for several parsec-scale “plumes,” the nature of which remains unclear. Our data also reveal significant (a few tens of percent) flux variation of M31* at 6 GHz, on timescales of hours to days. Furthermore, a curious decrease of the meanmore » flux density, by ∼50%, is found between VLA observations taken during 2002–2005 and our new observations, which might be associated with a substantial increase in the mean X-ray flux of M31* starting in 2006.« less

Authors:
;  [1];  [2]; ;  [3]
  1. School of Astronomy and Space Science, Nanjing University, Nanjing 210023 (China)
  2. National Radio Astronomy Observatory, Socorro, NM 87801 (United States)
  3. Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China)
Publication Date:
OSTI Identifier:
22663211
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 845; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; CONFIGURATION; COSMIC X-RAY SOURCES; FLUX DENSITY; GALAXIES; GALAXY NUCLEI; GHZ RANGE; PLUMES; SCHWARZSCHILD RADIUS; SPECTRA; SUPERMASSIVE STARS; X RADIATION

Citation Formats

Yang, Yang, Li, Zhiyuan, Sjouwerman, Loránt O., Yuan, Feng, and Shen, Zhi-Qiang, E-mail: lizy@nju.edu.cn. Very Large Array Multiband Monitoring Observations of M31*. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8265.
Yang, Yang, Li, Zhiyuan, Sjouwerman, Loránt O., Yuan, Feng, & Shen, Zhi-Qiang, E-mail: lizy@nju.edu.cn. Very Large Array Multiband Monitoring Observations of M31*. United States. doi:10.3847/1538-4357/AA8265.
Yang, Yang, Li, Zhiyuan, Sjouwerman, Loránt O., Yuan, Feng, and Shen, Zhi-Qiang, E-mail: lizy@nju.edu.cn. Sun . "Very Large Array Multiband Monitoring Observations of M31*". United States. doi:10.3847/1538-4357/AA8265.
@article{osti_22663211,
title = {Very Large Array Multiband Monitoring Observations of M31*},
author = {Yang, Yang and Li, Zhiyuan and Sjouwerman, Loránt O. and Yuan, Feng and Shen, Zhi-Qiang, E-mail: lizy@nju.edu.cn},
abstractNote = {The Andromeda galaxy (M31) hosts one of the nearest and most quiescent supermassive black holes, which provides a rare, but promising opportunity for studying the physics of black hole accretion at the lowest state. We have conducted a multifrequency, multi-epoch observing campaign, using the Karl G. Jansky Very Large Array (VLA) in its extended configurations in 2011–2012, to advance our knowledge of the still poorly known radio properties of M31*. For the first time, we detect M31* at 10, 15, and 20 GHz and measure its spectral index, α ≈ −0.45 ± 0.08 (S{sub ν} ∝ ν {sup α}), over the frequency range of 5–20 GHz. The relatively steep spectrum suggests that the observed radio flux is dominated by the optically thin part of a putative jet, which is located at no more than a few thousand Schwarzschild radii from the black hole. On the other hand, our sensitive radio images show little evidence for an extended component, perhaps except for several parsec-scale “plumes,” the nature of which remains unclear. Our data also reveal significant (a few tens of percent) flux variation of M31* at 6 GHz, on timescales of hours to days. Furthermore, a curious decrease of the mean flux density, by ∼50%, is found between VLA observations taken during 2002–2005 and our new observations, which might be associated with a substantial increase in the mean X-ray flux of M31* starting in 2006.},
doi = {10.3847/1538-4357/AA8265},
journal = {Astrophysical Journal},
number = 2,
volume = 845,
place = {United States},
year = {Sun Aug 20 00:00:00 EDT 2017},
month = {Sun Aug 20 00:00:00 EDT 2017}
}