Multiwavelength Observations of Sgr A*. II. 2019 July 21 and 26

Joseph M. Michail, Farhad Yusef-Zadeh, Mark Wardle, Devaky Kunneriath, Joseph L. Hora, Howard Bushouse, Giovanni G. Fazio, Sera Markoff, Howard A. Smith

Research output: Contribution to journalArticlepeer-review

Abstract

We report on the final two days of a multiwavelength campaign of Sgr A* observing in the radio, submillimeter, infrared (IR), and X-ray bands in 2019 July. Sgr A* was remarkably active, showing multiple flaring events across the electromagnetic spectrum. We detect a transient ∼35 minute periodicity feature in Spitzer light curves on 2019 July 21. Time-delayed emission was detected in Atacama Large Millimeter/submillimeter Array light curves, suggesting a hotspot within the accretion flow on a stable orbit. On the same night, we observe a decreased flux in the submillimeter light curve following an X-ray flare detected by Chandra, and we model the feature with an adiabatically expanding synchrotron hotspot occulting the accretion flow. The event is produced by a plasma 0.55 R S in radius with an electron spectrum p = 2.84. It is threaded by a ∼130 Gauss magnetic field and expands at 0.6% the speed of light. Finally, we reveal an unambiguous flare in the IR, submillimeter, and radio, demonstrating that the variable emission is intrinsically linked. We jointly fit the radio and submillimeter light curves using an adiabatically expanding synchrotron hotspot and find it is produced by a plasma with an electron spectrum p = 0.59, 187 Gauss magnetic field, and radius 0.47 R S that expands at 0.029c. In both cases, the uncertainty in the appropriate lower and upper electron energy bounds may inflate the derived equipartition field strengths by a factor of 2 or more. Our results confirm that both synchrotron- and adiabatic-cooling processes are involved in the variable emission’s evolution at submillimeter and IR wavelengths.

Original languageEnglish (US)
Article number52
JournalAstrophysical Journal
Volume971
Issue number1
DOIs
StatePublished - Aug 1 2024

Funding

We are grateful to Sean Carey, Dan Marrone, and Steven Willner for useful comments that strengthened this manuscript. We additionally thank the referee for providing very helpful and constructive feedback. This work is partially supported by NSF grant AST-2305857 and through SOSP21A-003 and SOSPADA-026 from the NRAO. S.M. is grateful for support from the Dutch Research Council (NWO) VICI award (grant 639.043.513) and the European Research Council (ERC) SyG \u201CBlackHolistic\u201D (grant 101071643). G.G.F., J.L.H., and H.A.S. acknowledge support for this work from the NASA ADAP program under NASA grant 80NSSC18K0416. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2018.A.00050.T. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. This work is based on archival data obtained with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. The scientific results reported in this article are based in part on data obtained from the Chandra Data Archive. This research has made use of software provided by the Chandra X-ray Center (CXC) in the application packages CIAO. This research has made use of data obtained from the Chandra Source Catalog, provided by the CXC as part of the Chandra Data Archive. This research was supported in part through the computational resources and staff contributions provided for the Quest high-performance computing facility at Northwestern University, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology.

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint

Dive into the research topics of 'Multiwavelength Observations of Sgr A*. II. 2019 July 21 and 26'. Together they form a unique fingerprint.

Cite this