VLBA24A-105
Simultaneous Radio and Millimeter Monitoring of Sgr A* with JWST and EHT
Abstract
We propose three joint full-track VLA and VLBA+GBT observations concurrent with the already-approved James Webb Space Telescope (3x8 hours) and Event Horizon Telescope campaign of Sgr A* in April 2024. This joint proposal is part of a more extensive multiwavelength effort spanning through X-ray energies. Simultaneously observing this source across many bands will characterize its variability, providing constraints on the underlying accretion flow's physical parameters and flaring events. One proposed analysis is the full-polarization modeling of adiabatically expanding hotspots embedded within the accretion flow. Infrared (JWST), submillimeter (phased array ALMA/SMA), and radio (VLA/VLBA+GBT) coverage of detected flares will observe the emission from its initial production through its expansion. These data will constrain the flaring emission properties, allowing us to disentangle Sgr A*'s intrinsic variability, which is critical for obtaining high-fidelity images of the event horizon. GBT observations are requested to acquire fringe detections to all antennas and extract high-sensitivity light curves, particularly at 86 GHz. When combined with data from ALMA/SMA, we can constrain the spectral index near the submm bump, probing the region in the accretion flow where the optical depth changes significantly. These data will provide priors on the event horizon shadow image and its interpretation.
Investigators
| Name | Institution |
|---|---|
| GBT Operator | Green Bank Observatory |
| Joseph Michail * | Northwestern University |
| Farhad Yusef-Zadeh | Northwestern University |
| Mark Wardle | Macquarie University |
| Geoffrey Bower | Academia Sinica |
| Daryl Haggard | McGill University |
| Sera Markoff | Amsterdam, Universiteit van |
| Kazuhiro Hada | Istituto Nazionale di Astrofisica; National Astronomical Observatory of Japan |
| Joseph Neilsen | Villanova University |
| Michael Nowak | Washington University in St. Louis |
| Garrett Keating | California at Berkeley, University of; Harvard-Smithsonian Center for Astrophysics |
| Ramprasad Rao | Center for Astrophysics | Harvard & Smithsonian |
| Mark Gurwell | Center for Astrophysics | Harvard & Smithsonian |
| Thomas Krichbaum | Max-Planck-Institut für Radioastronomie |
| Howard Bushouse | Space Telescope Science Institute |
* indicates the PI