The Galactic center supermassive black hole is by far the closest
example for studying the mechanisms of accretion onto such
objects. Sgr A* is the fluctuating source of electromagnetic
radiation derived from the accretion flow or perhaps a related
jet. The variable radiation has been detected at radio, submillimeter
(submm), near infrared (NIR), and X-ray wavelengths. Recent numerical
general relativistic magneto-hydrodynamic (GRMHD) flare models across
the electromagnetic spectrum indicate that variability may be
connected to a tilted inner disk or to the black hole gravitationally
lensing a bright spot in the accretion flow. Different models predict
different amplitudes of flaring, and observations can therefore
distinguish between strong-mean- magnetization accretion and weak
magnetization. Disentangling the power source and emission mechanisms
of the flares is a central challenge to our understanding of the
Sgr A* accretion flow.
2019 Campaign InformationAdditional observations of Spitzer/IRAC 4.5 μm plus Chandra 2–8 keV observations were carried out in the summer of 2019. There were three epochs lasting 16 hours each. Dates and times (UTC) are given in the table below.
Results of Previous CampaignsSgr A* has been observed at 4.5 μm with Spitzer/IRAC on eight visits of ~24 hours each, and 3 visits of 16 hours each. The last seven of these visits have complete simultaneous X-ray observations with Chandra. There is also some simultaneous coverage with ALMA and the Submillimeter Array and with other telescopes with publications in preparation.
Times of all Spitzer visits are:
Results and data are reported in the publications listed below. Major
results of the infrared observations, including most existing
ground-based near infrared data, are:
Access to DataThe original Spitzer data in the above table can be downloaded from the Spitzer Heritage Archive. The reduced Spitzer and other IR data from 2017 and prior years can be downloaded from the Witzel et al. (2018) paper in MRT-format or accessed on VizieR. The Chandra X-ray data can be downloaded from the Chandra X-ray center. The Boyce et al. (2019) paper provides a table that gives the information on the associated Chandra and Spitzer observations from the 2017 and prior epoch observations.
The objectives of the Chandra and Spitzer
observations to (1) probe the accretion physics of Sgr A* on
event-horizon scales via multi-wavelength monitoring and (2) detect
any effect of the object G2 on Sgr A*. Only such long-duration,
continuous, multi-wavelength observations can achieve a comprehensive
view of the dominant emission process(es) and quantify the physical
properties near the event horizon. Theoretical models are increasing
in physical sophistication, and our study will provide essential
constraints for the next generation of models.
ContactsFor more information, contact:
Giovanni Fazio, Joe Hora, or Steve Willner.
Last updated: Friday, 27-Mar-2020 13:01:32 EDT