Journal
ASTROPHYSICAL JOURNAL
Volume 845, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/aa7da6
Keywords
accretion, accretion disks; black hole physics; Galaxy: center; radiation mechanisms: non-thermal
Categories
Funding
- Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant
- Fonds de recherche du Quebec-Nature et Technologies (FRQNT) Nouveaux Chercheurs Grant
- Vidi grant - Netherlands organization for scientific research (NWO)
- NSERC Discovery Grant
- NSERC Discovery Accelerator Supplement
- NASA through the Hubble Postdoctoral Fellowship program [HST-HF2-51343.001-A]
- Bundesministerium fur Wirtschaft und Technologie/Deutsches Zentrum fur Luft-und Raumfahrt (BMWI/DLR) [FKZ 50 OR 1604]
- Max Planck Society
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Monitoring of Sagittarius. A* from X-ray to radio wavelengths has revealed structured variability-including X-ray flares-but it is challenging to establish correlations between them. Most studies have focused on variability in the X-ray and infrared, where variations are often simultaneous, and because long time series at submillimeter and radio wavelengths are limited. Previous work on submillimeter and radio variability hints at a lag between X-ray flares and their candidate submillimeter or radio counterparts, with the long wavelength data lagging the X-ray. However, there is only one published time lag between an X-ray flare and a possible radio counterpart. Here we report nine contemporaneous X-ray and radio observations of Sgr. A*. We detect significant radio variability peaking greater than or similar to 176 minutes after the brightest X-ray flare ever detected from Sgr. A*. We also report other potentially associated X-ray and radio variability, with the radio peaks appearing less than or similar to 80 minutes after these weaker X-ray flares. Taken at face value, these results suggest that stronger X-ray flares lead to longer time lags in the radio. However, we also test the possibility that the variability at X-ray and radio wavelengths is not temporally correlated. We cross-correlate data from mismatched X-ray and radio epochs and obtain comparable correlations to the matched data. Hence, we find no overall statistical evidence that X-ray flares and radio variability are correlated, underscoring a need for more simultaneous, long duration X-ray-radio monitoring of Sgr. A*.
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