تقرير
Near-Infrared Flux Distribution of Sgr A* from 2005-2022: Evidence for an Enhanced Accretion Episode in 2019
| العنوان: | Near-Infrared Flux Distribution of Sgr A* from 2005-2022: Evidence for an Enhanced Accretion Episode in 2019 |
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| المؤلفون: | Weldon, Grant C., Do, Tuan, Witzel, Gunther, Ghez, Andrea M., Gautam, Abhimat K., Becklin, Eric E., Morris, Mark R., Martinez, Gregory D., Sakai, Shoko, Lu, Jessica R., Matthews, Keith, Hosek Jr., Matthew W., Haggard, Zoë |
| سنة النشر: | 2023 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena |
| الوصف: | Sgr A* is the variable electromagnetic source associated with accretion onto the Galactic center supermassive black hole. While the near-infrared (NIR) variability of Sgr A* was shown to be consistent over two decades, unprecedented activity in 2019 challenges existing statistical models. We investigate the origin of this activity by re-calibrating and re-analyzing all of our Keck Observatory Sgr A* imaging observations from 2005-2022. We present light curves from 69 observation epochs using the NIRC2 imager at 2.12 $\mu$m with laser guide star adaptive optics. These observations reveal that the mean luminosity of Sgr A* increased by a factor of $\sim$3 in 2019, and the 2019 light curves had higher variance than in all time periods we examined. We find that the 2020-2022 flux distribution is statistically consistent with the historical sample and model predictions, but with fewer bright measurements above 0.6 mJy at the $\sim$2$\sigma$ level. Since 2019, we have observed a maximum $K_s$ (2.2 $\mu$m) flux of 0.9 mJy, compared to the highest pre-2019 flux of 2.0 mJy and highest 2019 flux of 5.6 mJy. Our results suggest that the 2019 activity was caused by a temporary accretion increase onto Sgr A*, possibly due to delayed accretion of tidally-stripped gas from the gaseous object G2 in 2014. We also examine faint Sgr A* fluxes over a long time baseline to search for a quasi-steady quiescent state. We find that Sgr A* displays flux variations over a factor of $\sim$500, with no evidence for a quiescent state in the NIR. Comment: Accepted to ApJ Letters, 26 pages, 15 figures |
| نوع الوثيقة: | Working Paper |
| URL الوصول: | http://arxiv.org/abs/2308.09749 |
| رقم الأكسشن: | edsarx.2308.09749 |
| قاعدة البيانات: | arXiv |
| الوصف غير متاح. |