Multiwavelength Variability of Sagittarius A* in 2019 July

Haggard, Daryl; Witzel, G.; Fellenberg, S. D. von; Willner, S. P.; Becklin, E. E.; Do, Tuan; Eckart, A.; Fazio, G. G.; Gurwell, M. A.; Hora, J. L.; Markoff, Sera; Morris, Mark; Neilsen, Joseph; Nowak, M.; Smith, H. A.; S., Zhang,

doi:10.3847/1538-4357/ac6104

Cited by 12 publications

(25 citation statements)

References 125 publications

(215 reference statements)

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“…Third, the SED of NIR-X-ray flares can be modeled with a synchrotron or synchrotron self-Compton sphere localized in the accretion flow (Dodds-Eden et al 2011;Ponti et al 2017;Witzel et al 2021;GRAVITY Collaboration et al 2021;Boyce et al 2022). Fourth, the flare of Sgr A* shows signatures in linear polarization (Q-U loops) in NIR and submillimeter observations, consistent with a localized hot spot in the accretion flow (Marrone et al 2006;GRAVITY Collaboration et al 2020d;Wielgus et al 2022).…”

Section: Moving Average Representation Of the Light Curvementioning

confidence: 89%

“…Also, other non-lognormal, log-rightskewed distributions match the data (Dodds-Eden et al 2009;Meyer et al 2014;Do et al 2019;GRAVITY Collaboration et al 2020a). Second, the spectral slope during high flux states is positive (νL ν ∝ ν ∼+0.5 ), while for fainter flux states it decreases, indicating a transition from flaring to quiescence (Eisenhauer et al 2005;Krabbe et al 2006;Gillessen et al 2006;Dodds-Eden et al 2010;Hornstein et al 2007;Eckart et al 2009;Ponti et al 2017;GRAVITY Collaboration et al 2021;Boyce et al 2022).…”

Section: Moving Average Representation Of the Light Curvementioning

confidence: 99%

“…The extension of NIR and X-ray flares to the (sub)millimeter and radio regimes is difficult. While numerous studies have found tentative evidence in favor of a temporally delayed extension to longer wavelengths (e.g., Yusef-Zadeh et al 2006Eckart et al 2009;Witzel et al 2021;Boyce et al 2022;Michail et al 2021), the correlation in total intensity measurements remains difficult to establish. Recent X-ray and polarimetric millimeter observations by Wielgus et al (2022), however, seem to confirm a delay of ∼ 30 minute between a bright X-ray flare and an increase in millimeter flux.…”

Section: Introductionmentioning

confidence: 99%

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General relativistic effects and the near-infrared and X-ray variability of Sgr A* I

Fellenberg

Witzel

Bauböck

et al. 2023

A&A

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The near-infrared (NIR) and X-ray emission of Sagittarius A* shows occasional bright flares that are assumed to originate from the innermost region of the accretion flow. We identified 25 4.5 µm and 24 X-ray flares in archival data obtained with the Spitzer and Chandra observatories. With the help of general relativistic ray-tracing code, we modeled trajectories of "hot spots" and studied the light curves of the flares for signs of the effects of general relativity. Despite their apparent diversity in shape, all flares share a common, exponential impulse response, a characteristic shape that is the building block of the variability. This shape is symmetric, that is, the rise and fall times are the same. Furthermore, the impulse responses in the NIR and X-ray are identical within uncertainties, with an exponential time constant τ ∼ 15 min. The observed characteristic flare shape is inconsistent with hot-spot orbits viewed edgeon. Individually modeling the light curves of the flares, we derived constraints on the inclination of the orbital plane of the hot spots with respect to the observer (i ∼ 30 • , < 75 • ) and on the characteristic timescale of the intrinsic variability (tenths of minutes).

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Section: Moving Average Representation Of the Light Curvementioning

confidence: 89%

Section: Moving Average Representation Of the Light Curvementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

General relativistic effects and the near-infrared and X-ray variability of Sgr A* I

Fellenberg

Witzel

Bauböck

et al. 2023

A&A

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Section: Moving Average Representation Of the Light Curvementioning

confidence: 99%

General relativistic effects and the near-infrared and X-ray variability of Sgr A* I

von Fellenberg,

Witzel,

Bauböck

et al. 2023

Preprint

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The near-infrared (NIR) and X-ray emission of Sagittarius A* shows occasional bright flares that are assumed to originate from the innermost region of the accretion flow. We identified 25 4.5 µm and 24 X-ray flares in archival data obtained with the Spitzer and Chandra observatories. With the help of general relativistic ray-tracing code, we modeled trajectories of "hot spots" and studied the light curves of the flares for signs of the effects of general relativity. Despite their apparent diversity in shape, all flares share a common, exponential impulse response, a characteristic shape that is the building block of the variability. This shape is symmetric, that is, the rise and fall times are the same. Furthermore, the impulse responses in the NIR and X-ray are identical within uncertainties, with an exponential time constant τ ∼ 15 min. The observed characteristic flare shape is inconsistent with hot-spot orbits viewed edgeon. Individually modeling the light curves of the flares, we derived constraints on the inclination of the orbital plane of the hot spots with respect to the observer (i ∼ 30°, < 75°) and on the characteristic timescale of the intrinsic variability (tens of minutes).

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“…Additionally, a high abundance of bright NIR events were observed with VLT in 2019 relative to other years (Gravity Collaboration et al 2020). Heightened activity was also seen in the radio (e.g., Murchikova & Witzel 2021;Boyce et al 2022;Cheng et al 2023) and X-ray regimes (e.g., Pavlinsky 2019;Degenaar et al 2019). These observations collectively suggest that Sgr A * displayed unusual behavior in 2019, making this era useful for understanding the timevariable accretion flow onto the black hole.…”

Section: Introductionmentioning

confidence: 98%

Near-infrared Flux Distribution of Sgr A* from 2005–2022: Evidence for an Enhanced Accretion Episode in 2019

Weldon,

Do,

Witzel

et al. 2023

ApJL

Self Cite

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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 recalibrating and reanalyzing 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 μm with laser-guide star adaptive optics. These observations reveal that the mean luminosity of Sgr A* increased by a factor of ∼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 ∼2σ level. Since 2019, we have observed a maximum K s (2.2 μm) 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 ∼500, with no evidence for a quiescent state in the NIR.

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Multiwavelength Variability of Sagittarius A* in 2019 July

Cited by 12 publications

References 125 publications

General relativistic effects and the near-infrared and X-ray variability of Sgr A* I

General relativistic effects and the near-infrared and X-ray variability of Sgr A* I

General relativistic effects and the near-infrared and X-ray variability of Sgr A* I

Near-infrared Flux Distribution of Sgr A* from 2005–2022: Evidence for an Enhanced Accretion Episode in 2019

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