Near-infrared polarimetry as a tool for testing properties of accreting supermassive black holes

Zamaninasab, M.; Eckart, A.; Dovčiak, Michal; Karas, V.; Schödel, R.; Witzel, G.; Sabha, Nesrin; García-Marín, M.; Kunneriath, D.; Mužić, K.; Straubmeier, C.; Valencia-S., M.; Zensus, J. A.

doi:10.1111/j.1365-2966.2010.18139.x

Cited by 27 publications

(30 citation statements)

References 81 publications

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“…Only rapid millimeter to X-ray variability (Baganoff et al 2001;Genzel et al 2003;Ghez et al 2004Mauerhan et al 2005Eckart et al 2004Eckart et al , 2006aEckart et al , 2008Yusef-Zadeh et al 2008) as well as significant polarization features in the near-infrared (Eckart et al 2006b;Zamaninasab et al 2010Zamaninasab et al , 2011 indicate the presence of matter on relativistic orbits close to SgrA*. However, the radius at which the electrons become relativistic and suppress Faraday rotation within a thermal electron gas is unclear.…”

Section: Resultsmentioning

confidence: 99%

“…The overall model - as a sum of all three components -is shown as a thick black solid line. In the framework of previously described multi-spot models or evolving hot-spot models (Eckart et al 2008;Yuan et al 2009; see also Pecháček et al 2008;Zamaninasab et al 2011), the adoption of three components is a reasonable assumption. The offset flux densities above which we attribute the flux density to the flare event are listed in Table 2.…”

Section: An Adiabatic Expansion Model Of the May 2009 Datamentioning

confidence: 99%

“…In addition to either spiral arm models (Karas et al 2007;Falanga et al 2007) or jet/jet-base models (Falcke & Markoff 2000Markoff 2005;Markoff et al 2007), recent attempts to explain the emission from the compact region around SgrA* have been based on a hot-spot/disk model (Eckart et al 2006b;Broderick & Loeb 2006), multi-spot models, or even evolving hot-spot models (Eckart et al 2008;Yuan et al 2009; see also Pecháček et al 2008;Zamaninasab et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Millimeter to X-ray flares from Sagittarius A*

Eckart

García-Marín

Vogel

et al. 2012

A&A

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146

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Context. We report on new simultaneous observations and modeling of the millimeter, near-infrared, and X-ray flare emission of the source Sagittarius A* (SgrA*) associated with the super-massive (4 × 10 6 M ) black hole at the Galactic center. Aims. We study the applicability of the adiabatic synchrotron source expansion model and study physical processes giving rise to the variable emission of SgrA* from the radio to the X-ray domain. Methods. Our observations were carried out on 18 May 2009 using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope, the ACIS-I instrument aboard the Chandra X-ray Observatory, the LABOCA bolometer at the Atacama Pathfinder EXperiment (APEX), and the CARMA mm telescope array at Cedar Flat, California. Results. The X-ray flare had an excess 2−8 keV luminosity between 6 and 12×10 33 erg s −1 . The observations reveal flaring activity in all wavelength bands that can be modeled as the signal from an adiabatically expanding synchrotron self-Compton (SSC) component.Modeling of the light curves shows that the sub-mm follows the NIR emission with a delay of about three-quarters of an hour with an expansion velocity of about v exp ∼ 0.009c. We find source component sizes of around one Schwarzschild radius, flux densities of a few Janskys, and spectral indices α of about +1 (S (ν) ∝ ν −α ). At the start of the flare, the spectra of the two main components peak just short of 1 THz. To statistically explain the observed variability of the (sub-)mm spectrum of SgrA*, we use a sample of simultaneous NIR/X-ray flare peaks and model the flares using a synchrotron and SSC mechanism. Conclusions. These parameters suggest that either the adiabatically expanding source components have a bulk motion larger than v exp or the expanding material contributes to a corona or disk, confined to the immediate surroundings of SgrA*. For the bulk of the synchrotron and SSC models, we find synchrotron turnover frequencies in the range of 300−400 GHz. For the pure synchrotron models, this results in densities of relativistic particles of the order of 10 6.5 cm −3 and for the SSC models, the median densities are about one order of magnitude higher. However, to obtain a realistic description of the frequency-dependent variability amplitude of SgrA*, models with higher turnover frequencies and even higher densities are required.

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Section: Resultsmentioning

confidence: 99%

Section: An Adiabatic Expansion Model Of the May 2009 Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Millimeter to X-ray flares from Sagittarius A*

Eckart

García-Marín

Vogel

et al. 2012

A&A

Self Cite

146

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“…At least five independent investigations based on X-ray, near-IR, and radio observations have suggested that a jet is emanating from SgrA * . These studies have found discrepant values for the jet position angle (PA) and inclination (Markoff et al 2007;Muno et al 2008;Broderick et al 2011;Zamaninasab et al 2011;Yusef-Zadeh et al 2012;Shahzamanian et al 2015). It is possible that some of the gas approaching Sgr A * is pushed away as part of an expanding hot plasma driven by flaring and jet activity, resulting in Sgr A * ʼs low radiative efficiency.…”

Section: Introductionmentioning

confidence: 99%

SGR A* and Its Environment: Low-Mass Star Formation, the Origin of X-Ray Gas and Collimated Outflow

Yusef‐Zadeh

Wardle

Schödel

et al. 2016

ApJ

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We present high-resolution multiwavelength radio continuum images of the region within 150″ of SgrA * , revealing a number of new extended features and stellar sources in this region. First, we detect a continuous 2″ east-west ridge of radio emission, linking SgrA * and a cluster of stars associated with IRS 13 N and IRS 13E. The ridge suggests that an outflow of east-west blob-like structures is emerging from SgrA * . In particular, we find arc-like radio structures within the ridge with morphologies suggestive of photoevaporative protoplanetary disks. We use infrared K s and L′ fluxes to show that the emission has similar characteristics to those of a protoplanetary disk irradiated by the intense radiation field at the Galactic center. This suggests that star formation has taken place within the S-cluster 2″ from SgrA * . We suggest that the diffuse X-ray emission associated with Sgr A * is due to an expanding hot wind produced by the mass loss from B-type main sequence stars, and/or the disks of photoevaporation of low mass young stellar objects (YSOs) at a rate of ∼10 −6  M yr −1 . The proposed model naturally reduces the inferred accretion rate and is an alternative to the inflow-outflow style models to explain the underluminous nature of Sgr A * . Second, on a scale of 5″ from Sgr A * , we detect new cometary radio and infrared sources at a position angle PA∼50°which is similar to that of two other cometary sources X3 and X7, all of which face Sgr A * . In addition, we detect a striking tower of radio emission at a PA∼50°-60°along the major axis of the Sgr A East supernova remnant shell on a scale of 150″ from Sgr A * . We suggest that the cometary sources and the tower feature are tracing interaction sites of a mildly relativistic jet from Sgr A * with the atmosphere of stars and the nonthermal Sgr A East shell at a PA∼50°-60°with´-, and opening angle 10°. Lastly, we suggest that the east-west ridge of radio emission traces an outflow that is potentially associated with past flaring activity from Sgr A * . The position angle of the outflow driven by flaring activity is close to −90°.

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“…The variations in the emission are caused by circulating plasmoids which are anchored above an accretion disk (see e.g. Broderick & Loeb 2005;Meyer et al 2006;Dovčiak et al 2006;Noble et al 2007;Dexter & Agol 2009;Yuan et al 2009;Zamaninasab et al 2011) until they are eventually released.…”

Section: Introductionmentioning

confidence: 99%

Variations in emission from episodic plasmoid ejecta around black holes

Younsi¹,

Wu²

2015

Mon. Not. R. Astron. Soc.

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The X-ray and radio flares observed in X-ray binaries and active galactic nuclei (AGN) are attributed to energetic electrons in the plasma ejecta from the accretion flows near the black hole in these systems. It is argued that magnetic reconnection could occur in the coronae above the accretion disk around the black hole, and that this drives plasmoid outflows resembling the solar coronal mass ejection (CME) phenomenon. The X-ray and radio flares are emission from energetic electrons produced in the process. As the emission region is located near the black hole event horizon, the flare emission would be subject to special-and general-relativistic effects. We present calculations of the flaring emission from plasmoids orbiting around a black hole and plasmoid ejecta launched from the inner accretion disk when general-relativistic effects are crucial in determining the observed time-dependent properties of the emission. We consider fully general-relativistic radiative transfer calculations of the emission from evolving ejecta from black hole systems, with proper accounting for differential arrival times of photons emitted from the plasmoids, and determine the emission lightcurves of plasmoids when they are in orbit and when they break free from their magnetic confinement. The implications for interpreting time-dependent spectroscopic observations of flaring emission from accreting black holes are discussed.

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Near-infrared polarimetry as a tool for testing properties of accreting supermassive black holes

Cited by 27 publications

References 81 publications

Millimeter to X-ray flares from Sagittarius A*

Millimeter to X-ray flares from Sagittarius A*

SGR A* and Its Environment: Low-Mass Star Formation, the Origin of X-Ray Gas and Collimated Outflow

Variations in emission from episodic plasmoid ejecta around black holes

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