The Multifrequency Behavior of Sagittarius A*

Eckart, A.; Fazeli, Nastaran; Busch, G.; Shahzamanian, B.; Subroweit, M.; Peißker, F.; Sabha, Nesrin; Valencia-S., M.; Horrobin, M.; Straubmeier, C.; Rost, Steffen; Schneeloch, Jana; Borkar, A.; Karas, Vladimír; Britzen, S.; Zensus, J. A.; Kamali, F.

doi:10.48550/arxiv.1806.00284

Cited by 5 publications

(5 citation statements)

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“…a poloidal configuration. On the other hand, the bright X-ray flares often exhibit a double-peak structure (Karssen et al 2017;Ponti et al 2017), which is fitted well by the combination of lensing and Doppler-boosting of a hot spot emission due to its motion along the trajectory that is close to edge-on with respect to the observer (Eckart et al 2018). Already the first hot-spot models of Sgr A* flaring activity implied the departure from face-on orientation, with the inclination of i ≤ 145 • (Meyer et al 2006).…”

Section: Discussionmentioning

confidence: 88%

Effect of Electromagnetic Interaction on Galactic Center Flare Components

Tursunov,

Zajaček,

Eckart

et al. 2019

Preprint

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Recently, near-infrared GRAVIY@ESO observations at 2.2 µm have announced the detection of three bright "flares" in the vicinity of the Galactic center black hole that exhibited orbital motion at the radius about 6−11 gravitational radii of 4.14×10 6 M black hole. There are indications of the presence of a large-scale, organized component of the magnetic field at the Galactic center. Electromagnetic effects on the flare dynamics were previously not taken into account despite that the relativistic motion of a plasma in magnetic field leads to the charge separation and non-negligible net charge density in the plasma. Applying various approaches we find the net charge number density of the flare components of the order of 10 −3 − 10 −4 cm −3 , while the particles total number density is of the order of 10 6 − 10 8 cm −3 . However, even such a tiny excess of charged particles in the quasi-neutral plasma can sufficiently affect the dynamics of flare components, which can then lead to discrepancies in the measurements of spin of the supermassive black hole. Analyzing the dynamics of recent flares in the case of the rapidly rotating black hole a > 0.5, we also constrain the inclination angle between magnetic field and the spin axis to α < 50 • , as for larger angles the motion of the hot spot is strongly chaotic.

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Section: Discussionmentioning

confidence: 88%

Effect of Electromagnetic Interaction on Galactic Center Flare Components

Tursunov,

Zajaček,

Eckart

et al. 2019

Preprint

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“…While the 𝐹 𝑋 pacemaker affecting the X-ray flares is a modulation of the major energy source of these flares at the epicyclic frequency, with the IR pacemaker the situation is different. The origin of the IR flares, along with those in X-ray, is a much discussed theme in the literature (Eckart et al 2004;Dodds-Eden et al 2009Yusef-Zadeh et al 2009;Younsi and Wu 2015;Li et al 2017;Chael et al 2018;Eckart et al 2018;Witzel et al 2018;Ripperda et al 2020 and references therein). However, as stated by many researchers in the field the cause of the erratic outbursts of the flares or the physical origin of the episodic acceleration of electrons that presumably gives rise to the flare outbursts are not well understood (e.g.…”

Section: The Nir Pacemakermentioning

confidence: 99%

Possible Evidence from the Flaring Activity of Sgr A* for a Star at a Distance of ∼3.3 Schwarzschild Radii from the Black Hole

Leibowitz

2020

ApJ

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The frequent flaring events in the X-ray and the NIR radiation of Sgr A* seem not to be periodic in time. However, statistical regularities, here termed 'modulations by a pacemaker', are found in the recorded arrival times of both types of events. The characteristic time of the X-ray pacemaker is 149 min and that of the NIR pacemaker is 40 min. Their reality as derived from observed data can be accepted at larger than 4. 6𝜎 and 3.8𝜎 levels of statistical confidence, respectively. These results can be interpreted as evidence for a star that revolves around the BH of Sgr A* in a slightly elliptical precessing orbit, at a distance of 3-3.5Schwarzschild radii of the BH. The period of the X-ray pacemaker, which is not a periodicity of the flare occurrences themselves, is the epicyclic period of the star orbital motion. This is the time interval between 2 successive passages of the star through the pericenter of its orbit.The NIR pacemaker period is the mean sidereal binary period of the star revolution. The X-ray flares originate in episodes of intense mass loss from the star that occur preferably near the pericenter phase of the binary revolution. The NIR flares originate or are triggered by processes that are internal to the star. The radiation emitted in the direction of Earth is slightly modulated by the changing aspect ratio of the two components of the BH/star binary to the line of sight from Earth at the sidereal binary frequency.

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“…Variation in the observed spectral shift due to Doppler effects Though the effects of the time variation in the observed VLBI-Data are weak compared with the eclipse effect of the SMBHB, the possibility of time variation when observing VLBI-Data can be considered. Except for the case of burst time radiation, the power law spectra of the radio emissions from Sgr A* is known to have the index of 0.3 [27]. In the regular state of the average condition of the accretion of the plasma, we assume that the radio wave emission spectra P j (ω) for SMBH-j ( j=Gaa or Gab) is…”

Section: Construction Of the Drwp-model To Show The Origin Of Time Va...mentioning

confidence: 99%

Untitled

2022

EESRR

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In 2011, by 1.3 mm wavelength VLBI radio wave observations of the SgrA*, Fish, V. L. et al showed that the emissions tightly related to the formation of a black hole shadow have a remarkably large time-varying feature within a region of less than 50 μas. The present paper suggests that the origin of the time variation in the observed emission is due to effects of the orbital motion of the existing super-massive black hole binary orbiting at SgrA* with a period of 2150±2.5 s. This suggestion is based on observations of decameter radio wave pulses from SgrA*. We show a good correlation between the time variation in the coherent flux density of the VLBI results and the time variation model of estimated emission intensities based on the periodic motion of the super-massive black hole binary by applying parameters deduced from the decameter radio wave pulse observation model (DRWP-Model). With further confirmation by Fourier analyses of the potential periodicity of the VLBI data that show the same periods of DRWP Model, we conclude that the time variation detected by the 1.3 mm wavelength radio wave VLBI is evidence of an existing super-massive black hole at Sgr A*.

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The Multifrequency Behavior of Sagittarius A*

Cited by 5 publications

References 0 publications

Effect of Electromagnetic Interaction on Galactic Center Flare Components

Effect of Electromagnetic Interaction on Galactic Center Flare Components

Possible Evidence from the Flaring Activity of Sgr A* for a Star at a Distance of ∼3.3 Schwarzschild Radii from the Black Hole

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