X-RAY DIAGNOSTICS OF GIANT MOLECULAR CLOUDS IN THE GALACTIC CENTER REGION AND PAST ACTIVITY OF Sgr A*

Odaka, Hirokazu; Aharonian, F.; Watanabe, Shin; Tanaka, Yasuyuki; Khangulyan, D.; Takahashi, Tadayuki

doi:10.1088/0004-637x/740/2/103

Cited by 68 publications

(96 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…That and the short decay time lead them to rule out that scenario. In principle, the details of the morphology of scattered and fluorescing X-rays, its spectrum, and the time variations of both can all be used as diagnostics of the structure of a cloud, the placement of the cloud with respect to the source of the incident flare, and the temporal profile of that flare (Sunyaev & Churazov 1998;Odaka et al 2011). However, this is clearly a complex inverse problem.…”

Section: Sgr B2mentioning

confidence: 99%

“…However, this is clearly a complex inverse problem. In their theoretical study motivated by Sgr B2, Odaka et al (2011) point out that, because X-rays with energies above 20 keV can penetrate much deeper into a cloud, the distribution of the ratio of the hard continuum emission to the intensity of the 6.4 keV fluorescent line can be a useful additional probe for the internal cloud structure, as well as for its relative placement. The fading of Sgr B2 is will unfortunately complicate the future application of these models to that one cloud, but the expanding spherical shell of X-rays that underlies the current paradigm should eventually illuminate another cloud in the central molecular zone.…”

Section: Sgr B2mentioning

confidence: 99%

“…Capelli et al (2012) thereby offer preliminary estimates of the line-of-sight displacements of some clouds from Sgr A*. It is not clear, however, that they have accounted for the differential penetration into the clouds of the K-shell ionizing photons and the adjacent X-ray continuum, which Odaka et al (2011) argue can also give rise to an angle-dependent line-to-continuum ratio.…”

Section: Duration and Multiplicity Of Flashesmentioning

confidence: 99%

“…With this measurement accuracy, it would be possible to improve estimates of the amount and distribution of dark mass in the Milky Way and to possibly recalibrate rungs of the cosmic distance ladder (e.g. Olling & Merrifield 2000;Majewski et al 2006).…”

Section: Measuring the Central Gravitational Potential Through Stellamentioning

confidence: 99%

See 3 more Smart Citations

Galactic center research: manifestations of the central black hole

Morris

Meyer

Ghez

2012

Res. Astron. Astrophys.

View full text Add to dashboard Cite

This review summarizes a few of the frontiers of Galactic center research that are currently the focus of considerable activity and attention. It is aimed at providing a necessarily incomplete sketch of some of the timely work being done on phenomena taking place in, or originating in, the central few parsecs of the Galaxy, with particular attention to topics related to the Galactic black hole (GBH). We have chosen to expand on the following exciting topics: 1) the characterization and the implications for the variability of emission from the GBH, 2) the strong evidence for a powerful X-ray flare in the Galactic center within the past few hundred years, and the likelihood that the GBH is implicated in that event, 3) the prospects for detecting the "shadow" of the GBH, 4) an overview of the current state of research on the central S-star cluster, and what has been learned from the stellar orbits within that cluster, and 5) the current hypotheses for the origin of the G2 dust cloud that is projected to make a close passage by the GBH in 2013.

show abstract

Section: Sgr B2mentioning

confidence: 99%

Section: Sgr B2mentioning

confidence: 99%

Section: Duration and Multiplicity Of Flashesmentioning

confidence: 99%

Section: Measuring the Central Gravitational Potential Through Stellamentioning

confidence: 99%

See 2 more Smart Citations

Galactic center research: manifestations of the central black hole

Morris

Meyer

Ghez

2012

Res. Astron. Astrophys.

View full text Add to dashboard Cite

show abstract

“…To this end we follow the parameterization by Odaka et al (2011), who discuss different possible positions of the B2 cloud (see their Fig. 3).…”

Section: Reprocessing By An Extended Cloudmentioning

confidence: 99%

Multiple accretion events as a trigger for Sagittarius A* activity

Kunneriath¹,

Karas²,

Das

2013

Proc. IAU

View full text Add to dashboard Cite

Context. Gas clouds are present in the Galactic centre, where they orbit around the supermassive black hole. Collisions between these clumps reduce their angular momentum, and as a result some of the clumps are set on a plunging trajectory. Constraints can be imposed on the nature of past accretion events based on the currently observed X-ray reflection from the molecular clouds surrounding the Galactic centre. Aims. We discuss accretion of clouds in the context of enhanced activity of Sagittarius A* during the past few hundred years. We put forward a scenario according to which gas clouds bring material close to the horizon of the black hole on 0.1 parsec scale. Methods. We have modelled the source intrinsic luminosity assuming that multiple events occur at various moments in time. These events are characterized by the amount of accreted material and the distribution of angular momentum. We parameterized the activity in the form of a sequence of discrete events, followed the viscous evolution, and calculated the luminosity of the system from the time-dependent accretion rate across the inner boundary. Results. Accreting clumps settle near a circularization radius, spread there during the viscous time, and subsequently feed the black hole over a certain period. A significant enhancement (by factor of ten) of the luminosity is only expected if the viscous timescale of the inflow is very short. On the other hand, the increase in source activity is expected to be much less prominent if the latter timescale is longer and a considerable fraction of the material does not reach the centre. Conclusions. A solution is obtained under two additional assumptions: (i) the radiative efficiency is a decreasing function of the Eddington ratio; (ii) the viscous decay of the luminosity proceeds somewhat faster than the canonical L(t) ∝ t −5/3 profile. We applied our scheme to the case of G2 cloud in the Galactic centre to obtain constraints on the core-less gaseous cloud model.

show abstract

Traces of Past Activity in the Galactic Centre

Ponti

Morris

Terrier

et al. 2013

Astrophysics and Space Science Proceedings

View full text Add to dashboard Cite

The Milky Way centre hosts a supermassive Black Hole (BH) with a mass of ∼ 4 × 10 6 M ⊙ . Sgr A*, its electromagnetic counterpart, currently appears as an extremely weak source with a luminosity L ∼ 10 −9 L Edd . The lowest known Eddington ratio BH. However, it was not always so; traces of "glorious" active periods can be found in the surrounding medium. We review here our current view of the Xray emission from the Galactic Center (GC) and its environment, and the expected signatures (e.g. X-ray reflection) of a past flare. We discuss the history of Sgr A*'s past activity and its impact on the surrounding medium. The structure of the Central Molecular Zone (CMZ) has not changed significantly since the last active phase of Sgr A*. This relic torus provides us with the opportunity to image the structure of an AGN torus in exquisite detail.

show abstract

X-RAY DIAGNOSTICS OF GIANT MOLECULAR CLOUDS IN THE GALACTIC CENTER REGION AND PAST ACTIVITY OF Sgr A*

Cited by 68 publications

References 35 publications

Galactic center research: manifestations of the central black hole

Galactic center research: manifestations of the central black hole

Multiple accretion events as a trigger for Sagittarius A* activity

Traces of Past Activity in the Galactic Centre

Contact Info

Product

Resources

About