Polarization: A Method to Reveal the True Nature of the Dusty S-Cluster Object (DSO/G2)

Shahzamanian, B.; Eckart, A.; Valencia-S., M.; Sabha, Nesrin

doi:10.3390/galaxies6010013

Cited by 3 publications

(4 citation statements)

References 15 publications

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“…In conclusion, the rotating spots are a viable scenario capable to explain the occurrence about once per day of modulated flares from within a few milli-arcseconds of the Sagittarius A* supermassive black hole. 12,18 However, the astrophysically realistic scenarios have to account not only for the time-scales of gradual dispersion of the orbiting features by tidal effects 1,19 but also for the effects of plasma influencing the light propagation through a non-vacuum spacetime near the black hole. 2,13…”

Section: Discussionmentioning

confidence: 99%

Polarimetry and strong gravity effects from spots orbiting near a black hole

Karas,

Dovciak,

Svoboda

et al. 2019

Preprint

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We study the modulation of the observed radiation flux and the associated changes in the polarization degree and angle that are predicted by the orbiting spot model for flares from accreting black holes. The geometric shape of the emission region influences the resulting model lightcurves, namely, the emission region of a spiral shape can be distinguished from a simpler geometry of a small orbiting spot.We further explore this scheme for the observed flares from the supermassive black hole in the context of Galactic center (Sgr A*). Our code simulates the lightcurves for a wide range of parameters. The energy dependence of the changing degree and angle of polarization should allow us to discriminate between the cases of a rotating and a non-rotating black hole.

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Section: Discussionmentioning

confidence: 99%

Polarimetry and strong gravity effects from spots orbiting near a black hole

Karas,

Dovciak,

Svoboda

et al. 2019

Preprint

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“…LT precession is a genuine gravito-magnetic (Machian) effect of General Relativity (Barbour & Pfister 1995;Ciufolini & Wheeler 1995;Ruffini & Sigismondi 2003); indeed, rotation (spin) of the central object stands behind LT precession and it combines with other influences, for example due to an extended distribution of nearby gravitating matter and/or higher multipoles caused by aspherical deformation (flattening) of the central source of the gravitational field, and the oblateness of the dense nuclear star-cluster (Schödel et al 2014;Neumayer et al 2020). Let us note that attempts to constrain the spin of Sgr A* were already carried out in numerous independent works (Melia et al 2001;Iorio 2011;Fragione & Loeb 2020), however, a definitive answer about the spin orientation is still missing (Shahzamanian & Eckart 2015). While the GRAVITY instrument helped set an upper limit on the extended mass (Heißel et al 2022;Peißker et al 2022), the EHT collaboration revealed the inclination and dimensions of the Schwarzschild radius of Sgr A* (Event Horizon Telescope Collaboration 2022a).…”

Section: Lense-thirring Effectmentioning

confidence: 99%

Candidate young stellar objects in the S-cluster: Kinematic analysis of a subpopulation of the low-mass G objects close to Sgr A*

Peißker,

Zajaček,

Melamed

et al. 2024

A&A

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Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole Sgr A* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H − K and K − L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and mid-infrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of Sgr A* are much shorter (≪2 yr) than the epochs covered by the observations (≈15 yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20°, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of Sgr A*. Alternatively, the gravitational influence of Sgr A* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement.

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“…Zajacek, Karas & Eckart 2014, Zajacek et al 2016). Shahzamanian et al (2016) model the DSO as a combination of a bow shock and a bipolar wind of the central star. This model is consistent with the DSO's total flux density and the polarization degree.…”

Section: Infrared Polarimetry Of Sgra*mentioning

confidence: 99%

“…Here we present a brief description of the accretion process acting onto SgrA* from a statistical analysis of emission at different wavelengths. We also explore the geometrical properties of SgrA* accretion flow and of the DSO via infrared polarimetry (Shahzamanian et al 2015(Shahzamanian et al , 2016.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Activity and the Conditions of Star-formation at the Galactic Center

Eckart

Valencia-S.²,

Shahzamanian

et al. 2017

Proceedings of Frontier Research in Astrophysics – II — PoS(FRAPWS2016)

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The Galactic Center is the closest galactic nucleus that can be studied with unprecedented angular resolution and sensitivity. We summarize recent basic observational results on Sagittarius A* and the conditions for star formation in the central stellar cluster. We cover results from the radio, infrared, and X-ray domain and include results from simulation as well. From (sub-)mm and near-infrared variability and near-infrared polarization data we find that the SgrA* system (supermassive black hole spin, a potential temporary accretion disk and/or outflow) is well ordered in its geometrical orientation and in its emission process that we assume to reflect the accretion process onto the supermassive black hole (SMBH).

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Polarization: A Method to Reveal the True Nature of the Dusty S-Cluster Object (DSO/G2)

Cited by 3 publications

References 15 publications

Polarimetry and strong gravity effects from spots orbiting near a black hole

Polarimetry and strong gravity effects from spots orbiting near a black hole

Candidate young stellar objects in the S-cluster: Kinematic analysis of a subpopulation of the low-mass G objects close to Sgr A*

Nuclear Activity and the Conditions of Star-formation at the Galactic Center

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