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:10.22323/1.306.0048

Cited by 3 publications

(6 citation statements)

References 39 publications

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“…Their emission may be weakened or blocked completely depending on the gas column density along the line of sight. The hard (2-10 keV) X-ray and mid-infrared wavebands provide powerful, complementary methods for identifying and studying AGN over a wide range of intrinsic obscuration (Eckart et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Spitzer/IRAC Tarafından Seçilen AGN'lerin X-ışın Özellikleri

Ikiz

2021

Erzincan Üniversitesi Fen Bilimleri Enstitüsü Dergisi

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Spitzer/IRAC color selection is a powerful tool to identify hot accreting nuclei, that is to say AGN, in galaxies. In this study, mid-infrared detected candidate 36 AGNs are used that are selected from the Spitzer Survey of Stellar Structures in Galaxies (S 4 G) sample consisting of more than 2500 galaxies together with its extension sample of more than 400 galaxies by İkiz et al., (2020). Mid-infrared color selection method is tested by examining the X-ray properties of the galaxies via the XMM-Newton and Chandra. Using the X-ray data, we demonstrate that galaxies displaying hot mid-infrared nuclei stand out as (candidate) active galaxies. 64% of mid-infrared-selected AGN are detected at X-ray energies in XMM-Newton and Chandra data. It has been hypothesized that IRAC sources with AGN colors that lack X-ray detections are predominantly highluminosity AGN that are obscure.

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Section: Introductionmentioning

confidence: 99%

Spitzer/IRAC Tarafından Seçilen AGN'lerin X-ışın Özellikleri

Ikiz

2021

Erzincan Üniversitesi Fen Bilimleri Enstitüsü Dergisi

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“…In some bright X-ray flares these characteristic shapes may be visible Karssen et al, 2017;. Figure 1.7, obtained from Eckart et al (2018), shows the data of two bright X-ray flares fitted with a hotspot flare model from Karssen et al (2017). In these plots, the "shoulder" is due to gravitational lensing when the hotsopt is behind the black hole.…”

Section: Variability and Flaresmentioning

confidence: 99%

“…The electromagnetic radiation from Sgr A * has been detected in several wavelengths (e.g., Genzel et al 2010;Morris et al 2012;Eckart et al 2018), with the exceptions being the visible band and gamma-rays.…”

Section: Multiwavelength Emissionmentioning

confidence: 99%

“…This plot was created based on models from ; Narayan et al (1998); Narayan and McClintock (2008) and using data from several works (radio from Falcke et al 1998;Zhao et al 2003;IR from Eckart et al 2018 and references in there; and X-ray from Baganoff et al 2001Baganoff et al , 2003Porquet et al 2003Porquet et al , 2008. Source: Eckart et al (2018); .…”

Section: The Two States Of Sagittarius a *mentioning

confidence: 99%

“…Sgr A * has been detected in most of the electromagnetic spectrum (e.g., . In Figure 1.6 we show a sketch, created by Eckart et al (2018) The compact radio source Sgr A * 's radio emission, discovered in the 1970s, is clearly detectable at all times and shows only moderate flux and spectral variations. The variable NIR source associated with the accretion flow around Sgr A * was unambiguously identified in the first years of this millennium Ghez et al, 2004).…”

Section: The Two States Of Sagittarius a *mentioning

confidence: 99%

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Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope

Cafardo¹

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Sagittarius A * (Sgr A * )-the supermassive black hole (SMBH) in the center of our galaxy-has been identified in most of the electromagnetic spectrum, from radio to Xrays. Diffuse gamma-ray emission has been observed around Sgr A * and a gamma-ray point source has been detected coinciding with the SMBH's position, although there is still no definitive association between the two. In this work, we have used ∼11 years of Fermi Large Area Telescope (LAT) observations of the point source 4FGL J1745.6−2859 and performed a detailed analysis across four energy bands. Our goal is to elucidate the nature of the gamma-ray emission at the Galactic Center (GC) and whether it is associated with the SMBH. We find that the centroids of the emission approach Sgr A * 's location as the energy increases and they are spatially associated with gas-rich regions in the GC.Assuming that the gamma-ray point source is located at the GC, we estimate a luminosity of 2.61 × 10 36 erg s −1 in the 100 MeV to 500 GeV energy range. This is consistent with Sgr A * 's bolometric luminosity. Based on the point source properties, we ruled out several potential candidates for its nature and favor a cosmic ray origin accelerated by-or in the vicinity of-the SMBH. We also created light curves (LCs), with time bins as short as 15 days, in search of variability in the 4FGL J1745.6−2859 gamma-ray flux. In contrast with Sgr A * 's flaring behavior in longer wavelengths, we detect that its gamma-ray flux distribution is compatible with a Gaussian, representative of a normal random process, hinting that the gamma-ray emission mechanism differs substantially from the low-energy regime. Finally, 4FGL J1745.6−2859's spectral energy distribution (SED) shows a "piondecay bump" characteristic of gamma-ray hadronic emission. Its SED is also compatible with several hadronic models for Sgr A * 's gamma-ray emission. Our results indicate that the point source at the GC is indeed the gamma-ray counterpart of Sgr A * in the GeV range. The characteristics of this emission-its spatial coincidence with gas reservoirs, energetics, lack of variability and SED-suggest that hadronic processes are likely behind its origin.

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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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The Multifrequency Behavior of Sagittarius A*

Cited by 3 publications

References 39 publications

Spitzer/IRAC Tarafından Seçilen AGN'lerin X-ışın Özellikleri

Spitzer/IRAC Tarafından Seçilen AGN'lerin X-ışın Özellikleri

Exploring Sagittarius A* in gamma-rays with Fermi LAT Telescope

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

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