Coordinated mm/sub-mm observations of Sagittarius A* in May 2007

Kunneriath, D.; Eckart, A.; Vogel, S. N.; Sjouwerman, Loránt O.; Wiesemeyer, H.; Schödel, R.; Baganoff, F. K.; Morris, Mark; Bertram, Thomas; Dovčiak, Michal; Dowries, D.; Duschl, W. J.; Karas, V.; König, S.; Krichbaum, T. P.; Krips, M.; Lu, R.-S.; Markoff, Sera; Mauerhan, Jon C.; Meyer, L.; Moultaka, J.; Mužić, Koraljka; Najarro, F.; Schüster, K.; Straubmeier, C.; Thum, C.; Witzel, G.; Zamaninasab, M.; Zensus, J. A.

doi:10.1088/1742-6596/131/1/012006

Cited by 3 publications

(5 citation statements)

References 41 publications

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“…The typical time scale of these millimeter fluctuations is about 1.5 to 2.5 hours. A similar variability, both in terms of amplitude and typical timescale is observed at submillimeter wavelengths (Eckart et al 2006a, Yusef-Zadeh 2006a, Marrone et al 2006, Kunneriath et al 2008. The luminosity fluctuations of Sgr A* at near-infrared wavelengths are about one order of magnitude larger than at radio wavelengths.…”

Section: Variable Emissionsupporting

confidence: 54%

“…Following the discovery of X-ray and infrared flares of Sgr A* a number of research groups have conducted simultaneous multi-wavelength observations covering all accessible frequencies from the radio to -rays (Eckart et al 2004, Yusef-Zadeh et al 2006b, Kunneriath et al 2008, Marrone et al 2008, Aharonian et al 2008, Dodds-Eden et al 2009). These multi-wavelength observations reveal the salient characteristics and the broad-band SED of Sgr A*'s variable emission.…”

Section: Flaresmentioning

confidence: 99%

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The Galactic Center massive black hole and nuclear star cluster

2010

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2. The nuclear star cluster ……………………………………………………. 7 2.1 The nuclear cluster of cool, old stars 2.2 The disk(s) of young O/WR-stars 2.3 The central S-star cluster and the distribution of B-stars 2.4 Is there an 'equilibrium' central stellar cusp ? 2.5 Stellar mass function 2.6 Chemical abundances 3. Interstellar matter …………………………………………………………. 35 3.1 Ionized gas in Sgr A West 3.2 Neutral gas 3.3 Dust and extinction toward the Galactic Center 3.4 Hot gas and high energy emission 4. Testing the black hole paradigm: is Sgr A* a massive black hole? ………. 43 4.1 Evidence for a central compact mass from gas motions 4.2 Evidence from stellar radial and proper motions 4.3 Constraints from stellar orbits 4.4 Very Long Baseline Interferometry of Sgr A* 4.5 Does Sgr A* have an event horizon? 4.6 Could Sgr A* be a binary ? 4.7 Alternatives to a black hole configuration 5. Mass distribution in the nuclear cluster …………………………………. 57 5.1 Outlier high velocity stars 5.2 Dark matter in the central parsec ? 5.3 Comparison to earlier statistical mass estimates 5.4 Does IRS 13E contain an intermediate mass black hole? 5.5 The distance to the Galactic Center 6. Paradox of youth: how did the young stars get into the central parsec? …. 6.1 Star formation history in the central parsecs 6.2 In situ star formation or in-spiral of clusters ? 6.3 Origin of B-stars in the central cusp: migration or scattering? 6.4 What powers the central parsec ? 7. Accretion and emission close to the central black hole ………………... 93 7.1 Steady emission from Sgr A* across the electromagnetic spectrum 7.2 Variable emission 7.3 Flares 7.4 Accretion onto the black hole 8. Concluding Remarks and Outlook …………………………………….. References …………………………………………………………….... _____________________________________________________________ , with β ranging from 1.5 to 2.3 in the analyses of Paumard et al. (2006), Lu et al. ( 2009) and Bartko et al. (2009Bartko et al. ( , 2010. The inner cutoff of the clockwise system is remarkably sharp. There are six O/WR-stars projected between 0.96" and 1.5" but none inside of 0.96".

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Section: Variable Emissionsupporting

confidence: 54%

Section: Flaresmentioning

confidence: 99%

The Galactic Center massive black hole and nuclear star cluster

2010

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“…In Fig. 1, we also show the daily flux density averages of the 7 mm VLBA observations that were conducted in parallel (Lu et al 2008(Lu et al , 2009Kunneriath et al 2008). The VLBA data follow the overall trend of the combined CARMA/ATCA/30 m light-curve very well.…”

Section: The MM Datamentioning

confidence: 75%

“…The main results are: 2 bright NIR flares (16 mJy and 10 mJy), a ∼0.4 Jy mm flare, and a possible weaker third flare in the NIR and mm in the combined ATCA, CARMA, IRAM 30 m mm/sub-mm light curve from May 2007, and a bright NIR flare in May 2008 also covered by the CARMA 3 mm observations. We present updated versions of light curves first presented in Kunneriath et al (2008), a more detailed description of the methods used to obtain them, and physical models to explain the flaring activity. The observations and data reduction are described in Sect.…”

Section: Introductionmentioning

confidence: 99%

Coordinated NIR/mm observations of flare emission from Sagittarius A*

Kunneriath

Witzel²,

Eckart

et al. 2010

A&A

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Context. We report on a successful, simultaneous observation and modelling of the millimeter (mm) to near-infrared (NIR) flare emission of the Sgr A* counterpart associated with the supermassive (4 × 10 6 M ) black hole at the Galactic centre (GC). We present a mm/sub-mm light curve of Sgr A* with one of the highest quality continuous time coverages. Aims. We study and model the physical processes giving rise to the variable emission of Sgr A*. Methods. Our non-relativistic modelling is based on simultaneous observations carried out in May 2007 and 2008, using the NACO adaptive optics (AO) instrument at the ESO's VLT and the mm telescope arrays CARMA in California, ATCA in Australia, and the 30 m IRAM telescope in Spain. We emphasize the importance of multi-wavelength simultaneous fitting as a tool for imposing adequate constraints on the flare modelling. We present a new method for obtaining concatenated light curves of the compact mm-source Sgr A* from single dish telescopes and interferometers in the presence of significant flux density contributions from an extended and only partially resolved source. Results. The observations detect flaring activity in both the mm domain and the NIR. Inspection and modelling of the light curves show that in the case of the flare event on 17 May 2007, the mm emission follows the NIR flare emission with a delay of 1.5 ± 0.5 h. On 15 May 2007, the NIR flare emission is also followed by elevated mm-emission. We explain the flare emission delay by an adiabatic expansion of source components. For two other NIR flares, we can only provide an upper limit to any accompanying mmemission of about 0.2 Jy. The derived physical quantities that describe the flare emission give a source component expansion speed of v exp ∼ 0.005c−0.017c, source sizes of about one Schwarzschild radius, flux densities of a few Janskys, and spectral indices of α = 0.6 to 1.3. These source components peak in the THz regime. Conclusions. These parameters suggest that either the adiabatically expanding source components have a bulk motion greater than v exp or the expanding material contributes to a corona or disk, confined to the immediate surroundings of Sgr A*. Applying the flux density values or limits in the mm-and X-ray domain to the observed flare events constrains the turnover frequency of the synchrotron components that are on average not lower than about 1 THz, such that the optically thick peak flux densities at or below these turnover frequencies do not exceed, on average, about ∼1 Jy.

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“…The use of this expansion model for the flares of Sgr A is motivated by: the timelags separating X-ray/NIR flares from sub-mm flares (Tab. 3); the timelags separating X-ray/NIR flares from radio flares (Yusef-Zadeh et al 2009;Kunneriath et al 2008); the timelags between different radio bands within the same flare (Yusef-Zadeh et al 2006b) 6 ; the increase of linear polarization as sub-mm flares reach their maximum (Marrone et al 2008); the similarity between the flare timescales in X-ray/NIR and mm/sub-mm, which suggests that energy losses are not dominated by radiative cooling, with expansion a good alternative candidate 7 . Fig.…”

Section: Plasmoid Expansionmentioning

confidence: 99%

Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sagittarius A*

Trap

Goldwurm

Dodds-Eden

et al. 2011

A&A

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Aims. The radiative counterpart of the supermassive black hole at the Galactic center (GC), Sgr A , is subject to frequent flares that are visible simultaneously in X-rays and the near-infrared (NIR). Often, enhanced radio variability from centimeter to sub-millimeter wavelengths is observed to follow these X-ray/NIR eruptions. We present here a multi-wavelength campaign carried out in April 2009, with the aim of characterizing this broadband flaring activity. Methods. Concurrent data from the XMM-Newton/EPIC (2-10 keV), VLT/NACO (2.1 μm, 3.8 μm), APEX/LABOCA (870 μm), and Fermi/LAT (0.1-200 GeV) instruments are employed to derive light curves and spectral energy distributions of new flares from Sgr A . Results. We detected two relatively bright NIR flares, both associated with weak X-ray activity, one of which was followed by a strong sub-mm outburst ∼200 min later. Photometric spectral information on a NIR flare was obtained for the first time with NACO, giving a power-law photon index α = −0.4 ± 0.3 (F ν ∝ ν α ). The first attempt to detect flaring activity from the Fermi GC source 1FGL J1745.6-2900 is also reported. We model NIR, X-ray, and sub-mm flares in the context of non-thermal emission processes. We find that the simplest scenario involving a single expanding plasmoid releasing synchrotron NIR/sub-mm and synchrotron selfCompton X-ray radiation is inadequate to reproduce the data, but we offer suggestions to reconcile the basic elements of the theory and the observations.

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Coordinated mm/sub-mm observations of Sagittarius A* in May 2007

Cited by 3 publications

References 41 publications

The Galactic Center massive black hole and nuclear star cluster

The Galactic Center massive black hole and nuclear star cluster

Coordinated NIR/mm observations of flare emission from Sagittarius A*

Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sagittarius A*

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