SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light‐Month

Eisenhauer, F.; Genzel, R.; Alexander, Tal; Abuter, R.; Paumard, T.; Ott, Thomas; Gilbert, Andrea M.; Gillessen, S.; Horrobin, M.; Trippe, Sascha; Bonnet, Henri; Dumas, Christophe; Hubin, N.; Kaufer, A.; Kissler-Patig, M.; Monnet, G.; Ströbele, Stefan; Szeifert, T.; Eckart, A.; Schödel, R.; Zucker, S.

doi:10.1086/430667

Cited by 612 publications

(837 citation statements)

References 79 publications

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“…For observational purposes we also compute the apparent I magnitude for the candidates assuming M I = −4.6 (Battinelli & Demers 2005b). To determine the galactocentric distances for our candidates we adopt a distance between the Sun and the Galactic center R 0 = 7.62 ± 0.32 kpc (Eisenhauer et al 2005). This value was essentially confirmed by near infrared observations of red clump stars close to the Galactic Center (Nishiyama et al 2006).…”

Section: Distance Estimatesmentioning

confidence: 99%

C stars as kinematic probes of the Milky Way disk from 9 to 15 kpc

Demers¹,

Battinelli²

2007

A&A

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Context. The availability, from 2MASS, of a large homogeneous sample of Galactic C stars and the recognition that their absolute magnitude can be accurately determined offer the possibility to use them as kinematical probes to investigate motions in the thin or thick disks. Aims. Determine the radial velocities for 70 C stars, a few degrees from the Galactic plane and distributed in longitudes from 60 • to 220 • . Methods. Spectra, with a resolution of 4300, were obtained with the DAO 1.8 m telescope during 6 beautiful nights in October 2006. Results. The rotation velocities of C stars with 60 • < < 150 • suggest a flat rotation curve to 15 kpc. A number of stars have velocities that do not fit the thin disk rotation. Some of them, toward = 200 • are most probably members of the Canis Major overdensity. Conclusions. Effort should be made to extend the rotation curve to more that 20 kpc.Key words. stars: carbon -stars: kinematics -Galaxy: disk -Galaxy: kinematics and dynamics IntroductionThe importance of galactic potentials in shaping the chemodynamical evolution of stellar populations is well known. Unfortunately, the surface mass distribution of the Milky Way is still poorly constrained, even while our knowledge of Galactic stellar abundance distributions grows ever more detailed. One reason for this shortcoming is the difficulty of determining the Galactic rotation curve in the outer disk.Recently, Carignan et al. (2006) which they might have been born but still relatively young, with smaller random velocities than older tracers (e.g. planetary nebulae). They are believed to be members of the thin disk population (e.g. Feast et al. 2006).In the late 80's, Aaronson and collaborators recognized that C stars could be useful bright kinematical probes (Aaronson et al. 1989(Aaronson et al. , 1990. They collected hundreds of radial velocities of disk (b ≈ 0 • ) C stars, with JHK photometry. The fact that these C stars were extremely unevenly distributed in galactic latitude made the interpretation of their results unreliable (Schechter et al. 1988). A study of the kinematics of the C stars toward the anticenter was published by Metzger & Schechter (1994). Beside the untimely death of Aaronson we believe there are two main reasons why these data never yielded significant insights in the kinematics of the outer disk: 1) the selection of C stars from objective-prism spectra leads to highly inhomogeneous samples containing faint bluish C stars mixed with brighter genuine N-type C stars (see Demers et al. 2002) thus artificially increasing the observed K absolute magnitude spread; 2) the estimate of distances and colors for stars with b ≈ 0 • requires a quite accurate knowledge of the extinction across the disk.More recently, Nakashima et al. (2000) obtained the rotation curve of the outer disk using the radial velocity of a few C-and O-rich SiO maser emission Miras located very close to the Galactic plane. Absolute I magnitudes were deduced from the Mira's P − L relation. Not knowing individual reddening, the a...

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Section: Distance Estimatesmentioning

confidence: 99%

C stars as kinematic probes of the Milky Way disk from 9 to 15 kpc

Demers¹,

Battinelli²

2007

A&A

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“…Schödel et al 2002;Ghez et al 2003;Eisenhauer et al 2005;Ghez et al 2005). In contrast to gas, the orbits of the stars are governed by gravitation only and therefore provide an excellent tracer for the gravitational potential in our Galactic center.…”

Section: Introductionmentioning

confidence: 99%

Stellar winds near massive black holes – the case of the S-stars

Lützgendorf

Helm

Pelupessy

et al. 2016

Mon. Not. R. Astron. Soc.

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The Galactic center provides a unique laboratory to study the interaction of a supermassive black hole (SMBH) with its gaseous and stellar environment. Simulations to determine the accretion of stellar winds from the surrounding O-stars onto the black hole have been performed earlier, but in those the presence of the S-star system was ignored. The S-stars are a group of young massive B-stars in relatively close orbits around the black hole. Here we simulate those stars in order to study their contribution to the accretion rate, without taking the more distant and massive O-stars into account. We use the Astrophysical Multi-purpose Software Environment (AMUSE) to combine gravitational physics, stellar evolution and hydrodynamics in a single simulation of the S-stars orbiting the supermassive black hole, and use this framework to determine the amount of gas that is accreted onto the black hole. We find that the accretion rate is sensitive to the wind properties of the S-stars (rate of mass-loss and terminal velocity). Our simulations are consistent with the observed accretion rate of the black hole only if the stars exhibit high wind massloss rates that are comparable with those of evolved 7-10 Myr old stars with masses of M = 19 − 25 M ⊙ . This is in contrast with observations that have shown that these stars are rather young, main-sequence B-stars. We therefore conclude that the S-stars cannot account for the accretion rate alone.

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“…Multi-wavelength detections of the radio point source at sub-millimeter, X-ray, and infrared wavelengths have also been made, showing that the luminosity associated with the black hole is many orders of magnitudes below that of active galactic nuclei (AGN) with comparable masses [5]. These observations have also shown that the emission from Sgr A* is variable [e.g., [6][7][8][9][10]. Although it is now easily detected in its bright states when its flux increases by up to an order of magnitude over time scales of 1 to 3 hours, Sgr A* is difficult to detect in its faintest states at X-ray wavelengths because of the strong diffuse background, and in the near-infrared because of confusion with nearby stellar sources [6,9].…”

Section: Introductionmentioning

confidence: 99%

Testing for periodicities in near-IR light curves of Sgr A*

Do¹,

Ghez²,

Morris³

et al. 2008

J. Phys.: Conf. Ser.

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Abstract. We present the results of near-infrared (2 µm) monitoring of Sgr A*-IR with 1 minute time sampling using laser guide star adaptive optics (LGS AO) system at the Keck II telescope. Sgr A*-IR was observed continuously for up to three hours on each of seven nights, between 2006 May and 2007 August. Sgr A*-IR is detected at all times and is continuously variable. These observations allow us to investigate Nyquist sampled periods ranging from about 2 minutes to an hour. Of particular interest are periods of ∼20 min, which corresponds to a quasi-periodic (QPO) signal claimed based upon previous near-infrared observations and interpreted as the orbit of a 'hot spot' at or near the last stable orbit of a spinning black hole. We investigate these claims by comparing periodograms of the light curves with models for red noise and find no significant deviations that would indicate QPO activity at any time scale probed in the study. We find that the variability of Sgr A* is consistent with a model based on correlated noise with a power spectrum having a frequency dependence of ∼ f −2.5 , consistent with that observed in AGNs. Furthermore, the periodograms show power down to the minimum sampling time of 2 min, well below the period of the last stable orbit of a maximally spinning black hole, indicating that the Sgr A*-IR light curves observed in this study is unlikely to be from the Keplerian motion of a single 'hot spot' of orbiting plasma.

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SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light‐Month

Cited by 612 publications

References 79 publications

C stars as kinematic probes of the Milky Way disk from 9 to 15 kpc

C stars as kinematic probes of the Milky Way disk from 9 to 15 kpc

Stellar winds near massive black holes – the case of the S-stars

Testing for periodicities in near-IR light curves of Sgr A*

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