The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy’s Central Black Hole: A Paradox of Youth

Ghez, A. M.; Duchêne, Gaspard; Matthews, K.; Hornstein, S. D.; Tanner, Angelle; Larkin, James E.; Morris, Mark; Becklin, E. E.; Salim, Samir; Kremenek, Ted; Thompson, D.J.; Soifer, B. T.; Neugebauer, G.; McLean, Ian S.

doi:10.1086/374804

Cited by 630 publications

(726 citation statements)

References 29 publications

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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%

“…⋆ E-mail: email@address (AVR); otheremail@otheraddress (ANO) Schödel et al (2002) and Ghez et al (2003) carried out high resolution near-IR imaging and spectroscopy of the central region of our Milky Way. They found a star (nowadays known as S2) closely bound to a central massive object with an orbital period of 15.2 years (see also Gillessen et al 2009a).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

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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“…Over 120 members of the YNC have been identified via spectroscopy showing either hydrogen and helium lines or featureless blue continuum characteristic of hot Wolf-Rayet (WR) or OB stars (Allen et al 1990;Krabbe et al 1991Krabbe et al , 1995Blum et al 1995;Tamblyn et al 1996;Najarro et al 1997;Ghez et al 2003;Paumard et al 2006;Bartko et al 2010;Do et al 2013). The current generation of surveys utilize adaptive optics fed integral field spectroscopic instruments such as OSIRIS on Keck or SINFONI on VLT.…”

Section: The Young Nuclear Clustermentioning

confidence: 99%

Young stars in the Galactic center

Lu¹,

Ghez

Morris

et al. 2013

Proc. IAU

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Abstract. The central parsec of our Galaxy hosts not only a supermassive black hole, but also a large population of young stars (age <6 Myr) whose presence is puzzling given how inhospitable the region is for star formation. The strong tidal forces require gas densities many orders of magnitude higher than is found in typical molecular clouds. Kinematic observations of this young nuclear cluster show complex structures, including a well-defined inner disk, but also a substantial off-disk population. Spectroscopic and photometric measurements indicate the initial mass function (IMF) differs significantly from the canonical IMF found in the solar neighborhood. These observations have led to a number of proposed star formation scenarios, such as an infalling massive star cluster, a single infalling molecular cloud, or cloud-cloud collisions. I will review recent works on the young stars in the central parsec and discuss connections with young nuclear star clusters in other galaxies, such as M31, and with star formation in the larger central molecular zone.

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“…[1][2][3][4]. 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].…”

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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The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy’s Central Black Hole: A Paradox of Youth

Cited by 630 publications

References 29 publications

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

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

Young stars in the Galactic center

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

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