Stellar orbits near Sagittarius A

By A. Eckart, R. Genzel, T. Ott, R. Schoedel. 2002

140 citations recorded by the source corpus.

The SHARP/NTT stellar proper motion data now cover an interval from 1992 to 2000 and allow us to determine orbital accelerations for some of the most central stars of the Galaxy. We confirm the stellar acceleration measurements obtained by Ghez et al. with NIRC at the Keck telescope. Our analysis differs in three main points from that of Ghez et al.: (1) we combine the high-precision but shorter time-scale NIRC/Keck data with the lower precision but longer time-scale SHARP/NTT data set; (2) we statistically correct the observed accelerations for geometrical projection effects; (3) we exclude star S8 from the analysis of the amount and position of the central mass. From the combined SHARP/NTT and NIRC/Keck data sets we show that the stars S2, and most likely S1 and S8 as well, are on bound, fairly inclined (60°<i<80°), and eccentric (0.4<e<0.95) orbits around a central dark mass. The combination of both data sets results in a position of this central mass of and of the nominal radio position of Sgr A*. The mean statistically corrected enclosed mass derived from accelerations is Macc=(5±3)×106 M⊙ with current radial separations of S1 and S2 from Sgr A* of about 8–10 mpc. This enclosed mass estimate is derived from individual stellar orbits as close to the massive black hole at the centre of the Milky Way as currently possible. Although the uncertainties are large, this estimate is fully consistent with the enclosed mass range of (2.6–3.3)×106 M⊙ derived by Genzel et al. from radial and/or proper motion velocities of a homogenized sample of sources. Star S8 was excluded from the analysis, since for the current proper motion velocity and radial separation from the centre we find that the measured acceleration requires orbital motion around a compact object with a mass in excess of 3×106 M⊙. The data suggest either that this star was or is subject to a close interaction with a different object or that its position measurements are influenced by the emission of a different cluster star. Therefore we base the analysis of the enclosed mass solely on the available data for stars S1 and S2. We also discuss two late-type stars with projected separations from Sgr A* of about 0.5 and 1 arcsec. In addition to proper motions, these stars have known radial velocities. Orbit calculations indicate that such stars are very likely at larger physical distances from the centre and part of the larger scale central stellar cluster with a core radius of approximately 0.3 pc.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/25eb3ca443df5a8d1773d486db3ba0ad9dddb90b

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In Astronomy and Astrophysics

1. T. Alexander
2. R. Genzel
3. A. Ghez
4. A. Eckart
5. T. Ott
6. F. Antonini
7. R. Schödel
8. K. Matthews

In Atomic and Molecular Physics, and Optics

1. T. Alexander
2. T. Ott
3. R. Genzel
4. A. Eckart
5. A. Ghez
6. R. Schödel
7. Mark R. Morris
8. R. Schoedel

In Instrumentation

1. T. Alexander
2. M. Miller
3. A. Eckart
4. R. Schödel
5. R. Genzel
6. A. Ghez
7. F. Rasio
8. E. Colbert

Citations in the corpus

• AN IMPROVED DISTANCE AND MASS ESTIMATE FOR SGR A* FROM A MULTISTAR ORBIT ANALYSIS (2016, background): “G A ] 1 9 Ju l 2 accelerations of these stars implies that they move in the gravitational potential of a concentrated dark mass (Eckart & Genzel 1997; Ghez et al. 1998; Ghez et al. 2000; Eckart et al. 2002).”
• Polarimetry of near-infrared flares from Sagittarius A* (2006, background): “…(3.6 ± 0.3)× 106 M Massive Black Hole (MBH) at the center of the Milky Way at the position of the compact radio source SgrA* (Eisenhauer et al. 2005; Ghez et al. 2005; Eisenhauer et al. 2003; Schödel et al. 2003; Eckart et al. 2002; Schödel et al. 2002, for a recent review see Eckart et al. 2005).”
• Fluorescent iron lines as a probe of astrophysical black hole systems (2002, background): “Furthermore, studies of the orbital dynamics (which now include measured accelerations as well as velocities; [17,18]) constrain the central mass to be extremely compact.”
• Formation of Massive Black Holes in Dense Star Clusters. I. Mass Segregation and Core Collapse (2003, background): “The evidence is particularly compelling for a BH of mass ≃ 4 × 10 6 M ⊙ at the center of our own Galaxy (Eckart et al. 2002; Ghez et al. 2000, 2003; Schödel et al. 2002).”
• A DISK OF YOUNG STARS AT THE GALACTIC CENTER AS DETERMINED BY INDIVIDUAL STELLAR ORBITS (2008, unknown): “′′4 (0.016 pc, Ghez et al. 2000; Eckart et al. 2002; Ghez et al. 2005b; Eisenhauer et al. 2005).”
• Stellar Dynamics in the Central Arcsecond of Our Galaxy (2003, methodology): “The gravitational potential in the central 0.5 pc is dominated by that of a point mass (Eckart &Genzel 1997; Genzel et al. 2000; Ghez et al. 2000; Eckart et al. 2002; Schödel et al. 2002).”
• A star in a 15.2-year orbit around the supermassive black hole at the centre of the Milky Way (2002, methodology): “Measurements of stellar velocities 2–7 and the discovery of variable X-rayemission 8 have provided strong evidence in favour of such a black hole at the centre of the Milky Way, but have hitherto been unable to rule out conclusively the presence of alternative concentrations of mass.”
• Stellar Orbits around the Galactic Center Black Hole (2003, background): “…value obtained from the velocity dispersion analysis and its location to that inferred for Sgr A* by Menten et al. (1997), Ghez et al. (2000) and Eckart et al. (2002) obtained the first crude orbital solutions; these experiments revealed that orbital periods for S0-2 and S0-1 could be as short…”
• The Stellar Cusp around the Supermassive Black Hole in the Galactic Center (2003, unknown): “…data (projected mass estimators, Jeans equation modeling, nonparametric modeling) imply that the ð2 3:3Þ 106 M central dark mass is concentrated on scales less than 10 lt-days (Eckart & Genzel 1996, 1997; Ghez et al. 1998, 2000; Genzel et al. 2000; Chakrabarti & Saha 2001; Eckart et al. 2002).”
• The Need for a Second Black Hole at the Galactic Center (2003, background): “Measurement of significant deviations from linear motion has yielded orbital solutions for several of the stars closest (< 0.016 pc) to the supermassive black hole (SBH) at the Galactic center(Eckart et al. 2002; Ghez et al. 2000, 2003a,b; Schödel et al. 2002).”
• Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole with Stellar Orbits (2008, background): “Patience alone permitted new astrometric measurements that yielded the first accelerations (Ghez et al. 2000; Eckart et al. 2002), which suggested that the orbital period of the best characterized star, S0-2, could be as short as 15 yr.”
• The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy’s Central Black Hole: A Paradox of Youth (2003, background): “…of the sky, yielding estimates of the projected velocities (Eckart & Genzel 1996; Ghez et al. 1998), projected accelerations (Ghez et al. 2000; Eckart et al. 2002), and three-dimensional orbital motions (Schödel et al. 2002; Ghez et al. 2003), which each provided a successively stronger case…”
• Intermediate - mass black holes (2003, background): “…orbits have been tracked around the ∼ 3× 106 M⊙ black hole in the center of our Galaxy (e.g., Eckart & Genzel 1996; Ghez et al. 1998; Ghez et al. 2000; Eckart et al. 2002; Schödel et al. 2002; Ghez et al. 2003a,b), following up earlier observations of gas motion in the Galactic center that…”
• The nuclear star cluster of the Milky Way: proper motions and mass (2009, background): “Mass estimates of Sgr A* based on proper motions (e.g. Ghez et al. 1998; Chakrabarty & Saha 2001; Eckart et al. 2002; Genzel et al. 2000) have routinely provided lower values than what has been found by the analysis of stellar orbits.”