Evidence of a Decreased Binary Fraction for Massive Stars within 20 milliparsecs of the Supermassive Black Hole at the Galactic Center

Chu, Devin S; Do, Tuan; Ghez, A. M.; Gautam, Abhimat K.; O'Neil, K.; Hosek, Matthew W; Hees, A.; Naoz, Smadar; Sakai, Shoko; Lu, Jessica R.; Chen, Zhuo; Bentley, Rory O; Becklin, Eric E; Matthews, K.

doi:10.3847/1538-4357/acc93e

Cited by 8 publications

(17 citation statements)

References 66 publications

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“…The full 1129 star sample is listed in Appedix Table 7. There are 102 known young stars in our sample: 101 confirmed to be earlytype (Wolf-Rayet (W-R), O type, or B type) with spectroscopic observations reported in previous publications (Blum et al 2003;Paumard et al 2006;Bartko et al 2009;Gillessen et al 2009;Pfuhl et al 2011;Do et al 2013;Feldmeier-Krause et al 2015;Chu 2020), and the star S2-36 with spectroscopic observations reported in this work (Appendix C). The known young stars used in our analysis are listed in Table 2.…”

Section: Stellar Samplementioning

confidence: 66%

“…The young star stellar binary fraction is of particular importance for constraints on star formation in the GC, and the implications of the high binary fraction are considered in more detail in Section 4.2. We consider our measurements of the GC binary fraction with the recent measurement of a low binary fraction for the GC young S stars by Chu et al (2023), and what the combined results can inform about the GC dynamical environment in Section 4.3. Finally, other implications for the GC environment from our results are considered in Section 4.4.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, spectroscopic surveys of the GC stellar population will be more deeply sensitive to less edge-on inclination binary systems, allowing a more complete census of the binary population. With groundbased AO data sets, sensitivity to binary stars at  ¢ m 16 K (corresponding to B-type and more luminous stars for the GC young star population) can be reached (Do et al 2019b;Chu et al 2023). Ongoing spectroscopic surveys with JWST will allow deeper spectroscopy to  ¢ m 19 K (corresponding to A-type and more luminous stars for the GC young star population).…”

Section: Dependence Of Binary Fraction Measurement On Mock Population...mentioning

confidence: 99%

“…However, since the inferred binary fraction can be affected by observational cadence and experimental precision, previous GC studies have been limited in their constraints on the underlying intrinsic binary fraction of GC young stars. Chu et al (2023) used spectroscopic observations to constrain the intrinsic binary fraction of young B stars in the S-star population, located 1″ from Sgr A * (corresponding to 0.04 pc from the SMBH), finding that it can be at most 47% with their null detection. This study was sensitive to a median of ≈50 km s −1 in RV variation, corresponding to a median upper limit on binary companion mass of 3.7 M e for the 16 young stars in their sample.…”

Section: Introductionmentioning

confidence: 99%

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An Estimate of the Binary Star Fraction among Young Stars at the Galactic Center: Possible Evidence of a Radial Dependence

Gautam,

Do,

Ghez

et al. 2024

ApJ

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We present the first estimate of the intrinsic binary fraction of young stars across the central ≈0.4 pc surrounding the supermassive black hole (SMBH) at the Milky Way Galactic center (GC). This experiment searched for photometric variability in 102 spectroscopically confirmed young stars, using 119 nights of 10″ wide adaptive optics imaging observations taken at W. M. Keck Observatory over 16 yr in the K ′ -[2.1 μm] and H-[1.6 μm] bands. We photometrically detected three binary stars, all of which are situated more than 1″ (0.04 pc) from the SMBH and one of which, S2-36, is newly reported here with spectroscopic confirmation. All are contact binaries or have photometric variability originating from stellar irradiation. To convert the observed binary fraction into an estimate of the underlying binary fraction, we determined the experimental sensitivity through detailed light-curve simulations, incorporating photometric effects of eclipses, irradiation, and tidal distortion in binaries. The simulations assumed a population of young binaries, with stellar ages (4 Myr) and masses matched to the most probable values measured for the GC young star population, and underlying binary system parameters (periods, mass ratios, and eccentricities) similar to those of local massive stars. As might be expected, our experimental sensitivity decreases for eclipses narrower in phase. The detections and simulations imply that the young, massive stars in the GC have a stellar binary fraction ≥71% (68% confidence), or ≥42% (95% confidence). This inferred GC young star binary fraction is consistent with that typically seen in young stellar populations in the solar neighborhood. Furthermore, our measured binary fraction is significantly higher than that recently reported by Chu et al. based on radial velocity measurements for stars ≲1″ of the SMBH. Constrained with these two studies, the probability that the same underlying young star binary fraction extends across the entire region is <1.4%. This tension provides support for a radial dependence of the binary star fraction, and therefore, for the dynamical predictions of binary merger and evaporation events close to the SMBH.

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Section: Stellar Samplementioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Section: Dependence Of Binary Fraction Measurement On Mock Population...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An Estimate of the Binary Star Fraction among Young Stars at the Galactic Center: Possible Evidence of a Radial Dependence

Gautam,

Do,

Ghez

et al. 2024

ApJ

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“…As discussed above we will show in an accompanying paper that this correlation arises naturally from the perturbation of an intermediate-mass companion (X. Zheng et al 2024, in preparation) without invoking any tidal-disruption-of-binary hypothesis (Hills 1988;Chu et al 2023). 4)).…”

Section: Summary and Discussionmentioning

confidence: 88%

The Orbital Structure and Selection Effects of the Galactic Center S-star Cluster

Burkert,

Gillessen,

Lin

et al. 2024

ApJ

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The orbital distribution of the S-star cluster surrounding the supermassive black hole in the center of the Milky Way is analyzed. A tight dependence of the pericenter distance r p on orbital eccentricity e ⋆ is found, log ( r p ) ∼ ( 1 − e ⋆ ) , which cannot be explained simply by a random distribution of semimajor axis and eccentricities. No stars are found in the region with high e ⋆ and large log ( r p ) or in the region with low e ⋆ and small log ( r p ) . Although the sample is still small, the G-clouds show a very similar distribution. The likelihood P ( log ( r p ) , ( 1 − e ⋆ ) ) to determine the orbital parameters of S-stars is determined. P is very small for stars with large e ⋆ and large log ( r p ) . S-stars might exist in this region. To determine their orbital parameters, one however needs observations over a longer time period. On the other hand, if stars would exist in the region of low log ( r p ) and small e ⋆, their orbital parameters should by now have been determined. That this region is unpopulated therefore indicates that no S-stars exist with these orbital characteristics, providing constraints for their formation. We call this region, defined by log ( r p / AU ) < 1.57 + 2.6 ( 1 − e ⋆ ) , the zone of avoidance. Finally, it is shown that the observed frequency of eccentricities and pericenter distances is consistent with a random sampling of log ( r p ) and e ⋆ if one takes into account the fact that no stars exist in the zone of avoidance and that orbital parameters cannot yet be determined for stars with large r p and large e ⋆.

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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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Evidence of a Decreased Binary Fraction for Massive Stars within 20 milliparsecs of the Supermassive Black Hole at the Galactic Center

Cited by 8 publications

References 66 publications

An Estimate of the Binary Star Fraction among Young Stars at the Galactic Center: Possible Evidence of a Radial Dependence

An Estimate of the Binary Star Fraction among Young Stars at the Galactic Center: Possible Evidence of a Radial Dependence

The Orbital Structure and Selection Effects of the Galactic Center S-star Cluster

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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