Confusing Binaries: The Role of Stellar Binaries in Biasing Disk Properties in the Galactic Center

Abstract

The population of young stars near the Supermassive black hole (SMBH) in the Galactic Center (GC) has presented an unexpected challenge to theories of star formation. Kinematics measurements of these stars have revealed a stellar disk structure (with an apparent 20% disk membership) that has provided important clues to the origin of these mysterious young stars. However many of the apparent disk properties are difficult to explain, including the low disk membership fraction and the high eccentricities, given the youth of this population. Thus far, all efforts to derive the properties of this disk have made the simplifying assumption that stars at the GC are single stars. Nevertheless, stellar binaries are prevalent in our Galaxy, and recent investigations suggested that they may also be abundant in the Galactic Center. Here we show that binaries in the disk can largely alter the apparent orbital properties of the disk. The motion of binary members around each other adds a velocity component, which can be comparable to the magnitude of the velocity around the SMBH in the GC. Thus, neglecting the contribution of binaries can significantly vary the inferred stars' orbital properties. While the disk orientation is unaffected the apparent disk's 2D width will be increased to about 11.2• , similar to the observed width. For a population of stars orbiting the SMBH with zero eccentricity, unaccounted for binaries will create a wide apparent eccentricity distribution with an average of 0.23. This is consistent with the observed average eccentricity of the stars' in the disk. We suggest that this high eccentricity value, which poses a theoretical challenge, may be an artifact of binary stars. Finally, our results suggest that the actual disk membership might be significantly higher than the one inferred by observations that ignore the contribution of binaries, alleviating another theoretical challenge.

Monitoring dusty sources in the vicinity of Sagittarius A*

“…Nevertheless, there are as yet no such detections of X-ray and radio counterparts of the dusty sources. Naoz et al (2018) discuss, that binaries could play a major role by contributing and explaining observed properties of the GC disk. With that, the number of similar objects as discussed here could be much higher but also expected.…”

“…They might be dust embedded pre-main-sequence stars presumably forming a small bow shock (Shahzamanian et al 2016;Zajaček et al 2017). Yoshikawa et al (2013), Yusef-Zadeh et al (2017a), and Naoz et al (2018) discuss and show several plausible scenarios that underline the presence of binaries, YSOs, and intrinsically polarized low-mass stars as well as bow-shock sources in the GC close to Sgr A*.…”

A population of dust-enshrouded objects orbiting the Galactic black hole

“…To estimate the binary fraction from the current number of G objects, we assume that all observed G objects are binary merger products (indeed we expect a large fraction of binaries in the Galactic Centre based on the orbital configuration of the stellar disk 56 ). We assume that all six of the G objects discussed here are relatively recent binary mergers, and that their progenitor binary systems were formed in the latest known star formation event 4-6 Myr ago.…”

Black hole and neutron star mergers in galactic nuclei: the role of triples

“…There are at least 3 known stellar binaries within the central 0.2 pc of the Galactic Centre (e.g. Naoz et al 2018;Ott et al 1999;Rafelski et al 2007). What's more, it is still possible that many of the observed S-stars are unresolved binaries (e.g.…”