Constraining Compact Object Formation with 2M0521

Abstract

We show that the recently discovered binary 2M05215658+4359220 (2M0521), comprised of a giant star (GS) orbiting a suspected black hole (BH) in a ∼ 80 day orbit, may be instrumental in shedding light on uncertain BH-formation physics and can be a test case for studying wind accretion models. Using binary population synthesis with a realistic prescription for the star formation history and metallicity evolution of the Milky Way, we analyze the evolution of binaries containing compact objects (COs) in orbit around GSs with properties similar to 2M0521. We find ∼ 10 2 − 10 3 CO-GS binaries in the Milky Way observable by Gaia and 0 − 12 BH-GS and 0 − 1 neutron star-GS binaries in the Milky Way with properties similar to 2M0521. We find that all CO-GSs with P orb < 5 yr, including 2M0521, go through a common envelope (CE) and hence form a class of higher mass analogs to white dwarf post-CE binaries. We further show how the component masses of 2M0521-like binaries depend strongly on the supernova-engine model we adopt. Thus, an improved measurement of the orbit of 2M0521, imminent with Gaia's third data release, will strongly constrain its component masses and as a result inform supernova-engine models widely used in binary population synthesis studies. These results have widespread implications for the origins and properties of CO binaries, especially those detectable by LIGO and LISA. Finally, we show that the reported X-ray non-detection of 2M0521 is a challenge for wind accretion theory, making 2M0521-like CO-GS binaries a prime target for further study with accretion models.

Weighing the Darkness: Astrometric Mass Measurement of Hidden Stellar Companions Using Gaia

“…We find that, for an average of 75 observations, the total number of systems that have mass measurements of σ M 3 2 M −2 tot / M 3 2 M −2 tot < 0.1 is 45±7 BH-GS binaries and 90±9 NS-GS binaries (see Table 1). We note that this is fewer by a factor of 2 compared to the numbers deemed observable by Gaia in Breivik et al (2019). This is because in that earlier work we used an older, more optimistic estimate of the astrometric precision of Gaia.…”

“…These estimates are produced under the assumption of one particular parameterization of binary evolution. In Breivik et al (2019), we demonstrate that the population of astrometric binaries containing a BH depends strongly on which parameters we choose to adopt; in that work, we focused on two separate BH mass functions from Fryer et al (2012). Although we do not explicitly compare the two different prescriptions here, each will certainly affect the resulting yield of detached BH systems that Gaia will detect.…”

“…We apply this estimate to the simulated population of BHs and NSs orbiting giant stars (GSs) that are observable by Gaia in Breivik et al (2019). We find that, for an average of 75 observations, the total number of systems that have mass measurements of σ M 3 2 M −2 tot / M 3 2 M −2 tot < 0.1 is 45±7 BH-GS binaries and 90±9 NS-GS binaries (see Table 1).…”

The Supersonic Project: SIGOs, A Proposed Progenitor to Globular Clusters, and Their Connections to Gravitational-wave Anisotropies

“…We stress, however, that Figure 6 and this discussion represent an ideal case where we assume that all SIGOs are directly linked to globular clusters and that their distribution (as well as the distribution of BH mergers) does not vary with redshift. While SIGOs may be linked to globular clusters (e.g., Naoz & Narayan 2014;Chiou et al 2019), it is unlikely that all SIGOs become globular clusters (e.g., Popa et al 2016;Chiou et al 2021) and we have yet to test the redshift evolution of 14 However, other processes have been suggested to be comparable, from isolating binaries (e.g., Belczynski et al 2016;de Mink & Mandel 2016;Marchant et al 2016;Breivik et al 2019Breivik et al , 2020 to dynamical evolution at nuclear star clusters at the center of galaxies (e.g., Hoang et al 2018;Stephan et al 2019;Wang et al 2021). SIGOs over large ranges.…”

All-sky visible and near infrared space astrometry

“…These populations will substantially impact a broad range of fields. For instance, the astrometric detection of even a handful of stellar-mass black holes with main sequence or giant companions will resolve outstanding problems in accretion physics and black hole formation physics [38]. A NIR mission would allow exoplanet or compact object detection around cooler, lower mass stars than those observed by Gaia.…”