Searching for solar siblings in APOGEE and Gaia DR2 with N-body simulations

Abstract

We make use of APOGEE and Gaia data to identify stars that are consistent with being born in the same star cluster as the Sun. We limit our analysis to stars that match solar abundances within their uncertainties, as they could have formed from the same Giant Molecular Cloud (GMC) as the Sun. We constrain the range of orbital actions that solar siblings can have with a suite of simulations of solar birth clusters evolved in static and time-dependent tidal fields. In the static tidal field, which contains a bulge, disk, and halo, simulated solar siblings all have 5.8 < J R < 7.4 km s −1 kpc, 1848 < L z < 1868 km s −1 kpc, and 0.27 < J z < 0.49 km s −1 kpc. Given the actions of stars in APOGEE and Gaia , we find one star (Solar Sibling 1) that meets these criteria and shares chemistry with the Sun. Incorporating the effects of a bar and spiral arms increases the range of possible J R and L z for cluster escapers, extending the candidate list to 203 stars. Adding GMCs to the potential can eject solar siblings out of the plane of the disk and increase their J z , resulting in a final candidate list of 550 stars. The entire suite of simulations indicate that solar siblings should have J R < 116 km s −1 kpc, 353 < L z < 2110 km s −1 kpc, and J z < 0.8 km s −1 kpc. Given these criteria, it is most likely that the Sun's birth cluster has reached dissolution and is not the commonly cited open cluster M67.

Keeping It Cool: Much Orbit Migration, yet Little Heating, in the Galactic Disk

“…From our model fit, 95% of these stars should currently have 550 kpc km s −1 L z 2770 kpc km s −1 and J R 130 kpc km s −1 . This is roughly consistent with the results of Webb et al (2020), who used simulations to investigate the present-day positions of solar siblings in the (L z , J R , J z ) space in different possible potentials and constrained present-day solar siblings' angular momenta to 353 kpc km s −1 L z 2110 kpc km s −1 and J R 116 kpc km s −1 . The exact values of these bounds should depend on the detailed history of the Milky Way disk, but their model gives an angular momentum range of about 2000 kpc km s −1 , which is close to our 2σ(τ) value.…”

“…Therefore, the Sun could well have been born in a (possibly now fully disrupted) birth cluster that is different from the usual candidate cluster M67, which is known to have a similar age and metallicity to those of the Sun (Yadav et al 2008;Heiter et al 2014). Recent work has shown that M67 is unlikely to be the Sun's birth cluster, but this is not fully ruled out (Jørgensen & Church 2020;Webb et al 2020). Instead, the Sun's birth cluster could have formed at the same radius and time, but at a distinct azimuth from M67.…”

An upper limit for the growth of inner planets?

“…If such a cluster initially had ∼ 10 4 members (Hurley et al 2005), this would be consistent with constraints from the Solar System properties (Portegies Zwart 2009;Adams 2010;Pfalzner 2013;Moore et al 2020). However, this scenario remains a subject of debate (Jørgensen & Church 2020;Webb et al 2020).…”

Bridging the Planet Radius Valley: Stellar Clustering as a Key Driver for Turning Sub-Neptunes into Super-Earths

“…Both options are not without difficulties. The overdensities arising from phase space clustering at birth may disperse on sub-Gyr timescales (Krumholz et al 2019;Webb et al 2020), much shorter than the ages considered here. This problem could be alleviated by the prediction that the destabilising effects of encounters persist well after a planetary system has escaped the birth environment (e.g.…”