Analysis of Selected Runaway Stars in the Orion Nebula Based on Data from the Gaia EDR3 Catalogue

ABSTRACT Planetary systems appear to form contemporaneously around young stars within young star-forming regions. Within these environments, the chances of survival, as well as the long-term evolution of these systems, are influenced by factors such as dynamical interactions with other stars and photoevaporation from massive stars. These interactions can also cause young stars to be ejected from their birth regions and become runaways. We present examples of such runaway stars in the vicinity of the Orion Nebula Cluster (ONC) found in Gaia DR2 data that have retained their discs during the ejection process. Once set on their path, these runaways usually do not encounter any other dense regions that could endanger the survival of their discs or young planetary systems. However, we show that it is possible for star–disc systems, presumably ejected from one dense star-forming region, to encounter a second dense region, in our case the ONC. While the interactions of the ejected star–disc systems in the second region are unlikely to be the same as in their birth region, a second encounter will increase the risk to the disc or planetary system from malign external effects.

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Runaway and walkaway stars from the ONC with Gaia DR2

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1228 ◽

2020 ◽

Vol 495 (3) ◽

pp. 3104-3123 ◽

Cited By ~ 7

Author(s):

Christina Schoettler ◽

Jos de Bruijne ◽

Eero Vaher ◽

Richard J Parker

Keyword(s):

Initial Conditions ◽

Young Star ◽

Three Dimensions ◽

Orion Nebula ◽

Star Forming ◽

Star Forming Regions ◽

Trace Back ◽

Runaway Stars ◽

Gaia Dr2 ◽

Age Estimates

ABSTRACT Theory predicts that we should find fast, ejected (runaway) stars of all masses around dense, young star-forming regions. N-body simulations show that the number and distribution of these ejected stars could be used to constrain the initial spatial and kinematic substructure of the regions. We search for runaway and slower walkaway stars within 100 pc of the Orion Nebula Cluster (ONC) using Gaia DR2 astrometry and photometry. We compare our findings to predictions for the number and velocity distributions of runaway stars from simulations that we run for 4 Myr with initial conditions tailored to the ONC. In Gaia DR2, we find 31 runaway and 54 walkaway candidates based on proper motion, but not all of these are viable candidates in three dimensions. About 40 per cent are missing radial velocities, but we can trace back nine 3D runaways and 24 3D walkaways to the ONC, all of which are low/intermediate mass (<8 M⊙). Our simulations show that the number of runaways within 100 pc decreases the older a region is (as they quickly travel beyond this boundary), whereas the number of walkaways increases up to 3 Myr. We find fewer walkaways in Gaia DR2 than the maximum suggested from our simulations, which may be due to observational incompleteness. However, the number of Gaia DR2 runaways agrees with the number from our simulations during an age of ∼1.3–2.4 Myr, allowing us to confirm existing age estimates for the ONC (and potentially other star-forming regions) using runaway stars.

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On the formation of runaway stars BN and x in the Orion Nebula Cluster

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732472 ◽

2018 ◽

Vol 612 ◽

pp. L7 ◽

Cited By ~ 10

Author(s):

J. P. Farias ◽

J. C. Tan

Keyword(s):

Star Formation ◽

Massive Star ◽

Close Binary ◽

Orion Nebula ◽

Massive Star Formation ◽

Star Forming ◽

Runaway Stars

We explore scenarios for the dynamical ejection of stars BN and x from source I in the Kleinmann-Low nebula of the Orion Nebula Cluster (ONC), which is important because it is the closest region of massive star formation. This ejection would cause source I to become a close binary or a merger product of two stars. We thus consider binary-binary encounters as the mechanism to produce this event. By running a large suite of N-body simulations, we find that it is nearly impossible to match the observations when using the commonly adopted masses for the participants, especially a source I mass of 7 M⊙. The only way to recreate the event is if source I is more massive, that is, ~20 M⊙. However, even in this case, the likelihood of reproducing the observed system is low. We discuss the implications of these results for understanding this important star-forming region.

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