TY - CONF
T1 - Finding the Primordial Binary Population in Sco OB2: on the interpretation of binary star observations
AU - Kouwenhoven, M. B. N.
AU - Brown, A. G. A.
AU - Portegies Zwart, S. F.
AU - Kaper, L.
PY - 2007/8/1
Y1 - 2007/8/1
N2 - The majority of stars form in of a binary or multiple systems. Detailed knowledge on the properties of binary systems thus provides important information about the process of star formation. It is difficult to study the binary population during star formation due to the large interstellar extinction. However, after the first massive stars have formed, the interstellar gas is quickly removed by stellar winds, and a freshly exposed population, the "primordial binary population" (PBP), is born. OB associations are the prime targets for finding the PBP. Due to their youth and low stellar density, the binary population has only modestly changed since formation. We targeted Sco OB2 for our study, as this is the nearest young OB association. Finding the PBP in Sco OB2 involves three steps: (1) performing observations and a literature study to obtain as much information on binarity as possible, (2) finding the true binary population by removing the selection effects from the binarity dataset, and (3) going back in time, to the PBP, by correcting for the effects of stellar and dynamical evolution that have changed the binary population over time. We present the results of our study. We have performed two binarity surveys with the adaptive optics instruments ADONIS and NACO (in order to fill up the gap between the close spectroscopic and wide visual binaries), and combine our results with literature data. We simulate associations and study the selection effects using "synthetic observations" of visual, spectroscopic, and astrometric binaries in our simulated association. By varying the association properties and performing synthetic observations, we find which properties of the binary population correspond best to the true observations, and find the true binary population. We present the results of detailed N-body simulations (including stellar and binary evolution), which we use to derive the primordial binary population in Sco OB2.
AB - The majority of stars form in of a binary or multiple systems. Detailed knowledge on the properties of binary systems thus provides important information about the process of star formation. It is difficult to study the binary population during star formation due to the large interstellar extinction. However, after the first massive stars have formed, the interstellar gas is quickly removed by stellar winds, and a freshly exposed population, the "primordial binary population" (PBP), is born. OB associations are the prime targets for finding the PBP. Due to their youth and low stellar density, the binary population has only modestly changed since formation. We targeted Sco OB2 for our study, as this is the nearest young OB association. Finding the PBP in Sco OB2 involves three steps: (1) performing observations and a literature study to obtain as much information on binarity as possible, (2) finding the true binary population by removing the selection effects from the binarity dataset, and (3) going back in time, to the PBP, by correcting for the effects of stellar and dynamical evolution that have changed the binary population over time. We present the results of our study. We have performed two binarity surveys with the adaptive optics instruments ADONIS and NACO (in order to fill up the gap between the close spectroscopic and wide visual binaries), and combine our results with literature data. We simulate associations and study the selection effects using "synthetic observations" of visual, spectroscopic, and astrometric binaries in our simulated association. By varying the association properties and performing synthetic observations, we find which properties of the binary population correspond best to the true observations, and find the true binary population. We present the results of detailed N-body simulations (including stellar and binary evolution), which we use to derive the primordial binary population in Sco OB2.
M3 - Paper
ER -