Abstract
We estimated the contribution of binary systems to the velocity dispersion inside OB-associations derived from Gaia DR2 proper motions. The maximum contribution to the velocity dispersion is given by the systems with the period of revolution of \(P = 5.9\) yr whose components shift by a distance of about the diameter of the system during the base-line time of Gaia DR2 observations. We employed two methods to study the motion of the photocenter of the binary system: the first one uses the total displacement between the initial and final visibility periods and the second one is based on solving a system of \(n\) equations defining the displacements at the times \({{t}_{n}}\). The first and second methods yield very similar \({{\sigma }_{{bn}}}\) values of 0.90 and 0.87 km/s, respectively. Taking into account the fact that orbits are elliptical slightly decreases the inferred \({{\sigma }_{{bn}}}\). We estimated the eccentricity-averaged \(\overline {{{\sigma }_{{bn}}}} \) value to be \(\overline {{{\sigma }_{{bn}}}} = 0.81\) km/s assuming that the orbital eccentricities of massive binary systems are distributed uniformly in the \(e \in [0,0.9]\) interval. The choice of the exponent \(\gamma \) in the power-law distribution, \({{p}_{q}} \sim {{q}^{\gamma }}\), of the component-mass ratios \(q = {{M}_{2}}{\text{/}}{{M}_{1}}\) of binary systems appears to have little effect on \({{\sigma }_{{bn}}}\). A change of \(\gamma \) from 0 (flat distribution) to \( - \)2.0 (preponderance of systems with low-mass components) changes \({{\sigma }_{{bn}}}\) from 0.90 to 1.07 km/s. The paper is based on a presentation made at the conference “Astrometry yesterday, today, tomorrow” (SAI MSU, Oct. 14–16, 2019).
Similar content being viewed by others
REFERENCES
T. Prusti, J. H. J. de Bruijne, A. G. A. Brown, A. Vallenari, et al., Astron. Astrophys. 595, A1 (2016).
A. G. A. Brown, A. Vallenari, T. Prusti, de J. H. J. Bruijne, et al., Astron. Astrophys. 616, A1 (2018).
L. Lindegren, J. Hernandez, A. Bombrun, S. Klioner, et al., Astron. Astrophys. 616, A2 (2018).
V. A. Ambartsumian, Astron. Zh. 26, 3 (1949).
C. Blaha and R. M. Humphreys, Astron. J. 98, 1598 (1989).
B. G. Elmegreen, Mon. Not. R. Astron. Soc. 203, 1011 (1983).
R. B. Larson, Mon. Not. R. Astron. Soc. 194, 809 (1981).
M. R. Krumholz, C. D. Matzner, and C. F. McKee, Astrophys. J. 653, 361 (2006).
A. M. Melnik and A. K. Dambis, Mon. Not. R. Astron. Soc. 472, 3887 (2017).
A. M. Melnik and A. K. Dambis, Mon. Not. R. Astron. Soc. 493, 2339 (2020).
D. B. Sanders, N. Z. Scoville, and P. M. Solomon, A-strophys. J. 289, 373 (1985).
B. D. Mason, D. R. Gies, W. I. Hartkopf, W. G. Bagnuolo, T. ten Brummelaar, and H. A. McAlister, -Astron. J. 115, 821 (1998).
H. Sana, in The Lives and Death-Throes of Massive Stars, Proc. IAU Symp. 329, 110 (2017).
H. Sana, A. de Koter, S. E. de Mink, P. R. Dunstall, et al., Astron. Astrophys. 550, A107 (2013).
M. Moe and R. di Stefano, Astrophys. J. Suppl. 230, 15 (2017).
F. Arenou, X. Luri, C. Babusiaux, C. Fabricius, et al., Astron. Astrophys. 616, A17 (2018).
C. Fabricius, U. Bastian, J. Portell, J. Castaneda, et al., Astron. Astrophys. 595, A3 (2016).
N. Duric, Advanced Astrophysics (Cambridge Univ. Press, Cambridge, UK, 2004).
E. J. Aldoretta, S. M. Caballero-Nieves, D. R. Gies, E. P. Nelan, et al., Astron. J. 149, 26 (2015).
E. Öpik, Publ. Observ. Astron. Univ. Tartu 28, 1 (1924).
H. A. Abt, Ann. Rev. Astron. Astrophys. 21, 343 (1983).
H. Sana and C. J. Evans, IAU Symp. 272, 474 (2011).
D. Michalik, L. Lindegren, and D. Hobbs, Astron. A-strophys. 574, A115 (2015).
H. A. Kobulnicky, D. C. Kiminki, M. J. Lundquist, J. Burke, et al., Astrophys. J. Suppl. 213, 34 (2014).
O. Y. Malkov, V. S. Tamazian, J. A. Docobo, and D. A. Chulkov, Astron. Astrophys. 546, A69 (2012).
G. N. Duboshin, Celestial Mechanics: The Main Problems and the Methods (Moscow, Nauka, 1975) [in Russian].
J. M. A. Danby, Fundamentals of Celestial Mechanics, 2nd ed. (Willmann-Bell, Richmond, VA, 1988).
P. C. Myers, T. M. Dame, P. Thaddeus, R. S. Cohen, R. F. Silverberg, E. Dwek, and M. G. Hauser, Astrophys. J. 301, 398 (1986).
N. J. Evans, M. M. Dunham, J. K. Jorgensen, M. L. Enoch, et al., Astrophys. J. Suppl. 181, 321 (2009).
P. Garcia, L. Bronfman, L.-A. Nyman, T. M. Dame, and A. Luna, Astrophys. J. Suppl. 212, 2 (2014).
ACKNOWLEDGMENTS
This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data P-rocessing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.
Funding
A.D. acknowledges the support from the Russian Foundation for Basic Research (project nos. 18-02-00890 and 19-02-00611).
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Melnik, A.M., Dambis, A.K. Contribution of Binary Stars to the Velocity Dispersion inside OB Associations with Gaia DR2 Data. Astron. Rep. 65, 71–81 (2021). https://doi.org/10.1134/S106377292033001X
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1134/S106377292033001X