Abstract
This chapter explores how we might use the observed statistics of blue stragglers in globular clusters to shed light on their formation. This means we will touch on topics also discussed elsewhere in this book, such as the discovery and implications of bimodal radial distributions and the “double sequences” of blue stragglers that have recently been found in some clusters. However, we will focus particularly on the search for a “smoking gun” correlation between the number of blue stragglers in a given globular cluster and a physical cluster parameter that would point towards a particular formation channel. As we shall see, there is little evidence for an intrinsic correlation between blue straggler numbers and stellar collision rates, even in dense cluster cores. On the other hand, there is a clear correlation between blue straggler numbers and the total (core) mass of the cluster. This would seem to point towards a formation channel involving binaries, rather than dynamical encounters. However, the correlation between blue straggler numbers and actual binary numbers—which relies on recently determined empirical binary fractions—is actually weaker than that with core mass. We explain how this surprising result may be reconciled with a binary formation channel if binary fractions depend almost uniquely on core mass. If this is actually the case, it would have significant implications for globular cluster dynamics more generally.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Notes
- 1.
Strictly speaking, we are talking here about clusters with high specific collision rates, i.e. clusters in which each binary undergoes many encounters.
- 2.
If M i > 18 M⊙, we assume the star has turned into a black hole, so that M f = 10 M⊙; if 7 M⊙ < M i < 18 M⊙, we assume the star has turned in a neutron star, so that M f = 1. 4 M⊙; finally, if M to (t) < M i < 7 M⊙, we assume the star has become a white dwarf, so that M f = 0. 5 M⊙. These mass ranges, as well as the main sequence lifetimes, are estimated using SSE (Hurley et al. 2000).
- 3.
We were careful not to rule out the possibility that the relevant binary population may be affected by dynamical encounters . However, we also noted that the absence of a scaling with collision rates seemed hard to understand in any scenario involving lots of dynamical encounters (see Sect. 13.1).
- 4.
- 5.
References
Chatterjee, S., Rasio, F. A., Sills, A., Glebbeek, E.: ApJ 777, 106 (2013)
Clark, G. W.: ApJL 199, L143 (1975)
Davies, M. B., Piotto, G., de Angeli, F.: MNRAS 349, 129 (2004)
Eggleton, P. P., Fitchett, M. J., Tout, C. A.: ApJ 347, 998 (1989)
Eggleton, P. P., Fitchett, M. J., Tout, C. A.: ApJ 354, 387 (1990)
Fabian, A. C., Pringle, J. E., Rees, M. J.: MNRAS 172, 15P (1975)
Ferraro, F. R., Beccari, G., Dalessandro, E., et al.: Nature 462, 1028 (2009)
Ferraro, F. R., Paltrinieri, B., Fusi Pecci, F., et al.: A&A 324, 915 (1997)
Ferraro, F. R., Sabbi, E., Gratton, R., et al.: ApJL 647, L53 (2006)
Hurley, J. R., Pols, O. R., Tout, C. A.: MNRAS 315, 543 (2000)
Hut, P., McMillan, S., Goodman, J., et al.: PASP 104, 981 (1992)
Katz, J. I.: Nature 253, 698 (1975)
Knigge C., Leigh N., Sills A.: Nature 457, 288 (2009)
Lanzoni, B., Dalessandro, E., Ferraro, F. R., et al.: ApJ 663, 267 (2007a)
Lanzoni, B., Dalessandro, E., Perina, S., et al.: ApJ 670, 1065 (2007b)
Leigh N., Geller A. M.: MNRAS 425, 2369 (2012)
Leigh N., Knigge C., Sills A., et al.: MNRAS 428, 897 (2013)
Leigh N., Sills A., Knigge C.: ApJ 661, 210 (2007)
Leigh N., Sills A., Knigge C.: ApJ 678, 564 (2008)
Leigh N., Sills A., Knigge C.: MNRAS 415, 3771 (2011)
Leigh N., Sills A.: MNRAS 410, 2370 (2011)
Mason, E., Diaz, M., Williams, R. E., Preston, G., Bensby, T.: A&A 516, A108 (2010)
Mapelli, M., Sigurdsson, S., Colpi, M., et al.: ApJL 605, L29 (2004)
Mapelli, M., Sigurdsson, S., Ferraro, F. R., et al.: MNRAS 373, 361 (2006)
Milone, A. P., Piotto, G., Bedin, L. R., et al.: A&A 540, A16 (2012)
Milone, A. P., Piotto, G., Bedin, L. R., Sarajedini, A.: Mem. Soc. Astron. Ital. 79, 623 (2008)
Nakano, S., Nishiyama, K., Kabashima, F., et al.: IAU Circ. 8972, 1 (2008)
Piotto, G., De Angeli, F., King, I. R., et al.: ApJL 604, L109 (2004)
Piotto, G., King, I. R., Djorgovski, S. G., et al.: A&A 391, 945 (2002)
Pooley, D., Hut, P.: ApJL 646, L143 (2006)
Pooley, D., Lewin, W. H. G., Anderson, S. F., et al.: ApJL 591, L131 (2003)
Sabbi, E., Ferraro, F. R., Sills, A., Rood, R. T.: ApJ 617, 1296 (2004)
Sarajedini, A., Bedin, L. R., Chaboyer, B., et al.: AJ 133, 1658 (2007)
Sills, A., Faber, J. A., Lombardi, J. C., Jr., Rasio, F. A., Warren, A. R.: ApJ 548, 323 (2001)
Sills, A., Glebbeek, E., Chatterjee, S., Rasio, F. A.: ApJ 777, 105 (2013)
Sollima, A., Beccari, G., Ferraro, F. R., Fusi Pecci, F., Sarajedini, A.: MNRAS 380, 781 (2007)
Sollima, A., Lanzoni, B., Beccari, G., Ferraro, F. R., Fusi Pecci, F.: A&A 481, 701 (2008)
Tylenda, R., Hajduk, M., Kamiński, T., et al.: A&A 528, A114 (2011)
Udalski, A.: Acta Astronomica 53, 291 (2003)
Warren, S. R., Sandquist, E. L., Bolte, M.: ApJ 648, 1026 (2006)
Acknowledgements
I am extremely grateful to the organisers of the ESO workshop that led to the production of this book. Special thanks are due to Henri Boffin, whose patience as an editor was almost literally unlimited.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2015 Springer-Verlag Berlin Heidelberg
About this chapter
Cite this chapter
Knigge, C. (2015). Blue Stragglers in Globular Clusters: Observations, Statistics and Physics. In: Boffin, H., Carraro, G., Beccari, G. (eds) Ecology of Blue Straggler Stars. Astrophysics and Space Science Library, vol 413. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-662-44434-4_13
Download citation
DOI: https://doi.org/10.1007/978-3-662-44434-4_13
Published:
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-662-44433-7
Online ISBN: 978-3-662-44434-4
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)