Hostname: page-component-84b7d79bbc-tsvsl Total loading time: 0 Render date: 2024-07-29T20:16:50.871Z Has data issue: false hasContentIssue false
  • English
  • Français

Detection of Nine M8.0–L0.5 Binaries: The Very Low Mass Binary Population and Its Implications for Brown Dwarf Formation Theories

Published online by Cambridge University Press:  26 May 2016

Laird M. Close ,
Nick Siegler  and
Melanie Freed
Laird M. Close
Affiliation:
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson AZ, USA 85721–0065; lclose@as.arizona.edu
Nick Siegler
Affiliation:
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson AZ, USA 85721–0065; lclose@as.arizona.edu
Melanie Freed
Affiliation:
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson AZ, USA 85721–0065; lclose@as.arizona.edu

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Use of the highly sensitive Hōkūpa'a/Gemini curvature wave-front sensor has allowed for the first time direct adaptive optics (AO) guiding on very low mass (VLM) stars with SpT=M8.0–L0.5. A survey of 39 such objects detected 9 VLM binaries (7 of which were discovered for the first time to be binaries). Most of these systems (55%) are tight (separation < 5 AU) and have similar masses (ΔKs < 0.8 mag; 0.85 < q < 1.0). However, 2 systems (LHS 2397a, and 2M2331016-040618) have large ΔKs > 2.38 mag and consist of a VLM star orbited by a much cooler L6.5–L8.5 brown dwarf companion. Based on our initial flux limited (Ks < 12 mag) survey of 39 M8.0–L0.5 stars (mainly from the sample of Gizis et al. 2000) we find a binary fraction in the range 19±7% for M8.0–L0.5 binaries with separations > 2.6 AU. This is slightly less than the 32 ± 9% measured for more massive (M0–M4) stars over the same separation range (Fischer & Marcy 1992). It appears M8.0–L0.5 binaries (as well as L and T dwarf binaries) have a much smaller semi-major axis distribution peak (~ 4 AU) compared to more massive M and G stars which have a broad peak at larger ~ 30 AU separations. We also find no VLM binaries (Mtot < 0.18M⊙) with separations > 20 AU. We find that a velocity “kick” of ~ 3 km/s can reproduce the observed cut-off in the semi-major axis distribution at ˜ 20 AU. This kick may have been from the VLM system being ejected from its formation mini-cluster.

Type
Part 6. Searches for Substellar Companions
Information
Symposium - International Astronomical Union , Volume 211: Brown Dwarfs , 2003 , pp. 249 - 256
Copyright
Copyright © Astronomical Society of the Pacific 2001 

References

Bate, Matthew R.; Bonnell, Ian A.; Bromm, Volker 2002, MNRAS, 332, L65 Google Scholar
Reipurth, B. & Clarke, C. 2002, AJ, 122, 432 Google Scholar
Burgasser, A.J., Kirkpatrick, J.D., & Brown, M.E. 2002, BAAS, 34, #11.05 Google Scholar
Burrows, A., Hubbard, W. B., Lunine, J. I., Marley, M. S., Saumon, D. 2000, Protostars and Planets IV (Tucson: University of Arizona Press, eds Mannings, V., Boss, A.P., Russell, S. S.), p. 1339 Google Scholar
Basri, G., Martín, E. L. 1999, AJ, 118, 2460 Google Scholar
Caloi, V., Cardini, D., D'Antona, F., Badiali, M., Emanuele, A., Mazzitelli, I. 1999, A&A, 351, 925.Google Scholar
Chabrier, G., Baraffe, I., Allard, F., & Hauschildt, P. 2000, ApJ, 542, 464 Google Scholar
Close, L.M., Potter, D., Brandner, W., Lloyd-Hart, M., Liebert, J., Burrows, A., & Siegler, N. 2002a, ApJ, 566, 1095.Google Scholar
Close, L.M., Siegler, N., Potter, D., Brandner, W., Liebert, J. 2002b, ApJ, 567, L53.CrossRefGoogle Scholar
Close, L.M. Siegler, N., & Freed, M., 2002, ApJ, submitted.Google Scholar
Dahn, C. et al. 2002 ApJ, 124, 1170 Google Scholar
Duquennoy, A., Mayor, M. 1991, A&A, 248, 485 Google Scholar
Fischer, D. A., Marcy, G. W. 1992, ApJ, 396, 178 Google Scholar
Freed, M., Close, L.M., & Siegler, N. 2002, ApJL, submitted Google Scholar
Gizis, J.E., Kirkpatrick, J.D., Burgasser, A., Reid, I.N., Monet, D.G., Liebert, J., Wilson, J.C. 2001, ApJ, 551, L163 Google Scholar
Gizis, J.E., Monet, D.G., Reid, I.N., Kirkpatrick, J.D., Liebert, J., Williams, R.J. 2000, AJ, 120, 1085 CrossRefGoogle Scholar
Kirkpatrick, J. Davy; Reid, I. Neill; Liebert, James; Gizis, John E.; Burgasser, Adam J.; Monet, David G.; Dahn, Conard C.; Nelson, Brant; Williams, Rik J. 2000, AJ, 120, 447 CrossRefGoogle Scholar
Koerner, D. W., Kirkpatrick, J. Davy, McElwain, M. W., Bonaventura, N. R. 1999, ApJ, 526, L25 Google Scholar
Lane, B.F., Zapatero Osorio, M.R., Britton, M.C., Martín, E.L., Kulkarni, S.R. 2001, ApJ, 560, 390 Google Scholar
Martín, E.L., Brandner, W., Basri, G. 1999, Science, 283, 5408, 1718 Google Scholar
Martín, E. L., Koresko, C. D., Kulkarni, S. R., Lane, B. F., Wizinowich, P. L. 2000 ApJ, 529, L37 Google Scholar
Nakajima, T., Oppenheimer, B. R., Kulkarni, S. R., Golimowski, D. A., Matthews, K., Durrance, S. T. 1995, NATURE, 378, 463 Google Scholar
Potter, D. et al. 2002a ApJ, 567, 113 Google Scholar
Reid, I. Neill; Gizis, John E. 1997a AJ, 113, 2246 Google Scholar
Reid, I. Neill; Gizis, John E. 1997b AJ, 114, 1992 Google Scholar
Reid, I. N., Gizis, J.E., Kirkpatrick, J.D., Koerner, D. W. 2001a, AJ, 121, 489 Google Scholar
Reid, I. N., Burgasser, A. J., Cruz, K. L., Kirkpatrick, J. D., Gizis, J. E. 2001b, AJ, 121, 1710 Google Scholar
Reid, I. N. et al. 2002, AJ, 124, 519 CrossRefGoogle Scholar
Siegler, N., Close, L.M., Mamajek, E., Freed, M. 2002, ApJ, in prep Google Scholar
Stetson, P. B. 1987, PASP, 99, 191 CrossRefGoogle Scholar
van Altena, W.F., Lee, J.T., & Hoffleit, D 1995, The General Catalog of Trigonometric Stellar Parallaxes (4th ed.; New Haven: Yale University Observatory)Google Scholar