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Title: WD0837+185: THE FORMATION AND EVOLUTION OF AN EXTREME MASS-RATIO WHITE-DWARF-BROWN-DWARF BINARY IN PRAESEPE

Abstract

There is a striking and unexplained dearth of brown dwarf companions in close orbits (<3 AU) around stars more massive than the Sun, in stark contrast to the frequency of stellar and planetary companions. Although rare and relatively short-lived, these systems leave detectable evolutionary end points in the form of white-dwarf-brown-dwarf binaries and these remnants can offer unique insights into the births and deaths of their parent systems. We present the discovery of a close (orbital separation {approx}0.006 AU) substellar companion to a massive white dwarf member of the Praesepe star cluster. Using the cluster age and the mass of the white dwarf, we constrain the mass of the white dwarf progenitor star to lie in the range 3.5-3.7 M{sub Sun} (B9). The high mass of the white dwarf means the substellar companion must have been engulfed by the B star's envelope while it was on the late asymptotic giant branch (AGB). Hence, the initial separation of the system was {approx}2 AU, with common envelope evolution reducing the separation to its current value. The initial and final orbital separations allow us to constrain the combination of the common envelope efficiency ({alpha}) and binding energy parameters ({lambda}) for the AGB starmore » to {alpha}{lambda} {approx} 3. We examine the various formation scenarios and conclude that the substellar object was most likely captured by the white dwarf progenitor early in the life of the cluster, rather than forming in situ.« less

Authors:
; ; ; ; ;  [1];  [2];  [3];  [4]
  1. Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)
  2. Science and Technology Research Institute, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom)
  3. School of Mathematics and Physics, University of Tasmania, Hobart, Tasmania 7001 (Australia)
  4. Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)
Publication Date:
OSTI Identifier:
22078442
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 759; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMPTOTIC SOLUTIONS; BINARY STARS; BINDING ENERGY; GALACTIC EVOLUTION; MASS; ORBITS; STAR CLUSTERS; SUN; WHITE DWARF STARS

Citation Formats

Casewell, S. L., Burleigh, M. R., Wynn, G. A., Alexander, R. D., Lawrie, K. A., Jameson, R. F., Napiwotzki, R., Dobbie, P. D., and Hodgkin, S. T., E-mail: slc25@le.ac.uk. WD0837+185: THE FORMATION AND EVOLUTION OF AN EXTREME MASS-RATIO WHITE-DWARF-BROWN-DWARF BINARY IN PRAESEPE. United States: N. p., 2012. Web. doi:10.1088/2041-8205/759/2/L34.
Casewell, S. L., Burleigh, M. R., Wynn, G. A., Alexander, R. D., Lawrie, K. A., Jameson, R. F., Napiwotzki, R., Dobbie, P. D., & Hodgkin, S. T., E-mail: slc25@le.ac.uk. WD0837+185: THE FORMATION AND EVOLUTION OF AN EXTREME MASS-RATIO WHITE-DWARF-BROWN-DWARF BINARY IN PRAESEPE. United States. doi:10.1088/2041-8205/759/2/L34.
Casewell, S. L., Burleigh, M. R., Wynn, G. A., Alexander, R. D., Lawrie, K. A., Jameson, R. F., Napiwotzki, R., Dobbie, P. D., and Hodgkin, S. T., E-mail: slc25@le.ac.uk. Sat . "WD0837+185: THE FORMATION AND EVOLUTION OF AN EXTREME MASS-RATIO WHITE-DWARF-BROWN-DWARF BINARY IN PRAESEPE". United States. doi:10.1088/2041-8205/759/2/L34.
@article{osti_22078442,
title = {WD0837+185: THE FORMATION AND EVOLUTION OF AN EXTREME MASS-RATIO WHITE-DWARF-BROWN-DWARF BINARY IN PRAESEPE},
author = {Casewell, S. L. and Burleigh, M. R. and Wynn, G. A. and Alexander, R. D. and Lawrie, K. A. and Jameson, R. F. and Napiwotzki, R. and Dobbie, P. D. and Hodgkin, S. T., E-mail: slc25@le.ac.uk},
abstractNote = {There is a striking and unexplained dearth of brown dwarf companions in close orbits (<3 AU) around stars more massive than the Sun, in stark contrast to the frequency of stellar and planetary companions. Although rare and relatively short-lived, these systems leave detectable evolutionary end points in the form of white-dwarf-brown-dwarf binaries and these remnants can offer unique insights into the births and deaths of their parent systems. We present the discovery of a close (orbital separation {approx}0.006 AU) substellar companion to a massive white dwarf member of the Praesepe star cluster. Using the cluster age and the mass of the white dwarf, we constrain the mass of the white dwarf progenitor star to lie in the range 3.5-3.7 M{sub Sun} (B9). The high mass of the white dwarf means the substellar companion must have been engulfed by the B star's envelope while it was on the late asymptotic giant branch (AGB). Hence, the initial separation of the system was {approx}2 AU, with common envelope evolution reducing the separation to its current value. The initial and final orbital separations allow us to constrain the combination of the common envelope efficiency ({alpha}) and binding energy parameters ({lambda}) for the AGB star to {alpha}{lambda} {approx} 3. We examine the various formation scenarios and conclude that the substellar object was most likely captured by the white dwarf progenitor early in the life of the cluster, rather than forming in situ.},
doi = {10.1088/2041-8205/759/2/L34},
journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 2,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}