Benchmark ultra-cool dwarfs in widely separated binary systems

Zhang, Z. H.; Pinfield, D. J.; Day-Jones, A. C.; Burningham, B.; Jones, H. R. A.
Bibliographical reference

Research, Science and Technology of Brown Dwarfs and Exoplanets: Proceedings of an International Conference held in Shangai on Occasion of a Total Eclipse of the Sun, Shangai, China, Edited by E.L. Martin; J. Ge; W. Lin; EPJ Web of Conferences, Volume 16, id.06014

Advertised on:
7
2011
Number of authors
5
IAC number of authors
0
Citations
1
Refereed citations
1
Description
Ultra-cool dwarfs as wide companions to subgiants, giants, white dwarfs and main sequence stars can be very good benchmark objects, for which we can infer physical properties with minimal reference to theoretical models, through association with the primary stars. We have searched for benchmark ultra-cool dwarfs in widely separated binary systems using SDSS, UKIDSS, and 2MASS. We then estimate spectral types using SDSS spectroscopy and multi-band colors, place constraints on distance, and perform proper motions calculations for all candidates which have sufficient epoch baseline coverage. Analysis of the proper motion and distance constraints show that eight of our ultra-cool dwarfs are members of widely separated binary systems. Another L3.5 dwarf, SDSS 0832, is shown to be a companion to the bright K3 giant η Cancri. Such primaries can provide age and metallicity constraints for any companion objects, yielding excellent benchmark objects. This is the first wide ultra-cool dwarf + giant binary system identified.