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Title: The solar neighborhood. XXXI. Discovery of an unusual red+white dwarf binary at ∼25 pc via astrometry and UV imaging

We report the discovery of a nearby M5.0V dwarf at 24.6 pc, SCR 1848–6855, that is orbited by an unusual companion causing an astrometric perturbation of more than 200 mas. This is by far the largest perturbation found to date among more than 700 targets observed during our long-term astrometry/photometry program at the CTIO 0.9 m telescope. We present here a suite of astrometric, photometric, and spectroscopic observations of this high proper motion (∼1.''3 yr{sup –1}) system in an effort to reveal the nature of this unusual binary. The measured near-UV and optical U band fluxes exceed those expected for comparable M5.0V stars, and excess flux is also detected in the spectral range 4000-7000 Å. The elusive companion has been detected in HST-STIS+MAMA images at 1820 Å and 2700 Å, and our analysis shows that it is probably a rare, cool, white dwarf with T = 4600-5500 K. Given the long-term astrometric coverage, the prospects for an accurate mass determination are excellent, although as yet we can only provide limits on the unusual companion's mass.
Authors:
; ; ;  [1] ;  [2] ;  [3] ;  [4]
  1. Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302 (United States)
  2. US Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001 (United States)
  3. Department of Physics and Astronomy, Hunter College, 695 Park Avenue, New York, NY 10065 (United States)
  4. Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States)
Publication Date:
OSTI Identifier:
22340035
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 147; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; DISTANCE; DISTURBANCES; IMAGES; MASS; PERTURBATION THEORY; PHOTOMETRY; PROPER MOTION; RED DWARF STARS; TELESCOPES; WHITE DWARF STARS