Astronomy and Astrophysics – Astrophysics
Scientific paper
2008-07-03
Astronomy and Astrophysics
Astrophysics
5 pages, 4 figures, accepted for publication in Astronomy and Astrophysics
Scientific paper
(abridged) We describe the discovery of an extremely wide pair of low-mass stars with a common large proper motion and discuss their possible membership in a Galactic halo stream crossing the Solar neighbourhood. (...) The late-type (M7) dwarf SSSPM J2003$-$4433 and the ultracool subdwarf SSSPM J1930$-$4311 (sdM7) sharing the same very large proper motion of about 860 mas/yr were found in the same sky region with an angular separation of about 6\degr. From the comparison with other high proper motion catalogues we have estimated the probability of a chance alignment of the two new large proper motions to be less than 0.3%. From the individually estimated spectroscopic distances of about $38^{+10}_{-7}$ pc and $72^{+21}_{-16}$ pc, respectively for the M7 dwarf and the sdM7 subdwarf, and in view of the accurate agreement in their large proper motions we assume a common distance of about 50 pc and a projected physical separation of about 5 pc. The mean heliocentric space velocity of the pair $(U,V,W)=(-232, -170, +74)$ km/s, based on the correctness of the preliminary radial velocity measurement for only one of the components and on the assumption of a common distance and velocity vector, is typical of the Galactic halo population. The large separation and the different metallicities of dwarfs and subdwarfs make a common formation scenario as a wide binary (later disrupted) improbable, although there remains some uncertainty in the spectroscopic classification scheme of ultracool dwarfs/subdwarfs so that a dissolved binary origin cannot be fully ruled out yet. It seems more likely that this wide pair is part of an old halo stream. (...)
Kharchenko Nina V.
Lodieu Nicolas
McCaughrean Mark J.
Scholz Ralf-Dieter
No associations
LandOfFree
An extremely wide and very low-mass pair with common proper motion. Is it representative of a nearby halo stream? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with An extremely wide and very low-mass pair with common proper motion. Is it representative of a nearby halo stream?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and An extremely wide and very low-mass pair with common proper motion. Is it representative of a nearby halo stream? will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-115780