UScoCTIO 108
UScoCTIO 108 is a binary system, approximately 470 light-years away in the Upper Scorpius (USco) OB association. The primary, UScoCTIO 108A, with mass around 0.06 solar masses, is a brown dwarf or low-mass red dwarf. The secondary, UScoCTIO 108B, with a mass around the deuterium burning limit of 13 Jupiter masses, would be classified as either a brown dwarf or an extrasolar planet.[2]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 05m 53.94s[1] |
| Declination | −18° 18′ 42.7″[1] |
| Characteristics | |
| Spectral type | M7[2] |
| Astrometry | |
| Proper motion (μ) | RA: -7.4 ± 4.6[3] mas/yr Dec.: -20.4 ± 4.6[3] mas/yr |
| Distance | 473 ± 6 ly (145 ± 2[2] pc) |
| Details | |
| Mass | 0.057 ± 0.019[2] M☉ |
| Luminosity | 0.011+0.06 −0.03[2] L☉ |
| Temperature | 2700 ± 100[2] K |
| Radius | 0.46 R☉ |
| Database references | |
| SIMBAD | data |
 UScoCTIO 108 B's orbit | |
| Position (relative to A) | |
|---|---|
| Epoch of observation | J2007.5 |
| Angular distance | 4.6 ± 0.1″ [2] |
| Position angle | 177 ± 1° [2] |
| Observed separation (projected) | ~670 AU [2] |
| Characteristics | |
| Spectral type | M9.5 ± 0.5[4] |
| Details | |
| Mass | 0.015+0.009 −0.004[4] M☉ |
| Radius | 0.16 ± 0.01[4] R☉ |
| Luminosity | 0.00065 ± 0.00007[4] L☉ |
| Surface gravity (log g) | 4.0 ± 0.5[4] cgs |
| Temperature | 2300 ± 100[4] K |
| Other designations | |
UscoCTIO 108b[5] | |
| Database references | |
| SIMBAD | data |
The primary component of the system was discovered in 2000 as a possible member of the Upper Scorpius association, based on its position in a HR diagram, in a search for new member of the association by the Cerro Tololo Inter-American Observatory (CTIO), where it received the designation UScoCTIO 108.[6] Later, spectroscopic and photometric observations confirmed that the object is a real member of the association, showing signs of low gravity and youth, and estimated a mass of 60 times the mass of Jupiter (MJ), an effective temperature of 2,800 K and a spectral type of M7. The low mass indicates that the object is not able to sustain hydrogen fusion, making it a brown dwarf.[2]
The secondary member of the system was found in 2008 as an object located at a separation of 4.6 arcseconds, which corresponds to a physical separation of more than 670 AU, and is also a confirmed member of the Upper Scorpius association.[2] Its spectrum shows it is also a cold substellar object, with an effective temperature of 2,300 K and a spectral type of M9.5.[4] Its mass was originally estimated at 14 MJ,[2] very close to the nominal boundary between planets and brown dwarf, but a recent revision of the age of the Upper Scorpius association to 11 million years increased this value to 16 MJ, indicating that the object is likely a low mass brown dwarf.[7] The physical association between the two brown dwarfs has not been confirmed by observation of common proper motion, but is considered very likely given the proximity between them.[2][3]
The minimum separation between the two brown dwarfs, 670 AU, is much larger than the mean of other similar mass systems, and indicates that the pair (if they really form a binary system) is very weakly bound, with an escape velocity for the secondary component of only 0.4 km/s. Considering the average stellar density in an association like Upper Scorpius, it is estimated that perturbations by passing stars will cause the rupture of the system in a few million years.[2]
Observations by the infrared telescope WISE revealed excess emission at 12 and 22 μm, indicating the presence of a debris disk around the brown dwarf.[8]
References
- UScoCTIO 108, entry, SIMBAD. Accessed on line June 17, 2008.
- V. J. S. Bejar; M. R. Zapatero Osorio; A. Perez-Garrido; C. Álvarez; et al. (February 2008). "Discovery of a Wide Companion near the Deuterium-burning Mass Limit in the Upper Scorpius Association". Astrophysical Journal. 673 (2): L185–L189. arXiv:0712.3482. Bibcode:2008ApJ...673L.185B. doi:10.1086/527557. S2CID 55896247.
- Ginski, C.; et al. (November 2014). "Astrometric follow-up observations of directly imaged sub-stellar companions to young stars and brown dwarfs". Monthly Notices of the Royal Astronomical Society. 444 (3): 2280–2302. arXiv:1409.1850. Bibcode:2014MNRAS.444.2280G. doi:10.1093/mnras/stu1586. S2CID 119118750.
- Bonnefoy, M.; et al. (February 2014). "A library of near-infrared integral field spectra of young M-L dwarfs". Astronomy & Astrophysics. 562: A127, 26 pp. arXiv:1306.3709. Bibcode:2014A&A...562A.127B. doi:10.1051/0004-6361/201118270. S2CID 53064211.
- NAME UScoCTIO 108b, entry, SIMBAD. Accessed on line June 17, 2008.
- Ardila, David; Martín, Eduardo; Basri, Gibor (July 2000). "A Survey for Low-Mass Stars and Brown Dwarfs in the Upper Scorpius OB Association". The Astronomical Journal. 120 (1): 479–487. arXiv:astro-ph/0003316. Bibcode:2000AJ....120..479A. doi:10.1086/301443. S2CID 118809084.CS1 maint: multiple names: authors list (link)
- Pecaut, Mark J.; Mamajek, Eric E.; Bubar, Eric J. (February 2012). "A Revised Age for Upper Scorpius and the Star Formation History among the F-type Members of the Scorpius-Centaurus OB Association". The Astrophysical Journal. 746 (2): article 154, 22 pp. arXiv:1112.1695. Bibcode:2012ApJ...746..154P. doi:10.1088/0004-637X/746/2/154. S2CID 118461108.
- Morales, Farisa Y.; Padgett, D. L.; Bryden, G.; Werner, M. W.; Furlan, E. (September 2012). "WISE Detections of Dust in the Habitable Zones of Planet-bearing Stars". The Astrophysical Journal. 757 (1): artigo 7, 6 pp. Bibcode:2012ApJ...757....7M. doi:10.1088/0004-637X/757/1/7.
External links
- Star: UScoCTIO 108, Extrasolar Planets Encyclopaedia. Accessed on line June 17, 2008.