Groombridge 1618
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| Observation data Epoch J2000.0 |
|
|---|---|
| Constellation (pronunciation) |
Ursa Major |
| Right ascension | 10h 11m 22.1411s[1] |
| Declination | +49° 27′ 15.252″[1] |
| Apparent magnitude (V) | 6.61[1] |
| Characteristics | |
| Spectral type | K5 V[1] |
| U-B color index | 1.28[1] |
| B-V color index | 1.38[1] |
| Variable type | Flare star |
| Astrometry | |
| Radial velocity (Rv) | -26.1[1] km/s |
| Proper motion (μ) | RA: -1361.65[1] mas/yr Dec.: -505.14[1] mas/yr |
| Parallax (π) | 205.23 ± 0.81[1] mas |
| Distance | 15.89 ± 0.06 ly (4.87 ± 0.02 pc) |
| Absolute magnitude (MV) | 8.17 |
| Details | |
| Mass | 0.64[2] M☉ |
| Radius | 0.59±0.03[3] R☉ |
| Surface gravity (log g) | 4.5[1] |
| Luminosity | 0.046 L☉ |
| Temperature | 4,000[1] K |
| Metallicity | 191% Sun[4] |
| Rotation | 8.7-28.1 days (0.9-2.9 km/s) |
| Age | 1 × 109 years |
| Other designations | |
Groombridge 1618 is a star in the constellation Ursa Major. It is located relatively close to Earth, at a distance of less than 16 light years. This is an orange dwarf star of spectral type K5 V.
This star has a relatively high proper motion across the sky, making it an early candidate for parallax measurement. In 1884 the parallax was measured at 0″.322 ± 0″.023 (which is larger than the modern value of 0″.205).[5]
It is a flare star with behavior similar to UV Ceti. The chromosphere has been shown to be active and possesses star spots comparable to a Sun spot. It has a greater luminosity than most flare stars, which are typically red dwarfs, but is less active. The level of activity may suggest that this is a somewhat youthful star.
A search for an excess amount of infrared emission from this star by the Infrared Space Observatory came up negative, implying that Groombridge 1618 does not possess a debris disk (such as Vega).[6] If this star does have a companion, astrometric measurements appear to place an upper bound of 3–12 times the mass of Jupiter on such a hypothetical object (for orbital periods in the range of 5–50 years). [7]
[edit] See also
[edit] References
- ^ a b c d e f g h i j k l SIMBAD Query Result: NSV 4765 -- Flare Star. Centre de Données astronomiques de Strasbourg. Retrieved on 2007-06-24.
- ^ Staff (June 8, 2007). RECONS. Georgia State University. Retrieved on 2007-06-24.
- ^ Perrin, M.-N.; Karoji, H. (1987). "Stellar radius determination from IRAS 12-micron fluxes". Astronomy and Astrophysics 172: 235–240.
- ^ Woolf, V.; Wallerstein, G. (2005). "Metallicity measurements using atomic lines in M and K dwarf stars". ''Monthly Notices of the Royal Astronomical Society 356: 963-968. doi:.
- ^ Ball, Robert S. (1884). "On the Annual Parallax of Groombridge 1618". Dunsink Observatory Publications 5 (2): 187-217.
- ^ R.J. Laureijs et al (2002). "A 25 micron search for Vega-like disks around main-sequence stars with ISO". Astronomy & Astrophysics 387: L285-L293.
- ^ Hershey, J. L.; Borgman, E. R. (1978). "Upper Limits on the Mass of a Dark Companion of Groombridge 1618 from the 40-year Sproul Plate Series". Bulletin of the American Astronomical Society, 10: 630.
[edit] External links
- Groombridge 1618. Sol Company. Retrieved on 2007-06-24.
- ARICNS 4C00785. Astronomisches Rechen-Institut. Retrieved on 2007-06-24.
