SR 12 (star)
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| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 16h 27m 19.51s[1] |
| Declination | −24° 41′ 40.4″[1] |
| Apparent magnitude (V) | 13.09 to 13.53[2] |
| Characteristics | |
| Evolutionary stage | T Tauri star[3] |
| Spectral type | M3 + M8[4] |
| Variable type | rotational variable[5] |
| Astrometry | |
| Radial velocity (Rv) | −5.65±0.01[6] km/s |
| Proper motion (μ) | RA: −7.703±1.088 mas/yr[1] Dec.: −25.327±0.829 mas/yr[1] |
| Parallax (π) | 8.9034±0.4288 mas[1] |
| Distance | 370 ± 20 ly (112 ± 5 pc) |
| Position (relative to SR 12A)[7] | |
| Component | SR 12B |
| Epoch of observation | 2022.2827 |
| Angular distance | 0.1118±0.0011″ |
| Position angle | 76.2±1.1° |
| Details | |
| SR 12A | |
| Mass | 0.36+0.16 −0.07[5] M☉ |
| Radius | 2.0±0.3[5] R☉ |
| Temperature | 3428[8] K |
| Rotation | 3.4 to 3.6 days[2] |
| Age | 2[4] Myr |
| SR 12B | |
| Temperature | 2500[8] K |
| Other designations | |
| EM* SR 12, 2MASS J16271951-2441403, ISO-Oph 130, ROX 21, TIC 175629526, V2247 Oph, WDS J16273-2442AB | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
SR 12 (also known as V2247 Oph) is a weak-line T-Tauri binary that has a planetary-mass companion with a detected accretion disk.[4]
SR 12 was discovered by Otto Struve and Mogens Rudkjøbing in 1949 as an emission-line star with a spectral type of M. The first letters of their names were used to name the star, together with the star number in their catalog.[9] It was also observed as an x-ray source with the Einstein Observatory, having the designation ROX 21.[10] The binary was discovered with the help of lunar occultations and speckle interferometry in 1987.[11]
The binary is located in the ρ Ophiuchi star-forming region and is a weak-line T-Tauri binary, meaning it still accretes gaseous material from a circumstellar disk.[8] There are differences in spectral type classifications of the individual stars.[4] A K4/M2.5 binary was suggested,[12] as well as a M3+M8 binary.[8][4] The binary is separated by about 0.21 arcseconds,[3] which corresponds to a separation of 24 AU.[4] Speckle interferometry from SOAR does however find a lower separation of 0.1118 ±1.1 arcseconds.[7]
The star is a variable with a rotation period that changes between 3.4 and 3.6 days. This is due to stellar spots at different latitudes corresponding to different rotation periods, which indicates photospheric shearing.[2][5] The magnetic surface of the primary was mapped in 2010. The magnetic field showed changes within 1 week. Excess emissions concentrated at mid-latitude are seen as a footprint of an accretion funnel.[5] The binary does not have any detection of circumbinary dust from Spitzer and ALMA observations.[4]
