Stephenson 2 DFK 49
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Scutum |
| Right ascension | 18h 39m 05.586s[1] |
| Declination | −06° 04′ 26.58″[1] |
| Characteristics | |
| Evolutionary stage | Red supergiant[2] or post red supergiant[3] |
| Spectral type | K4[2] |
| Apparent magnitude (K) | 7.324[1] |
| Astrometry | |
| Radial velocity (Rv) | 109.4[2] km/s |
| Details | |
| Radius | 1,074[2] (884[4]-1,300[3]) R☉ |
| Luminosity | 245,000[2] (132,000[4]-390,000[3])) L☉ |
| Temperature | 3920±112[2] (3700[4]-4000[3]) K |
| Other designations | |
Stephenson 2 DFK 49, Stephenson 2-11, 2MASS J18390558-0604265, MSX6C G026.1215-00.0345 | |
| Database references | |
| SIMBAD | data |
Stephenson 2 DFK 49 or Stephenson 2-11 is a post red supergiant[3] star in the constellation Scutum, in the massive open cluster Stephenson 2. It is possibly one of the largest known stars with radius estimates ranging from almost 1,000 solar radii[4] to 1,300 solar radii.[3] If the upper estimate is correct then Stephenson 2 DFK 49 has a volume 2.2 billion times that of the Sun. If it was placed at the center of the Solar System, its photosphere will potentially approach or engulf Jupiter's orbit.
Observation history
The open cluster Stephenson 2 was discovered by American astronomer Charles Bruce Stephenson in 1990 in the data obtained by a deep infrared survey.[2][5] The cluster is also known as RSGC2, one of several massive open clusters in Scutum, each containing multiple red supergiants.[6] The 49th brightest star in the K band was given an identifier number of 49.[2] The authors noted that the star had significant extinction and noted that its spectral type places it near yellow hypergiants on the Hertzsprung–Russell diagram.[2]
In a later study from 2010, the same star was given the identifier number 11, and was grouped with a proposed cluster assumed to be associated with Stephenson 2, Stephenson 2-SW.[7] Another study studied 57 red supergiant stars across the galaxy and gave estimates of the stars' properties, like luminosity and temperature. Later on, it was noted yet again due to evidence for mass loss from its SED, and is located in a similar place to IRC +10420 on the Hertzsprung-Russell diagram.[3]
Properties
Stephenson 2 DFK 49 was known to be an interesting object since its home cluster was first studied in depth.[2] In 2007, a study of the red supergiants in Stephenson 2 estimated its properties, and determined a luminosity of 245,000 solar luminosities and a temperature of 3,700 K.[2] In 2012, a study published the properties of numerous red supergiants, including Stephenson 2-DFK 49. The study estimated somewhat different properties for the star, also estimating it temperature at 3,700 Kelvin but its luminosity at a somewhat lower 132,000 solar luminosities.[4]
References
- ^ a b c Cutri, Roc M.; et al. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
- ^ a b c d e f g h i j k Davies, B.; Figer, D. F.; Kudritzki, R. P.; MacKenty, J.; Najarro, F.; Herrero, A. (2007). "A Massive Cluster of Red Supergiants at the Base of the Scutum‐Crux Arm". The Astrophysical Journal. 671 (1): 781–801. arXiv:0708.0821. Bibcode:2007ApJ...671..781D. doi:10.1086/522224. S2CID 1447781.
- ^ a b c d e f g Humphreys, Roberta M.; Helmel, Greta; Jones, Terry J.; Gordon, Michael S. (2020). "Exploring the Mass Loss Histories of the Red Supergiants". The Astronomical Journal. 160 (3): 145. arXiv:2008.01108. Bibcode:2020AJ....160..145H. doi:10.3847/1538-3881/abab15. S2CID 220961677.
- ^ a b c d e Fok, Thomas K. T; Nakashima, Jun-ichi; Yung, Bosco H. K; Hsia, Chih-Hao; Deguchi, Shuji (2012). "Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters". The Astrophysical Journal. 760 (1): 65. arXiv:1209.6427. Bibcode:2012ApJ...760...65F. doi:10.1088/0004-637X/760/1/65. S2CID 53393926.
- ^ Stephenson, C. B. (1990). "A possible new and very remote galactic cluster". The Astronomical Journal. 99: 1867. Bibcode:1990AJ.....99.1867S. doi:10.1086/115464.
- ^ Negueruela, I.; González-Fernández, C.; Marco, A.; Clark, J. S.; Martínez-Núñez, S. (2010). "Another cluster of red supergiants close to RSGC1". Astronomy and Astrophysics. 513: A74. arXiv:1002.1823. Bibcode:2010A&A...513A..74N. doi:10.1051/0004-6361/200913373. S2CID 118531372.
- ^ Deguchi, Shuji; Nakashima, Jun-Ichi; Zhang, Yong; Chong, Selina S. N.; Koike, Kazutaka; Kwok, Sun (2010). "SiO and H2O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk". Publications of the Astronomical Society of Japan. 62 (2): 391–407. arXiv:1002.2492. Bibcode:2010PASJ...62..391D. doi:10.1093/pasj/62.2.391. S2CID 24396370.
