Astronomy:XO-2
XO-2 is a binary star system about 490 light-years (150 parsecs) away in the constellation Lynx. It consists of two components, XO-2N and XO-2S, both of which host planetary systems.[1]
Star system
This system is unusual in that the stars are not typically referred to as components A & B, but are designated based on their positions in the sky: XO-2N is the northern star and XO-2S is the southern star.
Both of the stars are slightly cooler than the Sun and are nearly identical to each other. The system has a magnitude of 11 and cannot be seen with the naked eye but is visible through a small telescope. These stars are also notable for their large proper motions.[2][3]
XO-2N and XO-2S have a separation of approximately 4,600 AU.[4]
Planetary systems
Two planets were reported to orbit around XO-2S in 2014 using the radial velocity method. One of them is Jupiter-mass and another has a mass comparable to Saturn.[1] A 2024 study found evidence for a third, super-Jupiter mass planet around XO-2S.[5]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥0.26±0.01 MJ | 0.1347±0.0025 | 18.220±0.001 | 0.15±0.02 | — | — |
| c | ≥1.38±0.05 MJ | 0.4737+0.0085 −0.0088 |
120.059±0.013 | 0.149±0.006 | — | — |
| d | ≥3.71+1.2 −0.51 MJ |
5.46+0.85 −0.40 |
4,696+1,133 −489 |
0.091+0.028 −0.018 |
— | — |
There is one confirmed exoplanet orbiting XO-2N. XO-2Nb, which is classified as a hot Jupiter, was discovered by the XO Telescope using the transit method around XO-2N in 2007. It was initially the only known planet in the system and was referred to as XO-2b.[4] A long-period variation in the radial velocity of XO-2N was detected in 2015, which could be explained by either a second planet or a stellar activity cycle. The stellar activity explanation is considered more likely,[6] and is further supported by a 2024 study.[5]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 0.597±0.021 MJ | 0.03668(9) | 2.615859719(54) | <0.006 | 87.47±0.37° | 1.033±0.023 RJ |
See also
Other systems with multiple planet-hosting stars:
Notes
References
- ↑ 1.0 1.1 Desidera, S. et al. (2014). "The GAPS programme with HARPS-N at TNG. IV. A planetary system around XO-2S". Astronomy and Astrophysics 567 (6). doi:10.1051/0004-6361/201424339. Bibcode: 2014A&A...567L...6D.
- ↑ "TYC 3413-210-1". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=TYC+3413-210-1.
- ↑ "TYC 3413-5-1". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=TYC+3413-5-1.
- ↑ 4.0 4.1 Burke, Christopher J. et al. (2007). "XO-2b: Transiting Hot Jupiter in a Metal-rich Common Proper Motion Binary". The Astrophysical Journal 671 (2): 2115–2128. doi:10.1086/523087. Bibcode: 2007ApJ...671.2115B.
- ↑ 5.0 5.1 5.2 Ruggieri, A. et al. (April 2024). "The GAPS Programme at TNG. LIII. New insights on the peculiar XO-2 system". Astronomy & Astrophysics 684: A116. doi:10.1051/0004-6361/202348042. Bibcode: 2024A&A...684A.116R.
- ↑ 6.0 6.1 Damasso, M. et al. (2015). "The GAPS programme with HARPS-N at TNG. V. A comprehensive analysis of the XO-2 stellar and planetary systems". Astronomy & Astrophysics 575. doi:10.1051/0004-6361/201425332. Bibcode: 2015A&A...575A.111D.
- ↑ Wang, Weilong; Gu, Shenghong; Wang, Xiaobin; Sun, Leilei; Lee, Byeong-Cheol; Kwok, Chi-Tai; Hui, Ho-Keung; Dou, Jiangpei et al. (June 2025). "Observations and Studies on the Transiting Systems HAT-P-36, XO-2 and WASP-76" (in en). The Astronomical Journal 169 (6): 342. doi:10.3847/1538-3881/add1de. ISSN 0004-6256. Bibcode: 2025AJ....169..342W.
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- Fernandez, Jose M. et al. (2009). "The Transit Light Curve Project. XII. Six Transits of the Exoplanet XO-2b". The Astronomical Journal 137 (6): 4911–4916. doi:10.1088/0004-6256/137/6/4911. Bibcode: 2009AJ....137.4911F.
- Narita, Norio et al. (2011). "XO-2b: a Prograde Planet with a Negligible Eccentricity and an Additional Radial Velocity Variation". Publications of the Astronomical Society of Japan 63 (6): L67–L71. doi:10.1093/pasj/63.6.l67. Bibcode: 2011PASJ...63L..67N.
- Sing, D. K. et al. (2011). "Gran Telescopio Canarias OSIRIS transiting exoplanet atmospheric survey: detection of potassium in XO-2b from narrowband spectrophotometry". Astronomy and Astrophysics 527. doi:10.1051/0004-6361/201015579. Bibcode: 2011A&A...527A..73S.
External links
- NASA PlanetQuest: Planet race heats up: 1 month, 32 discoveries
- "XO-2". Exoplanets. http://media4.obspm.fr/exoplanets/base/etoile.php?nom=XO-2.
Coordinates: 
07h 48m 06.468s, +50° 13′ 32.96″
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