XO-2 (star) - Wikipedia

Binary star system in the constellation Lynx For other uses, see XO-2 (disambiguation). XO-2

Observation dataEpoch J2000      Equinox J2000
Constellation	Lynx[1]
XO-2S
Right ascension	07h 48m 07.4814s[2]
Declination	+50° 13′ 03.2554″[2]
Apparent magnitude (V)	11.12±0.03[3]
XO-2N
Right ascension	07h 48m 06.4723s[4]
Declination	+50° 13′ 32.9206″[4]
Apparent magnitude (V)	11.18±0.03[3]
Characteristics
Spectral type	K0V + K0V[3]
Astrometry
XO-2S
Radial velocity (Rv)	46.94±0.27[2] km/s
Proper motion (μ)	RA: −29.308(15) mas/yr[2] Dec.: −154.233(13) mas/yr[2]
Parallax (π)	6.6721±0.0151 mas[2]
Distance	489 ± 1 ly (149.9 ± 0.3 pc)
Absolute magnitude (MV)	5.74[5]
XO-2N
Radial velocity (Rv)	47.45±0.44[4] km/s
Proper motion (μ)	RA: −29.552(15) mas/yr[4] Dec.: −154.227(11) mas/yr[4]
Parallax (π)	6.6588±0.0158 mas[4]
Distance	490 ± 1 ly (150.2 ± 0.4 pc)
Absolute magnitude (MV)	5.74[5]
Details[6]
XO-2S
Mass	0.9624±0.0073[7] M☉
Radius	1.011±0.019[7] R☉
Luminosity	0.79±0.14 L☉
Surface gravity (log g)	4.420±0.094 cgs
Temperature	5,325±37 K
Metallicity [Fe/H]	0.32±0.08 dex
Rotation	26.0±0.6 d
Rotational velocity (v sin i)	1.5±0.3 km/s
Age	7.1+2.5−2.9 Gyr
XO-2N
Mass	0.96±0.05 M☉
Radius	0.998+0.033−0.032 R☉
Luminosity	0.70±0.04 L☉
Surface gravity (log g)	4.43±0.10 cgs
Temperature	5,290±18 K
Metallicity [Fe/H]	0.37±0.07 dex
Rotation	41.6±1.1 d
Rotational velocity (v sin i)	1.07±0.09 km/s
Age	7.8+1.2−1.3 Gyr
Other designations
XO-2S: LSPM J0748+5013S, TYC 3413-210-1, GSC 03413-00210, 2MASS J07480748+5013032[8]
XO-2N: BD+50 1471, LSPM J0748+5013N, TOI-1720, TIC 356473034, TYC 3413-5-1, GSC 03413-00005, 2MASS J07480647+5013328[9]
Database references
SIMBAD	XO-2S
XO-2N
Exoplanet Archive	data

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.[10]

Star system

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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.[8][9]

XO-2N and XO-2S have a separation of approximately 4,600 AU.[3]

Planetary systems

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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.[10] A 2024 study found evidence for a third, super-Jupiter mass planet around XO-2S.[11]

The XO-2S planetary system[11]

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.[3] 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.[11]

The XO-2N planetary system[a]

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

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Other systems with multiple planet-hosting stars:

• 55 Cancri
• HD 20781 & HD 20782
• HD 133131
• WASP-94
• Struve 2398

Notes

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1. ^ Mass and eccentricity: Damasso et al. 2015[6]Other properties: Wang et al. (2025)[7]

References

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1. ^ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
2. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
3. ^ a b c d e 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. arXiv:0705.0003. Bibcode:2007ApJ...671.2115B. doi:10.1086/523087. S2CID 13468914.
4. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
5. ^ a b Benavides, Rafael; Francisco Rica; Esteban Reina; Julio Castellanos; Ramón Naves; Luis Lahuerta; Salvador Lahuerta (2010). "New Wide Common Proper Motion Binaries". Journal of Double Star Observations. 6 (1): 30. Bibcode:2010JDSO....6...30B.
6. ^ a b c 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 A111. arXiv:1501.01424. Bibcode:2015A&A...575A.111D. doi:10.1051/0004-6361/201425332.
7. ^ a b c Wang, Weilong; Gu, Shenghong; Wang, Xiaobin; Sun, Leilei; Lee, Byeong-Cheol; Kwok, Chi-Tai; Hui, Ho-Keung; Dou, Jiangpei; Xiang, Yue; Cao, Dongtao; Xu, Fukun (June 2025). "Observations and Studies on the Transiting Systems HAT-P-36, XO-2 and WASP-76". The Astronomical Journal. 169 (6): 342. Bibcode:2025AJ....169..342W. doi:10.3847/1538-3881/add1de. ISSN 0004-6256.
8. ^ a b "TYC 3413-210-1". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-01-28.
9. ^ a b "TYC 3413-5-1". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-01-28.
10. ^ a b 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) L6. arXiv:1407.0251. Bibcode:2014A&A...567L...6D. doi:10.1051/0004-6361/201424339. S2CID 118567085.
11. ^ a b c Ruggieri, A.; Desidera, S.; et al. (April 2024). "The GAPS Programme at TNG. LIII. New insights on the peculiar XO-2 system". Astronomy & Astrophysics. 684: A116. arXiv:2401.17876. Bibcode:2024A&A...684A.116R. doi:10.1051/0004-6361/202348042.

Further reading

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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. arXiv:0903.2687. Bibcode:2009AJ....137.4911F. doi:10.1088/0004-6256/137/6/4911. S2CID 7113991.
• 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. arXiv:1110.6136. Bibcode:2011PASJ...63L..67N. doi:10.1093/pasj/63.6.l67. S2CID 119269227.
• 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 A73. arXiv:1008.4795. Bibcode:2011A&A...527A..73S. doi:10.1051/0004-6361/201015579. S2CID 56545385.

External links

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• NASA PlanetQuest: Planet race heats up: 1 month, 32 discoveries
• "XO-2". Exoplanets. Archived from the original on 2016-03-03. Retrieved 2009-04-28.

v t e Constellation of Lynx
List of stars in Lynx Lynx in Chinese astronomy
Stars	Bayer α ψ10 Aur (16) Flamsteed 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 (Alsciaukat) 32 33 34 35 36 38 50 Cam 5 LMi 10 UMa Variable Y RR SW SZ UX BO DU HR 3028 3612 3809 HD 48948 75898 (Stribor) Other J0815+4729 WASP-13 (Gloas) XO-2 XO-4 (Koit) XO-5 (Absolutno)
Exoplanets 6 Lyncis b WASP-13b (Cruinlagh) XO-2Nb XO-4b (Hämarik) XO-5b (Makropulos)
Nebulae Jones-Emberson 1 Lynx Arc
Galaxies	NGC 2273 2326 2444 2445 2461 2472 2473 2484 2500 2519 2528 2537 2541 2552 2683 2719 2776 2782 2798 2829 2832 2844 Other 3C 171 3C 186 APM 08279+5255 B2 0902+34 IC 2233 IRAS 09104+4109 Markarian 382 OJ 508 UGC 4653 UGC 4881 UGC 4904
Galaxy clusters 2XMM J083026+524133 Abell 569 Abell 576 Lynx Supercluster NGC 2841 group
Astronomical events SN 2007uy SN 2008D
Category