XO-2

For other uses, see XO-2 (disambiguation).

XO-2

Observation data Epoch 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	0.98±0.05  M☉
Radius	1.02+0.09 −0.06  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 [7]
XO-2N: BD+50 1471, LSPM J0748+5013N, TOI-1720, TIC 356473034, TYC 3413-5-1, GSC 03413-00005, 2MASS J07480647+5013328 [8]
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. ^[9]

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. ^{[7] [8]}

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

Planetary systems

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. ^[10]

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. ^[9] A 2024 study found evidence for a third, super-Jupiter mass planet around XO-2S. ^[10]

The XO-2N planetary system ^[6]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	0.597±0.021  MJ	0.03673(64)	2.61585922(28)	<0.006	87.96+0.42 −0.34 °	1.019±0.031  RJ

The XO-2S planetary system ^[10]

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	—	—

See also

• HD 20781 and HD 20782
• HD 133131
• Lists of exoplanets

References

1. Roman, Nancy G. (1987). "Identification of a Constellation From a Position". Publications of the Astronomical Society of the Pacific. 99 (617): 695–699. Bibcode:1987PASP...99..695R. doi: 10.1086/132034 . Vizier query form
2. 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. 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. 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. 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. 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. "TYC 3413-210-1". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2018-01-28.
8. "TYC 3413-5-1". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2018-01-28.
9. 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.
10. 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

• 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

• 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.