XO-1

For the laptop with the same name, see OLPC XO-1.

XO-1 is a magnitude 11 G-type main-sequence star located approximately 530 light-years away^[2] in the constellation Corona Borealis. XO-1 has a mass and radius similar to the Sun. In 2006 the extrasolar planet XO-1b was discovered orbiting XO-1 by the transit method using the XO Telescope.^[3]

XO-1 / Moldoveanu

This artist's impression shows a dramatic close-up of the extrasolar planet XO-1b passing in front of a Sun-like star 600 light-years from Earth. The Jupiter-sized planet is in a tight four-day orbit around the star. Credit: NASA, ESA and G. Bacon (STScI)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Corona Borealis[1]
Right ascension	16h 02m 11.8462s[2]
Declination	+28° 10′ 10.420″[2]
Apparent magnitude (V)	11.19 ± 0.03[3]
Characteristics
Spectral type	G1V[3]
Apparent magnitude (B)	11.85 ± 0.04[3]
Apparent magnitude (V)	11.19 ± 0.03[3]
Apparent magnitude (J)	9.939 ± 0.022[4]
Apparent magnitude (H)	9.601 ± 0.017[4]
Apparent magnitude (K)	9.527 ± 0.015[4]
Variable type	Planetary transit variable[3]
Astrometry
Proper motion (μ)	RA: −17.349(12) mas/yr[2] Dec.: 14.780(15) mas/yr[2]
Parallax (π)	6.1489 ± 0.0136 mas[2]
Distance	530 ± 1 ly (162.6 ± 0.4 pc)
Absolute magnitude (MV)	5.02+0.14 −0.16[5]
Details
Mass	1.027+0.057 −0.061[5] M☉
Radius	0.94 ± 0.02[6] R☉
Luminosity	0.86+0.12 −0.10[5] L☉
Surface gravity (log g)	4.50 ± 0.01[7] cgs
Temperature	5738 ± 65[7] K
Metallicity [Fe/H]	−0.06 ± 0.07[7] dex
Rotational velocity (v sin i)	1.1 ± 1.0[7] km/s
Age	1.0+3.1 −0.9[5] Gyr
Other designations
Moldoveanu, BD+28 2507, TYC 2041-1657-1, GSC 02041-01657, 2MASS J16021184+2810105[8]
Database references
SIMBAD	data

The star XO-1 is named Moldoveanu. The name was selected in the NameExoWorlds campaign by Romania, during the 100th anniversary of the IAU. Moldoveanu is the highest peak in Romania.^[9][10][11]

Planetary system

The XO Project is an international team of professional and amateur astronomers which discovered the Jupiter-sized planet orbiting around XO-1. The team, led by Peter R. McCullough of the Space Telescope Science Institute in Baltimore, includes four amateur astronomers from North America and Europe. The planet was confirmed using the Harlan J. Smith Telescope and Hobby-Eberly Telescope at McDonald Observatory of the University of Texas.^[3] An independent confirmation of the planet was made by the Wide Angle Search for Planets project.^[12] In 2019, the planet was named Negoiu, after Negoiu Peak in Romania.

Further observations with the NICMOS instrument on board the Hubble Space Telescope detected the presence of water vapor, methane, and carbon dioxide in the atmosphere of XO-1b.^[13] However an independent reinvestigation of the same data was unable to reproduce these results.^[14]

The XO-1 planetary system^[15][16]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b / Negoiu	0.907±0.022 MJ	0.04914±0.00045	3.94150514(20)	<0.019	88.84±0.22°	1.199±0.017 RJ

See also

• List of transiting extrasolar planets

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. McCullough, P. R.; et al. (2006). "A Transiting Planet of a Sun-like Star". The Astrophysical Journal. 648 (2): 1228–1238. arXiv:astro-ph/0605414. Bibcode:2006ApJ...648.1228M. doi:10.1086/505651. S2CID 8100425.
4. Skrutskie, Michael F.; et al. (1 February 2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708. ISSN 0004-6256. S2CID 18913331. Vizier catalog entry
5. Torres, Guillermo; et al. (2008). "Improved Parameters for Extrasolar Transiting Planets". The Astrophysical Journal. 677 (2): 1324–1342. arXiv:0801.1841. Bibcode:2008ApJ...677.1324T. doi:10.1086/529429. S2CID 12899134.
6. Burke, Christopher J.; et al. (2010). "NICMOS Observations of the Transiting Hot Jupiter XO-1b". The Astrophysical Journal. 719 (2): 1796–1806. arXiv:1006.1953. Bibcode:2010ApJ...719.1796B. doi:10.1088/0004-637X/719/2/1796. S2CID 118798621.
7. Torres, Guillermo; et al. (2012). "Improved Spectroscopic Parameters for Transiting Planet Hosts". The Astrophysical Journal. 757 (2). 161. arXiv:1208.1268. Bibcode:2012ApJ...757..161T. doi:10.1088/0004-637X/757/2/161. S2CID 16580774.
8. "TYC 2041-1657-1". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-10-14.
9. "Romania | NameExoworlds". Archived from the original on 2019-12-18.
10. "Approved names". NameExoworlds. Retrieved 2020-01-02.
11. "International Astronomical Union | IAU". www.iau.org. Retrieved 2020-01-02.
12. Wilson, D. M.; et al. (2006). "SuperWASP Observations of the Transiting Extrasolar Planet XO-1b". The Publications of the Astronomical Society of the Pacific. 118 (847): 1245–1251. arXiv:astro-ph/0607591. Bibcode:2006PASP..118.1245W. doi:10.1086/507957. S2CID 118916713.
13. Tinetti, G.; et al. (2010). "Probing the Terminator Region Atmosphere of the Hot-Jupiter XO-1b with Transmission Spectroscopy". The Astrophysical Journal Letters. 712 (2): L139–L142. arXiv:1002.2434. Bibcode:2010ApJ...712L.139T. doi:10.1088/2041-8205/712/2/L139. S2CID 118588637.
14. Gibson, N. P.; et al. (2011). "A new look at NICMOS transmission spectroscopy of HD 189733, GJ-436 and XO-1: no conclusive evidence for molecular features". Monthly Notices of the Royal Astronomical Society. 411 (4): 2199–2213. arXiv:1010.1753. Bibcode:2011MNRAS.411.2199G. doi:10.1111/j.1365-2966.2010.17837.x. S2CID 118506224.
15. Bonomo, A. S.; et al. (2017). "The GAPS Programme with HARPS-N at TNG . XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets". Astronomy and Astrophysics. 602 A107. arXiv:1704.00373. Bibcode:2017A&A...602A.107B. doi:10.1051/0004-6361/201629882. S2CID 118923163.
16. Southworth, John; et al. (2018). "Physical properties and optical-infrared transmission spectrum of the giant planet XO-1 b". Monthly Notices of the Royal Astronomical Society. 481 (3): 4261–4276. arXiv:1809.03775. Bibcode:2018MNRAS.481.4261S. doi:10.1093/mnras/sty2488. S2CID 119503789.

External links

• SpaceDaily: Astronomers Catch Planet By Unusual Means (May 19, 2006)
• "XO-1". Exoplanets. Archived from the original on 2016-03-03. Retrieved 2009-04-28.