Astronomy:AB Pictoris

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Short description: Star in the constellation Pictor
AB Pictoris

Coronagraphic image of AB Pictoris showing its tiny companion (bottom left). The data was obtained on 16 March 2003 with NACO on the VLT, using a 1.4 arcsec occulting mask on top of AB Pictoris.
Observation data
Equinox J2000.0]] (ICRS)
Constellation Pictor
Right ascension  06h 19m 12.913s[1]
Declination −58° 03′ 15.53″[1]
Apparent magnitude (V) 9.13[2]
Characteristics
Evolutionary stage main sequence[1]
Spectral type K1V(e)[2]
B−V color index 0.861±0.027[3]
Variable type BY Dra[4]
Astrometry
Radial velocity (Rv)22.6±0.3[2] km/s
Proper motion (μ) RA: 14.314±0.015[1] mas/yr
Dec.: 45.234±0.017[1] mas/yr
Parallax (π)19.9452 ± 0.0124[1] mas
Distance163.5 ± 0.1 ly
(50.14 ± 0.03 pc)
Absolute magnitude (MV)5.82[3]
Details
Mass0.90±0.10[5] M☉
Radius0.92±0.03[6] R☉
Luminosity0.51[3] L☉
Surface gravity (log g)4.40±0.09[7] cgs
Temperature5,006±81[7] K
MetallicityTemplate:M/H[7]
Rotation3.90±0.08 d[8]
Rotational velocity (v sin i)10.87±0.08[8] km/s
Age13.3+1.1
−0.6[9] Myr
Other designations
AB Pic, CD−58 1409, CPD−58 670, HD 44627A, 44627, HIP 30034, SAO 234448, PPM 335089[10]
Database references
SIMBADdata

AB Pictoris (abbreviated AB Pic, also catalogued as HD 44627) is a K-type main-sequence star, located 163.5 light-years away in the southern constellation of Pictor.[1] It was initially identified as a member of the young (30 million years old) Tucana–Horologium association,[11] but later shown to be part of the Carina association.[9] The star has been classified as a BY Draconis variable,[4] indicating it has an active chromosphere. It is an X-ray source and displays emission lines in its spectrum.[12][2]

In 2005 it was announced that an astronomical object (AB Pictoris b, abbreviated AB Pic b) had been imaged in 2003 and 2004 close to and apparently in orbit around the star. Its mass suggests that it is at the borderline between being a brown dwarf or a planet.[13]

Planetary system

A visual band light curve for AB Pictoris. The main plot shows the long-term variability, and the inset plot shows the periodic variation. Adapted from Kiraga (2012)[14]

In 2003 and 2004, an object (now catalogued as AB Pictoris b) was observed close to the star by a team of astronomers at the European Southern Observatory. Since it had common proper motion with AB Pictoris, it was concluded that it was physically close to the star. Its spectral type was estimated as between L0V and L3V.

Using evolutionary models, the companion's mass was initially estimated as from 13 to 14 Jupiter masses.[13] However, because modelling such young objects was difficult at the time, this estimate is very uncertain; some models give masses as low as 11 Jupiter masses or as high as 70 Jupiter masses.[15] As it is not known if the mass of the object exceeds the deuterium burning limit of 13 Jupiter masses, it is not clear whether the object should be classified as an extrasolar planet or a brown dwarf.[13] Later measurements gave lower masses of 9.1±1.1 and 10.5±2.1 MJ in 2025,[16] and 10±1 MJ in 2022, assuming an age of 13.3 Myr based on membership to the Carina association.[17][16] These values are well within the planetary-mass regime.[18] However, one 2024 study re-determined the age of the Carina association to 28±11 Myr,[19] yielding a larger mass of 12.9+0.3
−1.0 MJ that may be over the deuterium limit.[18]

Initial temperature estimates varied from 1600 K to 2400 K.[15] In 2010 a team obtained the spectrum of AB Pic b with VLT/SINFONI. This confirmed this object as an L-dwarf with low surface gravity, matching a spectral type of L0-L1. It also constrained the temperature to 2000+100
−300 Kelvin.[20] One 2012 study found that AB Pic b has a lower temperature of 1400-1700 K and possibly a lower mass (7-14 MJ, from figure 13).[21] A 2014 analysis did find a temperature of 1800+100
−200 K and a mass of 10-14 MJ.[22] The planet shows several molecular and atomic absorption lines in the spectrum. The most notable are water vapor, carbon monoxide, potassium and sodium. The planetary orbit is significantly misaligned with its spin axis orientation (obliquity), possibly due to gravitational interactions with the additional inner planet.[17]

An additional planet, AB Pictoris c, was first suspected by combining direct imaging, radial velocity and the astrometric acceleration from AB Pic A.[17] The planet was confirmed in 2025 with a re-analysis of the Gaia excess noise and the proper motion anomaly.[23]

The planetary system
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(years) 		Eccentricity Inclination Radius
c 2.5–9[23] MJ 3–5[23] — — — —
b 12.9+0.3
−1.0[18] MJ 		242+109
−56[18] 		— 0.54+0.32
−0.30[18] 		90±12[17]° 1.53±0.03[17] RJ

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Torres, C. A. O. et al. (September 12, 2006). "Search for associations containing young stars (SACY)". Astronomy & Astrophysics 460 (3): 695–708. doi:10.1051/0004-6361:20065602. ISSN 0004-6361. Bibcode: 2006A&A...460..695T. 
  3. ↑ 3.0 3.1 3.2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  4. ↑ 4.0 4.1 Samus', N. N et al. (2017). "General catalogue of variable stars". Astronomy Reports. GCVS 5.1 61 (1): 80. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  5. ↑ Ghezzi, L.; Cunha, K.; Smith, V. V.; de Araújo, F. X.; Schuler, S. C.; de la Reza, R. (August 19, 2010). "Stellar Parameters and Metallicities of Stars Hosting Jovian and Neptunian Mass Planets: A Possible Dependence of Planetary Mass on Metallicity". The Astrophysical Journal 720 (2): 1290–1302. doi:10.1088/0004-637X/720/2/1290. ISSN 0004-637X. Bibcode: 2010ApJ...720.1290G. 
  6. ↑ van Belle, Gerard T.; von Braun, Kaspar (2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars". The Astrophysical Journal 694 (2): 1085–1098. doi:10.1088/0004-637X/694/2/1085. Bibcode: 2009ApJ...694.1085V. 
  7. ↑ 7.0 7.1 7.2 Baburaj, Aneesh; Konopacky, Quinn M.; Theissen, Christopher A.; Gerasimov, Roman; Hoch, Kielan K. W. (January 2026). "A High-resolution Spectroscopic Survey of Directly Imaged Companion Hosts. II. Diversity in C/O Ratios among Host Stars" (in en). The Astronomical Journal 171 (1): 21. doi:10.3847/1538-3881/ae1a6b. ISSN 0004-6256. Bibcode: 2026AJ....171...21B. 
  8. ↑ 8.0 8.1 Bowler, Brendan P. et al. (April 2023). "Rotation Periods, Inclinations, and Obliquities of Cool Stars Hosting Directly Imaged Substellar Companions: Spin-Orbit Misalignments Are Common". The Astronomical Journal 165 (4): 164. doi:10.3847/1538-3881/acbd34. 164. Bibcode: 2023AJ....165..164B. 
  9. ↑ 9.0 9.1 Booth, Mark; del Burgo, Carlos; Hambaryan, Valeri V (2020-12-15). "The age of the carina young association and potential membership of HD 95086" (in en). Monthly Notices of the Royal Astronomical Society 500 (4): 5552–5560. doi:10.1093/mnras/staa3631. ISSN 0035-8711. Bibcode: 2021MNRAS.500.5552B. 
  10. ↑ "V* AB Pic". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=V%2A+AB+Pic. 
  11. ↑ Inseok Song, B. Zuckerman; Bessell, M. S. (December 2003). "New Members of the TW Hydrae Association, β Pictoris Moving Group, and Tucana/Horologium Association". The Astrophysical Journal 599 (1): 342–350. doi:10.1086/379194. Bibcode: 2003ApJ...599..342S. 
  12. ↑ Haakonsen, Christian Bernt; Rutledge, Robert E. (September 2009). "XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources". The Astrophysical Journal Supplement 184 (1): 138–151. doi:10.1088/0067-0049/184/1/138. Bibcode: 2009ApJS..184..138H. 
  13. ↑ 13.0 13.1 13.2 Chauvin, G.; Lagrange, A. -M.; Zuckerman, B.; Dumas, C.; Mouillet, D.; Song, I.; Beuzit, J. -L.; Lowrance, P. et al. (2005). "A companion to AB Pic at the planet/Brown dwarf boundary". Astronomy and Astrophysics 438 (3): L29–L32. doi:10.1051/0004-6361:200500111. Bibcode: 2005A&A...438L..29C. 
  14. ↑ Kiraga, M. (March 2012). "ASAS Photometry of ROSAT Sources. I. Periodic Variable Stars Coincident with Bright Sources from the ROSAT All Sky Survey". Acta Astronomica 62 (1): 67–95. Bibcode: 2012AcA....62...67K. 
  15. ↑ 15.0 15.1 Neuhaeuser, Ralph (2005). "Homogeneous comparison of directly detected planet candidates: GQ Lup, 2M1207, AB Pic". ESO Workshop Proceedings on Multiple Stars. 
  16. ↑ 16.0 16.1 Palma-Bifani, P.; Bonnefoy, M.; Chauvin, G.; Rojo, P.; Baudoz, P.; Charnay, B.; Denis, A.; Hoch, K. et al. (September 2025). "The planetary-mass-limit VLT/SINFONI library: Spectral extraction and atmospheric characterization via forward modeling" (in en). Astronomy and Astrophysics 701: A51. doi:10.1051/0004-6361/202554894. ISSN 0004-6361. Bibcode: 2025A&A...701A..51P. https://ui.adsabs.harvard.edu/abs/2025A&A...701A..51P/abstract. 
  17. ↑ 17.0 17.1 17.2 17.3 17.4 Palma-Bifani, P. et al. (2023). "Peering into the young planetary system AB Pic. Atmosphere, Orbit, Obliquity & Second Planetary Candidate". Astronomy & Astrophysics 670: A90. doi:10.1051/0004-6361/202244294. Bibcode: 2023A&A...670A..90P. 
  18. ↑ 18.0 18.1 18.2 18.3 18.4 Lazzoni, Cecilia; Zurlo, Alice; Desidera, Silvano; Bernardi, Andrea; Pérez, Sebastian; Mesa, Dino; Barbato, Domenico; Nogueira, Pedro Henrique; Dasgupta, Anuroop (2026-03-25). "SaNDi-SHoP: Searching for Satellites'N'Disks with a Star-Hopping Program I. Analysis of the close surroundings of DI companions". arXiv:2603.24796 [astro-ph.EP].
  19. ↑ Gratton, R.; Bonavita, M.; Mesa, D.; Desidera, S.; Zurlo, A.; Marino, S.; D'Orazi, V.; Rigliaco, E. et al. (May 2024). "Stellar companions and Jupiter-like planets in young associations" (in en). Astronomy and Astrophysics 685: A119. doi:10.1051/0004-6361/202348393. ISSN 0004-6361. Bibcode: 2024A&A...685A.119G. 
  20. ↑ Bonnefoy, M.; Chauvin, G.; Rojo, P.; Allard, F.; Lagrange, A. -M.; Homeier, D.; Dumas, C.; Beuzit, J. -L. (2010-03-01). "Near-infrared integral-field spectra of the planet/brown dwarf companion AB Pictoris b". Astronomy and Astrophysics 512: A52. doi:10.1051/0004-6361/200912688. ISSN 0004-6361. Bibcode: 2010A&A...512A..52B. 
  21. ↑ Patience, J.; King, R. R.; De Rosa, R. J.; Vigan, A.; Witte, S.; Rice, E.; Helling, Ch.; Hauschildt, P. (2012-04-01). "Spectroscopy across the brown dwarf/planetary mass boundary. I. Near-infrared JHK spectra". Astronomy and Astrophysics 540: A85. doi:10.1051/0004-6361/201118058. ISSN 0004-6361. Bibcode: 2012A&A...540A..85P. 
  22. ↑ Bonnefoy, M.; Chauvin, G.; Lagrange, A. -M.; Rojo, P.; Allard, F.; Pinte, C.; Dumas, C.; Homeier, D. (2014-02-01). "A library of near-infrared integral field spectra of young M-L dwarfs". Astronomy and Astrophysics 562: A127. doi:10.1051/0004-6361/201118270. ISSN 0004-6361. Bibcode: 2014A&A...562A.127B. 
  23. ↑ 23.0 23.1 23.2 Lagrange, A.-M.; Kiefer, F.; Rubini, P.; Squicciarini, V.; Chomez, A.; Milli, J.; Zurlo, A.; Bouvier, J.; Delorme, P. (2025-01-17). "Searching for substellar companion candidates with Gaia. III. Search for companions to members of young associations". arXiv:2501.10488 [astro-ph.EP].



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