Nu Pictoris

ν Pictoris
Location of ν Pictoris (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Pictor
Right ascension 06h 22m 55.82671s
Declination −56° 22′ 11.8909″
Apparent magnitude (V) 5.60
Characteristics
Spectral type A1mA3-A9 + KV
U−B color index 0.12
B−V color index 0.26
Astrometry
Radial velocity (Rv)+6.7±2.9 km/s
Proper motion (μ) RA: −39.96 mas/yr
Dec.: −20.13 mas/yr
Parallax (π)20±1 mas
Distance163 ± 8 ly
(50 ± 3 pc)
Absolute magnitude (MV)+2.18
Orbit
Period (P)452+13
−16 d
Semi-major axis (a)0.0312"
(1.56 au)
Eccentricity (e)0.20+0.35
−0.19
Inclination (i)116+12
−10°
Longitude of the node (Ω)53+166
−16°
Periastron epoch (T)2448660
Argument of periastron (ω)
(secondary)		109±53°
Details
A
Mass1.7 M☉
Radius1.85 R☉
Luminosity15.4±0.4 L☉
Surface gravity (log g)3.97 cgs
Temperature7,700 K
Metallicity [Fe/H]−0.03 dex
Rotation2.21 days
Rotational velocity (v sin i)42.8 km/s
Age800 Myr
B
Mass0.8 M☉
Radius0.72 R☉
Temperature4,800 K
Age800 Myr
Other designations
ν Pic, CPD−56°1072, GC 8274, HD 45229, HIP 30342, HR 2320, SAO 234473, TYC 8542-1469-1
Database references
SIMBADdata

ν Pictoris, Latinized as Nu Pictoris, is a binary star system in the southern constellation Pictor. It is visible to the naked eye as a dim point of light with an apparent visual magnitude of 5.60. The system is located around 163 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +7 km/s.

Characteristics

Binarity

Hipparcos satellite astrometry showed that ν Pictoris moved in a way that was not consistent with the proper motion and annual parallax of a single star. The unusual measurements were not readily identifiable as being due to orbital motion, and it was referred to as having a stochastic solution to its astrometry. Later analysis derived an orbit, although nothing was known about the companion except its approximate mass and motion about the visible star.

The companion was directly detected in 2026 using interferometric data taken in 2024 by the GRAVITY instrument aboard the Very Large Telescope, revealing it to be a K-type main-sequence star. The projected separation of 0.17 au is much smaller than the orbital semi-major axis, which could suggest that the projected separation is much smaller than the actual separation, a possibility further supported by the nearly edge-on orientation of the orbit. A more exotic hypothesis is that Nu Pictoris is a triple system, on which the companion responsible for the astrometric anomalies is, in fact, a third undetected star, either a white dwarf or red dwarf.

The pair orbit each other with a period of 452 days, a semi-major axis of 1.56 au, and an eccentricity of 0.2.

Physical characteristics

The primary, component A, is a metal-lined Am star with a stellar classification of A1mA3-A9. It has 1.7 times the Sun's mass, 1.85 times the radius of the Sun and is radiating 15 times the Sun's luminosity from its photosphere at an effective temperature of 7,700 K. The secondary, component B, has 0.8 times the Sun's mass, 0.72 times the Sun's radius, and a temperature of 4,800 K. The system is a source for X-ray emission and exhibits stellar flares, both of which are coming from the companion.

References

  1. 1 2 3 4 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. 1 2 3 4 5 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  3. 1 2 Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars. Vol. 1. Ann Arbor: Dept. of Astronomy, University of Michigan. Bibcode:1975mcts.book.....H.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Waisberg, Idel; Klein, Ygal; Katz, Boaz (2026-08-18). "Hidden Companions to Intermediate-mass Stars. XXXIX. Discovery of a 0.8 M☉ Companion to the Flaring Am Star Nu Pictoris". Research Notes of the AAS. 10 (8): 240. doi:10.3847/2515-5172/ae9a71. ISSN 2515-5172.
  5. 1 2 Feinstein, A. (1974). "Photoelectric UBVRI observations of AM stars". Astronomical Journal. 79: 1290. Bibcode:1974AJ.....79.1290F. doi:10.1086/111675.
  6. 1 2 Goldin, A.; Makarov, V. V. (September 2006). "Unconstrained Astrometric Orbits for Hipparcos Stars with Stochastic Solutions". The Astrophysical Journal Supplement Series. 166 (1): 341–350. arXiv:astro-ph/0606293. Bibcode:2006ApJS..166..341G. doi:10.1086/505939. S2CID 15673734.
  7. 1 2 3 4 Goldin, A. (2007). "Astrometric Orbits for Hipparcos Stochastic Binaries". The Astrophysical Journal Supplement Series. 173 (1): 137–142. arXiv:0706.0361. Bibcode:2007ApJS..173..137G. doi:10.1086/520513. S2CID 119586069.
  8. 1 2 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  9. ↑ Stassun, Keivan G.; et al. (2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467.
  10. ↑ Gontcharov, G. A. (2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters. 38 (12): 771. arXiv:1606.08814. Bibcode:2012AstL...38..771G. doi:10.1134/S1063773712120031.
  11. 1 2 Balona, L. A. (2019). "Evidence for spots on hot stars suggests major revision of stellar physics". Monthly Notices of the Royal Astronomical Society. 490 (2): 2112. arXiv:1910.01584. Bibcode:2019MNRAS.490.2112B. doi:10.1093/mnras/stz2808.
  12. ↑ "nu. Pic". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 28 December 2016.