AFGL 4106
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Carina[1] |
| Right ascension | 10h 23m 19.48s[2] |
| Declination | −59° 32′ 04.6″[2] |
| Apparent magnitude (V) | 8.52 - 9.1[1] |
| Characteristics | |
| Apparent magnitude (B) | 10.59±0.06[3] |
| Apparent magnitude (G) | 8.125±0.005[2] |
| Apparent magnitude (J) | 4.406±0.200[4] |
| Apparent magnitude (H) | 3.432±0.208[4] |
| Apparent magnitude (K) | 2.970±0.236[4] |
| Variable type | LC[1] |
| Primary | |
| Evolutionary stage | Post-red supergiant[5] |
| Spectral type | A7Ie–F0:I[6][5][1] |
| Secondary | |
| Evolutionary stage | Red supergiant[5] |
| Spectral type | M0:I[5][1] |
| Astrometry | |
| Radial velocity (Rv) | −6.63±2.27[2] km/s |
| Proper motion (μ) | RA: −6.676±0.340[2] mas/yr Dec.: −1.455±0.350[2] mas/yr |
| Parallax (π) | 1.0611±0.297 mas[2] |
| Distance | approx. 3,100 ly (approx. 900 pc) |
| Details | |
| Primary | |
| Mass | 14.5[5] M☉ |
| Radius | 209±12[5] R☉ |
| Luminosity | 79,000±1,800[5] L☉ |
| Temperature | 6,723±196[5] K |
| Age | 13.8 or ≲2-3[5] Myr |
| Secondary | |
| Mass | 8.7[5] M☉ |
| Radius | 567±99[5] R☉ |
| Luminosity | 38000±1100[5] L☉ |
| Temperature | 3,394±264[5] K |
| Age | 30 or ≲2-3[5] Myr |
| Other designations | |
| AFGL 4106, RAFGL 4106, HD 302821, CD-58 3221, CPD-58 2154, GLMP 275, GSC 08612-00531, IRAS 10215-5916, PPM 769227, TYC 8612-531-1, UCAC2 5544670, UCAC4 153-046024[7] | |
| Database references | |
| SIMBAD | data |
AFGL 4106 (also known as HD 302821) is a binary star system located in the constellation of Carina. The system consists of two stars; an M-type red supergiant star, and a smaller, more evolved F-type post-red supergiant. The system is also surrounded by a large circumstellar envelope of 208 AU.[5]
Observational history
AFGL 4106 was first observed in 1986 by IRAS.[8] It and its dust envelope was first characterised in 1999, in which it was discovered to be a binary star and was later characterised in 2025 by the Very Large Telescope.[5][9]
Distance
A distance of 940±260 pc can be derived from the star's parallax determined by Gaia. This does however include a significant amount of astrometric noise and is therefore likely unreliable.[2][5] Using a probabilistic method to reduce noise results in a distance of 1470+590
−400 pc.[5] Both are inconsistent with the distance of the apparently nearby Carina Nebula, where the star system was initially thought to have originated from and is at a distance of 2610 pc, unless when comparing its E(B-V) of 1.07±0.2, derived from previous observations and Gaia spectroscopy, to Gaia-2MASS maps of interstellar dust which results in a distance of 3190+450
−190 pc.[5][9][10]
Star system
AFGL 4106 contains two supergiants in different stages of evolution. The primary, an A-F type supergiant, has passed its red supergiant phase, whereas the secondary is an active red supergiant. They have a separation of 865±102 AU and complete an orbit once every ~4500 days.[5]
Primary and secondary
The primary is a post-red supergiant with an initial mass of approximately 15 M☉ and an effective temperature of 6723 K, while the secondary is less evolved and has an initial mass of ~9 M☉ and an effective temperature of 3394 K.
Its relative proximity and similar proper motion to Westerlund 2 indicates that the system could have formed there. While respective ages of 13.8 Myr and 30 Myr for the primary and secondary are not consistent with the 2–3 Myr age of the cluster, their ages also highly differ, which instead indicates an unusual evolutionary pathway due to binary interaction. This may however not apply to the primary due to the large separation but could still be plausible if a close third companion had interacted with the system or if there had been a merger.[5]
AFGL 4106 was first thought to have formed in the Carina Nebula due to its apparent proximity of 2.1°. This is also consistent with their distances being similar, however, this also applies to Westerlund 2, which has an apparent distance of 1.8° and a distance of 4130 pc. Comparing their proper motions with that of the star system shows that it would have likely formed in Westerlund 2.[5][9]
Possible third companion
A third companion has not yet been detected but may explain estimates of the primary and secondary's large age difference and difference with the age of the nearby Westerlund 2 without requiring new stellar evolutionary models. It could also have explained the apparent oscillations derived from variations in the ellipticity of the surrounding ejecta, however, to match observations, the star would orbit near enough that the total system mass would have to be 1700 M☉, which is not possible.[5]
Nebula
The surrounding nebula shows a highly complex morphology, which is attributed to influence from the companion star and a complex ejection mechanism.[5]
It is also elliptical, with an eccentricity of 0.5, and the semi-minor axis of the nebula is aligned with the proper motion of the star system which indicates deceleration by the interstellar medium.[5]
See also
References
- ^ a b c d e "VSX : Detail for HD 302821". vsx.aavso.org. Retrieved 2026-03-15.
- ^ a b c d e f g h 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.
- ^ Høg, E.; Fabricius, C.; Makarov, V. V. (3 January 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. Bibcode:2000A&A...355L..27H.
- ^ a b c "2MASS J10231951-5932046". vizier.cds.unistra.fr. Retrieved 2026-06-14.
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y Tomassini, G.; Lagadec, E.; Mellah, I. El; Oudmaijer, R. D.; Chiavassa, A.; N'Diaye, M.; Laverny, P. de; Nardetto, N.; Matter, A. (2026-02-12), "Characterising the post-red supergiant binary system AFGL 4106 and its complex nebula with SPHERE/VLT", Astronomy & Astrophysics, 706: A5, arXiv:2512.01543, doi:10.1051/0004-6361/202557705, retrieved 2026-03-13
- ^ Suárez, O.; García-Lario, P.; Manchado, A.; Manteiga, M.; Ulla, A.; Pottasch, S. R. (2006). "A spectroscopic atlas of post-AGB stars and planetary nebulae selected from the IRAS point source catalogue". Astronomy & Astrophysics. 458 (1): 173–180. arXiv:astro-ph/0608080. doi:10.1051/0004-6361:20054108. ISSN 0004-6361.
- ^ "AFGL 4106". simbad.u-strasbg.fr. Retrieved 2026-06-10.
- ^ "IRAS 10215-5916". vizier.cds.unistra.fr. Retrieved 2026-06-14.
- ^ a b c Molster, F. J.; Waters, L. B. F. M.; Trams, N. R.; van Winckel, H.; Decin, L.; van Loon, J. Th.; Jäger, C.; Henning, Th.; Käufl, H.-U.; De Koter, A.; Bouwman, J. (23 February 1999). "The composition and nature of the dust shell surrounding the binary AFGL 4106". Astronomy and Astrophysics. 350: 163–180. arXiv:astro-ph/9908065. Bibcode:1999A&A...350..163M.
- ^ Lallement, R.; Vergely, J. L.; Babusiaux, C.; Cox, N. L. J. (4 March 2022). "Updated Gaia-2MASS 3D maps of Galactic interstellar dust". Astronomy & Astrophysics. 661: 12. arXiv:2203.01627. Bibcode:2022A&A...661A.147L. doi:10.1051/0004-6361/202142846.