HD 164270
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 01m 43.145s |
| Declination | −32° 42′ 55.16″ |
| Apparent magnitude (V) | 8.74 |
| Characteristics | |
| Evolutionary stage | Wolf–Rayet |
| Spectral type | WC |
| Apparent magnitude (G) | 8.56 |
| Astrometry | |
| Proper motion (μ) | RA: +1.724±0.024 mas/yr Dec.: −0.640±0.016 mas/yr |
| Parallax (π) | 0.3696±0.0243 mas |
| Distance | 8,800 ± 600 ly (2,700 ± 200 pc) |
| Absolute magnitude (MV) | −4.6 |
| Details | |
| Mass | 6 M☉ |
| Radius | 4.1 R☉ |
| Luminosity | 79,000 L☉ |
| Temperature | 48,000 K |
| Other designations | |
| Hen 3-1555, V4072 Sgr, CD−32°13623, HD 164270, HIP 88287, SAO 209609, TIC 265405113, TYC 7395-31-1, IRAS 17584-3243, 2MASS J18014314−3242551, Gaia DR3 4042922573453831936 | |
| Database references | |
| SIMBAD | data |
HD 164270, (also known as WR 103 or V4072 Sagittarii), is a Wolf–Rayet star of the carbon subtype (WC) located in the constellation of Sagittarius. The star exhibits low-amplitude photometric and radial velocity variations with a period of 1.754 days, interpreted as arising from a single-line spectroscopic binary system containing a low-mass companion, possibly a neutron star. It has experienced occasional dramatic fading events of nearly 1 magnitude, though these are not definitively linked to eclipses.
Observation
As a late-type carbon-rich Wolf–Rayet star, HD 164270 displays broad emission lines dominated by carbon and oxygen in its spectrum, indicative of a strong stellar wind. Models accounting for line blanketing and wind clumping yield an effective temperature of approximately 48,000 K, a luminosity of about 79,400 times that of the Sun (log(L/L☉) ≈ 4.9), and a mass-loss rate of roughly 10−5 M☉/yr for a volume filling factor of 0.1. The terminal wind velocity is around 1,400 km/s. Abundances derived from optical and mid-infrared diagnostics include C/He ≈ 0.2 and O/He ≈ 0.01 by number, with neon and sulfur abundances elevated relative to solar values (Ne/He ≈ 2.2×10−3 and S/He ≈ 5.1×10−5).
Variability
HD 164270 displays cyclic photometric variations with a period of 1.75404 days and an amplitude of ~0.03 magnitude in the visible (increasing at shorter wavelengths), manifesting as a double-wave light curve per cycle. Emission-line radial velocities vary with a single wave per cycle and low amplitude (~20–30 km/s), consistent with orbital motion in a binary system.
In addition to these short-period variations, the star has undergone rare, deep fading events, including drops of nearly 1 magnitude observed in June 1980 and September 1909. The 1980 event showed no color change, and archival plate analysis limits possible periods for recurrence to 17.7, 35.4, or 70.8 years. These events may represent partial eclipses by a large, cool companion or could arise from alternative mechanisms such as a precessing accretion disk influenced by a third body, or nonradial pulsations. No definitive eclipses have been confirmed in the short-period binary orbit.
References
- 1 2 3 4 5 6 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.
- ↑ Ducati, J. R. (2002). "VizieR Online Data Catalog: Stellar Photometry in Johnson's 11-color system (Ducati, 2002)". VizieR Online Data Catalog. 2237: II/237. Bibcode:2002yCat.2237....0D.
- 1 2 "Wolf-Rayet Star Catalogue". pacrowther.staff.shef.ac.uk. Retrieved 2026-02-10.
- ↑ Stephenson, C. B.; Sanduleak, N. (1971). "Luminous stars in the Southern Milky Way". Publications of the Warner & Swasey Observatory. 1: 1. Bibcode:1971PW&SO...1a...1S.
- ↑ Houk, N. (1982). Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0. Bibcode:1982mcts.book.....H.
- 1 2 3 4 5 6 7 8 Crowther, Paul A.; Morris, P. W.; Smith, J. D. (January 2006). "An Ultraviolet to Mid-Infrared Study of the Physical and Wind Properties of HD 164270 (WC9) and Comparison to BD +30 3639 ([WC9])". The Astrophysical Journal. 636 (2): 1033–1044. arXiv:astro-ph/0509343. Bibcode:2006ApJ...636.1033C. doi:10.1086/498051. ISSN 0004-637X.
- 1 2 "HD 164270". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2026-02-10.
- 1 2 3 4 Isserstedt, J.; Moffat, A. F. J. (1981). "The variable, single-line WC 9 Wolf-rayet star HD 164270 with a low-mass companion". Astronomy and Astrophysics. 96: 133–137. Bibcode:1981A&A....96..133I. ISSN 0004-6361.
- 1 2 3 4 5 Moffat, Anthony F. J.; Lamontagne, Robert; Cerruti, Miguela (1986). "The variable WC9 star HD 164270 revisited - A close binary with a precessing disk?". Publications of the Astronomical Society of the Pacific. 98: 1170. Bibcode:1986PASP...98.1170M. doi:10.1086/131917. ISSN 0004-6280.
- ↑ van der Hucht, K. A.; Conti, P. S. (1981). "The Iron Curtain of the WC 9 Star HD 164270". Effects of Mass Loss on Stellar Evolution. Astrophysics and Space Science Library. Vol. 89. pp. 35–37. Bibcode:1981ASSL...89...35V. doi:10.1007/978-94-009-8500-1_4. ISBN 978-94-009-8502-5.
- 1 2 3 Massey, P.; Lundstrom, I.; Stenholm, B. (1984). "The curious case of the 'eclipsing' WC9 star HD 164270". Publications of the Astronomical Society of the Pacific. 96: 618. Bibcode:1984PASP...96..618M. doi:10.1086/131393. ISSN 0004-6280.
