HD 164270
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 01m 43.15s[1] |
| Declination | −32° 42′ 55.2″[1] |
| Apparent magnitude (V) | 8.74[2] |
| Characteristics | |
| Evolutionary stage | Wolf-Rayet |
| Spectral type | WC[3][4] |
| Astrometry | |
| Proper motion (μ) | RA: 1.724[1][5] mas/yr Dec.: -0.64[1][5] mas/yr |
| Parallax (π) | 0.2538 ± 0.0609 mas |
| Distance | approx. 13,000 ly (approx. 3,900 pc) |
| Other designations | |
HD 164270, WR 103, V4072 Sgr, CD-32 13623, Hen 3-1555, HIP 88287, IRAS 17584-3243, SAO 209609, TIC 265405113, TYC 7395-31-1, 2MASS J18014314-3242551, Gaia DR3 4042922573453831936[1] | |
| Database references | |
| SIMBAD | data |
HD 164270, (also known as WR 103 or V4072 Sagittarii),[6][1] is a Wolf–Rayet star of the carbon subtype (WC) located in the constellation of Sagittarius.[7] 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.[8][7] It has experienced occasional dramatic fading events of nearly 1 magnitude, though these are not definitively linked to eclipses.[8]
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.[7][9] 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.[9] The terminal wind velocity is around 1,400 km/s.[10] 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).[9]
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.[8] 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.[7][8]
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.[11] 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.[11] 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.[8][11] No definitive eclipses have been confirmed in the short-period binary orbit.
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "HD 164270". simbad.cds.unistra.fr. Retrieved 2026-02-10.
- ↑ 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.
- ↑ Stephenson, C. B.; Sanduleak, N. (1971). "Luminous stars in the Southern Milky Way". Publications of the Warner & Swasey Observatory. 1: 1.
- ↑ Houk, N. (1982). "Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0". Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0.
- ↑ Collaboration, Gaia (2018). "VizieR Online Data Catalog: Gaia DR2 (Gaia Collaboration, 2018)". VizieR Online Data Catalog. 1345: I/345. doi:10.26093/cds/vizier.1345.
- ↑ "Wolf-Rayet Star Catalogue". pacrowther.staff.shef.ac.uk. Retrieved 2026-02-10.
- ↑ 7.0 7.1 7.2 7.3 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. ISSN 0004-6361.
- ↑ 8.0 8.1 8.2 8.3 8.4 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. doi:10.1086/131917. ISSN 0004-6280.
- ↑ 9.0 9.1 9.2 Crowther, Paul A.; Morris, P. W.; Smith, J. D. (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. doi:10.1086/498051. ISSN 0004-637X.
- ↑ van der Hucht, K. A.; Conti, P. S. (1981). "The iron curtain of the WC9 star HD 164270". IAU Colloquium 59: Effects of Mass Loss on Stellar Evolution. 89: 35–37. doi:10.1007/978-94-009-8500-1_4.
- ↑ 11.0 11.1 11.2 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. doi:10.1086/131393. ISSN 0004-6280.
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