Astronomy:HD 164270
File:Sagittarius constellation map.svg | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 01m 43.145s[1] |
| Declination | −32° 42′ 55.16″[1] |
| Apparent magnitude (V) | 8.74[2] |
| Characteristics | |
| Evolutionary stage | Wolf–Rayet[3] |
| Spectral type | WC[4][5] |
| Apparent magnitude (G) | 8.56[1] |
| Astrometry | |
| Proper motion (μ) | RA: +1.724±0.024[1] mas/yr Dec.: −0.640±0.016[1] mas/yr |
| Parallax (π) | 0.3696 ± 0.0243[1] mas |
| Distance | 8,800 ± 600 ly (2,700 ± 200 pc) |
| Absolute magnitude (MV) | −4.6[6] |
| Details | |
| Mass | 6[6] M☉ |
| Radius | 4.1[6] R☉ |
| Luminosity | 79,000[6] L☉ |
| Temperature | 48,000[6] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 164270, (also known as WR 103 or V4072 Sagittarii),[3][7] is a Wolf–Rayet star of the carbon subtype (WC) located in the constellation of Sagittarius.[8] 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.[9][8] It has experienced occasional dramatic fading events of nearly 1 magnitude, though these are not definitively linked to eclipses.[9]
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.[8][6] 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.[6] 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).[6]
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.[9] 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.[8][9]
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.[9][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 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.
- ↑ Ducati, J. R. (2002). "VizieR Online Data Catalog: Stellar Photometry in Johnson's 11-color system (Ducati, 2002)" (in en). VizieR Online Data Catalog 2237: II/237. Bibcode: 2002yCat.2237....0D.
- ↑ 3.0 3.1 "Wolf-Rayet Star Catalogue". http://pacrowther.staff.shef.ac.uk/WRcat/.
- ↑ Stephenson, C. B.; Sanduleak, N. (1971). "Luminous stars in the Southern Milky Way" (in en). Publications of the Warner & Swasey Observatory 1: 1. Bibcode: 1971PW&SO...1a...1S.
- ↑ Houk, N. (1982) (in en). Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0. Bibcode: 1982mcts.book.....H.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 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])" (in en). The Astrophysical Journal 636 (2): 1033–1044. doi:10.1086/498051. ISSN 0004-637X. Bibcode: 2006ApJ...636.1033C.
- ↑ 7.0 7.1 "HD 164270". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+164270.
- ↑ 8.0 8.1 8.2 8.3 Isserstedt, J.; Moffat, A. F. J. (1981). "The variable, single-line WC 9 Wolf-rayet star HD 164270 with a low-mass companion" (in en). Astronomy and Astrophysics 96: 133–137. ISSN 0004-6361. Bibcode: 1981A&A....96..133I.
- ↑ 9.0 9.1 9.2 9.3 9.4 Moffat, Anthony F. J.; Lamontagne, Robert; Cerruti, Miguela (1986). "The variable WC9 star HD 164270 revisited - A close binary with a precessing disk?" (in en). Publications of the Astronomical Society of the Pacific 98: 1170. doi:10.1086/131917. ISSN 0004-6280. Bibcode: 1986PASP...98.1170M.
- ↑ van der Hucht, K. A.; Conti, P. S. (1981). "The Iron Curtain of the WC 9 Star HD 164270" (in en). Effects of Mass Loss on Stellar Evolution. Astrophysics and Space Science Library. 89. pp. 35–37. doi:10.1007/978-94-009-8500-1_4. ISBN 978-94-009-8502-5. Bibcode: 1981ASSL...89...35V.
- ↑ 11.0 11.1 11.2 Massey, P.; Lundstrom, I.; Stenholm, B. (1984). "The curious case of the 'eclipsing' WC9 star HD 164270" (in en). Publications of the Astronomical Society of the Pacific 96: 618. doi:10.1086/131393. ISSN 0004-6280. Bibcode: 1984PASP...96..618M.
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