HD 164270
Wolf–Rayet star
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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 data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| 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 mas[1] |
| 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 | |
| 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[7] | |
| Database references | |
| SIMBAD | data |
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.