V356 Sagittarii
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Min I: 7.66
Min II: 7.24[3]
 Light curves for V356 Sagittarii, in three photometric bands. Plotted from data published by Wilson and Woodward (1995).[1] | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 47m 52.331s[2] |
| Declination | −20° 16′ 28.24″[2] |
| Apparent magnitude (V) | 6.84 Min I: 7.66 Min II: 7.24[3] |
| Characteristics | |
| Spectral type | B3V + A2II[4] |
| B−V color index | 0.120±0.029[5] |
| Variable type | Detached Algol(?)[3] |
| Astrometry | |
| Radial velocity (Rv) | 7.0±4.4[5] km/s |
| Proper motion (μ) | RA: +0.525 mas/yr[2] Dec.: −4.847 mas/yr[2] |
| Parallax (π) | 1.4783±0.0289 mas[2] |
| Distance | 2,210 ± 40 ly (680 ± 10 pc) |
| Orbit[6] | |
| Period (P) | 8.896106 d |
| Eccentricity (e) | 0.01566±0.01360 |
| Argument of periastron (ω) (secondary) | 288.71851±0.42683° |
| Semi-amplitude (K1) (primary) | 72.17896±1.25080 km/s |
| Semi-amplitude (K2) (secondary) | 190 km/s |
| Details | |
| Primary | |
| Mass | 11.0[7] M☉ |
| Radius | 9.07[7] R☉ |
| Surface gravity (log g) | 3.96±0.10[4] cgs |
| Temperature | 16,500±750[4] K |
| Rotational velocity (v sin i) | 350[4] km/s |
| Secondary | |
| Mass | 3.0[7] M☉ |
| Radius | 13.2[7] R☉ |
| Surface gravity (log g) | 2.82±0.10[4] cgs |
| Temperature | 8,600±300[4] K |
| Rotational velocity (v sin i) | 90[4] km/s |
| Other designations | |
| V356 Sgr, BD−20°5268, GC 25739, HD 173787, HIP 92235, SAO 187294, PPM 268914[8] | |
| Database references | |
| SIMBAD | data |
V356 Sagittarii is an eclipsing binary star system in the southern constellation of Sagittarius, abbreviated V356 Sgr. It has a peak apparent visual magnitude of 6.84, which decreases to 7.66 during the primary eclipse and 7.24 with the secondary eclipse.[3] Based on parallax measurements, this system is located at a distance of approximately 2,210 light years from the Sun.[2]
In 1929, the Japanese astronomer Kanda discovered that the star, then called BD-20°5268, is a variable star. It was given its variable star designation, V356 Sagittarii, in 1930.[9]
This is a double-lined spectroscopic binary system with an orbital period of 8.896 days.[6] It is a massive, interacting system with a circular orbit, where the secondary component has filled its Roche lobe and is transferring matter to its companion. The primary is a B-type main-sequence star with a stellar classification of B3V. It was originally the lower mass component,[10] but now has about 11 times the mass of the Sun.[7] The secondary is an evolved supergiant star[10] with a present-day class of A2II.[4] It has been stripped of much of its original mass,[10] leaving behind the exposed core of a star.[11] The transfer of matter is creating an accretion disk in orbit around the primary.[10]
At least some of the material stripped from the current secondary component has likely been lost from the system. A relatively small change in the orbital period has been observed, but the period is fairly stable over time, which may mean the mass transfer is intermittent.[10] Ultraviolet emission has been observed with the FUSE space observatory, indicating the presence of hot circumstellar matter. This emission shows little variation during a total eclipse, suggesting the material lies perpendicular to the accretion disk. This could represent a bipolar jet of matter from the primary.[12]
