 A photoelectric (yellow)light curve for V923 Aquilae, plotted from data presented by Lynds (1960).[1] The length of a full phase cycle is 0.8518 days. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 19h 30m 33.12199s[2] |
| Declination | +03° 26′ 39.8583″[2] |
| Apparent magnitude (V) | 6.06[3] 5.98 to 6.18[4] |
| Characteristics | |
| Evolutionary stage | Main sequence[5] |
| Spectral type | B7III[6] |
| U−Bcolor index | −0.31[3] |
| B−Vcolor index | −0.019±0.008[7] |
| Variable type | Be star[4] |
| Astrometry | |
| Radial velocity (Rv) | −26.0±7.4[7] km/s |
| Proper motion (μ) | RA: 11.717[2]mas/yr Dec.: 3.089[2]mas/yr |
| Parallax (π) | 3.6705±0.0607 mas[2] |
| Distance | 890 ± 10 ly (272 ± 5 pc) |
| Absolute magnitude (MV) | −0.87[7] |
| Details[5] | |
| Primary | |
| Mass | 6.2±0.3 M☉ |
| Luminosity | 1517+158 −143 L☉ |
| Surface gravity (log g) | 3.64±0.21 cgs |
| Temperature | 16,580±400 K |
| Rotational velocity (v sin i) | 275±17 km/s |
| Secondary | |
| Mass | ~0.5 M☉ |
| Other designations | |
| V923 Aql,BD+03°4043,HD 183656,HIP 95929,HR 7415,SAO 0124704[8] | |
| Database references | |
| SIMBAD | data |
V923 Aquilae is avariablebinary star[9] system in theequatorialconstellation ofAquila. It has the designation HD 183656 from theHenry Draper Catalogue; V932 Aql is thevariable star designation. The system is dimly visible to the naked eye with anapparent visual magnitude that fluctuates around 6.06.[3] It is located at a distance of approximately 890 light years from theSun based onparallax,[2] but is drifting closer with aradial velocity of around −26 km/s.[7]
This system was first identified as a likelyspectroscopic binary byW. E. Harper in 1937, who noted it showed "narrow intense lines of peculiar spectrum".[10]P. W. Merrill andC. G. Burwell identified it as ashell star in 1949.[11][12] Merrill andA. L. Lowen showed in 1953 that the shell displayed large radial velocity variations.[13] A photometric study byC. R. Lynds in 1960 showed the system varied in brightness with an amplitude of more than 0.1 in magnitude and a characteristic period of 0.85 days, although it does not behave periodically over long time intervals.[1]
A more thorough investigation by P. Koubský and associates in 1989 using long-term radial velocity measurements determined this is a spectroscopic binary with anorbital period of 214.75 days. There is also an overlaying long-term cyclical variation of changing amplitude and period. The modelled binary system shows a primary with a class of around B5–7e and a low mass secondary separated by around 250 times the radius of the Sun (250 R☉). They hypothesized that the long-term variation was due to an envelope created by a mass transfer from the secondary component to the primary.[14] However, the mass transfer concept was later brought into question and remains unverified as of 2004.[9]
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