3 Vulpeculae (abbreviated 3 Vul) is a binary star system in the northern constellation of Vulpecula,[9] located around 366 light years away from the Sun.[2] 3 Vulpeculae is its Flamsteed designation. It is visible to the naked eye as a faint, blue-white hued star with a baseline apparent visual magnitude of 5.18.[3]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Vulpecula |
| Right ascension | 19h 22m 50.8856s[2] |
| Declination | +26° 15′ 44.667″[2] |
| Apparent magnitude (V) | 5.18[3] |
| Characteristics | |
| Spectral type | B6 III[4] |
| B−V color index | −0.119±0.001[3] |
| Variable type | SPB[5][6] |
| Astrometry | |
| Radial velocity (Rv) | −14.1±1.1[3] km/s |
| Proper motion (μ) | RA: 0.922(124) mas/yr[2] Dec.: −10.270(163) mas/yr[2] |
| Parallax (π) | 8.9071 ± 0.1685 mas[2] |
| Distance | 366 ± 7 ly (112 ± 2 pc) |
| Absolute magnitude (MV) | −0.17[3] |
| Orbit[5] | |
| Period (P) | 367.7 |
| Eccentricity (e) | 0.15 |
| Semi-amplitude (K1) (primary) | 6.8 km/s |
| Details | |
| A | |
| Mass | 4.16[5] M☉ |
| Luminosity | 286+64 −52[7] L☉ |
| Surface gravity (log g) | 4.30[5] cgs |
| Temperature | 14,343[5] K |
| Rotational velocity (v sin i) | 15.5[8] km/s |
| B | |
| Mass | 0.6 - 1.1[5] M☉ |
| Age | 25[5] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
3 Vul has been nicknamed "the Observer's Nightmare" (or its Latin free translation, "Spectatori Error Inextricabilis") by some astronomers[10][5] because it is difficult to study as its orbital period is close to a year, and additionally it is pulsating with a period close to a day.[5] From a twenty-year spectroscopic study, Hube and Aikman established a 367-day orbital period, and noted the presence of non-radial pulsations in the primary star. From sparse photometry, the authors also established the star's light variability. They suggested that the primary is a member of the 53 Persei class of variable stars.[11] Such stars are now collectively known by the term slowly pulsating B-type stars. Its photometric variation led to a variable star designation, as V377 Vulpeculae, but the non-reproducibility of the light curve made determination of the pulsation period elusive.
Continuous monitoring of the star by the Transiting Exoplanet Survey Satellite has revealed a beat-period phenomenon in the light curve, which causes the luminosity variations to fluctuate in amplitude. The pulsations are non-radial, that is, the star's photosphere varies in shape rather than volume; different parts of the star are expanding and contracting simultaneously. These gravity waves, or g-mode waves, can be indicative of the interior structure of the star.[citation needed]
The primary member, designated component A, is a most likely a B-type main-sequence star[7] with a stellar classification of B6 III.[4] The star has 4.16[5] times the mass of the Sun and is radiating 286[7] times the Sun's luminosity from its photosphere at an effective temperature of 14,343 K.[5] The secondary has an estimated 0.6–1.1 solar masses.[5]