HD 43317
Variable star in the constellation Orion
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HD 43317 is a variable star in the equatorial constellation of Orion, the hunter. It has an apparent visual magnitude of 6.63,[1] which is faint enough to be a challenge to view with the naked eye under good conditions. Based on parallax measurements, it is located at a distance of approximately 1,050 light years from the Sun. It is drifting further away with a heliocentric radial velocity of about 13 km/s.[6] This star is a member of an open cluster designated OCSN 63.[9]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Orion[1] |
| Right ascension | 06h 15m 47.013s[2] |
| Declination | +04° 17′ 01.10″[2] |
| Apparent magnitude (V) | 6.63[1] |
| Characteristics | |
| Evolutionary stage | Main sequence[3] |
| Spectral type | B3.5 V[3] or B3 IV[4] |
| U−B color index | −0.646[1] |
| B−V color index | −0.164±0.010[1] |
| Variable type | SPB/β Cep hybrid[5] |
| Astrometry | |
| Radial velocity (Rv) | 13.0±4.4[6] km/s |
| Proper motion (μ) | RA: −4.231 mas/yr[2] Dec.: −3.765 mas/yr[2] |
| Parallax (π) | 3.0975±0.0517 mas[2] |
| Distance | 1,050 ± 20 ly (323 ± 5 pc) |
| Absolute magnitude (MV) | −1.13[1] |
| Details | |
| Mass | 5.8+0.1 −0.2[3] M☉ |
| Radius | 3.39[7] R☉ |
| Luminosity | 737.5[1] L☉ |
| Surface gravity (log g) | 4.0±0.1[3] cgs |
| Temperature | 17,350±750[3] K |
| Rotation | 0.897673(4) d[3] |
| Rotational velocity (v sin i) | 115±9[3] km/s |
| Age | 28.4[7] Myr |
| Other designations | |
| CoRoT 3412, BD+04° 1181, FK5 2478, HD 43317, HIP 29739, HR 2232, SAO 113653, PPM 150182[8] | |
| Database references | |
| SIMBAD | data |
Observations
During 2009–2010, HD 43317 was observed by the CoRoT space telescope during the LRa03 (long run) sequence for asteroseismological purposes. This program lasted for a period of 150.41 days, during which the star was under almost constant observation. After being combined with HARPS data, the star was classified as a hybrid slowly pulsating B-type star and a Beta Cephei variable. Both g (gravity) and p (pressure) mode pulsations were detected. It is spinning rapidly at about half of its critical velocity.[10]
The photometry and spectrometry of HD 43317 showed rotational modulation of regions with temperature or chemical differences. These are an indirect indicator of a magnetic field. In addition, X-ray emission was detected by ROSAT, which also suggests a potential magnetic field. A magnetic field was directly detected with the Téléscope Bernard Lyot during 2012. The longitudinal field strength was found to vary with the 21.5 h rotation period, ranging from −140 G to 180 G.[11] Modelling of the star's dipolar field found a strength between 1 and 1.5 kG. This is strong enough to force uniform rotation in the outer radiative zone of the star.[5]
The CoRoT light curve of the star displays 35 different frequencies, of which 28 are not related to the rotation period. Seismic modeling of the star determined a stellar mass equal to 5.8 times the mass of the Sun. At the core, the central mass fraction of hydrogen is 54%, compared to 70% for a newly formed main sequence star and 0.1% at the end of main sequence lifetime. Spectroscopic analysis shows an effective temperature of around 17,350 in the stellar atmosphere. A refined estimate of the surface magnetic field strength found a value of 1,312±332 G.[13] The magnetic field near the core has a seismically modelled strength of 5×105 G. HD 43317 is the first main sequence star for which an interior magnetic field strength has been inferred.[3]
This star has an estimated radius of 3.39 times the girth of the Sun,[7] and is radiating 737.5[1] times the Sun's luminosity. It is about 28.4 million years old.[7]