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Variable star in the constellation Eridanus From Wikipedia, the free encyclopedia
HD 28843, also known as HR 1441 and DZ Eridani, is a star about 550 light years from the Earth, in the constellation Eridanus.[1] It is a 5th magnitude star, so it will be faintly visible to the naked eye of an observer far from city lights. It is a variable star, whose brightness varies slightly from 5.70 to 5.84 during its 1.374 day rotation period.[2][9] It is a member of the μ Tauri Association, a group of young stars within the larger Cassiopeia-Taurus Structure.[3]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 04h 32m 37.55373s[1] |
| Declination | −03° 12′ 34.3448″[1] |
| Apparent magnitude (V) | 5.70 - 5.84[2] |
| Characteristics | |
| Spectral type | B9III[3] |
| U−B color index | −0.55[4] |
| B−V color index | −0.14[4] |
| Variable type | SX Arietis[5] |
| Astrometry | |
| Radial velocity (Rv) | 18±7[3] km/s |
| Proper motion (μ) | RA: 18.227±0.068[1] mas/yr Dec.: −16.177±0.054[1] mas/yr |
| Parallax (π) | 5.8958 ± 0.0608 mas[1] |
| Distance | 553 ± 6 ly (170 ± 2 pc) |
| Absolute magnitude (MV) | −0.7[6] |
| Details | |
| Mass | 4.20±0.6[7] M☉ |
| Radius | 3.4[1] R☉ |
| Luminosity | 324+57 −48[7] L☉ |
| Surface gravity (log g) | 3.86[1] cgs |
| Temperature | 14800±200[7] K |
| Metallicity [Fe/H] | −0.166[8] dex |
| Rotation | 1.37381±0.00001 d[9] |
| Rotational velocity (v sin i) | 91[7] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
In 1969 Mercedes Jaschek et al. determined that HD 28843 is a helium-weak star, based on its B-V color index being bluer (more negative) than would be expected for a star with its spectral type.[12] In 1977, Robert Davis reported that the star has an overabundance of silicon.[13] It is classified as a chemically peculiar star.[14]
Henning Jorgensen et al. reported that HD 28843 was a "suspected variable star" in 1971.[15] The variability of the star was firmly established in 1977 by Holger Pedersen and Bjarne Thomsen, during a spectroscopic and photometric study of helium weak and helium strong stars. They determined its period to be 1.374±0.006 days.[16] In 1978 the star was given the variable star designation DZ Eridani.[17]
Ermanno Borra et al. reported in 1983 the detection of the magnetic field of HD 28843, and estimated its strength to be a few hundred gauss.[18] Later data from the International Ultraviolet Explorer implied a field strength of 250 gauss.[19]
M. Farthmann et al. reported in 1994 that high spectral resolution observations of the 4471Å spectral line of neutral helium can be explained if HD 28843 has two helium-enriched circular "caps" separated by a region with a dramatically lower helium abundance.[20]
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