V354 Cephei
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cepheus |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | 10.82 to 11.35[2] |
| Characteristics | |
| Spectral type | M2.5 Iab[3] – M3.5 Ib[4] |
| B−V Template:Engvar | +3.18[5] |
| Variable type | Lc[2] |
| Astrometry | |
| Proper motion (μ) | RA: –3.151[1] mas/yr Dec.: –2.398[1] mas/yr |
| Parallax (π) | 0.2161±0.0388 mas[1] |
| Distance | Script error: No such module "val". ly (Script error: No such module "val". pc)[6] |
| Absolute magnitude (MV) | –7.57 (variable)[5] |
| Absolute bolometric magnitude (Mbol) | -8.51[7] |
| Details | |
| Radius | 1,139[7]Template:Efn Template:Solar radius |
| Luminosity | 76,000[8] – 199,500[7]Template:Efn Template:Solar luminosity |
| Surface gravity (log g) | –0.5[5] cgs |
| Temperature | Script error: No such module "val".[7] K |
| Metallicity [Fe/H] | {{{metal_fe2}}} dex |
| Other designations | |
| V354 Cep, 2MASS J22333464+5853470, IRAS 22317+5838 | |
| Database references | |
| SIMBAD | data |
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V354 Cephei is a red supergiant star located within the Milky Way. It is an irregular variable located over 13,000 light-years away from the Sun. It has an estimated radius of Script error: No such module "convert"..[7] If it were placed in the center of the Solar System, it would extend to between the orbits of Mars and Jupiter.
Identification
V354 Cephei is identified as a red supergiant variable star and included on surveys such as IRAS and 2MASS, but prior to its inclusion in the General Catalogue of Variable Stars in 1981, it was referred to only by its listings on relatively obscure catalogs.[9] It is too faint to be included in catalogs such as the Henry Draper Catalogue or Bonner Durchmusterung. It was included on a 1947 Dearborn Observatory survey as star 41575, but that ID is hardly ever used.[10]
V354 Cephei has been referred to as Case 75.[5][9] This is from one of several listings of cool stars made using the Burrell Schmidt telescope at the Warner and Swasey Observatory of Case Western Reserve University, although Case 75 is mistakenly identified as the nearby F3V star BD+58°2450.[11] The carbon star AT Persei is listed as star 75 in another of the survey papers and is also known as Case 75. The SIMBAD astronomical portal prefers to restrict that usage to AT Persei and has devised a different unique acronym for V354 Cephei.[12]
Distance
V354 Cephei is near the Cepheus OB1 stellar association and considered a likely member. This association is at a distance of between 2,750 and 3,500 parsecs,[8][13]Template:Efn but currently thought to be at 3,400 parsecs based on reliable Gaia Data Release 2 parallaxes of neighbouring OB stars.[14] Its Gaia Data Release 2 parallax is Script error: No such module "val".,[15] implying a much smaller distance of around Script error: No such module "val"..[16] The Gaia Early Data Release 3 parallax is Script error: No such module "val"., implying a larger distance. Both Gaia results carry significant statistical margin of error, as well as indicators that the astrometric excess noise is far beyond acceptable levels so that the parallax should be considered unreliable.[15][1]
Properties
The properties of V354 Cephei are disputed, but the star is classed as a cool supergiant star with a spectral and luminosity class given as M2.5 Iab, indicating it is an intermediate-size luminous supergiant, but was later given as M3.5 Ib, indicating it is rather a less luminous supergiant.[3][4]
A 2005 study led by Levesque described the four red supergiant stars, KW Sagittarii, V354 Cephei, KY Cygni and Mu Cephei as the largest and most luminous galactic red supergiants with radii of roughly Template:Solar radius and bolometric luminosity of roughly Template:Solar luminosity, which is consistent with the empirical upper radius and luminosity boundary for the red supergiants. Despite it, larger sizes and luminosities have been published for few other galactic red supergiants, such as VV Cephei A and the peculiar star VY Canis Majoris at Template:Solar radius and Template:Solar radius. V354 Cephei, based on a MARCS model, was found to be the largest and most luminous of these four stars measured, with a high luminosity of Template:Solar luminosity and consequently very large size of Template:Solar radius based on the assumption of an effective temperature of Script error: No such module "val"..[5]
Newer calculations of the luminosity of V354 Cep determined the luminosity of the star to be somewhat much lower, below Template:Solar luminosity.[8][18] A 2011 study notes the discrepancy but is unable to explain it.[8] There are similar differences in the visual extinctions derived, between two and six magnitudes.[3][5] Other more recent published data assumes the smaller Gaia distance, and hence derives lower luminosities.[18]
Notes
References
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- ↑ a b c d e f Template:Cite Gaia EDR3
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- ↑ a b c Script error: No such module "Citation/CS1".
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- ↑ a b c d e f g Script error: No such module "Citation/CS1".
- ↑ Script error: No such module "Citation/CS1". Data about this star can be seen here.
- ↑ a b c d e Script error: No such module "Citation/CS1".
- ↑ a b c d Script error: No such module "Citation/CS1".
- ↑ a b Script error: No such module "Citation/CS1".
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- ↑ Template:Cite simbad
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- ↑ a b Template:Cite DR2
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- ↑ a b Script error: No such module "Citation/CS1".
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