Phi Persei

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Template:Short description

φ Persei
Template:Location mark
Location of φ Persei (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus[1]
Right ascension Template:RA[2]
Declination Template:DEC[2]
Apparent magnitude (V) 4.06[3] (3.96 - 4.11[4])
Characteristics
Spectral type B2Vep[5] + sdO[6]
U−B Template:Engvar −0.92[3]
B−V Template:Engvar −0.04[3]
Variable type γ Cas[4]
Astrometry
Radial velocity (Rv)+0.80[7] km/s
Proper motion (μ) RA: +24.59[2] mas/yr
Dec.: −14.01[2] mas/yr
Parallax (π)4.54±0.20 mas[2]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)−3.11[8]
Orbit[8][9]
Period (P)126.6731 days
Semi-major axis (a)Script error: No such module "val".
Inclination (i)77.6°
Longitude of the node (Ω)295.7°
Periastron epoch (T)2456110.03
Semi-amplitude (K1)
(primary)		9.97 km/s
Semi-amplitude (K2)
(secondary)		81.3 km/s
Details
A
Mass9.6[10] Template:Solar mass
Radius5.5 - 8.0[8] Template:Solar radius
Luminosity14,454[10] Template:Solar luminosity
Surface gravity (log g)4.46[11] cgs
Temperature29,300[10] K
Rotational velocity (v sin i)440[11] km/s
B
Mass1.14[12] Template:Solar mass
Radius1.3[12] Template:Solar radius
Luminosity6,310[10] Template:Solar luminosity
Surface gravity (log g)4.2[10] cgs
Temperature53,000[12] K
Metallicity [Fe/H]{{{metal_fe2}}} dex
AgeScript error: No such module "val".[10] Myr
Other designations
φ Persei, φ Per, Phi Per, 54 Andromedae, BD+49°444, FK5 57, GC 2102, HD 10516, HIP 8068, HR 496, PPM 26670, SAO 22554
Database references
SIMBADdata

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Phi Persei (Phi Per, φ Persei, φ Per) is a class B2Vep fourth-magnitude star in the constellation Perseus, location about 720 light-years from Earth.

System

File:Phi Persei.jpg
φ Persei in optical light

Phi Persei is spectroscopic binary consisting of a blue main sequence primary of class B2 and a hot subdwarf secondary. The two stars have an orbit of 217 days and are separated by about Template:Solar radius.[10] Phi Persei is a runaway star and extrapolating its space velocity backwards by the modelled age of the system (57 million years) places it within the Alpha Persei cluster.[6]

The primary star rotates rapidly with a projected equatorial velocity of Script error: No such module "val".. Due to its rapid rotation, the primary star has a polar radius about Template:Solar radius and an equatorial radius of about Template:Solar radius. With an effective temperature of nearly Script error: No such module "val"., it has a bolometric luminosity nearly 15,000 times higher than the Sun. The rapidly-spinning star is surrounded by a circumstellar disk. The binary orbit, the spin of the primary star, and the disk are all seen nearly edge-on. There are no eclipses, but models of the system show that the disk significantly obscures the primary star.[6] The primary formed as a Template:Solar mass star and has accreted material from its companion.[10]

The secondary star is also a class O subdwarf, hotter than the primary but smaller and less massive. It is proposed that it is the core of a Template:Solar mass star, with the outer layers stripped as it expanded away from the main sequence. Its luminosity is higher than expected for a normal Template:Solar mass helium star, which suggests it may have evolved to helium shell burning.[10] Although the subdwarf has a bolometric luminosity about half that of the primary, it emits most of its radiation as ultraviolet, being only about 3% as bright as the primary at visible wavelengths.[6]

Variability

File:PhiPerLightCurve.png
A blue-light light curve for Phi Persei, adapted from Božić et al. (1995)[13]

Phi Persei is a variable star with both rapid and longterm variations in its brightness and spectrum. Variations occur on a daily timescale which may be related to the rotation of the primary star. Any variations originating with the secondary are difficult to detect due to its comparative faintness. Slower variations, including deep fades, are also seen. Some of the variations may correspond to the orbital period, possibly eclipses of gas streams or hot spots, but the occasional deep fades do not match any particular orbital phase. The variations are classified as γ Cassiopeiae-type, shell stars with eruptions and irregular fading.[13]

Naming

Flamsteed followed Ptolemy in treating φ Persei as being in Andromeda and gave it the designation 54 Andromedae. It is isolated from the main stars of Perseus, but lies within its formal borders.[14]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Heaven's Great General, refers to an asterism consisting of φ Persei, γ Andromedae, 51 Andromedae, 49 Andromedae, χ Andromedae, υ Andromedae, τ Andromedae, 56 Andromedae, β Trianguli, γ Trianguli and δ Trianguli. Consequently, the Chinese name for φ Persei itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx.).[15]

References

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  1. ↑ Template:Cite constellation
  2. ↑ a b c d e Script error: No such module "Citation/CS1". Vizier catalog entry
  3. ↑ a b c Script error: No such module "Citation/CS1".
  4. ↑ a b Script error: No such module "Citation/CS1".
  5. ↑ Script error: No such module "Citation/CS1".
  6. ↑ a b c d Script error: No such module "Citation/CS1".
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ a b c Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "citation/CS1".
  10. ↑ a b c d e f g h i Script error: No such module "Citation/CS1".
  11. ↑ a b Script error: No such module "Citation/CS1".
  12. ↑ a b c Script error: No such module "Citation/CS1".
  13. ↑ a b Script error: No such module "Citation/CS1".
  14. ↑ Script error: No such module "Citation/CS1".
  15. ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日 Template:Webarchive

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External links

Template:Stars of Perseus

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