IK Pegasi

IK Pegasi
	; Location of IK Pegasi.
Observation data; Epoch J2000 Equinox J2000
Constellation	Pegasus
Right ascension	21h 26m 26.66066s
Declination	+19° 22′ 32.3169″
Apparent magnitude (V)	6.08
Characteristics
A
Spectral type	A8m: or kA6hA9mF0
U−B color index	0.03
B−V color index	0.235±0.009
Variable type	Delta Scuti
B
Spectral type	DA
Astrometry
Radial velocity (Rv)	−9.7±0.2 km/s
Proper motion (μ)	RA: +80.964 mas/yr ; Dec.: +16.205 mas/yr
Parallax (π)	21.1287 ± 0.1410 mas
Distance	154 ± 1 ly ; (47.3 ± 0.3 pc)
Absolute magnitude (MV)	2.75
Details
A
Mass	1.65 M☉
Radius	1.47+0.07; −0.09 R☉
Luminosity	6.568±0.051 L☉
Surface gravity (log g)	4.25 cgs
Temperature	7,624+237; −181 K
Metallicity	117
Rotational velocity (v sin i)	< 32.5 km/s
Age	50–600 Myr
B
Mass	1.15 M☉
Radius	0.006 R☉
Luminosity	0.12 L☉
Surface gravity (log g)	8.95 cgs
Temperature	35,500 K
Other designations
	AB: IK Peg, BD+18° 4794, HD 204188, HIP 105860, HR 8210, SAO 107138.
	B: WD 2124+191, EUVE J2126+193.
Database references
SIMBAD	data

IK Pegasi (or HR 8210) is a binary star system in the constellation Pegasus. It is just luminous enough to be seen with the unaided eye, at a distance of about 154 light years from the Solar System.

The primary (IK Pegasi A) is an A-type main-sequence star that displays minor pulsations in luminosity. It is categorized as a Delta Scuti variable star and it has a periodic cycle of luminosity variation that repeats itself about 22.9 times per day.^[7] Its companion (IK Pegasi B) is a massive white dwarf—a star that has evolved past the main sequence and is no longer generating energy through nuclear fusion. They orbit each other every 21.7 days with an average separation of about 31 million kilometres, or 19 million miles, or 0.21 astronomical units (AU). This is smaller than the orbit of Mercury around the Sun.

IK Pegasi B is the nearest known supernova progenitor candidate. When the primary begins to evolve into a red giant, it is expected to grow to a radius where the white dwarf can accrete matter from the expanded gaseous envelope. When the white dwarf approaches the Chandrasekhar limit of 1.4 solar masses (M_☉),^[12] it may explode as a Type Ia supernova.^[13]

^ ^a ^b ^c ^d ^e ^f ^g ^h Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
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^ Mazzali, P. A.; Röpke, F. K.; Benetti, S.; Hillebrandt, W. (2007). "A Common Explosion Mechanism for Type Ia Supernovae". Science (PDF). 315 (5813): 825–828. arXiv:astro-ph/0702351v1. Bibcode:2007Sci...315..825M. doi:10.1126/science.1136259. PMID 17289993. S2CID 16408991.
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[Anderson2012-2] Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).

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[13] Mazzali, P. A.; Röpke, F. K.; Benetti, S.; Hillebrandt, W. (2007). "A Common Explosion Mechanism for Type Ia Supernovae". Science (PDF). 315 (5813): 825–828. arXiv:astro-ph/0702351v1. Bibcode:2007Sci...315..825M. doi:10.1126/science.1136259. PMID 17289993. S2CID 16408991.

[mnras262-14] Cite error: The named reference mnras262 was invoked but never defined (see the help page).

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Observation data Epoch J2000 Equinox J2000
Location of IK Pegasi.
Constellation	Pegasus
Right ascension	21^h 26^m 26.66066^s^[1]
Declination	+19° 22′ 32.3169″^[1]
Apparent magnitude (V)	6.08^[2]
Characteristics
A
Spectral type	A8m:^[3] or kA6hA9mF0^[4]
U−B color index	0.03^[5]
B−V color index	0.235±0.009^[2]
Variable type	Delta Scuti^[3]
B
Spectral type	DA^[6]
Astrometry

Radial velocity (R_v)	−9.7±0.2^[2] km/s
Proper motion (μ)	RA: +80.964^[1] mas/yr Dec.: +16.205^[1] mas/yr
Parallax (π)	21.1287 ± 0.1410 mas^[1]
Distance	154 ± 1 ly (47.3 ± 0.3 pc)
Absolute magnitude (M_V)	2.75^[2]

Details
A
Mass	1.65^[7] `M`_☉
Radius	1.47+0.07 −0.09^[1] `R`_☉
Luminosity	6.568±0.051^[1] `L`_☉
Surface gravity (log g)	4.25^[7] cgs
Temperature	7,624+237 −181^[1] K
Metallicity	117^[7]^[8]
Rotational velocity (v sin i)	< 32.5^[8] km/s
Age	50–600^[7] Myr
B
Mass	1.15^[9] `M`_☉
Radius	0.006^[6] `R`_☉
Luminosity	0.12^{[nb 1]} `L`_☉
Surface gravity (log g)	8.95^[6] cgs
Temperature	35,500^[9] K
Other designations

AB: IK Peg, BD+18° 4794, HD 204188, HIP 105860, HR 8210, SAO 107138.^[5]
B: WD 2124+191, EUVE J2126+193.^[10]^[11]
Database references
SIMBAD	data