21 Aquilae information

21 Aquilae
	; An ultraviolet band light curve for V1288 Aquilae, adapted from Veto (1980)
Observation data; Epoch J2000 Equinox J2000
Constellation	Aquila
Right ascension	19h 13m 42.70120s
Declination	+02° 17′ 37.3103″
Apparent magnitude (V)	5.06 - 5.16
Characteristics
Spectral type	B8II-III(Hg?)
U−B color index	−0.399
B−V color index	−0.065
Variable type	α2 CVn
Astrometry
Radial velocity (Rv)	−5.2 km/s
Proper motion (μ)	RA: +10.102 mas/yr ; Dec.: −0.825 mas/yr
Parallax (π)	4.7730 ± 0.1052 mas
Distance	680 ± 20 ly ; (210 ± 5 pc)
Absolute magnitude (MV)	−2.12
Details
Mass	6.7 M☉
Radius	6.2 R☉
Luminosity	704 L☉
Surface gravity (log g)	3.95 cgs
Temperature	12,014 K
Metallicity [Fe/H]	−0.20 dex
Rotation	9.3 d
Rotational velocity (v sin i)	17 km/s
Age	165 Myr
Other designations
	21 Aql, V1288 Aql, BD+02°3824, FK5 3537, HD 179761, HIP 94477, HR 7287, SAO 124408, WDS J19137+0218A
Database references
SIMBAD	data

21 Aquilae is a solitary^[14] variable star in the equatorial constellation of Aquila. It has the variable star designation V1288 Aql; 21 Aquilae is its Flamsteed designation. This object is visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of about 5.1. The star is located at a distance of around 680 light-years (210 parsecs) from Earth, give or take a 20 light-year margin of error. It is moving closer to the Earth with a heliocentric radial velocity of –5 km/s.^[6]

The stellar classification of this star is B8 II-III, with the luminosity class of II-III suggesting that the spectrum displays elements of both a giant star and a bright giant. It is a chemically peculiar star of the Mercury-Manganese type (CP3),^[10] although some catalogues consider that status to be doubtful.^[15] This is a probable Alpha² Canum Venaticorum variable that ranges in visual magnitude from 5.06 down to 5.16.^[3] The star is radiating 704 times the luminosity of the Sun from its photosphere at an effective temperature of 12,014 K; this gives it the blue-white glow of a B-type star.^[16]

21 Aquilae is catalogued as an optical double star, having a 12th magnitude companion 37″ away as of 2010. It was first identified as a double star by John Herschel.^[17] The companion is a distant background object.^[18]

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^ ^a ^b ^c Cite error: The named reference Ghazaryan2018 was invoked but never defined (see the help page).
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[veto1980-1] Cite error: The named reference veto1980 was invoked but never defined (see the help page).

[GaiaDR3-2] Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).

[Samus2017-3] Cite error: The named reference Samus2017 was invoked but never defined (see the help page).

[cowley1972-4] Cite error: The named reference cowley1972 was invoked but never defined (see the help page).

[apj154_945-5] Cite error: The named reference apj154_945 was invoked but never defined (see the help page).

[rgcrv-6] Cite error: The named reference rgcrv was invoked but never defined (see the help page).

[Anderson2012-7] Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).

[fouesneau2022-8] Cite error: The named reference fouesneau2022 was invoked but never defined (see the help page).

[kervella2021-9] Cite error: The named reference kervella2021 was invoked but never defined (see the help page).

[Ghazaryan2018-10] Cite error: The named reference Ghazaryan2018 was invoked but never defined (see the help page).

[oelkers2018-11] Cite error: The named reference oelkers2018 was invoked but never defined (see the help page).

[gontcharov2012-12] Cite error: The named reference gontcharov2012 was invoked but never defined (see the help page).

[SIMBAD-13] Cite error: The named reference SIMBAD was invoked but never defined (see the help page).

[Eggleton2008-14] Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).

[renson2009-15] Cite error: The named reference renson2009 was invoked but never defined (see the help page).

[csiro-16] Cite error: The named reference csiro was invoked but never defined (see the help page).

[wds-17] Cite error: The named reference wds was invoked but never defined (see the help page).

[dr3b-18] Cite error: The named reference dr3b was invoked but never defined (see the help page).

Observation data Epoch J2000 Equinox J2000
An ultraviolet band light curve for V1288 Aquilae, adapted from Veto (1980)^[1]
Constellation	Aquila
Right ascension	19^h 13^m 42.70120^s^[2]
Declination	+02° 17′ 37.3103″^[2]
Apparent magnitude (V)	5.06 - 5.16^[3]
Characteristics
Spectral type	B8II-III(Hg?)^[4]
U−B color index	−0.399^[5]
B−V color index	−0.065^[5]
Variable type	α² CVn^[3]
Astrometry

Radial velocity (R_v)	−5.2^[6] km/s
Proper motion (μ)	RA: +10.102^[2] mas/yr Dec.: −0.825^[2] mas/yr
Parallax (π)	4.7730 ± 0.1052 mas^[2]
Distance	680 ± 20 ly (210 ± 5 pc)
Absolute magnitude (M_V)	−2.12^[7]

Details

Mass	6.7^[8] `M`_☉
Radius	6.2^[9] `R`_☉
Luminosity	704^[8] `L`_☉
Surface gravity (log g)	3.95^[8] cgs
Temperature	12,014^[8] K
Metallicity [Fe/H]	−0.20^[10] dex
Rotation	9.3 d^[11]
Rotational velocity (v sin i)	17^[10] km/s
Age	165^[12] Myr

Other designations
21 Aql, V1288 Aql, BD+02°3824, FK5 3537, HD 179761, HIP 94477, HR 7287, SAO 124408, WDS J19137+0218A^[13]
Database references
SIMBAD	data

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