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MT Pegasi

MT Pegasi

Visual light curve of MT Pegasi from observations by the All Sky Automated Survey between 2003 and 2009.[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Pegasus
Right ascension 23h 03m 04.977s[2]
Declination +20° 55′ 06.86″[2]
Apparent magnitude (V) 6.616[3]
Characteristics
Spectral type G1 V[4]
U−B color index +0.115[3]
B−V color index +0.633[5]
Variable type BY Dra[6]
Astrometry
Radial velocity (Rv)+2.084±0.005[7] km/s
Proper motion (μ) RA: −117.123 mas/yr[2]
Dec.: −28.530 mas/yr[2]
Parallax (π)41.1604 ± 0.0232 mas[2]
Distance79.24 ± 0.04 ly
(24.30 ± 0.01 pc)
Absolute magnitude (MV)4.65±0.03[3]
Details[8]
Mass1.066+0.020
−0.030 M☉
Radius1.01+0.04
−0.02 R☉
Luminosity1.07+0.12
−0.10 L☉
Surface gravity (log g)4.47+0.02
−0.04 cgs
Temperature5,885±44 K
Metallicity [Fe/H]−0.03±0.03[5] dex
Rotation5.82±1.47 days[9]
Rotational velocity (v sin i)3.2±0.05 km/s
Age1.20+2.16
−1.20 Gyr
Other designations
MT Peg, BD+20° 5264, HD 217813, HIP 113829, SAO 90973[10]
Database references
SIMBADdata

MT Pegasi is a single,[11] yellow-hued star in the northern constellation of Pegasus. It has the designation HD 217813 in the Henry Draper Catalogue; MT Pegasi is the variable star designation.[10] With an apparent visual magnitude of 6.616,[3] it is a dim star that is at or below the nominal limit for visibility with the naked eye. Based upon an annual parallax shift of 41.16 mas[2] as measured from Earth's orbit, it is located 79.24 light years away. This star is a member of the Ursa Major Moving Group, a collection of stars that originated in the same open cluster and now share a common motion through space.[12]

This is a G-type main-sequence star with a stellar classification of G1 V.[4] Harlan and Taylor (1970) had assigned it a class of G5 V,[13] but this gives a poor match to the color index.[14] HD 217813 was found to be variable in 1995 and hence it was given the variable star designation MT Pegasi (MT Peg). It displays brightness variations with a period of several days, which is caused by star spots that are modulated by the star's rotation period.[14] MT Peg is classified as a BY Draconis variable.[6]

MT Peg is considered a young solar analog, which means it is a solar-type star representative of how a young, more active Sun may have appeared when it was less than 1.5 billion years old.[9] The estimated age based upon the chromospheric activity level is 397 million years, per Gray et al. (2015).[9] Marsden et al. (2014) gave a larger age estimate of 1.2 billion years, but with a margin of error that overlaps the younger value.[8] Age estimates of the Ursa Major group are around 300 million years old.[12]

The star has 1.07 times the mass of the Sun and 1.01 times the Sun's radius.[8] It is spinning with a projected rotational velocity of 3.2 km/s,[8] giving it a rotation period of 5.8 days.[9] The elemental composition of the stellar atmosphere is similar to the Sun. MT Peg is radiating 1.07 times the Sun's luminosity from its photosphere at an effective temperature of 5,885 K.[8]

  1. ^ "ASAS All Stars Catalogue". All Sky Automated Survey. Retrieved 2 July 2023.
  2. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference Koen2010 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Gray2006 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Rich2017 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference gcvs2017 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Soubiran2013 was invoked but never defined (see the help page).
  8. ^ a b c d e Cite error: The named reference Marsden2014 was invoked but never defined (see the help page).
  9. ^ a b c d Cite error: The named reference Gray2015 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference fuhrmann2017 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference Ammler2005 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Harlan1970 was invoked but never defined (see the help page).
  14. ^ a b Cite error: The named reference Depasquale2000 was invoked but never defined (see the help page).

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