HN Pegasi

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HN Pegasi
HN Pegasi B.jpg
HN Peg B (circled)
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Pegasus
Right ascension 21h 44m 31.330s [1]
Declination +14° 46′ 18.98″ [1]
Apparent magnitude  (V)5.92 - 5.95 [2]
Characteristics
Spectral type G0 V CH-0.5 [3]
U−B color index +0.031 [4]
B−V color index +0.588 [4]
Variable type BY Dra [5]
Astrometry
Radial velocity (Rv)−16.68±0.09 [6]  km/s
Proper motion (μ)RA: +231.108  mas/yr [1]
Dec.: −113.200  mas/yr [1]
Parallax (π)55.148 ± 0.0348  mas [1]
Distance 59.14 ± 0.04  ly
(18.13 ± 0.01  pc)
Absolute magnitude  (MV)4.70 [7]
Details
HN Peg A
Mass 1.085±0.091 [5]   M☉
Radius 1.002±0.018 [5]   R☉
Luminosity (bolometric)1.090 [7]   L☉
Surface gravity (log g)4.45 [8]   cgs
Temperature 5,961 [8]   K
Metallicity [Fe/H]−0.06 [8]   dex
Rotation 4.84  d [9]
Rotational velocity (v sin i)12.81 [10]  km/s
Age 237±33 [5]   Myr
HN Peg B
Radius 0.101 [11]   R☉
Surface gravity (log g)4.81 [11]   cgs
Temperature 1,115 [11]   K
Other designations
HN Peg, BD+14°4668, FK5  3737, GJ  836.7, HD  206860, HIP  107350, HR  8314, SAO  107364 [12]
Database references
SIMBAD HN Peg A
HN Peg B

HN Pegasi is the variable star designation for a young, Sun-like star in the northern constellation of Pegasus. It has an apparent visual magnitude of 5.9, [4] which, according to the Bortle scale, indicates that it is visible to the naked eye from suburban skies. Parallax measurements put the star at a distance of around 59  light years from the Sun, [1] but it is drifting closer with a radial velocity of −16.7 km/s. [6]

This is a G-type main sequence star with a stellar classification of G0 V CH-0.5 [3] and an estimated age of just 237 million years. It has slightly more mass and a slightly larger radius than the Sun, [5] but a somewhat lower metallicity. [8] It is spinning relatively quickly, with an estimated rotation period of 4.84 [9] days.

The surface magnetic field of the star has a complex and variable geometry. It is a BY Draconis variable star with an active chromosphere, which means there is a rotational modulation of its luminosity due to star spots. Much like the Sun, the star spot activity undergoes a periodic cycle of maxima and minima lasting roughly 5.5±0.3 yr. [5] Its apparent magnitude varies between a maximum of 5.92 and a minimum of 5.95 over a period of 24.9 days. [2] However, the rotation period is on average 4.84 days. The star shows an anti-solar pattern of rotation, with the rotation rate steadily increasing during each cycle before dropping back to the initial value upon the start of a new cycle. [9]

In 2007, the discovery of a brown dwarf companion was announced. HN Peg B was spotted using the Spitzer Space Telescope at an angular separation of 43.2 arc sec, showing a methane emission characteristic of T-type dwarfs. The separation corresponds to a projected physical distance of 795  AU, [13] which is uncommonly wide for such brown dwarf companions. The estimated mass of the object is 28 MJ. Based upon its spectrum, HN Peg B has relatively thin cloud decks. [11]

This star displays an emission of infrared excess that suggests there is a circumstellar disk of debris in orbit. [7] HN Pegasi is most likely a thin disk population star. [8] It is a member of the nearby Hercules-Lyra association of stars that share a common motion through space. [5]

Related Research Articles

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85 Pegasi is a multiple star system 39.5 light years away in the constellation of Pegasus. The primary component is sixth magnitude 85 Pegasi A, which is a yellow dwarf like the Sun. The secondary component, 85 Pegasi B, is a ninth magnitude orange dwarf that takes 26.28 years to orbit at 10.3 AU around the primary in an elliptical orbit. The orbital distance ranges from 6.4 AU at periastron to 14.2 AU at apastron. 85 Pegasi B may itself be a binary, with a close, faint red dwarf companion separated by 2 AU from the primary. The mass would be 11% solar mass (M☉). All components in the star system including Star A are smaller, cooler and less massive, luminous, and metallic than the Sun and 51 Pegasi.

Gliese 412 is a pair of stars that share a common proper motion through space and are thought to form a binary star system. The pair have an angular separation of 31.4″ at a position angle of 126.1°. They are located 15.8 light-years distant from the Sun in the constellation Ursa Major. Both components are relatively dim red dwarf stars.

HD 17925 Star in the constellation Eridanus

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55 Pegasi Star in the constellation of Pegasus

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56 Pegasi Star in the constellation Pegasus

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Gliese 402 Star in the constellation Leo

Gliese 402 is a star located 22.7 light years from the Solar System. Located in the constellation of Leo, it is also known as Wolf 358 from its entry in Max Wolf's star catalogue. The stars nearest to Gliese 402 are Gliese 393, at 3.43 light years, Gliese 408, at 6.26 light years, and Gliese 382 at 6.66 light years.

9 Ceti Star in the constellation Cetus

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HD 219623 is a solitary star in the northern circumpolar constellation of Cassiopeia. HD 219623 is its Henry Draper Catalogue designation. It has an apparent visual magnitude of 5.59, which lies in the brightness range that is visible to the naked eye. According to the Bortle scale, it can be observed from dark suburban skies. Parallax measurements place it at an estimated distance of around 67.2 light years. It has a relatively high proper motion, advancing 262 mas per year across the celestial sphere.

MT Pegasi is a single, yellow-hued star in the northern constellation of Pegasus. With an apparent visual magnitude of 6.616, 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 41.12 mas as measured from Earth's orbit, it is located 79.31 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.

HD 111395 is a single, variable star in the northern constellation of Coma Berenices. It has the variable star designation LW Com, short for LW Comae Berenices; HD 111395 is the Henry Draper Catalogue designation. The star has a yellow hue and is just bright enough to be barely visible to the naked eye with an apparent visual magnitude that fluctuates around 6.29. Based upon parallax measurements, it is located at a distance of 55.8 light years from the Sun. The star is drifting closer with a radial velocity of −8.9 km/s. It is a member of the Eta Chamaeleontis stellar kinematic group.

References

  1. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID   227254300. Gaia EDR3 record for this source at VizieR.
  2. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009), "General Catalogue of Variable Stars (Samus+ 2007-2013)", VizieR On-line Data Catalog: B/GCVS, vol. 1, Bibcode:2009yCat....102025S.
  3. 1 2 Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal , 132 (1): 161–170, arXiv: astro-ph/0603770 , Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID   119476992.
  4. 1 2 3 Blanco, C.; et al. (1979), "Photoelectric observations of stars with variable H and K emission components. III", Astronomy and Astrophysics Supplement Series, 36: 297–306, Bibcode:1979A&AS...36..297B.
  5. 1 2 3 4 5 6 7 Boro Saikia, S.; et al. (January 2015), "Variable magnetic field geometry of the young sun HN Pegasi (HD 206860)", Astronomy & Astrophysics, 573: 16, arXiv: 1410.8307 , Bibcode:2015A&A...573A..17B, doi:10.1051/0004-6361/201424096, S2CID   53316047, A17.
  6. 1 2 Nidever, David L.; et al. (August 2002), "Radial Velocities for 889 Late-Type Stars", The Astrophysical Journal Supplement Series, 141 (2): 503–522, arXiv: astro-ph/0112477 , Bibcode:2002ApJS..141..503N, doi:10.1086/340570, S2CID   51814894.
  7. 1 2 3 Ertel, S.; et al. (May 2012), "A peculiar class of debris disks from Herschel/DUNES. A steep fall off in the far infrared", Astronomy & Astrophysics, 541: 14, arXiv: 1203.6784 , Bibcode:2012A&A...541A.148E, doi:10.1051/0004-6361/201118077, S2CID   5457432, A148.
  8. 1 2 3 4 5 Ramírez, I.; et al. (February 2013), "Oxygen abundances in nearby FGK stars and the galactic chemical evolution of the local disk and halo", The Astrophysical Journal, 764 (1): 78, arXiv: 1301.1582 , Bibcode:2013ApJ...764...78R, doi:10.1088/0004-637X/764/1/78, S2CID   118751608.
  9. 1 2 3 Messina, S.; Guinan, E. F. (October 2003), "Magnetic activity of six young solar analogues II. Surface Differential Rotation from long-term photometry", Astronomy and Astrophysics, 409 (3): 1017–1030, Bibcode:2003A&A...409.1017M, doi: 10.1051/0004-6361:20031161 .
  10. ↑ Martínez-Arnáiz, R.; et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter", Astronomy and Astrophysics, 520: A79, arXiv: 1002.4391 , Bibcode:2010A&A...520A..79M, doi:10.1051/0004-6361/200913725, S2CID   43455849.
  11. 1 2 3 4 Leggett, S. K.; et al. (August 2008), "HN Peg B: A Test of Models of the L to T Dwarf Transition", The Astrophysical Journal, 682 (2): 1256–1263, arXiv: 0804.1386 , Bibcode:2008ApJ...682.1256L, doi:10.1086/589146, S2CID   15701830.
  12. ↑ "V* HN Peg -- Variable of BY Dra type", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg , retrieved 2015-12-07.
  13. ↑ Luhman, K. L.; et al. (January 2007), "Discovery of Two T Dwarf Companions with the Spitzer Space Telescope", The Astrophysical Journal, 654 (1): 570–579, arXiv: astro-ph/0609464 , Bibcode:2007ApJ...654..570L, doi:10.1086/509073, S2CID   11576708.
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