HD 166

Last updated
HD 166
V439AndLightCurve.png
A light curve for V439 Andromedae, plotted from TESS data, [1] with the 6.23 day rotation period shown in red,
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Andromeda
Right ascension 00h 06m 36.7841s [2]
Declination +29° 01 17.4103 [2]
Apparent magnitude  (V)6.13 6.17 [3]
Characteristics
Spectral type K0Ve [3] [4]
U−B color index +0.30 [5]
B−V color index +0.755 [5]
Variable type BY Dra [3]
Astrometry
Radial velocity (Rv)−6.9±0.2 [4]  km/s
Proper motion (μ)RA: 380.092±0.060 [2]   mas/yr
Dec.: −177.573±0.037 [2]   mas/yr
Parallax (π)72.5764 ± 0.0498  mas [2]
Distance 44.94 ± 0.03  ly
(13.779 ± 0.009  pc)
Absolute magnitude  (MV)5.41 [6]
Details
Mass 0.889 [7]   M
Radius 0.9172±0.0090 [7]   R
Luminosity 0.6078±0.0099 [7]   L
Surface gravity (log g)4.49±0.09 [8]   cgs
Temperature 5509±34 [8]   K
Metallicity [Fe/H]0.00±0.03 [8]   dex
Rotation 6.23±0.01 days [9]
Rotational velocity (v sin i)4.1 [9]  km/s
Age 78±28 [8]   Myr
Other designations
BD+28°4704, GC 95, GSC 01735-02532, GSC 01735-00927, Gliese 5, HD 166, HIP  544, HR  8, SAO  73743, PPM  89410, NSV 33
Database references
SIMBAD data

HD 166 or V439 Andromedae (ADS 69 A) is a 6th magnitude star in the constellation Andromeda, approximately 45 light years away from Earth. It is a variable star of the BY Draconis type, varying between magnitudes 6.13 and 6.18 with a 6.23 days periodicity. [3] It appears within one degree of the star Alpha Andromedae [10] and is a member of the Hercules-Lyra association moving group. [4] It also happens to be less than 2 degrees from right ascension 00h 00m.

Contents

Star characteristics

HD 166 is a K-type main sequence star, cooler and dimmer than the Sun, and has a stellar classification of K0Ve [3] where the e suffix indicates the presence of emission lines in the spectrum. The star has a proper motion of 0.422 arcseconds per year in a direction 114.1° from north. It has an estimated visual luminosity of 61% of the Sun, [7] and is emitting like a blackbody with an effective temperature of 5,327K. [8] It has a diameter that is about 90% the size of the Sun [7] and a radial velocity of −6.9 km/s. [4] Age estimates range from as low as 78 million years old based on its chromospheric activity, [8] up to 9.6 billion years based on a comparison with theoretical evolutionary tracks. [7] X-ray emission has been detected from this star, with an estimated luminosity of 8.5×1028 erg s−1. [11]

An infrared excess has been detected around HD 166, most likely indicating the presence of a circumstellar disk at a radius of 7.5  AU. The temperature of this dust is 90 K. [12]

Variability

It has been found that the periodicity in the photometric variability of HD 166 is coincident with the rotation period. [9] This leads to its classification as a BY Draconis variable, where brightness variations are caused by the presence of large starspots on the surface and by chromospheric activity.

Related Research Articles

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Tau<sup>4</sup> Eridani Binary star system in the constellation Eridanus

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<span class="mw-page-title-main">HD 17925</span> Star in the constellation Eridanus

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HR 6806 or HD 166620 is a solitary, orange, main sequence, and Sun-like star located thirty-six light-years away, in the constellation Hercules. The star is smaller than the Sun, with around 79% of the solar mass and radius, and 35% of the solar luminosity. It appears to be rotating slowly with an estimated period of 42 days. In 1988, it was noticed that the star had an inactive chromosphere, with a surface magnetic field strength of only 1,500 G. From 1990 activity in the chromosphere increased, inline with a 16 year stellar cycle previously observed. But, sometime after 1994 chromospheric activity greatly reduced, and has stayed flat for more than 16 years. As of 2022, the star appears to have entered the equivalent of a Maunder minimum. The star is around six billion years of age.

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<span class="mw-page-title-main">V538 Aurigae</span> Star in constellation Auriga

V538 Aurigae is a single star in the northern constellation of Auriga. With an apparent visual magnitude of 6.23, this star requires good dark sky conditions to view with the naked eye. It is located at a distance of 40.0 light-years (12.3 pc) from Sun based on parallax. The star is drifting further away with a radial velocity of 0.9 km/s. It is a member of the Local Association, and is most likely a thin disk star.

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HD 30442 is a solitary star in the northern circumpolar constellation Camelopardalis. It is faintly visible to the naked eye with an apparent magnitude of 5.47 and is estimated to be 403 light years away from the Solar System. The object has a heliocentric radial velocity of −37 km/s, indicating that it is drifting closer.

<span class="mw-page-title-main">Theta Draconis</span> Binary star system in the constellation Draco

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<span class="mw-page-title-main">HD 190007</span> Star in the constellation Aquila

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<span class="mw-page-title-main">Chi Ceti</span> Double star in the constellation Cetus

Chi Ceti , is the Bayer designation for a double star in the equatorial constellation of Cetus. They appear to be common proper motion companions, sharing a similar motion through space. The brighter component, HD 11171, is visible to the naked eye with an apparent visual magnitude of 4.66, while the fainter companion, HD 11131, is magnitude 6.75. Both lie at roughly the same distance, with the brighter component lying at an estimated distance of 75.6 light years from the Sun based upon an annual parallax shift of 43.13 mass.

HD 126053 is the Henry Draper Catalogue designation for a star in the equatorial constellation of Virgo. It has an apparent magnitude of 6.25, which means it is faintly visible to the naked eye. According to the Bortle scale, it requires dark suburban or rural skies to view. Parallax measurements made by the Hipparcos spacecraft provide an estimated distance of 57 light years to this star. It is drifting closer with a heliocentric radial velocity of −19.2 km/s.

<span class="mw-page-title-main">9 Ceti</span> Star in the constellation Cetus

9 Ceti is a star in the equatorial constellation of Cetus. It has the variable star designation BE Ceti, while 9 Ceti is the Flamsteed designation. It has an apparent visual magnitude of 6.4, which is below the limit that can be seen with the naked eye by a typical observer. Based upon parallax measurements, this star is 69.6 light years away from the Sun.

HD 195564 is the Henry Draper Catalogue designation for a star in the southern constellation of Capricornus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.65. Parallax measurements give us an estimate of its distance as 81 light years. This is a candidate wide binary system as a faint companion star shares a common proper motion with the brighter primary component.

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.

c Ursae Majoris is the Bayer designation for a double-lined spectroscopic binary star system in the northern constellation of Ursa Major. It has an apparent visual magnitude of 5.18, which indicates that is visible to the naked eye. Parallax measurements yield an estimated distance of 66 light years from the Sun. The star is moving closer to the Earth with a heliocentric radial velocity of −14 km/s.

HD 46815 is a solitary star in the southern constellation Columba. It is faintly visible to the naked eye with an apparent magnitude of 5.4 and is estimated to be 408 light years away. However, it is receding with a heliocentric radial velocity of 32.2 km/s.

15 Delphini is a star in the equatorial constellation Delphinus. It has an apparent magnitude of 5.99, allowing it to be faintly seen with the naked eye. The star is relatively close at a distance of 99 light years but is receding with a heliocentric radial velocity of 4.1 km/s.

References

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