HD 166

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.[2] It appears within one degree of the star Alpha Andromedae[9] and is a member of the Hercules-Lyra association moving group.[3]

HD 166
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Andromeda
Right ascension  00h 06m 36.7841s[1]
Declination +29° 01′ 17.4103″[1]
Apparent magnitude (V) 6.13 – 6.17[2]
Characteristics
Spectral type K0Ve[2][3]
U−B color index +0.30[4]
B−V color index +0.755[4]
Variable type BY Dra[2]
Astrometry
Radial velocity (Rv)−6.9±0.2[3] km/s
Proper motion (μ) RA: 380.092±0.060[1] mas/yr
Dec.: −177.573±0.037[1] mas/yr
Parallax (π)72.5764 ± 0.0498[1] mas
Distance44.94 ± 0.03 ly
(13.779 ± 0.009 pc)
Absolute magnitude (MV)5.41[5]
Details
Mass0.889[6] M☉
Radius0.9172±0.0090[6] R☉
Luminosity0.6078±0.0099[6] L☉
Surface gravity (log g)4.49±0.09[7] cgs
Temperature5509±34[7] K
Metallicity [Fe/H]0.00±0.03[7] dex
Rotation6.23±0.01 days[8]
Rotational velocity (v sin i)4.1 [8] km/s
Age78±28[7] Myr
Other designations
BD+28°4704, GC 95, GSC 01735-02532, GSC 01735-00927, Gliese 5, HD 166, HIP 544, HR 8, SAO 73743, NSV 33
Database references
SIMBADdata

Star characteristics

HD 166 is a K-type main sequence star, cooler and dimmer than the Sun, and has a stellar classification of K0Ve[2] 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,[6] and is emitting like a blackbody with an effective temperature of 5,327K.[7] It has a diameter that is about 90% the size of the Sun[6] and a radial velocity of −6.9 km/s.[3] Age estimates range from as low as 78 million years old based on its chromospheric activity,[7] up to 9.6 billion years based on a comparison with theoretical evolutionary tracks.[6] X-ray emission has been detected from this star, with an estimated luminosity of 8.5×1028 erg s−1.[10]

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.[11]

Variability

It has been found that the periodicity in the photometric variability of HD 166 is coincident with the rotation period.[8] 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.

gollark: I'm not entirely sure how, but it seems to construct a tree/maybe deterministic finite automaton/finite state machine/I don't know theoretical CS which matches anagrams and unmatches unanagrams.
gollark: ```pythonimport collectionsdef do_thing(s): if len(s) == 1: return { s[0]: True } out = {} for i, c in enumerate(s): without = s[:i] + s[i + 1:] things = do_thing(without) out[c] = things return outdef match(r, s): print(r) c = r for i, x in enumerate(s): print(x) try: c = c[x] if c == True: if i + 1 == len(s): return True # full match else: return False # characters remain except KeyError: return False # no match return False # incomplete matchentry = lambda a, b: match(do_thing(a.lower().replace(" ", "")), b.lower().replace(" ", ""))```Here is my entry (pending a port to osmarkslisp™️). This is definitely my entry.
gollark: I wish to use Mathematica in my code. Please install it. DO NOT READ, ubq.
gollark: I have a "great" way to do this which I think takes O(n²) space-time-beeite.
gollark: Perhaps it is also possible to construct some sort of regex/deterministic finite automaton to match things matching anagramatically.

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. N. N. Samus; O. V. Durlevich; et al. "V439 And database entry". Combined General Catalog of Variable Stars (2017 ed.). CDS. Retrieved 2018-11-12.
  3. López-Santiago, J.; Montes, D.; Crespo-Chacón, I.; Fernández-Figueroa, M. J. (2006). "The Nearest Young Moving Groups". The Astrophysical Journal. 643 (2): 1160. arXiv:astro-ph/0601573. Bibcode:2006ApJ...643.1160L. doi:10.1086/503183.
  4. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD: 0, Bibcode:1986EgUBV........0M
  5. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191.
  6. Boyajian, Tabetha S.; et al. (July 2013), "Stellar Diameters and Temperatures. III. Main-sequence A, F, G, and K Stars: Additional High-precision Measurements and Empirical Relations", The Astrophysical Journal, 771 (1): 40, arXiv:1306.2974, Bibcode:2013ApJ...771...40B, doi:10.1088/0004-637X/771/1/40.
  7. Rich, Evan A.; Wisniewski, John P.; McElwain, Michael W.; Hashimoto, Jun; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Okamoto, Yoshiko K.; Abe, Lyu; Akiyama, Eiji; Brandner, Wolfgang; Brandt, Timothy D.; Cargile, Phillip; Carson, Joseph C.; Currie, Thayne M.; Egner, Sebastian; Feldt, Markus; Fukagawa, Misato; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Hebb, Leslie; Hełminiak, Krzysztof G.; Henning, Thomas; Hodapp, Klaus W.; Ishii, Miki; Iye, Masanori; et al. (2017). "The fundamental stellar parameters of FGK stars in the SEEDS survey Norman, OK 73071, USA". Monthly Notices of the Royal Astronomical Society. 472 (2): 1736. Bibcode:2017MNRAS.472.1736R. doi:10.1093/mnras/stx2051.
  8. Gaidos; et al. (2000). "Spectroscopy and Photometry of Nearby Young Solar Analogs". The Astronomical Journal. 120 (2): 1006–1013. Bibcode:2000AJ....120.1006G. CiteSeerX 10.1.1.43.4478. doi:10.1086/301488.
  9. Autostar Suite Astronomer Edition. CD-ROM. Meade, April 2006.
  10. Micela, G.; Favata, F.; Sciortino, S. (October 1997), "HIPPARCOS distances of X-ray selected stars: implications on their nature as stellar population", Astronomy and Astrophysics, 326: 221–227, Bibcode:1997A&A...326..221M
  11. Eiroa, C.; et al. (July 2013). "DUst around NEarby Stars. The survey observational results". Astronomy & Astrophysics. 555: A11. arXiv:1305.0155. Bibcode:2013A&A...555A..11E. doi:10.1051/0004-6361/201321050.
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