UX Lyncis

UX Lyncis is a variable star in the faint northern constellation of Lynx, positioned about 3° to the south of the 4th magnitude star 10 Ursae Majoris.^[9] This is a red-hued star near the lower threshold of visibility to the naked eye, having an apparent visual magnitude that fluctuates around 6.70.^[7] It is located at a distance of approximately 900 light years from the Sun based on parallax,^[2] and is drifting further away with a radial velocity of +39 km/s.^[7]

UX Lyncis

A visual band light curve for UX Lyncis. The top panel shows the variation over a period of years, and the lower plot shows the variation over a period of months. Adapted from Percy and Wilson (2001)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Lynx
Right ascension	09h 03m 47.10789s[2]
Declination	+38° 44′ 31.6542″[2]
Apparent magnitude (V)	6.6 - 6.78[3]
Characteristics
Evolutionary stage	AGB[4]
Spectral type	M3III[5] or M6III[6]
B−V color index	1.356±0.011[7]
Variable type	SRb:[4]
Astrometry
Radial velocity (Rv)	+38.60±0.64[7] km/s
Proper motion (μ)	RA: −17.176[2] mas/yr Dec.: −20.823[2] mas/yr
Parallax (π)	3.6035 ± 0.4422 mas[2]
Distance	approx. 900 ly (approx. 280 pc)
Absolute bolometric magnitude (Mbol)	−0.15[7]
Details
Radius	128.38+0.92 −9.89[2] R☉
Luminosity	1,766±242[2] L☉
Temperature	3302+135 −11[2] K
Other designations
UX Lyn, BD+39°2193, HD 77443, HIP 44481, SAO 61226, IRAS 09005+3856[8]
Database references
SIMBAD	data

The stellar classification of this star is M3III,^[5] while the infrared spectrum matches a class of M6III.^[6] It is an aging red giant on the asymptotic giant branch that has exhausted the supply of both hydrogen and helium in its core, then cooled and expanded. At present it has 128^[2] times the radius of the Sun, which is equivalent to 0.60 AU or 60% of the distance from the Sun to the Earth. On average, it radiates a luminosity approximately 1,766 times that of the Sun from its swollen photosphere at an effective temperature of 3,302 K.^[2] Infrared observations show little or no evidence for an oxygen-rich dusty shell around the star.^[4]

The variability of this star was reported by R. L. Walker in 1970 from the U.S. Naval Observatory.^[10] UX Lyncis has been classified as a semiregular variable ranging from magnitude 6.6 down to 6.78.^[3] Its changes in brightness are complex, with a shorter period of 37.3 days due to the star's pulsations, and a longer period of 420 days possibly due to the star's rotation or convectively induced oscillatory thermal (COT) mode.^[1] There is some evidence for an additional weak variability with a 29 day period.^[11]

References

1. Percy, John R.; et al. (2001). "Long-Term VRI Photometry of Small-Amplitude Red Variables. I. Light Curves and Periods". The Publications of the Astronomical Society of the Pacific. 113 (786): 983–96. Bibcode:2001PASP..113..983P. doi:10.1086/322153.
2. 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.
3. Watson, Christopher (4 January 2010). "UX Lyncis". AAVSO Website. American Association of Variable Star Observers. Retrieved 10 March 2016.
4. Sloan, G. C.; Price, S. D. (December 1998). "The Infrared Spectral Classification of Oxygen-rich Dust Shells". The Astrophysical Journal Supplement Series. 119 (2): 141–158. Bibcode:1998ApJS..119..141S. doi:10.1086/313156.
5. Sato, K.; Kuji, S. (November 1990). "MK classification and photometry of stars used for time and latitude observations at Mizusawa and Washington". Astronomy & Astrophysics Supplement Series. 85: 1069. Bibcode:1990A&AS...85.1069S.
6. Lebzelter, T.; Hron, J. (December 2003). "Technetium and the third dredge up in AGB stars. I. Field stars". Astronomy and Astrophysics. 411 (3): 533–542. arXiv:astro-ph/0310018. Bibcode:2003A&A...411..533L. doi:10.1051/0004-6361:20031458. S2CID 18879265.
7. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
8. "UX Lyn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-22.
9. Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. Vol. 2. Sky Publishing Corporation and the European Space Agency. p. 620. ISBN 0-933346-83-2.
10. Walker, R. L. (July 1970). "Light Variations of BD+39°2193". Information Bulletin on Variable Stars. 447: 1. Bibcode:1970IBVS..447....1W.
11. Percy, John R.; et al. (April 2003). "Multiperiodicity in Five Small-Amplitude Pulsating Red Giants". The Publications of the Astronomical Society of the Pacific. 115 (806): 479–483. Bibcode:2003PASP..115..479P. doi:10.1086/374199. S2CID 120018973.