A light curve for TYC 1031-1262-1, adapted from Antipin et al..[6] The upper plot shows the variability due to pulsations, with the orbit-related variability removed, and the lower plot shows orbit-related variability, with the pulsation effects removed.
The star's variability was first detected in 2005. In 2007, it was reported as the first eclipsing binary system with a type II Cepheid component to be detected in the Milky Way. It also had the shortest period of any known Cepheid binary at that time.[6] A follow-up study in 2013, however, argues that the pulsating component is too massive to be a type II Cepheid and thus is instead an anomalous Cepheid, an object located between classical Cepheids and type II Cepheids in the Hertzsprung-Russell diagram.[2] A similar object, NSV 10993 (V1135 Herculis), was discovered in 2008.[7]
Physical properties
The two components are both evolvedbright giants (luminosity class II), more luminous than normal giant stars but less so than supergiants.[a] The brighter of the pair (hereafter component "A") is the Cepheid that pulsates at a period of 4.15270 days, which is increasing at a rate of 2.46±0.54 min/yr for unknown reasons. It is 64% more massive than the Sun but has ballooned to 27 times the girth, radiating 764 times the luminosity of the Sun from its photosphere at an effective temperature of 5,880 K (5,610 °C; 10,120 °F), corresponding to its spectral type of F8II. Its dimmer G6II companion (B) is slightly less massive than the Sun and cooler at 4,890 K (4,620 °C; 8,340 °F), but has a radius 15 times larger and emits a little over 100 times the solar luminosity.[2]
A and B revolve around each other with an orbital period of 51.2857 days at a distance of 0.3701 AU (55,370,000 km), only twice the sum of their radii. As a result of this close proximity, the pulsation and evolution of A has been affected. Furthermore, A fills nearly 85% of its Roche lobe, while B occupies 61%, meaning that a loss or transfer of mass has likely occurred from A.[2] The amplitude of the brightness changes caused by one star eclipsing the other is relatively small, which implies that the two stars only partially eclipse each other.[6]
The star is a member of the thick disk population, located 970 parsecs (3,200 ly) from the Galactic plane.[2]
Nearby objects
Follow-up observations on the star in 2008 revealed nine new variable stars in the immediate vicinity, including seven eclipsing binaries, one RR Lyrae variable, and one long-period, irregular or semiregular variable star.[8]
See also
V1334 Cygni: a binary system containing a classical Cepheid variable.
Footnotes
^Despite giving both stars the luminosity class II, Sipahi et al. (2013)[2] simultaneously refers to both stars as supergiants in their conclusion.
^ abCutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
^Khruslov, A. V. (April 2008). "Pulsations in the Eclipsing Binary NSV 10993". Peremennye Zvezdy. 28 (4). Bibcode:2008PZ.....28....4K.
^Sokolovsky, K. V.; Elenin, L. (November 2008). "New Variable Stars Discovered Using the Tzec Maun Observatory Telescopes". Peremennye Zvezdy Prilozhenie. 8 (42). Bibcode:2008PZP.....8...42S.
