15 Cancri

Star in the constellation Cancer 15 Cancri Cancer IAU.svg center 280 right Red circle.svg 6 15 Cnc 569 260 Location of 15 Cancri (circled) J2000.0 Cancer 08 13 08.86806 +29 39 23.5368 5.53 - 5.65 main sequence A0:V:spSiSr −0.073 0.002 α2 CVn 25.0 0.8 −11.265 −19.506 4.6720 0.2238 −0.97 15 Cancri A 15 Cancri B 635.73 0.53 days 0.55 0.08 2422045 18 196 13 9.6 1.1 15 Cnc A 2.4 3.4 131 3.68 10,400 6.563 days 25 358 BM Cnc 15 Cnc +30°1664 68351 40240 3215 01939-01462 HD+68351 thumb|left|A light curve for BM Cancri, plotted from TESS data 15 Cancri is an α2 CVn-type variable star in the zodiac constellation of Cancer, located around 700 light years away. It has the variable star designation BM Cancri (BM Cnc); 15 Cancri (15 Cnc) is the Flamsteed designation. This system is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of about 5.6. It is moving away from the Earth with a heliocentric radial velocity of 25 km/s. Radial velocity measurements taken at the Dominion Astrophysical Observatory in Victoria, British Columbia Canada in 1918 and 1919 led to the determination that 15 Cancri is a single-lined spectroscopic binary system. The first orbit was calculated in 1973 by Helmut Abt and Michael Snowden with a period of 585 days however later measurements showed that the orbital period was 635 days. 15 Cancri A, the visible component, is an Ap star, a chemically peculiar star with an over-abundance of iron peak elements, particularly silicon, chromium, and strontium, in its spectrum. Like all Ap stars, 15 Cancri has a strong magnetic field. This magnetic field varies as it rotates and in 1968 the visual brightness of the star was shown to vary regularly over about four days. 15 Cancri was given the variable star designation BM Cancri in 1972 as a member of the α2 CVn class of variable stars. The period has since been measured more accurately at 3.3095 days, believed to be the rotational period of the star. In Johann Bayer’s Uranometria, this star was designated as Psi Geminorum. When the constellation borders were set in 1930, it was moved to Cancer, so the designation has been dropped. Notes "note" An alternate period of 475 days is possible but less likely. References 15 Cancri 2025-11-16 876666120047998592 Balona L. A. Rapidly oscillating TESS A-F main-sequence stars: Are the roAp stars a distinct class? Monthly Notices of the Royal Astronomical Society 2022 510 4 5743 10.1093/mnras/stac011 free 2109.02246 2022MNRAS.510.5743B Glagolevskij Yu. V. On Properties of Main Sequence Magnetic Stars Astrophysical Bulletin 2019 74 1 66 10.1134/S1990341319010073 2019AstBu..74...66G Kordopatis G. Schultheis M. McMillan P. J. Palicio P. A. De Laverny P. Recio-Blanco A. Creevey O. Álvarez M. A. Andrae R. Poggio E. Spitoni E. Contursi G. Zhao H. Oreshina-Slezak I. Ordenovic C. Bijaoui A. Stellar ages, masses, extinctions, and orbital parameters based on spectroscopic parameters of Gaia DR3 Astronomy and Astrophysics 2023 669 A104 10.1051/0004-6361/202244283 free 2206.07937 2023A&A...669A.104K MAST: Barbara A. Mikulski Archive for Space Telescopes https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html Space Telescope Science Institute 8 December 2021 1972IBVS..705....1M New Southern Variable Stars Information Bulletin on Variable Stars 705 1 Martins D. H. 1972 10.1086/149815 Photometric behavior of magnetic stars The Astrophysical Journal 154 945 1968 Stepien K. 1968ApJ...154..945S 10.1111/j.1365-2966.2011.20090.x A photometric study of chemically peculiar stars with the STEREO satellites - I. Magnetic chemically peculiar stars★ Monthly Notices of the Royal Astronomical Society 420 1 757–772 2012 Wraight K. T. Fossati L. Netopil M. Paunzen E. Rode-Paunzen M. Bewsher D. Norton A. J. 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Originally Published in: 2009yCat....102025S 1 etal Samus N. N. Durlevich O. V. 2009 1995ApJS...99..135A The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars Astrophysical Journal Supplement 99 135 Abt Helmut A. Morrell Nidia I. 1995 10.1086/192182 free http://www.ianridpath.com/startales/bayer.htm Bayer's Uranometria and Bayer letters Ian Ridpath Ian Ridpath 2017-11-27 Category:Cancer (constellation) Category:Alpha2 Canum Venaticorum variables Category:Magnetic chemically peculiar stars Category:Spectroscopic binaries Cancri, 15 Cancri, BM Category:Durchmusterung objects 068351 3215 040240 Category:A0V stars