仙女座Z

仙女座Z是一對由紅巨星和白矮星組合的共生聯星（英语：symbiotic binary）。它是激變變星的一種，被稱為共生變星，並且是這種變星的原型，所以共生變星也稱為仙女座Z型變星。 仙女座Z是一對聯星，這兩顆星的迴圈軌道週期為759天。 紅巨星的質量大約是太陽的兩倍，表面有效溫度僅2800K，但它的光度是太陽的880倍。白矮星在寧靜狀態的光度大約是太陽的1,000倍，但在活躍階段的光度會增加至10倍。它的溫度在寧靜狀態時是150,000K，在活躍時下降至低於100,000K。 仙女座Z是共生變星的原型，它是激變變星的一種類型。共生變星有多種多樣的群，通常分為幾個子群，其中一群以仙女座Z命名。 仙女座Z型變星，包括仙女座Z自身，顯示出不規則的變化，在間隔幾年爆發時，亮度會有數星等的改變。通常它們由一顆紅巨星和一顆白矮星星組成，以數年的周期在軌道上互繞著。紅巨星的恆星風會被白矮星電離，造成在軌道上不同的位置，星雲的輻射強度會稍有變化。這是在寧靜時的狀態，活躍時白矮星的體積增大、表面溫度下降，而變得更加明亮。整個聯星系統的亮度會增加2-4星等 。 自20世紀初以來，仙女座Z的頻譜一直被認為極其奇特。在明亮階段的早期頻譜，只相對於紅色的連續譜呈現明亮的發射線，對此的解釋為恆星被嵌入密集的雲氣內。當恆星的度度減弱時，光譜失去了雲氣被激發的譜線，並且發展出吸收譜線，就展現出天鵝座P剖面的吸收線。這樣的光譜很容易確認是一顆像新興的高溫星與一顆低溫恆星的組合。 在MK光譜分類，通常是一顆低溫的巨星，例如M4.5。確切的光譜類型被證明會改變，例如在1987年是M5，在1989年是M3.5。紅外線觀測的光譜類型是復合的M2III + B1eq。此處的光度分類III表示是一顆正常的巨星，特殊代碼eq指示出有發射譜線與天鵝座P剖面型的譜線。 2006年爆發之後，包括速度±1,150 公里/秒的微弱翼都有氫氣巴耳末發射線，準直的噴流則沿著系統的軸線發射。在2000年至2002年的長期爆發中，觀察到廣泛的無線電波。據認為，噴流只出現在明亮的爆發 。 Gaia Collaboration; Brown, A. G. A; Vallenari, A; Prusti, T; De Bruijne, J. H. J; Mignard, F; Drimmel, R; Babusiaux, C; Bailer-Jones, C. A. L; Bastian, U; Biermann, M; Evans, D. W; Eyer, L; Jansen, F; Jordi, C; Katz, D; Klioner, S. A; Lammers, U; Lindegren, L; Luri, X; O'Mullane, W; Panem, C; Pourbaix, D; Randich, S; Sartoretti, P; Siddiqui, H. I; Soubiran, C; Valette, V; Van Leeuwen, F; et al. Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties. Astronomy & Astrophysics. 2016, 595: A2. Bibcode:2016A&A...595A...2G. arXiv:1609.04172 . doi:10.1051/0004-6361/201629512.  Samus, N. N.; Durlevich, O. V.; et al. VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013). VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 2009, 1. Bibcode:2009yCat....102025S.  Shenavrin, V. I.; Taranova, O. G.; Nadzhip, A. E. Search for and study of hot circumstellar dust envelopes. Astronomy Reports. 2011, 55: 31. Bibcode:2011ARep...55...31S. doi:10.1134/S1063772911010070.  Martel, M. T; Gravina, R. UBV Observations of Symbiotic Stars in July and October 1982. Information Bulletin on Variable Stars. 1985, 2750: 1. Bibcode:1985IBVS.2750....1M.  Pourbaix, D; Tokovinin, A. A; Batten, A. H; Fekel, F. C; Hartkopf, W. I; Levato, H; Morrell, N. I; Torres, G; Udry, S. SB9: The ninth catalogue of spectroscopic binary orbits. Astronomy and Astrophysics. 2004, 424 (2): 727. Bibcode:2004A&A...424..727P. arXiv:astro-ph/0406573 . doi:10.1051/0004-6361:20041213.  Fekel, Francis C; Hinkle, Kenneth H; Joyce, Richard R; Skrutskie, Michael F. Infrared Spectroscopy of Symbiotic Stars. II. Orbits for Five S-Type Systems with Two-Year Periods. The Astronomical Journal. 2000, 120 (6): 3255. Bibcode:2000AJ....120.3255F. doi:10.1086/316872.  Leibowitz, Elia M; Formiggini, Liliana. Activity cycle of the giant star of Z Andromedae and its spin period. Mon. Not. R. Astron. Soc. 2008, 385: 445. Bibcode:2008MNRAS.385..445L. arXiv:0712.2120 . doi:10.1111/j.1365-2966.2008.12847.x.  Skopal, A. Discovery of the eclipse in the symbiotic binary Z Andromedae. The Astrophysical Journal. 2003, 401 (3): L17. Bibcode:2003A&A...401L..17S. arXiv:astro-ph/0304046 . doi:10.1051/0004-6361:20030332.  Sokoloski, J. L; Kenyon, S. J; Espey, B. R; Keyes, Charles D; McCandliss, S. R; Kong, A. K. H; Aufdenberg, J. P; Filippenko, A. V; Li, W; Brocksopp, C; Kaiser, Christian R; Charles, P. A; Rupen, M. P; Stone, R. P. S. A Combination Nova Outburst in Z Andromedae: Nuclear Shell Burning Triggered by a Disk Instability. The Astrophysical Journal. 2006, 636 (2): 1002. Bibcode:2006ApJ...636.1002S. arXiv:astro-ph/0509638 . doi:10.1086/498206.  Z Andromedae star. [2018-01-16]. （原始内容存档于2012-07-06）.  Plaskett, J. S. The composite stellar and nebular spectrum of Z Andromedae. Publications of the Dominion Astrophysical Observatory Victoria. 1928, 4: 119. Bibcode:1928PDAO....4..119P.  Swings, P; Struve, O. The Evolution of a Peculiar Stellar Spectrum: Z Andromedae. Astrophysical Journal. 1941, 93: 356. Bibcode:1941ApJ....93..356S. doi:10.1086/144272.  Mürset, U; Schmid, H. M. Spectral classification of the cool giants in symbiotic systems. Astronomy and Astrophysics Supplement. 1999, 137 (3): 473. Bibcode:1999A&AS..137..473M. doi:10.1051/aas:1999105.  Burmeister, M; Leedjärv, L. Evidence for bipolar jets from the optical spectra of the prototypical symbiotic star Z Andromedae. The Astrophysical Journal. 2006, 461: L5. Bibcode:2007A&A...461L...5B. arXiv:astro-ph/0611475 . doi:10.1051/0004-6361:20066630.  Tomov, N. A; Tomova, M. T; Taranova, O. G. Broad-band multicolour observations of the symbiotic binary Z And during quiescence and its activity at the end of 2002. The Astrophysical Journal. 2004, 428 (3): 985. Bibcode:2004A&A...428..985T. doi:10.1051/0004-6361:20041065.  Taranova, O. G; Tomov, N. A; Tomova, M. T; Shenavrin, V. I. The symbiotic system Z Andromedae during the flare of 2000–2002. Astronomy Reports. 2004, 48 (9): 742. Bibcode:2004ARep...48..742T. doi:10.1134/1.1800174.  Ikeda, Yuji; Akitaya, Hiroshi; Matsuda, Kentaro; Homma, Ken'Ichi; Seki, Munezo; Kawabata, Koji S; Hirata, Ryuko; Okazaki, Akira. Polarized Hα Wings in the Symbiotic Stars AG Draconis and Z Andromedae. The Astrophysical Journal. 2004, 604: 357. Bibcode:2004ApJ...604..357I. doi:10.1086/381877.  Tomov, N. A; Taranova, O. G; Tomova, M. T. Mass ejection by the symbiotic binary Z And during its 2000–2002 outburst. The Astrophysical Journal. 2003, 401 (2): 669. Bibcode:2003A&A...401..669T. doi:10.1051/0004-6361:20030140.  Sokoloski, J. L; Brocksopp, C; Kaiser, C; Seymour, N. A Radio "Jet" in the Prototypical Symbiotic Star Z Andromedae?. American Astron. Soc. Meeting. 2002, 201: 17.12. Bibcode:2002AAS...201.1712S.  Bisikalo, D. V; Boyarchuk, A. A; Kilpio, E. Yu; Kuznetsov, O. A. Structure of gas flows in Z and in quiescence and during outbursts. Astronomy Reports. 2002, 46 (12): 1022. Bibcode:2002ARep...46.1022B. doi:10.1134/1.1529260.  Gallego, M. C; Garcia, J. A; Vaquero, J. M; Sanchez Bajo, F. A Strange Attractor on a Daily Timescale in the Visual Observations of Z And?. Acta Astron. 1999, 49: 171. Bibcode:1999AcA....49..171G.  Sokoloski, J. L; Bildsten, Lars. Discovery of a Magnetic White Dwarf in the Symbiotic Binary Z Andromedae. The Astrophysical Journal. 1999, 517 (2): 919. Bibcode:1999ApJ...517..919S. arXiv:astro-ph/9812294 . doi:10.1086/307234.  Birriel, Jennifer J; Espey, Brian R; Schulte-Ladbeck, Regina E. Near-simultaneous Observations of Direct and Raman-scattered Linesin the Symbiotic Star Z Andromedae. The Astrophysical Journal. 1998, 507: L75. Bibcode:1998ApJ...507L..75B. doi:10.1086/311673.  Schmid, H. M; Schild, H. The polarimetric orbit of Z Andromedae. Astronomy & Astrophysics. 1997, 327: 219. Bibcode:1997A&A...327..219S.  Skopal, A; Vittone, A. A; Errico, L; Otsuka, M; Tamura, S; Wolf, M; Elkin, V. G. Structure of the hot object in the symbiotic prototype Z Andromedae during its 2000–03 active phase. The Astrophysical Journal. 2006, 453: 279. Bibcode:2006A&A...453..279S. arXiv:astro-ph/0603718 . doi:10.1051/0004-6361:20052917.  Skopal, A; Pribulla, T. The first detection of the bipolar jets from the symbiotic prototype Z and. The Astronomer's Telegram. 2006, 882. Bibcode:2006ATel..882....1S.  Sokoloski, J. L; Kenyon, S. J; Espey, B. R; Keyes, Charles D; McCandliss, S. R; Kong, A. K. H; Aufdenberg, J. P; Filippenko, A. V; Li, W; Brocksopp, C; Kaiser, Christian R; Charles, P. A; Rupen, M. P; Stone, R. P. S. A "Combination Nova" Outburst in Z Andromedae: Nuclear Shell Burning Triggered by a Disk Instability. The Astrophysical Journal. 2006, 636 (2): 1002. Bibcode:2006ApJ...636.1002S. arXiv:astro-ph/0509638 . doi:10.1086/498206.  Tomov, N. A; Tomova, M. T; Bisikalo, D. V. Bipolar ejection by the symbiotic binary system Z and during its 2006 outburst. Mon. Not. R. Astron. Soc. 2007, 376: L16. Bibcode:2007MNRAS.376L..16T. arXiv:astro-ph/0612502 . doi:10.1111/j.1745-3933.2007.00277.x.  Iudin, B. F. Choice of a model for Z Andromedae. Astronomicheskii Zhurnal. 1986, 63: 137. Bibcode:1986AZh....63..137I.  Image Z Andromedae AAVSO chart for Z Andromedae（页面存档备份，存于互联网档案馆） AAVSO long-term light curve of Z And[失效連結] Z Andromedae: The Prototype of the Symbiotic Class（页面存档备份，存于互联网档案馆） AAVSO