X-ray Variability and the Secondary Star

  • M. F. Corcoran
  • K. Ishibashi
Part of the Astrophysics and Space Science Library book series (ASSL, volume 384)


We discuss the history of X-ray observations of the η Car system, concentrating on the periodic variability discovered in the 1990s. We discuss the interpretation of these variations, concentrating on a model of the system as a “colliding-wind” binary. This interpretation allows the physical and orbital parameters of η Car and its companion star to be constrained.


Column Density Stellar Wind Contact Discontinuity Companion Star Secondary Star 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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The authors would like to acknowledge many fruitful discussions with a large number of colleagues, among them Kris Davidson, Ted Gull, Roberta Humphreys, Augusto Damineli, Jean Swank, Stephen White, Julian Pittard, David Henley, Tony Moffat, Stan Owocki, John Hillier, Virpi Niemela, Nolan Walborn, and many others too numerous to fully mention. This work was supported in part by Chandra grant GO3-4008A and NASA grant NAS5-32490. This research made use of software and data available from the High Energy Astrophysics Science Archive Research Center, and NASA’s Astrophysics Data System.


  1. 1.
    D.C. Abbott, The terminal velocities of stellar winds from early-type stars. ApJ. 225, 893–901 (1978)ADSCrossRefGoogle Scholar
  2. 2.
    A.A. Abdo et al., Fermi/large area telescope bright gamma-ray source list. ApJ. Suppl. 183, 46–66 (2009)ADSCrossRefGoogle Scholar
  3. 3.
    E. Behar, R. Nordon, N. Soker, A high-velocity transient outflow in η Carinae. ApJ. Lett. 666, L97–L100 (2007)ADSCrossRefGoogle Scholar
  4. 4.
    H.V. Bradt, R.E. Rothschild, J.H. Swank, X-ray timing explorer mission. A&A. Suppl. 97, 355–360 (1993)Google Scholar
  5. 5.
    A.M. Cherepashchuk, Detectability of Wolf-Rayet binaries from X rays. Sov. Astron. Lett. 2, 138-+ (1976)Google Scholar
  6. 6.
    T. Chlebowski, F.D. Seward, J. Swank, A. Szymkowiak, X-rays from Eta Carinae. ApJ. 281, 665–672 (1984)Google Scholar
  7. 7.
    M.F. Corcoran, X-ray monitoring of η Carinae: variations on a theme. AJ. 129, 2018–2025 (2005)ADSCrossRefGoogle Scholar
  8. 8.
    M.F. Corcoran, G.L. Rawley, J.H. Swank, R. Petre, First detection of x-ray variability of eta carinae. ApJ. Lett. 445, L121–L124 (1995)ADSCrossRefGoogle Scholar
  9. 9.
    M.F. Corcoran, K. Ishibashi, K. Davidson, J.H. Swank, R. Petre, J.H.M.M. Schmitt, Increasing X-ray emissions and periodic outbursts from the massive star Eta Carinae. Nature 390, 587-+ (1997)Google Scholar
  10. 10.
    M.F. Corcoran, R. Petre, J.H. Swank, S.A. Drake, K. Koyama, Y. Tsuboi, R. Viotti, A. Damineli, K. Davidson, K. Ishibashi, S. White, D. Currie, The ASCA X-Ray spectrum of eta Carinae. ApJ. 494, 381-+ (1998)Google Scholar
  11. 11.
    M.F. Corcoran, A.C. Fredericks, R. Petre, J.H. Swank, S.A. Drake, The X-Ray spectral evolution of η Carinae as seen by ASCA. ApJ. 545, 420–428 (2000)ADSCrossRefGoogle Scholar
  12. 12.
    M.F. Corcoran, K. Ishibashi, J.H. Swank, R. Petre, The X-Ray light curve of η Carinae: refinement of the orbit and evidence for phase-dependent mass loss. ApJ. 547, 1034–1039 (2001)ADSCrossRefGoogle Scholar
  13. 13.
    M.F. Corcoran, J.H. Swank, R. Petre, K. Ishibashi, K. Davidson, L. Townsley, R. Smith, S. White, R. Viotti, A. Damineli, The Chandra HETGS X-ray grating spectrum of η Carinae. ApJ. 562, 1031–1037 (2001)ADSCrossRefGoogle Scholar
  14. 14.
    M.F. Corcoran et al., Waiting in the wings: reflected X-ray emission from the Homunculus nebula. ApJ. 613, 381–386 (2004)ADSCrossRefGoogle Scholar
  15. 15.
    M.F. Corcoran, K. Hamaguchi, J.M. Pittard, C.M.P. Russell, S.P. Owocki, E.R. Parkin, A. Okazaki, Recent X-ray variability of η Carinae: the quick road to recovery. ApJ. 725, 1528–1535 (2010)ADSCrossRefGoogle Scholar
  16. 16.
    A. Damineli, The 5.52 year cycle of Eta Carinae. ApJ. Lett. 460, L49+ (1996)Google Scholar
  17. 17.
    A. Damineli, P.S. Conti, D.F. Lopes, Eta Carinae: a long period binary? New Astron. 2, 107–117 (1997)ADSCrossRefGoogle Scholar
  18. 18.
    A. Damineli, D.F. Lopes, P.S. Conti, Eta Carinae Binarity after the 1998 event. ASP Conf. Ser. 179, 288–294 (1999)ADSGoogle Scholar
  19. 19.
    A. Damineli, A. Kaufer, B. Wolf, O. Stahl, D.F. Lopes, F.X. de Araújo, η Carinae: binarity confirmed. ApJ. Lett. 528, L101–L104 (2000)ADSCrossRefGoogle Scholar
  20. 20.
    A. Damineli et al., The periodicity of the η Carinae events. MNRAS. 384, 1649–1656 (2008)ADSCrossRefGoogle Scholar
  21. 21.
    A. Damineli et al., A multispectral view of the periodic events in η Carinae. MNRAS. 386, 2330–2344 (2008)ADSCrossRefGoogle Scholar
  22. 22.
    K. Davidson, Is Eta Carinae a long-period Binary? New Astron. 2, 387-+ (1997)Google Scholar
  23. 23.
    K. Davidson, Why the binary hypothesis isn’t a Panacea. ASP Conf. Ser. 179, 304–315 (1999)ADSGoogle Scholar
  24. 24.
    K. Davidson, Unique spectroscopic problems related to Eta Carinae. ASP Conf. Ser. 242, 3–12 (2001)ADSGoogle Scholar
  25. 25.
    K. Davidson, Chandra meets Eta Carinae. ASP Conf. Ser. 262, 267–274 (2002)ADSGoogle Scholar
  26. 26.
    K. Davidson, The physical nature of η Carinae. ASP Conf. Ser. 332, 101-+ (2005)Google Scholar
  27. 27.
    K. Davidson, R.M. Humphreys, Eta Carinae and its environment. Annu. Rev. Astron. Astrophys. 35, 1–32 (1997)ADSCrossRefGoogle Scholar
  28. 28.
    K. Davidson, K. Ishibashi, M.F. Corcoran, The relationship between two periodicities observed in Eta Carinae. New Astron. 3, 241–245 (1998)ADSCrossRefGoogle Scholar
  29. 29.
    K. Davidson, K., Ishibashi, T.R., Gull, R.M. Humphreys, HST/STIS observations of the star during its recent event. ASP Conf. Ser. 179, 227–235 (1999)Google Scholar
  30. 30.
    K. Davidson, K. Ishibashi, T.R. Gull, R.M. Humphreys, N. Smith, η Carinae: testing a binary orbit model with the Hubble Space Telescope/Space Telescope Imaging Spectrograph. ApJ. Lett. 530, L107–L110 (2000)ADSCrossRefGoogle Scholar
  31. 31.
    K. Davidson, N. Smith, T.R. Gull, K. Ishibashi, D.J. Hillier, The shape and orientation of the Homunculus Nebula based on spectroscopic velocities. AJ. 121, 1569–1577 (2001)ADSCrossRefGoogle Scholar
  32. 32.
    K. Davidson, J. Martin, R.M. Humphreys, K. Ishibashi, T.R. Gull, O. Stahl, K. Weis, D.J. Hillier, A. Damineli, M. Corcoran, F. Hamann, A change in the physical state of η Carinae? AJ. 129, 900–906 (2005)ADSCrossRefGoogle Scholar
  33. 33.
    R.A. Duncan, S.M. White, J. Lim, G.J. Nelson, S.A. Drake, M.R. Kundu, Intense radio outburst from the supermassive star Eta Carinae. ApJ. Lett. 441, L73–L76 (1995)ADSCrossRefGoogle Scholar
  34. 34.
    D. Falceta-Gonalves, V. Jatenco-Pereira, Z. Abraham, Wind-wind collision in the η Carinae binary system: a shell-like event near periastron. MNRAS. 357, 895–902 (2005)ADSCrossRefGoogle Scholar
  35. 35.
    A. Feinstein, H.G. Marraco, On a possible three-year cycle of eta Car. A&A. 30, 271–273 (1974)ADSGoogle Scholar
  36. 36.
    W. Forman, C. Jones, L. Cominsky, P. Julien, S. Murray, G. Peters, H. Tananbaum, R. Giacconi, The fourth UHURU catalog of X-ray sources. ApJ. Suppl. 38, 357–412 (1978)ADSCrossRefGoogle Scholar
  37. 37.
    K.G. Gayley, S.P. Owocki, S.R. Cranmer, Sudden radiative braking in colliding hot-star winds. ApJ. 475, 786-+ (1997)Google Scholar
  38. 38.
    K.C. Gendreau, W.C., Cash, P. Gorenstein, D.L. Windt, P. Kaaret, C. Reynolds, MAXIM: the black hole imager. Proc. SPIE Int. Soc. Opt. Eng. 5488, 394–402 (2004)Google Scholar
  39. 39.
    R.E. Griffiths, A. Peacock, B.E.J. Pagel, Absence of soft X-rays from eta Car. Nature 250, 714–715 (1974)ADSCrossRefGoogle Scholar
  40. 40.
    K. Hamaguchi, M.F. Corcoran, T. Gull, K. Ishibashi, J.M. Pittard, D.J. Hillier, A. Damineli, K. Davidson, K.E. Nielsen, G.V. Kober, X-ray spectral variation of η Carinae through the 2003 X-ray minimum. ApJ. 663, 522–542 (2007)ADSCrossRefGoogle Scholar
  41. 41.
    D.B. Henley, M.F. Corcoran, J.M. Pittard, I.R. Stevens, K. Hamaguchi, T.R. Gull, Chandra X-ray grating spectrometry of η Carinae near X-ray minimum. I. Variability of the sulfur and silicon emission lines. ApJ. 680, 705–727 (2008)Google Scholar
  42. 42.
    R.W. Hill, G. Burginyon, R.J. Grader, T.M. Palmieri, F.D. Seward, J.P. Stoering, A soft X-ray survey from the Galactic center to VELA. ApJ. 171, 519-+ (1972)Google Scholar
  43. 43.
    D.J. Hillier, K. Davidson, K. Ishibashi, T. Gull, On the nature of the central source in η Carinae. ApJ. 553, 837–860 (2001)ADSCrossRefGoogle Scholar
  44. 44.
    D.J. Hillier et al., The UV scattering Halo and central source associated with Eta Carinae. ApJ. 642, 1098–1116 (2006)ADSCrossRefGoogle Scholar
  45. 45.
    D. Hoffleit, Elias and Francis Loomis on variable stars, 1866–69. JAAVSO. 13, 67–77 (1984)ADSGoogle Scholar
  46. 46.
    R.M. Humphreys, K. Davidson, The luminous blue variables: astrophysical geysers. PASP. 106, 1025–1051 (1994)ADSCrossRefGoogle Scholar
  47. 47.
    R.M. Humphreys, K. Davidson, M. Koppelman, The early spectra of Eta Carinae 1892 to 1941 and the onset of its high excitation emission spectrum. AJ. 135, 1249–1263 (2008)ADSCrossRefGoogle Scholar
  48. 48.
    R.C. Iping, G. Sonneborn, T.R. Gull, D.L. Massa, D.J. Hillier, Detection of a hot binary companion of η Carinae. ApJ. Lett. 633, L37–L40 (2005)ADSCrossRefGoogle Scholar
  49. 49.
    K. Ishibashi, Multiwavelength investigation of the supermassive star Eta Carinae. Doctoral Dissertation, University of Minnesota, (1999)Google Scholar
  50. 50.
    K. Ishibashi, Searching for physically acceptable parameters for Eta Carinae’s companion. ASP. Conf. Ser. 242, 53–54 (2001)ADSGoogle Scholar
  51. 51.
    K. Ishibashi, K. Davidson, M.F. Corcoran, J.H. Swank, R. Petre, K. Jahoda, Eta Carinae. IAU. Circ. 6668, 1-+ (1997)Google Scholar
  52. 52.
    K. Ishibashi, M.F. Corcoran, K. Davidson, S.A. Drake, J.H. Swank, R. Petre, Resolving X-ray temporal variations in Eta Carinae. ASP. Conf. Ser. 179, 266–274 (1999)ADSGoogle Scholar
  53. 53.
    K. Ishibashi, M.F. Corcoran, K. Davidson, J.H. Swank, R. Petre, S.A. Drake, A. Damineli, S. White, Recurrent X-ray emission variations of η Carinae and the binary hypothesis. ApJ. 524, 983–987 (1999)ADSCrossRefGoogle Scholar
  54. 54.
    K. Ishibashi et al., Discovery of a little homunculus within the Homunculus Nebula of η Carinae. AJ. 125, 3222–3236 (2003)ADSCrossRefGoogle Scholar
  55. 55.
    A. Kashi, N. Soker, Explaining the early exit of Eta Carinae from its 2009 X-ray minimum with the accretion model. ApJ. Lett. 701, L59–L62 (2009)ADSCrossRefGoogle Scholar
  56. 56.
    K. Koyama, I. Asaoka, N. Ushimaru, S. Yamauchi, R.H.D. Corbet, Hard X-ray emission from the Carina Nebula. ApJ. 362, 215–218 (1990)ADSCrossRefGoogle Scholar
  57. 57.
    R.-P. Kudritzki, J. Puls, Winds from hot stars. Annu. Rev. Astron. Astrophys. 38, 613–666 (2000)ADSCrossRefGoogle Scholar
  58. 58.
    L.D. Landau, E.M. Lifshitz, Fluid Mechanics, 2nd edn. (Pergamon, Oxford, 1987)MATHGoogle Scholar
  59. 59.
    J.-C. Leyder, R. Walter, G. Rauw, Hard X-ray emission from η Carinae. A&A. 477, L29–L32 (2008)ADSCrossRefGoogle Scholar
  60. 60.
    E. Loomis, On the period of η Argus. MNRAS. 29, 298-+ (1869)Google Scholar
  61. 61.
    J.C. Martin, K. Davidson, R.M. Humphreys, D.J. Hillier, K. Ishibashi, On the He II emission in η Carinae and the origin of its spectroscopic events. ApJ. 640, 474–490 (2006)ADSCrossRefGoogle Scholar
  62. 62.
    A. Mehner, K. Davidson, G.J. Ferland, R.M. Humphreys, High-excitation emission lines near Eta Carinae, and its likely companion star. ApJ. 710, 729–742 (2010)ADSCrossRefGoogle Scholar
  63. 63.
    A. Mehner, K. Davidson, R.M. Humphreys, J.C. Martin, G.J. Ferland, N.R. Walborn, A sea change in Eta Carinae. ApJ. Lett. 717, L22–L25 (2010)ADSCrossRefGoogle Scholar
  64. 64.
    A. Mehner, K. Davidson, J.C. Martin, R.M. Humphreys, K. Ishibashi, G.J. Ferland, Critical differences and clues in Eta Car’s 2009 event. ApJ. 740, 2 (2011)CrossRefGoogle Scholar
  65. 65.
    A.F.J. Moffat, M.F. Corcoran, Understanding the X-ray flaring from η Carinae. ApJ. 707, 603–704 (2009)CrossRefGoogle Scholar
  66. 66.
    D.J. Mullan, Displaced narrow absorption components in the spectra of mass-losing OB stars – Indications of corotating interaction regions? A&A. 165, 157–162 (1986)ADSGoogle Scholar
  67. 67.
    Y. Nazé, M.F. Corcoran, G. Koenigsberger, A.F.J. Moffat, First detection of phase-dependent colliding wind X-ray emission outside the Milky Way. ApJ. Lett. 658, L25–L28 (2007)ADSCrossRefGoogle Scholar
  68. 68.
    K.E. Nielsen, M.F. Corcoran, T.R. Gull, D.J., Hillier, K. Hamaguchi, S. Ivarsson, D.J. Lindler, Eta Carinae across the 2003.5 minimum: spectroscopic evidence for massive binary interactions. ApJ. 660, 669–686 (2007)Google Scholar
  69. 69.
    J.J. Nugent, K.A. Jensen, J.A. Nousek, G.P. Garmire, K.O. Mason, F.M. Walter, C.S. Bowyer, R.A. Stern, G.R. Riegler, HEAO A-2 soft X-ray source catalog. ApJ. Lett. 51, 1–28 (1983)Google Scholar
  70. 70.
    A.T. Okazaki, S.P. Owocki, C.M.P. Russell, M.F. Corcoran, Modelling the RXTE light curve of η Carinae from a 3D SPH simulation of its binary wind collision. MNRAS. 388, L39–L43 (2008)ADSCrossRefGoogle Scholar
  71. 71.
    R. Parkin, J.M. Pittard, A 3D dynamical model of the colliding winds in binary systems. MNRAS. 388, 1047–1061 (2008)ADSCrossRefGoogle Scholar
  72. 72.
    E.R. Parkin, J.M. Pittard, M.F. Corcoran, K. Hamaguchi, I.R. Stevens, 3D modelling of the colliding winds in η Carinae – evidence for radiative inhibition. MNRAS. 394, 1758–1774 (2009)ADSCrossRefGoogle Scholar
  73. 73.
    C. Payne-Gaposchkin, The Galactic Novae. Dover Publications, (1957)Google Scholar
  74. 74.
    J.M. Pittard, M.F. Corcoran, In hot pursuit of the hidden companion of eta Carinae: an X-ray determination of the wind parameters. A&A. 383, 636–647 (2002)ADSCrossRefGoogle Scholar
  75. 75.
    A.M.T. Pollock, M.F. Corcoran, I.R. Stevens, P.M. Williams, Bulk velocities, chemical composition, and ionization structure of the X-ray shocks in WR 140 near periastron as revealed by the Chandra gratings. ApJ. 629, 482–498 (2005)ADSCrossRefGoogle Scholar
  76. 76.
    O.F. Prilutskii, V.V. Usov, X rays from Wolf-Rayet binaries. Sov. Astron. 20, 2-+ (1976)Google Scholar
  77. 77.
    F.D. Seward, T. Chlebowski, X-ray emission from the Carina Nebula and the associated early stars. ApJ. 256, 530–542 (1982)ADSCrossRefGoogle Scholar
  78. 78.
    F.D. Seward, C.G. Page, M.J.L. Turner, K.A. Pounds, X-ray sources in the southern Milky Way. MNRAS. 177, 13P–20P (1976)ADSGoogle Scholar
  79. 79.
    F.D. Seward, W.R. Forman, R. Giacconi, R.E. Griffiths, F.R., Harnden, C. Jones, J.P. Pye, X-rays from Eta Carinae and the surrounding nebula. ApJ. Lett. 234, L55–L58 (1979)Google Scholar
  80. 80.
    S.N. Shore, An introduction to astrophysical hydrodynamics,  chapter 4. (Academic, San Diego, 1992)Google Scholar
  81. 81.
    N. Smith, K. Davidson, T.R. Gull, K. Ishibashi, D.J. Hillier, Latitude-dependent effects in the stellar wind of η Carinae. ApJ. 586, 432–450 (2003)ADSCrossRefGoogle Scholar
  82. 82.
    N. Soker, The binarity of Eta Carinae and its similarity to related astrophysical objects. ApJ. 619, 1064–1071 (2005)ADSCrossRefGoogle Scholar
  83. 83.
    N. Soker, Accretion by the secondary in η Carinae during the spectroscopic event. I. Flow parameters. ApJ. 635, 540–546 (2005)Google Scholar
  84. 84.
    O. Stahl, K. Weis, D.J. Bomans, K. Davidson, T.R. Gull, R.M. Humphreys, A spectroscopic event of η Car viewed from different directions: the data and first results. A&A. 435, 303–312 (2005)ADSCrossRefGoogle Scholar
  85. 85.
    J.E. Steiner, A. Damineli, Detection of He II λ4686 in η Carinae. ApJ. Lett. 612, L133–L136 (2004)ADSCrossRefGoogle Scholar
  86. 86.
    I.R. Stevens, J.M. Pittard, Eta Carinae: a colliding wind binary? ASP. Conf. Ser. 179, 295–303 (1999)ADSGoogle Scholar
  87. 87.
    I.R. Stevens, A.M.T. Pollock, Stagnation-point flow in colliding wind binary systems. MNRAS. 269, 226-+ (1994)Google Scholar
  88. 88.
    I.R. Stevens, J.M. Blondin, A.M.T. Pollock, Colliding winds from early-type stars in binary systems. ApJ. 386, 265–287 (1992)ADSCrossRefGoogle Scholar
  89. 89.
    M. Tavani et al.: Detection of gamma-ray emission from the Eta-Carinae region. ApJ. Lett. 698 L142–L146 (2009)ADSCrossRefGoogle Scholar
  90. 90.
    T. Takahashi, the NeXT team, The NeXT mission. 807 (2008) ArXiv e-printsGoogle Scholar
  91. 91.
    Y. Tsuboi, K. Koyama, M. Sakano, R. Petre, ASCA observations of Eta Carinae. Publ. Aston. Soc. Jpn. 49, 85–92 (1997)ADSGoogle Scholar
  92. 92.
    V.V. Usov, Stellar wind collision and X-ray generation in massive binaries. ApJ. 389, 635–648 (1992)ADSCrossRefGoogle Scholar
  93. 93.
    E. Verner, F. Bruhweiler, T. Gull, The binarity of η Carinae revealed from photoionization modeling of the spectral variability of the weigelt blobs B and D. ApJ. 624, 973–982 (2005)ADSCrossRefGoogle Scholar
  94. 94.
    S.M. White, R.A. Duncan, J. Lim, G.J. Nelson, S.A. Drake, M.R. Kundu, The radio source around Eta Carinae. ApJ. 429, 380–384 (1994)ADSCrossRefGoogle Scholar
  95. 95.
    P.A. Whitelock, M.W. Feast, B.S. Carter, G. Roberts, I.S. Glass, The infrared spectrum and variability of Eta Carinae. MNRAS. 203, 385–392 (1983)ADSGoogle Scholar
  96. 96.
    P.A. Whitelock, M.W. Feast, C. Koen, G. Roberts, B.S. Carter, Variability of Eta-Carinae. MNRAS. 270, 364-+ (1994)Google Scholar
  97. 97.
    P.A. Whitelock, M.W. Feast, F. Marang, E. Breedt, The 2003 shell event in Eta Carinae. MNRAS. 352, 447–456 (2004)ADSCrossRefGoogle Scholar
  98. 98.
    A.J. Willis, H. Schild, I.R. Stevens, ROSAT observations of γ Velorum (WC8+O9I). I. The discovery of colliding-wind X-ray emission. A&A. 298, 549-+ (1995)Google Scholar
  99. 99.
    R. Wolf, Schreiben des Herrn Prof. Wolf, Directors der Sternwarte in Zürich an den Herausgeber. Astron. Nachr. 60, 59-+ (1863)Google Scholar
  100. 100.
    R. Zanella, B. Wolf, O. Stahl, Spectroscopy of the shell episode of Eta CAR (1981–1983). A&A. 137, 79–84 (1984)ADSGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  1. 1.Center for Research and Exploration in Space Science & Technology, Code 662, Goddard Space Flight CenterGreenbeltUSA
  2. 2.Universities Space Research AssociationColumbiaUSA
  3. 3.Department of PhysicsNagoya UniversityNagoyaJapan

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