Tayler instability of magnetic field as possible reason for the period changes in Ap star 56 Ari

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Abstract

The physical mechanism responsible for the photometric period changes in chemically peculiar star 56 Ari was searched. It was previously shown that rate of the star’s period increase is few orders of magnitude larger than the rates expected from the evolutionary changes of the angular momentum or due to magnetic braking. Also no secular changes were detected in the surface structure or visibility of chemical spots which are responsible for the rotational modulation of stellar brightness. We hypothesise that period changes in 56 Ari are caused by the drift of surface magnetic and associated abundance structures as a result of the kink-type (Tayler) instability of the background magnetic field in the radiative zone of the star. Results of the numerical simulation presented in the paper yield growth and drift rates of the most rapidly developing non-axisymmetric mode of the instability, consistent with the observed rate of period changes in 56 Ari. The surface geometry of the 56 Ari magnetic field is also reproduces in the calculations. The proposed mechanism may also be used to explain the character of period changes in other Ap/Bp stars demonstrating such an effect.

About the authors

I. S. Potravnov

Institute of Astronomy of the Russian Academy of Sciences; Institute of Solar-Terrestrial Physics Siberian Branch of the Russian Academy of Sciences

Email: ilya.astro@gmail.com
Moscow, Russia; Irkutsk, Russia

L. L. Kitchatinov

Institute of Solar-Terrestrial Physics Siberian Branch of the Russian Academy of Sciences

Email: kit@iszf.irk.ru
Irkutsk, Russia

References

  1. D.W.N. Stibbs, Monthly Not. Roy. Astron. Soc. 110, 395 (1950).
  2. G. Michaud, 160, 641 (1970).
  3. G. Michaud, G. Alecian, and J. Richer, Atomic Diffusion in stars (Springer International Publishing, 2015).
  4. G. Alecian and S. Vauclair, Astron. and Astrophys. 101, 16 (1981).
  5. G. Michaud, C. Megessier, and Y. Charland, Astron. and Astrophys. 103, 244 (1981).
  6. T.G. Cowling, Monthly Not. Roy. Astron. Soc. 105, 166 (1945).
  7. D. Moss, Magnetic Fields Across the Hertzsprung-Russell Diagram, edited by G. Mathys, S.K. Solanki, and D.T. Wickramasinghe (San Francisco: ASP Press, 2001), ASP Conf. Proc. 248, 305 (2001).
  8. G. Alecian and M.J. Stift, Astron. and Astrophys. 516, id. A53 (2010).
  9. M.J. Stift and G. Alecian, Monthly Not. Roy. Astron. Soc. 457(1), 74 (2016).
  10. A. Belopolsky, Astron. Nachricht. 196(1), 1 (1913).
  11. F.A. Catalano and P. Renson, Astron. and Astrophys. Suppl. Ser. 127, 421 (1998).
  12. D.M. Pyper and S.J. Adelman, Publ. Astron. Soc. Pacific 132(1008), id. 024201 (2020).
  13. D.M. Pyper and S.J. Adelman, Publ. Astron. Soc. Pacific 133(1026), id.084203 (2021).
  14. D.M. Pyper, T. Ryabchikova, V. Malanushenko, R. Kuschnig, S. Plachinda, and I. Savanov, Publ. Astron. Soc. Pacific 339, 822 (1998).
  15. D.M. Pyper, I R. Stevens, and S.J. Adelman, Monthly Not. Roy. Astron. Soc. 431(3), 2106 (2013).
  16. C. Trigilio, P. Leto, G. Umana, C.S. Buemi, and F. Leone, Monthly Not. Roy. Astron. Soc. 384(4), 1437 (2008).
  17. Z. Mikulášek, J Krtika, J.G. W. Henry, J. Jank, et al., Astron. and Astrophys. 534, id. L5 (2011).
  18. Z. Mikulášek, Contrib. Astron. Observ. Skalnate Pleso 46(2), 95 (2016).
  19. M. Shultz, Th. Rivinius, B. Das, G.A. Wade, and P. Chandra, Monthly Not. Roy. Astron. Soc. 486(4), 5558 (2019).
  20. K. Stȩpień, Astron. and Astrophys. 337, 754 (1998).
  21. I. Potravnov, N. Piskunov, and T. Ryabchikova, Astron. and Astrophys. 689, id. A111 (2024).
  22. S.J. Adelman, R.J. Dukes, Jr., and D.M. Pyper, Astron. J. 104, 314 (1992).
  23. S.N. Shore and S.J. Adelman, 209, 816 (1976).
  24. B. Musielok, Inform. Bull. Var. Stars № 3257 (1988).
  25. S.J. Adelman, V. Malanushenko, T.A. Ryabchikova, and I. Savanov, Astron. and Astrophys. 375, 982 (2001).
  26. J. Krtika, Z. Mikulášek, T. Lüftinger, D. Shulyak, J. Zverko, J. Žižovský, and N.A. Sokolov, Astron. and Astrophys. 537, id. A14 (2012).
  27. Y. Pakhomov, I. Potravnov, A. Romanovskaya, and T. Ryabchikova, Universe 10(9), id. 341 (2024).
  28. L. Mestel and N.O. Weiss, Monthly Not. Roy. Astron. Soc. 226, 123 (1987).
  29. J. Krtika, Z. Mikulášek, G.W. Henry, P. Kurfürst, and M. Karlický, Monthly Not. Roy. Astron. Soc. 464(1), 933 (2017).
  30. K. Takahashi and N. Langer, Astron. and Astrophys. 696, id.A129 (2025)
  31. R.J. Tayler, Monthly Not. Roy. Astron. Soc. 161, 365 (1973).
  32. E. Pitts and R.J. Tayler, Monthly Not. Roy. Astron. Soc. 216, 139 (1985).
  33. H.C. Spruit, Astron. and Astrophys. 381, 923 (2002).
  34. G. Rüdiger, L.L. Kitchatinov, and D. Elstner, Monthly Not. Roy. Astron. Soc. 425(3), 2267 (2012).
  35. G. Rüdiger and L.L. Kitchatinov, Geophys. and Astrophys. Fluid Dyn. 104(2–3), 273 (2010).
  36. L.L. Kitchatinov, I.S. Potravnov, and A.A. Nepomnyashchikh, Astron. and Astrophys. 638, id. L9 (2020).
  37. A.J. Cannon and E.C. Pickering, The Henry Draper (HD) Catalogue. Vol.91: 0h, 1h, 2h and 3h, Ann. Harvard College Observ. 91 (1918).
  38. D. Shulyak, O. Kochukhov, G. Valyavin, B.-C. Lee, G. Galazutdinov, K.-M. Kim, I. Han, and T. Burlakova, Astron. and Astrophys. 509, id. A28 (2010).
  39. A.P. Hatzes, in Peculiar versus Normal Phenomena in A-type and Related Stars, IAU Colloquium № 138, held in Trieste, Italy, July 1992; edited by M.M. Dworetsky, F. Castelli, R. Faraggiana, (San Francisco, CA: ASPC Publisher, 1993), Proc. IAU Symp. 44, 258 (1993).
  40. T. Ryabchikova, G.A. Wade, and F. LeBlanc, in Modelling of Stellar Atmospheres, Proc. of the 210th Symposium of the IAU, held at Uppsala University, Uppsala, Sweden, 17–21 June, 2002; edited by N. Piskunov, W.W. Weiss, and D.F. Gray, (San Francisco, CA: ASPC Publisher, 2003), Proc. IAU Symp. 210, 301 (2003).
  41. I. Potravnov, et al., in preparation (2025).
  42. E.F. Borra and J.D. Landstreet, Astrophys. J. Suppl. 42, 421 (1980).
  43. M.E. Shultz, S. Owocki, Th. Rivinius, G.A. Wade, et al., Monthly Not. Roy. Astron. Soc. 499, 5379 (2020).
  44. O. Kochukhov and S. Bagnulo, Astron. and Astrophys. 450, 763 (2006).
  45. A.J. Deutsch, Astron. J. 58, 37 (1953).
  46. S.S. Provin, 118, 281 (1953).
  47. L.L. Kitchatinov and G. Rüdiger, Astron. and Astrophys. 478(1), 1 (2008).
  48. Л.Л. Кичатинов, Астрон. журн. 85(3), 279 (2008).
  49. H.C. Spruit, Astron. and Astrophys. 349, 189 (1999).
  50. S. Chandrasekhar, Hydrodynamic and hydromagnetic stability (Oxford: Clarendon Press, 1961).
  51. M. Goossens, D. Biront, and R.J. Tayler, Astrophys. Space Sci. 75(2), 521 (1981).
  52. B. Paxton, L. Bildsten, A. Dotter, F. Herwig, P. Lesaffre, and F. Timmes, Astrophys. J. Suppl. 192(1), id. 3 (2011).
  53. E.N. Parker, Astrophys. Space Sci 62(1), 135 (1979).
  54. D.W. Hughes and N.O. Weiss, J. Fluid Mech. 301, 383 (1995).
  55. P. Renson and J. Manfroid, Astron. and Astrophys. 498(3), 961 (2009).
  56. А.И. Богомазов, А.В. Тутуков, Астрон. журн. 86, 240 (2009).
  57. А.В. Тутуков, А.В. Федорова, Астрон. журн. 87(2), 178 (2010).
  58. F.R. N. Schneider, S.T. Ohlmann, P. Podsiadlowski, F.K. Ropke, S.A. Balbus, R. Pakmor, and V. Springel, Nature 574(7777), 211 (2019).
  59. G. Rüdiger, D. Elstner, and T.F. Stepinski, Astron. and Astrophys. 298, 934 (1995).
  60. M.V. Rekowski, G. Rüdiger, and D. Elstner, Astron. and Astrophys. 353, 813 (2000).
  61. V. Prat, S. Mathis, B. Buysschaert, J. Van Beeck, D.M. Bowman, C. Aerts, and C. Neiner, Astron. and Astrophys. 627, id. A64 (2019).
  62. S. Mathis, L. Bugnet, V. Prat, K. Augustson, S. Mathur, and R.A. Garcia, Astron. and Astrophys. 647, id. A122 (2021).

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