HR 7355 - another rapidly braking He-strong CP star?
|Název česky||HR 7355 - další rychle se brzdící heliová CP hvězda?|
|Druh||Článek v odborném periodiku|
|Časopis / Zdroj||Astronomy and Astrophysics|
|Fakulta / Pracoviště MU|
|Obor||Astronomie a nebeská mechanika, astrofyzika|
|Klíčová slova||stars: chemically peculiar; stars: variables: general; stars: individual: HR 7355; stars: rotation|
|Popis||Over two years, we acquired 114 new BV observations of HR 7355 at observatories in Arizona, U.S.A and Cape Town, South Africa. We performed period analyses of the new observations along with new analyses of 732 archival measurements from the Hipparcos and ASAS projects. We find that the light curves of HR 7355; in various filters are quite similar, with amplitudes 0.035(4), 0.036(4), and 0.038(3) mag in B, Hp, and V, respectively. The light curves are double-peaked, with unevenly deep minima. We substantially refine the rotational period to be P = 0.5214410(4)d, indicating that HR 7355gt; is the most rapidly rotating CP star known. Our period analyses reveal a possible lengthening of the rotational period with dP/dt/P = 2.4(8)x10-6 yr-1. We conclude that the shape and amplitude of HR 7355; light curves are typical of magnetic He-strong CP stars, for which light variations are the result of photospheric spots on the surface of a rotating star. We hypothesise that the light variations are caused mainly by an uneven distribution of overabundant helium on the star's surface. We briefly describe and discuss the cause of the rapid rotational braking of the star.|