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Photometric studies of three multiperiodic β Cephei stars: β CMa, 15 CMa and KZ Mus
We have carried out single and multisite photometry of the three βCephei stars β and 15 CMa as well as KZ Mus. For the two stars inCMa, we obtained 270h of measurement in the Strömgren uvy andJohnson V filters, while 150h of time-resolved Strömgren uvyphotometry was acquired for KZ Mus. All three stars are multiperiodicvariables, with three (β CMa) and four (15 CMa, KZ Mus) independentpulsation modes. Two of the mode frequencies of 15 CMa are newdiscoveries and one of the known modes showed amplitude variations overthe last 33yr. Taken together, this fully explains the diverse behaviourof the star reported in the literature.Mode identification by means of the amplitude ratios in the differentpassbands suggests one radial mode for each star. In addition, βCMa has a dominant l = 2 mode while its third mode is non-radial withunknown l. The non-radial modes of 15 CMa, which are l <= 3, form analmost equally split triplet that, if physical, would imply that we seethe star under an inclination angle larger than 55°. The strongestnon-radial mode of KZ Mus is l = 2, followed by the radial mode and adipole mode. Its weakest known mode is non-radial with unknown l,confirming previous mode identifications for the pulsations of the star.The phased light curve for the strongest mode of 15 CMa has a descendingbranch steeper than the rising branch. A stillstand phenomenon duringthe rise to maximum light is indicated. Given the low photometricamplitude of this non-radial mode this is at first sight surprising, butit can be explained by the aspect angle of the mode.
| Asteroseismological studies of three β Cephei stars: IL Vel, V433 Car and KZ Mus
We have acquired between 127 and 150 h of time-resolved multicolourphotometry for each of the three β Cephei stars IL Vel, V433 Carand KZ Mus over a time-span of 4 months from two observatories. Allthree objects are multiperiodic with at least three modes of pulsation.Mode identification from the relative colour amplitudes is performed. Weobtain unambiguous results for the two highest-amplitude modes of IL Vel(both are l= 1) and the three strongest modes of KZ Mus (l= 2, 0 and 1),but none for V433 Car. Spectroscopy shows the latter star to be a fastrotator (v sin i= 240 km s-1), whereas the other two havemoderate v sin i (65 and 47 km s-1, respectively).We performed model calculations using the Warsaw-New Jersey stellarevolution and pulsation code. We find that IL Vel is an object of about12 Msolar in the second half of its main-sequenceevolutionary track. Its two dipole modes are most probably rotationallysplit components of the mode originating as p1 on thezero-age main sequence; one of these modes is m= 0. V433 Car issuggested to be an unevolved 13-Msolar star just entering theβ Cephei instability strip. KZ Mus seems less massive (~12.7Msolar) and somewhat more evolved, and its radial mode isprobably the fundamental one. In this case its quadrupole mode would bethe one originating as g1, and its dipole mode would bep1.Two of our photometric comparison stars also turned out to be variable.HD 90434 is probably a new slowly pulsating B-type star, the dominantmode of which is a dipole, whereas the variability of HD 89768 seems tobe a result of binarity.It is suggested that mode identification of slowly rotating βCephei stars based on photometric colour amplitudes is reliable; weestimate that a relative accuracy of 3 per cent in the amplitudes issufficient for unambiguous identifications. Owing to the good agreementof our theoretical and observational results we conclude that theprospects for asteroseismology of multiperiodic slowly rotating βCephei stars are good.
| Multicolour Polarization and Co/ Observations Towards a Dark Filament in Musca
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993MNRAS.265....1A&db_key=AST
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