9,816 research outputs found

    KPD1930+2752 - a candidate Type Ia supernova progenitor

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    We present spectra of the pulsating sdB star KPD1930+2752 which confirm that this star is a binary. The radial velocities measured from the H-alpha and HeI6678 spectral lines vary sinusoidally with the same period (2h 17m) as the ellipsoidal variability seen by Billeres et al. (2000). The amplitude of the orbital motion (349.3+-2.7 km/s) combined with the canonical mass for sdB stars (0.5 solar masses) implies a total mass for the binary of 1.47+-0.01 solar masses The unseen companion star is almost certainly a white dwarf star. The binary will merge within about 200 million years due to gravitational wave radiation. The accretion of helium and other elements heavier than hydrogen onto the white dwarf which then exceeds the Chandrasekhar mass (1.4 solar masses) is a viable model for the cause of Type Ia supernovae. KPD1930+2752 is the first star to be discovered which is a good candidate for the progenitor of a Type Ia supernova of this type which will merge on an astrophysically interesting timescale.Comment: Accepted for publication in MNRAS. 4 pages, 2 figures. Added Institutio

    CNONa and 12C/13C in giants of 10 open clusters

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    Evolved low-mass stars of a wide range of metallicity bear signatures of a non-standard mixing event in their surface abundances of Li, C, and N, and in their 12C/13C ratio. A Na overabundance has also been reported in some giants of open clusters but remains controversial. The cause of the extra-mixing has been attributed to thermohaline convection that should take place after the RGB bump for low-mass stars and on the early-AGB for more massive objects. To track the occurrence of this process over a wide mass range, we derive in a homogeneous way the abundances of C, N, O, and Na, as well as the 12C/13C ratio in a sample of 31 giants of 10 open clusters with turn-off masses from 1.7 to 3.1 Msun. A group of first ascent red giants with M/Msun \leq 2.5 exhibits lower [N/C] ratios than those measured in clump giants of the same mass range, suggesting an additional increase in the [N/C] ratio after the first dredge-up. The sodium abundances corrected from NLTE are found to be about solar. [Na/Fe] shows a slight increase of 0.10 dex as a function of stellar mass in the 1.8 to 3.2 Msun range covered by our sample, in agreement with standard first dredge-up predictions. Our results do not support previous claims of sodium overabundances as high as +0.60 dex. An anti-correlation between 12C/13C and turn-off mass is identified and interpreted as being caused by a post-bump thermohaline mixing. Moreover, we find low 12C/13C ratios in a few intermediate-mass early-AGB stars, confirming that an extra-mixing process also operates in stars that do not experienced the RGB bump. In this case, the extra-mixing possibly acts on the early-AGB, in agreement with theoretical expectations for thermohaline mixing. [abridged]Comment: A&A accepted, revised versio

    Lithium in field Am and normal A-F-type stars

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    Preliminary abundances of lithium and a few other elements have been obtained for 31 field Am stars with good Hipparcos parallaxes, as well as for 36 normal A and F stars. Radial and projected rotational velocities were determined as well. We examine the Li abundance as a function of the stellar parameters: for normal stars, it is clearly bimodal for Teff < 7500 K, while Am-Fm stars are all somewhat Li-deficient in this range. The most Li-deficient stars - either Am or normal - tend to be at least slightly evolved, but the reverse is not true.Comment: 4 pages, 2 figures, poster presented at the conference "Element stratification in stars, 40 years of atomic diffusion", eds. G. Alecian, O. Richard and S. Vauclair, EAS Publication Series, in pres

    Pregnancy without ovarian function A case report

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    A 38-year-old nulliparous woman suffering from premature menopause was stimulated with oestradiol valerate in order to create an artificial endometrial cycle. Three oocytes were donated by a woman on an in vitro fertilisation cycle and were inseminated with the patient's husband's sperm. These were then transferred into the patient's uterus after the endometrium had been primed with progesterone to change it to the secretory phase. Pregnancy resulted and proceeded well. Gestation was terminated at the 34th week by caesarean section and 2 healthy boys and 1 girl were delivered

    Does rotation of B stars depend on metallicity? preliminary results from GIRAFFE spectra

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    We show the vsini distribution of main sequence B stars in sites of various metallicities, in the absolute magnitude range -3.34 < Mv < -2.17. These include Galactic stars in the field measured by Abt et al. (2002), members of the h & chi Per open clusters measured by North et al. (2004), and five fields in the SMC and LMC measured at ESO Paranal with the FLAMES-GIRAFFE spectrograph, within the Geneva-Lausanne guaranteed time. Following the suggestion by Maeder et al. (1999), we do find a higher rate of rapid rotators in the Magellanic Clouds than in the Galaxy, but the vsini distribution is the same in the LMC and in the SMC in spite of their very different metallicities.Comment: 2 pages, 1 figure, poster presented at the ESO/Arcetri Workshop on "Chemical abundances and mixing in stars in the Milky Way and its satellites", 13-17 Sept. 200

    The Effects of Musical Fit on Consumers' Ability to Freely Recall Related Products

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    Previous studies have claimed that music can prime the selection of certain products and influence consumers’ propensity to spend because it activates related knowledge of the world and subsequently raises the salience of certain products and behaviours associated with that music. The possibility that music can raise the salience of associated products has not been tested directly, however, and ought to manifest itself through enhanced ability to recall the products in question when associated music is played. Accordingly, this study investigated the impact of musical ‘fit’ on product recall. Participants were asked to list as many Malay and Indian food items as they could while listening to either Malay or Indian music. Among ethnically Chinese participants, more Malay food items were recalled when Malay music was played and more Indian food items were recalled when Indian music was played. Ethnically Malay and Indian participants were more likely to recall food from their own cultures, irrespective of the music played

    The Effects of Musical Fit on Consumers' Ability to Freely Recall Related Products

    Get PDF
    Previous studies have claimed that music can prime the selection of certain products and influence consumers’ propensity to spend because it activates related knowledge of the world and subsequently raises the salience of certain products and behaviours associated with that music. The possibility that music can raise the salience of associated products has not been tested directly, however, and ought to manifest itself through enhanced ability to recall the products in question when associated music is played. Accordingly, this study investigated the impact of musical ‘fit’ on product recall. Participants were asked to list as many Malay and Indian food items as they could while listening to either Malay or Indian music. Among ethnically Chinese participants, more Malay food items were recalled when Malay music was played and more Indian food items were recalled when Indian music was played. Ethnically Malay and Indian participants were more likely to recall food from their own cultures, irrespective of the music played

    A purely geometric distance to the binary star Atlas, a member of the Pleiades

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    We present radial velocity and new interferometric measurements of the double star Atlas, which permit, with the addition of published interferometric data, to precisely derive the orbital parameters of the binary system and the masses of the components. The derived semi-major axis, compared with its measured angular size, allows to determine a distance to Atlas of 132+-4 pc in a purely geometrical way. Under the assumption that the location of Atlas is representative of the average distance of the cluster, we confirm the distance value generally obtained through main sequence fitting, in contradiction with the early Hipparcos result (118.3+-3.5 pc).Comment: 5 pages, 3 figures, accepted for publication in A&A Letter
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