39 research outputs found

    Evidence for ablated flows in the shell of nova DQ Her

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    High-resolution longslit Halpha spectra of the shell of the old nova DQ Her have been obtained with the William Herschel Telescope using the ISIS spectrograph. An equatorial expansion velocity of 370+/-14 km/s is derived from the spectra which, in conjunction with a narrowband Halpha image of the remnant, allows a distance estimate of 525+/-28 pc. An equatorial ring which exhibits enhanced [NII] emission has also been detected and the inclination angle of the shell is found to be 86.8+/-0.2 degrees with respect to the line of sight. The spectra also reveal tails extending from the clumps in the shell, which have a radial velocity increasing along their length. This suggests the presence of a stellar wind, collimated in the polar direction, which ablates fragments of material from the clumps and accelerates them into its stream up to a terminal velocity of order 800-900 km/s.Comment: 7 pages, 6 figure

    Early spectral evolution of Nova Sgr 2004 (V5114 Sgr)

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    We present optical and near-infrared spectral evolution of the Galactic nova V5114 Sgr (2004) during few months after the outburst. We use multi-band photometry and line intensities derived from spectroscopy to put constrains on the distance and the physical conditions of the ejecta of V5114 Sgr. The nova showed a fast decline (t_2 \simeq 11 days) and spectral features of FeII spectroscopic class. It reached M_V = -8.7 \pm 0.2 mag at maximum light, from which we derive a distance of 7700 \pm 700 kpc and a distance from the galactic plane of about 800 pc. Hydrogen and Oxygen mass of the ejecta are measured from emission lines, leading to 10^{-6} and 10^{-7} M_\odot, respectively. We compute the filling factor of the ejecta to be in the range 0.1 -- 10^{-3} . We found the value of the filling factor to decrease with time. The same is also observed in other novae, then giving support to the idea that nova shells are not homogeneously filled in, rather being the material clumped in relatively higher density blobs less affected by the general expanding motion of the ejecta.Comment: accepted for publication in Astronomy & Astrophysics, 16 pages and 8 figure

    Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

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    The origin and abundances of the chemical elements

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    POST SINTERING HEAT TREATMENTS AND CREEP OF Si-Y-Al-O-N CERAMICS

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    International audienceFor two batches of pressureless sintered SiYAlON ceramics, it is demonstrated that the creep resistance may be improved by using powder bed heat treatments in nitrogen atmosphere.Sur deux nuances de céramiques de type SiYAlON, obtenues par frittage naturel, il est montré l'intérêt, pour améliorer la résistance au fluage, de traitements thermiques en lit de poudre sous atmosphère d'azote

    Frequency modulation in a multiple-cavity gas laser

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