Ahmed Daassou

A helium P-Cygni profile in RR Lyrae stars?

Context. Until 2006, helium emission lines had never been observed in RR Lyrae stars. For the first time, a pre-maximum helium emission in 11 RRab stars was observed during rising light (around the pulsation phase 0.92) and the reappearance of helium emission near maximum light (phase 0.0) in one RRab star: RV Oct. This post-maximum emission has been only observed in the He I λ5875.66 (D3) line. Its intensity is very weak, and its profile mimics a P-Cygni profile with the emission peak centered at the laboratory wavelength. The physical explanation for this unexpected line profile has not been proposed yet. Aims. Using new observations of RR Lyr, we investigate the physical origin of the presence of a P-Cygni profile in the He I λ5875.66 (D3) line. Methods. High-resolution spectra of RR Lyr, collected with a spectrograph eShel/C14 at the Oukaïmeden Observatory (Morocco) in 2013, were analyzed to understand the origin of the observed P-Cygni profile at D3. Results. When the shock intensity is moderate, helium emission cannot be produced in the shock wake, and consequently, the two consecutive helium emissions (preand post-maximum light emissions) are not observed. This is the most frequent case. When the shock intensity becomes high enough, a pre-maximum He I emission first occurs, which can be followed by the appearance of a P-Cygni profile if the shock intensity is still strong in the high atmosphere. The observation of a P-Cygni profile means that the shock wave is already detached from the photosphere. It is shown that the shock strongly first decelerates between the pulsation phases 0.90 and 1.04 from 130 km s−1 to 60 km s−1, probably before accelerating again to 80 km s−1 near phase 1.30. Conclusions. The presence of the P-Cygni profile seems to be a natural consequence of the large extension of the expanding atmosphere, which is induced by strong (radiative) shock waves propagating toward the high atmosphere. This kind of P-Cygni profile has already been observed in the Hα line of some RR Lyrae stars and long-period Cepheids.

Monitoring of the activity and composition of comets 41P/Tuttle-Giacobini-Kresak and 45P/Honda-Mrkos-Pajdusakova

We report on photometry and imaging of the Jupiter Family Comets 41P/Tuttle-Giacobini-Kresak and 45P/Honda-Mrkos-Pajdusakova with the TRAPPIST-North telescope. We observed 41P on 34 nights from February 16, 2017 to July 27, 2017 pre- and post-perihelion (r

Assessment of the potential of the new Belgo-Moroccan telescope TRAPPIST-North for high-precision exoplanet transit photometry

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Monitoring of comets activity and composition with the TRAPPIST-North telescope

=1.04 au), while we collected data for comet 45P from February 10 to March 30 after perihelion (r

An analytical model for the 0. 33 - 7. 85 micron transmission spectrum of HD189733b : Effect of stellar spots

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Oukaimeden Observatory: detection of exoplanet HD 189733b by the transit method

=0.53 au). We computed the production rates of the daughter species OH, NH, CN, C

Power and duration of impact flashes on the Moon: Implication for the cause of radiation

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Study of the plutino object (208996) 2003 AZ84 from stellar occultations: size, shape and topographic features

and C

First Lunar Flashes Observed from Morocco (ILIAD Network): Implications for Lunar Seismology

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Climatology of thermospheric neutral winds over Oukaïmeden Observatory in Morocco

and we measured the dust proxy, Af