Sergio Char

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We present here an analysis of the light curves of 5.3 million stars in the Small Magellanic Cloud observed by EROS (Expérience de Recherche d’Objets Sombres). One star exhibits a variation that is best interpreted as due to gravitational microlensing by an unseen object. This candidate was also reported by the MACHO collaboration. The Einstein radius(More)
We present final results from the first phase of the EROS search for gravitational microlensing of stars in the Magellanic Clouds by unseen deflectors (machos: MAssive Compact Halo Objects). The search is sensitive to events with time scales between 15 minutes and 200 days corresponding to deflector masses in the range 10 to a few M⊙. Two events were(More)
Arginyl-tRNA synthetase [L-Arg: tRNAArg ligase (AMP forming) EC] has been purified to homogeneity from Mycobacterium smegmatis SN2. The enzyme is a monomer of molecular weight 56,000. The kinetic patterns obtained by initial velocity and product inhibition studies are consistent with a rapid equilibrium random ter ter mechanism. Polyamines(More)
We are conducting a 377 ◦2 proper motion survey in the ∼V and I bands in order to determine the cool white dwarf contribution to the Galactic dark matter. Using the 250 ◦2 for which we possess three epochs, and applying selection criteria designed to isolate halo-type objects, we find no candidates in a 5500 pc effective volume for old, fast MV = 17 white(More)
We report the discovery of two L dwarfs (the new spectral class defined for dwarfs cooler than the M type) in a two-epoch CCD proper motion survey of 413 square degrees, complemented by infrared photometry from DENIS. One of them has a strong lithium line, which for very cool dwarfs is a proof of brown dwarf status. The other is a common proper motion(More)
We present the Period–Luminosity relations from 290 Cepheids towards the LMC and 590 Cepheids towards the SMC. The two data sets were obtained using the two wide field CCD cameras of the EROS 2 microlensing survey. We observe a significant slope change of the period–luminosity relation for the SMC fundamental mode Cepheids with periods shorter than 2 days.(More)
We present time-resolved optical spectroscopy and broad-band photometry of the rapidly-rotating southern K0 dwarf star AB Doradus, obtained during 1994 November. The data were obtained as part of a collaboration dedicated to MUlti-SIte COntinuous Spectroscopy (MUSICOS), and entailed coordinated observations on three continents to obtain the fullest phase(More)
We present a measurement of the microlensing optical depth toward the Galactic bulge based on the analysis of 15 contiguous 1 deg fields centered on (l = 2.◦5, b = −4.◦0) and containing N∗ = 1.42×10 6 clump-giant stars (belonging to the extended clump area) monitored during almost three bulge seasons by EROS (Expérience de Recherche d’Objets Sombres). We(More)
Recent surveys monitoring millions of light curves of resolved stars in the LMC have discovered several microlensing events. Unresolved stars could however significantly contribute to the microlensing rate towards the LMC. Monitoring pixels, as opposed to individual stars, should be able to detect stellar variability as a variation of the pixel flux. We(More)
The presence and abundance of MAssive Compact Halo Objects (MACHOs) towards the Large Mag-ellanic Cloud (LMC) can be studied with microlensing searches. The 10 events detected by the EROS and MA-CHO groups suggest that objects with 0:5M could ll 50% of the dark halo. This preferred mass is quite surprising , and increasing the presently small statistics is(More)