The scale dependence of quark and squark mass and flavor mixing is studied with the renormalizati... more The scale dependence of quark and squark mass and flavor mixing is studied with the renormalization group equations of broken N = 1 supergravity. The rotation matrix between charge -1/3 quarks and squarks turns out to be nearly equal to the Cabibbo-Kobayashi-Maskawa one. Gluino couplings then change flavor, but we find that their contribution to the K°-K ° mixing is generally smaller than the usual standard model result.
The presence of brown dwarfs in the dark galactic halo could be detected through their gravitatio... more The presence of brown dwarfs in the dark galactic halo could be detected through their gravitational lensing effect and experiments under way monitor about one million stars to observe a few lensing events per year. We show that if the photon flux from a galaxy is measured with a good precision, it is not necessary to resolve the stars and besides more events could be observed.
We report the discovery of a short-duration microlensing candidate in the northern field of the P... more We report the discovery of a short-duration microlensing candidate in the northern field of the POINT-AGAPE pixel lensing survey towards M31. The full-width half-maximum timescale is very short, t 1/2 = 1.8 days. Almost certainly, the source star has been identified on Hubble Space Telescope archival images, allowing us to infer an Einstein crossing time of t E = 10.4 days, a maximum magnification of A max ∼ 18, and a lens-source proper motion µ rel > 0.3 µas/day. The event lies projected at 8 ′ from the center of M31, which is beyond the bulk of the stellar lens population. The lens is likely to reside in one of three locations. It may be a star in the M31 disk, or a massive compact halo object (Macho) in either M31 or the Milky Way. The most probable mass is 0.06 M ⊙ for an M31 Macho, 0.02 M ⊙ for a Milky Way Macho and 0.2 M ⊙ for an M31 stellar lens. Whilst the stellar interpretation is plausible, the Macho interpretation is the most probable for halo fractions above 20%.
We present the AGAPE astrometric and photometric catalogue of 1579 variable stars in a 14 ′ ×10 ′... more We present the AGAPE astrometric and photometric catalogue of 1579 variable stars in a 14 ′ ×10 ′ field centred on M31. This work is the first survey devoted to variable stars in the bulge of M31. The R magnitudes of the objects and the B − R colours suggest that our sample is dominated by red long-period variable stars (LPV), with a possible overlap with Cepheid-like type II stars. Fits of the light curves with sinusoids suggest that a large fraction of the stars correspond to periodic or semi-periodic objects with periods longer than 100 days. Twelve nova candidates are identified. Correlations with other catalogues suggest that 2 novae could be recurrent novae and provide possible optical counterparts for 2 supersoft X-ray sources candidates observed with Chandra.
We have carried out a survey of the Andromeda galaxy for unresolved microlensing (pixel lensing).... more We have carried out a survey of the Andromeda galaxy for unresolved microlensing (pixel lensing). We present a subset of four short timescale, high signal-to-noise microlensing candidates found by imposing severe selection criteria: the source flux variation exceeds the flux of an R = 21 magnitude star and the full width at half maximum timescale is less than 25 days. Remarkably, in three out of four cases, we have been able to measure or strongly constrain the Einstein crossing time of the event. One event, which lies projected on the M 31 bulge, is almost certainly due to a stellar lens in the bulge of M 31. The other three candidates can be explained either by stars in M 31 and M 32 or by MACHOs.
M 31 is a very tempting target for a microlensing search of compact objects in galactic haloes. I... more M 31 is a very tempting target for a microlensing search of compact objects in galactic haloes. It is the nearest large galaxy, it probably has its own dark halo, and its tilted position with respect to the line of sight provides an unmistakable signature of microlensing. However most stars of M 31 are not resolved and one has to use the "pixel method": monitor the pixels of the image rather than the stars. AGAPE is the implementation of this idea. Data have been collected and treated during two autumns of observation at the 2 metre telescope of Pic du Midi. The process of geometric and photometric alignment, which must be performed before constructing pixel light curves, is described. Seeing variations are minimised by working with large super-pixels (2.1 ) compared with the average seeing. A high level of stability of pixel fluxes, crucial to the approach, is reached. Fluctuations of super-pixels do not exceed 1.7 times the photon noise which is 0.1% of the intensity for the brightest ones. With such stable data, 10 microlensing events are expected for a full "standard halo". With a larger field, a regular and short time sampling and a long lever arm in time, the pixel method will be a very efficient tool to explore the halo of M 31.
We report the discovery of a microlensing candidate projected 2 54 from the center of M32, on the... more We report the discovery of a microlensing candidate projected 2 54 from the center of M32, on the side closest to M31. The blue color (R − I = 0.00 ± 0.14) of the source argues strongly that it lies in the disk of M31, while the proximity of the line of sight to M32 implies that this galaxy is the most likely host of the lens. If this interpretation is correct, it would confirm previous arguments that M32 lies in front of M31. We estimate that of order one such event or less should be present in the POINT-AGAPE data base. If more events are discovered in this direction in a dedicated experiment, they could be used to measure the mass function of M32 up to an unknown scale factor. By combining microlensing observations of a binary-lens event with a measurement of the M31-M32 relative proper motion using the astrometric satellites SIM or GAIA, it will be possible to measure the physical separation of M31 and M32, the last of the six phase-space coordinates needed to assign M32 an orbit.
The scale dependence of quark and squark mass and flavor mixing is studied with the renormalizati... more The scale dependence of quark and squark mass and flavor mixing is studied with the renormalization group equations of broken N = 1 supergravity. The rotation matrix between charge -1/3 quarks and squarks turns out to be nearly equal to the Cabibbo-Kobayashi-Maskawa one. Gluino couplings then change flavor, but we find that their contribution to the K°-K ° mixing is generally smaller than the usual standard model result.
The presence of brown dwarfs in the dark galactic halo could be detected through their gravitatio... more The presence of brown dwarfs in the dark galactic halo could be detected through their gravitational lensing effect and experiments under way monitor about one million stars to observe a few lensing events per year. We show that if the photon flux from a galaxy is measured with a good precision, it is not necessary to resolve the stars and besides more events could be observed.
We report the discovery of a short-duration microlensing candidate in the northern field of the P... more We report the discovery of a short-duration microlensing candidate in the northern field of the POINT-AGAPE pixel lensing survey towards M31. The full-width half-maximum timescale is very short, t 1/2 = 1.8 days. Almost certainly, the source star has been identified on Hubble Space Telescope archival images, allowing us to infer an Einstein crossing time of t E = 10.4 days, a maximum magnification of A max ∼ 18, and a lens-source proper motion µ rel > 0.3 µas/day. The event lies projected at 8 ′ from the center of M31, which is beyond the bulk of the stellar lens population. The lens is likely to reside in one of three locations. It may be a star in the M31 disk, or a massive compact halo object (Macho) in either M31 or the Milky Way. The most probable mass is 0.06 M ⊙ for an M31 Macho, 0.02 M ⊙ for a Milky Way Macho and 0.2 M ⊙ for an M31 stellar lens. Whilst the stellar interpretation is plausible, the Macho interpretation is the most probable for halo fractions above 20%.
We present the AGAPE astrometric and photometric catalogue of 1579 variable stars in a 14 ′ ×10 ′... more We present the AGAPE astrometric and photometric catalogue of 1579 variable stars in a 14 ′ ×10 ′ field centred on M31. This work is the first survey devoted to variable stars in the bulge of M31. The R magnitudes of the objects and the B − R colours suggest that our sample is dominated by red long-period variable stars (LPV), with a possible overlap with Cepheid-like type II stars. Fits of the light curves with sinusoids suggest that a large fraction of the stars correspond to periodic or semi-periodic objects with periods longer than 100 days. Twelve nova candidates are identified. Correlations with other catalogues suggest that 2 novae could be recurrent novae and provide possible optical counterparts for 2 supersoft X-ray sources candidates observed with Chandra.
We have carried out a survey of the Andromeda galaxy for unresolved microlensing (pixel lensing).... more We have carried out a survey of the Andromeda galaxy for unresolved microlensing (pixel lensing). We present a subset of four short timescale, high signal-to-noise microlensing candidates found by imposing severe selection criteria: the source flux variation exceeds the flux of an R = 21 magnitude star and the full width at half maximum timescale is less than 25 days. Remarkably, in three out of four cases, we have been able to measure or strongly constrain the Einstein crossing time of the event. One event, which lies projected on the M 31 bulge, is almost certainly due to a stellar lens in the bulge of M 31. The other three candidates can be explained either by stars in M 31 and M 32 or by MACHOs.
M 31 is a very tempting target for a microlensing search of compact objects in galactic haloes. I... more M 31 is a very tempting target for a microlensing search of compact objects in galactic haloes. It is the nearest large galaxy, it probably has its own dark halo, and its tilted position with respect to the line of sight provides an unmistakable signature of microlensing. However most stars of M 31 are not resolved and one has to use the "pixel method": monitor the pixels of the image rather than the stars. AGAPE is the implementation of this idea. Data have been collected and treated during two autumns of observation at the 2 metre telescope of Pic du Midi. The process of geometric and photometric alignment, which must be performed before constructing pixel light curves, is described. Seeing variations are minimised by working with large super-pixels (2.1 ) compared with the average seeing. A high level of stability of pixel fluxes, crucial to the approach, is reached. Fluctuations of super-pixels do not exceed 1.7 times the photon noise which is 0.1% of the intensity for the brightest ones. With such stable data, 10 microlensing events are expected for a full "standard halo". With a larger field, a regular and short time sampling and a long lever arm in time, the pixel method will be a very efficient tool to explore the halo of M 31.
We report the discovery of a microlensing candidate projected 2 54 from the center of M32, on the... more We report the discovery of a microlensing candidate projected 2 54 from the center of M32, on the side closest to M31. The blue color (R − I = 0.00 ± 0.14) of the source argues strongly that it lies in the disk of M31, while the proximity of the line of sight to M32 implies that this galaxy is the most likely host of the lens. If this interpretation is correct, it would confirm previous arguments that M32 lies in front of M31. We estimate that of order one such event or less should be present in the POINT-AGAPE data base. If more events are discovered in this direction in a dedicated experiment, they could be used to measure the mass function of M32 up to an unknown scale factor. By combining microlensing observations of a binary-lens event with a measurement of the M31-M32 relative proper motion using the astrometric satellites SIM or GAIA, it will be possible to measure the physical separation of M31 and M32, the last of the six phase-space coordinates needed to assign M32 an orbit.
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Papers by Alain Bouquet