We present calculations of the heliospheric solar wind charge exchange (SWCX) emission spectra be... more We present calculations of the heliospheric solar wind charge exchange (SWCX) emission spectra below 0.3 keV that we compare with the soft X‐ray diffuse background (SXRB) emission detected in front of identified shadowing regions during the ROSAT All‐Sky Survey. We discuss combinations of SWCX spectra and thermal emission in an attempt to match the observed X‐ray fluxes and band ratios, while simultaneously being compatible with FUSE O VI emission measurements.
We study the EUV/soft X-ray emission induced by charge transfer between solar wind highly charged... more We study the EUV/soft X-ray emission induced by charge transfer between solar wind highly charged ions and neutral H and O of the Martian exosphere. Results are obtained using three-dimensional hybrid simulations of the global plasma environment of Mars, including photoionization and electron impact ionization of neutral H and O coronae. We calculate projected emission maps from different vantage points
Full-sky maps of backscattered solar Ly-alpha radiation recorded routinely by SOHO-SWAN between 1... more Full-sky maps of backscattered solar Ly-alpha radiation recorded routinely by SOHO-SWAN between 1996 and 2002 are compared with models allowing for any latitude dependence of the ionization of the interstellar hydrogen flow by the solar wind. Recent work on the calibration of the SWAN sensors for this period of time (Quémerais and Bertaux, 2002) as well as on the cleaning of the data and correction from stellar contamination allow to quantify the anisotropy degree of the solar wind mass flux, north-south asymetries and the temporal evolution of the fluxes.
Abstract A fraction of Voyager 1 and 2 UVS measurements of the interplanetary Lyman-alpha backgro... more Abstract A fraction of Voyager 1 and 2 UVS measurements of the interplanetary Lyman-alpha background during the 1977-1983 period (radial distance 1-18 AU) is presented and compared with results from current models of the interaction between the sun and the neutral interstellar gas. It is shown that there are some systematic departures from the predicted pattern: 1) the position and brightness of the upwind maximum emission region on one part, and the downwind/upwind intensity ratio on the other part are contradictory and require two different values of the solar ionization: the downwind emission is most likely larger than predicted. 2) there is an excess of emission from the anti-solar directions as compared with regions close to the sun when moving outwards. Possible explanations include incorrect modeling (multiple scattering, non stationary processes), and inhomogeneous wind flow as a result of the heliospheric interface perturbations.
The SWAN instrument on board SOHO is a Lyman-α (Lα) photometer able to map the sky intensity with... more The SWAN instrument on board SOHO is a Lyman-α (Lα) photometer able to map the sky intensity with a resolution of 1°, and a capability of microstepping (0.1°). SWAN is primarily devoted to the study of the large scale distribution of solar wind from its imprints on the interplanetary sky background, but was in addition extensively used to map the
Echelle spectra at high resolution (lambda/{DELTA}lambda= 90,000) of the nearby stars alpha Aql (... more Echelle spectra at high resolution (lambda/{DELTA}lambda= 90,000) of the nearby stars alpha Aql (Altaie r), alpha Lyr (Vega), alpha Cen and delta Cas, have been obtained with the Goddard High-Resolution Spectrograph (GHRS) on board the Hubble Space Telescope (HST), during the cycles 1 and 3. In all but one spectra, interstellar Fe II and Mg II absorption lines are detected
ABSTRACT Interstellar/interplanetary neutral H atoms which are observed towards the upwind (UW) a... more ABSTRACT Interstellar/interplanetary neutral H atoms which are observed towards the upwind (UW) and downwind (DW) directions do not originate from the same region of the heliospheric interface. If the neutral/plasma coupling is not negligible, the variations of the plasma properties with the distance to the stagnation line are imprinted in the neutral atoms and in the relationship between the UW and DW Lyman α spectral profiles, whatever the distance to the heliospheric shock and to the heliopause. This effect is checked both on the Prognoz 5/6 backscattered Lyman a data and in the case of the Baranov type interface. Hydrogen absorption cell data interpretation is much improved when inhomogeneities of the interstellar wind are taken into account. Lyman a profiles derived from the Montecarlo neutral flow model of Malama (1990) show the predicted macroscopic effects. These results tend to show that information on the type of the interface at the heliopause can be derived from precise Lyman a line shape measurements and from comparison with line shapes computed from a homogeneous interstellar flow model.
The solar neighbourhood is the closest and most easily studied sample of the Galactic interstella... more The solar neighbourhood is the closest and most easily studied sample of the Galactic interstellar medium, an understanding of which is essential for models of star formation and galaxy evolution. Observations of an unexpectedly intense diffuse flux of easily absorbed 1/4-kiloelectronvolt X-rays, coupled with the discovery that interstellar space within about a hundred parsecs of the Sun is almost completely devoid of cool absorbing gas, led to a picture of a 'local cavity' filled with X-ray-emitting hot gas, dubbed the local hot bubble. This model was recently challenged by suggestions that the emission could instead be readily produced within the Solar System by heavy solar-wind ions exchanging electrons with neutral H and He in interplanetary space, potentially removing the major piece of evidence for the local existence of million-degree gas within the Galactic disk. Here we report observations showing that the total solar-wind charge-exchange contribution is approximate...
Proceedings of the International Astronomical Union, 2013
We have developed a method allowing to extract DIBs from cool star spectra, based on combinations... more We have developed a method allowing to extract DIBs from cool star spectra, based on combinations of stellar synthetic, telluric transmission (when necessary), and DIB profile models. It is applicable when the star temperature, surface gravity and metallicity have been previously estimated. Such a method aims at extracting extensive data from stellar spectroscopic surveys such as the Gaia-ESO Survey in progress at the VLT. The method has been applied to several strong DIBs detected towards stars from various programs and located at various distances from the solar neighborhood to the Galactic Bulge. Here we illustrate the extraction of the 8620 Å DIB, and compare its strength to the one of the 6284 Å band, both for nearby and bulge stars.
We present calculations of the heliospheric solar wind charge exchange (SWCX) emission spectra be... more We present calculations of the heliospheric solar wind charge exchange (SWCX) emission spectra below 0.3 keV that we compare with the soft X‐ray diffuse background (SXRB) emission detected in front of identified shadowing regions during the ROSAT All‐Sky Survey. We discuss combinations of SWCX spectra and thermal emission in an attempt to match the observed X‐ray fluxes and band ratios, while simultaneously being compatible with FUSE O VI emission measurements.
We study the EUV/soft X-ray emission induced by charge transfer between solar wind highly charged... more We study the EUV/soft X-ray emission induced by charge transfer between solar wind highly charged ions and neutral H and O of the Martian exosphere. Results are obtained using three-dimensional hybrid simulations of the global plasma environment of Mars, including photoionization and electron impact ionization of neutral H and O coronae. We calculate projected emission maps from different vantage points
Full-sky maps of backscattered solar Ly-alpha radiation recorded routinely by SOHO-SWAN between 1... more Full-sky maps of backscattered solar Ly-alpha radiation recorded routinely by SOHO-SWAN between 1996 and 2002 are compared with models allowing for any latitude dependence of the ionization of the interstellar hydrogen flow by the solar wind. Recent work on the calibration of the SWAN sensors for this period of time (Quémerais and Bertaux, 2002) as well as on the cleaning of the data and correction from stellar contamination allow to quantify the anisotropy degree of the solar wind mass flux, north-south asymetries and the temporal evolution of the fluxes.
Abstract A fraction of Voyager 1 and 2 UVS measurements of the interplanetary Lyman-alpha backgro... more Abstract A fraction of Voyager 1 and 2 UVS measurements of the interplanetary Lyman-alpha background during the 1977-1983 period (radial distance 1-18 AU) is presented and compared with results from current models of the interaction between the sun and the neutral interstellar gas. It is shown that there are some systematic departures from the predicted pattern: 1) the position and brightness of the upwind maximum emission region on one part, and the downwind/upwind intensity ratio on the other part are contradictory and require two different values of the solar ionization: the downwind emission is most likely larger than predicted. 2) there is an excess of emission from the anti-solar directions as compared with regions close to the sun when moving outwards. Possible explanations include incorrect modeling (multiple scattering, non stationary processes), and inhomogeneous wind flow as a result of the heliospheric interface perturbations.
The SWAN instrument on board SOHO is a Lyman-α (Lα) photometer able to map the sky intensity with... more The SWAN instrument on board SOHO is a Lyman-α (Lα) photometer able to map the sky intensity with a resolution of 1°, and a capability of microstepping (0.1°). SWAN is primarily devoted to the study of the large scale distribution of solar wind from its imprints on the interplanetary sky background, but was in addition extensively used to map the
Echelle spectra at high resolution (lambda/{DELTA}lambda= 90,000) of the nearby stars alpha Aql (... more Echelle spectra at high resolution (lambda/{DELTA}lambda= 90,000) of the nearby stars alpha Aql (Altaie r), alpha Lyr (Vega), alpha Cen and delta Cas, have been obtained with the Goddard High-Resolution Spectrograph (GHRS) on board the Hubble Space Telescope (HST), during the cycles 1 and 3. In all but one spectra, interstellar Fe II and Mg II absorption lines are detected
ABSTRACT Interstellar/interplanetary neutral H atoms which are observed towards the upwind (UW) a... more ABSTRACT Interstellar/interplanetary neutral H atoms which are observed towards the upwind (UW) and downwind (DW) directions do not originate from the same region of the heliospheric interface. If the neutral/plasma coupling is not negligible, the variations of the plasma properties with the distance to the stagnation line are imprinted in the neutral atoms and in the relationship between the UW and DW Lyman α spectral profiles, whatever the distance to the heliospheric shock and to the heliopause. This effect is checked both on the Prognoz 5/6 backscattered Lyman a data and in the case of the Baranov type interface. Hydrogen absorption cell data interpretation is much improved when inhomogeneities of the interstellar wind are taken into account. Lyman a profiles derived from the Montecarlo neutral flow model of Malama (1990) show the predicted macroscopic effects. These results tend to show that information on the type of the interface at the heliopause can be derived from precise Lyman a line shape measurements and from comparison with line shapes computed from a homogeneous interstellar flow model.
The solar neighbourhood is the closest and most easily studied sample of the Galactic interstella... more The solar neighbourhood is the closest and most easily studied sample of the Galactic interstellar medium, an understanding of which is essential for models of star formation and galaxy evolution. Observations of an unexpectedly intense diffuse flux of easily absorbed 1/4-kiloelectronvolt X-rays, coupled with the discovery that interstellar space within about a hundred parsecs of the Sun is almost completely devoid of cool absorbing gas, led to a picture of a 'local cavity' filled with X-ray-emitting hot gas, dubbed the local hot bubble. This model was recently challenged by suggestions that the emission could instead be readily produced within the Solar System by heavy solar-wind ions exchanging electrons with neutral H and He in interplanetary space, potentially removing the major piece of evidence for the local existence of million-degree gas within the Galactic disk. Here we report observations showing that the total solar-wind charge-exchange contribution is approximate...
Proceedings of the International Astronomical Union, 2013
We have developed a method allowing to extract DIBs from cool star spectra, based on combinations... more We have developed a method allowing to extract DIBs from cool star spectra, based on combinations of stellar synthetic, telluric transmission (when necessary), and DIB profile models. It is applicable when the star temperature, surface gravity and metallicity have been previously estimated. Such a method aims at extracting extensive data from stellar spectroscopic surveys such as the Gaia-ESO Survey in progress at the VLT. The method has been applied to several strong DIBs detected towards stars from various programs and located at various distances from the solar neighborhood to the Galactic Bulge. Here we illustrate the extraction of the 8620 Å DIB, and compare its strength to the one of the 6284 Å band, both for nearby and bulge stars.
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Papers by R. Lallement