Spectral classification & physical parameters of the IPHAS CBe stars in the BCD system.

The INT Photometric Hα Survey (IPHAS) has detected tens of thousands of emission line objects in the Northern Galactic Plane. Spectroscopic follow-up has shown that the vast majority of them are Classical Be (CBe) stars, rapidly rotat- ing main sequence B type stars which develop an outflowing circumstellar disk by mechanisms not yet completely understood. In this work we present a study of the full catalogue of the CBe stars discovered by IPHAS. We have analyzed 805 low resolution spectra of 732 IPHAS CBe stars. With a semi-automatic proce- dure, which we evaluate at the first part of this work, we obtained the relevant physical parameters, including the effective temperature, surface gravity, absolute magnitude and distance, based on the techniques of the Barbier-Chalonge-Divan (BCD) spectrophotometric system. Also, we plot an HR diagram from which we extracted masses and ages. From the data in the catalogue we have determined for the sample a mean rotational velocity of 82% of the critical velocity, without any trend of variation with the spectral type. The data also confirm that the circumstellar discs rotate following a Keplerian velocity law. We found the ages of the stars evenly distributed be- tween the ZAMS and the TAMS, and hence our results do not support claims of an evolutionary nature of the Be phenomenon. The distribution of the stars does not present an apparent clustering in or around the Perseus or the Outer Arm regions. Instead, they appear scattered along the two arms and the space in between, with some stars spreaded along larger dis- tances, beyond the expected location of the Outer Arm. The density of the stars beyond the Perseus Arm displays a similar exponential decline at all longitudes along the Northern Galactic Plane. No evidence of an outer Arm beyond the Perseus Arm is present in our data.The INT Photometric Hα Survey (IPHAS) has detected tens of thousands of emission line objects in the Northern Galactic Plane. Spectroscopic follow-up has shown that the vast majority of them are Classical Be (CBe) stars, rapidly rotat- ing main sequence B type stars which develop an outflowing circumstellar disk by mechanisms not yet completely understood. In this work we present a study of the full catalogue of the CBe stars discovered by IPHAS. We have analyzed 805 low resolution spectra of 732 IPHAS CBe stars. With a semi-automatic proce- dure, which we evaluate at the first part of this work, we obtained the relevant physical parameters, including the effective temperature, surface gravity, absolute magnitude and distance, based on the techniques of the Barbier-Chalonge-Divan (BCD) spectrophotometric system. Also, we plot an HR diagram from which we extracted masses and ages. From the data in the catalogue we have determined for the sample a mean rotational velocity of 82% of the critical velocity, without any trend of variation with the spectral type. The data also confirm that the circumstellar discs rotate following a Keplerian velocity law. We found the ages of the stars evenly distributed be- tween the ZAMS and the TAMS, and hence our results do not support claims of an evolutionary nature of the Be phenomenon. The distribution of the stars does not present an apparent clustering in or around the Perseus or the Outer Arm regions. Instead, they appear scattered along the two arms and the space in between, with some stars spreaded along larger dis- tances, beyond the expected location of the Outer Arm. The density of the stars beyond the Perseus Arm displays a similar exponential decline at all longitudes along the Northern Galactic Plane. No evidence of an outer Arm beyond the Perseus Arm is present in our data

Airglow remote sensing of the seasonal variation of the Martian upper atmosphere: MAVEN limb observations and model comparison

We apply a new technique to remotely sense the seasonal altitude variation of the isobar level in this region. We present results from observations of airglow limb profiles collected during two Martian years with the Imaging UltraViolet Spectrograph (IUVS) onboard MAVEN. IUVS has collected tens of thousands of Martian airglow limb profiles since the Fall of 2014. We analyze the global dayglow dataset of the 297.2 nm emission corresponding to the O(3P-1S) forbidden transition. The vertical profile of this unique emission shows two peaks: one around 120 km and a second one near 80 km. We use both peaks to trace the altitude changes of the isobars in this atmospheric region. We map and compare them with the seasonal variations of the O(1S) with CO UV doublet peak. We find that the altitude of the level varies by up to 20 km. We show that the dayglow model overpredicts the lower peak altitude by 2–5 km from the observations while it underpredicts the upper peak altitude with the same offset. The best agreement near 80 km is obtained by decreasing the CO density by the Mars Climate Database (MCD) by about 40%

The Jovian ionospheric conductivity derived from a broadband precipitated electron distribution

The Pedersen ionospheric conductivity and conductance at Jupiter are computed assuming a broadband precipitating-electron flux and compared to values obtained when assuming a mono-energetic precipitating-electron flux. Among other results, it is found that the ratio between the broadband and the mono-energetic conductances depends on the electron mean energy of the precipitating-electron population. For a mono-energetic distribution, an optimal energy exists, around 30-40 keV, for which the conductance arising from the precipitation is maximal. If the mean electron energy is well below this optimal energy, the conductance calculated for a broadband distribution is enhanced compared to the mono-energetic case because part of the electron energy distribution reaches this optimal level. The conductance is also underestimated for a mono-energetic electron precipitation well above the optimal value. The opposite trend is observed around the optimal energy as most of the electrons of the broadband distribution have either lower or higher energies, while all electrons of the mono-energetic distribution have an energy close to the optimum

MARS OXYGEN GREEN LINE DAYGLOW FROM NOMAD/UVIS AND MODEL COMPARISON

The UVIS (UV and Visible Spectrometer) channel of the NOMAD (Nadir and Occultation for MArs Discovery) spectrometer onboard the ExoMars Trace Gas Orbiter performs limb observations of the dayside of the Mars atmosphere in both the visible and the ultraviolet domains since April 2019. The recently discovered visible emissions of the oxygen green line at 557.7 nm has here been investigated. The variations of the limb profile of this emission are studied over seasons. These average limb profiles are compared to photochemical model simulations with MAVEN/EUVM solar flux and the LMD GCM as inputs of the model. The global shape of the profile and the intensities are generally well reproduced. However, the peak altitude can sometimes be underestimated by the model and needs an adjustment of the CO2 density to reproduce the observations. We also compare the variations of the green line intensities over some individual UVIS limb tracking observations (observations of the atmosphere at a quasi-constant altitude) to model simulations and demonstrate a very good agreement. Finally, we show that the intensity and altitude of the lower emission peak are correlated with the solar Ly-α flux as expected from the theory of its production

Abel transform of exponential functions for planetary and cometary atmospheres with application to observation of 46P/Wirtanen and to the OI 557.7 nm emission at Mars.

Line-of-sight integration of emissions from planetary and cometary atmospheres is the Abel transform of the emission rate, under the spherical symmetry assumption. Indefinite integrals constructed from the Abel transform integral are useful for implementing remote sensing data analysis methods, such as the numerical inverse Abel transform giving the volume emission rate compatible with the observation. We obtain analytical expressions based on a suitable, non-alternating, series development to compute those indefinite integrals. We establish expressions allowing absolute accuracy control of the convergence of these series depending on the number of terms involved. We compare the analytical method with numerical computation techniques, which are found to be sufficiently accurate as well. Inverse Abel transform fitting is then tested in order to establish that the expected emission rate profiles can be retrieved from the observation of both planetary and cometary atmospheres. We show that the method is robust, especially when Tikhonov regularization is included, although it must be carefully tuned when the observation varies across many orders of magnitude. A first application is conducted over observation of comet 46P/Wirtanen, showing some variability possibly attributable to an evolution of the contamination by dust and icy grains. A second application is considered to deduce the 557.7 nm volume emission rate profile of the metastable oxygen atom in the upper atmosphere of planet Mars

Contemporaneous Observations of Jovian Energetic Auroral Electrons and Ultraviolet Emissions by the Juno Spacecraft

We present comparisons of precipitating electron flux and auroral brightness measurements made during several Juno transits over Jupiter's auroral regions in both hemispheres. We extract from the ultraviolet spectrograph (UVS) spectral imager H2 emission intensities at locations magnetically conjugate to the spacecraft using the JRM09 model. We use UVS images as close in time as possible to the electron measurements by the Jupiter Energetic Particle Detector Instrument (JEDI) instrument. The upward electron flux generally exceeds the downward component and shows a broadband energy distribution. Auroral intensity is related to total precipitated electron flux and compared with the energy-integrated JEDI flux inside the loss cone. The far ultraviolet color ratio along the spacecraft footprint maps variations of the mean energy of the auroral electron precipitation. A wide diversity of situations has been observed. The intensity of the diffuse emission equatorward of the main oval is generally in fair agreement with the JEDI downward energy flux. The intensity of the ME matches exceeds or remains below the value expected from the JEDI electron energy flux. The polar emission may be more than an order of magnitude brighter than associated with the JEDI electron flux in association with high values of the color ratio. We tentatively explain these observations by the location of the electron energization region relative to Juno's orbit as it transits the auroral region. Current models predict that the extent and the altitude of electron acceleration along the magnetic field lines are consistent with this assumption

The Mars atomic oxygen dayglow: predictions based on the OI 297.2 nm MAVEN/IUVS observations

The oxygen green line at 557.7 nm corresponds to the 1S →1D forbidden transition of the O atom. It shares the same upper level as the 1S→ 3P UV line at 297.2 nm. The green line is a major component of the visible terrestrial dayglow spectrum and accounts for the dominant color of the high-latitude auroral display. The 297.2 nm emission was first detected with spectrometers on board the Mariner missions. It has since has been observed at the limb in the Martian dayglow with the SPICAM (Mars Express) and IUVS (MAVEN) spectrographs. The sources of the 1S excitation in the Mars dayglow are electron impact on O, photodissociation and electron impact dissociation of CO2 and CO and dissociative recombination of O2+ ions.SCOO

Mars airglow observations from the Trace Gas Orbiter and MAVEN

The UVIS (UV and Visible Spectrometer) channel of the NOMAD (Nadir and Occultation for MArs Discovery) spectrometer on board the ExoMars Trace Gas Orbiter covers the spectral range 200-650 nm at a spectral resolution between 1.2 and 1.6 nm. It has made limb observations of the Martian dayglow since April 2019. Two pointing modes have been applied: (1) in the inertial mode, the spectrometer scans the atmosphere twice down to near the surface and provides altitude profiles of the dayglow; (2) in the tracking mode, the atmosphere is scanned at varying latitudes at a nearly constant altitude. Feature that have been identified include the OI 557.7 nm and 297.2 nm lines, the OI 630-636.4 nm red doublet, the CO Cameron bands, and the CO _{2} + B→X UV doublet and the A→X FDB bands. A statistical study of the vertical and seasonal distribution of the oxygen green and red lines at 557.7 nm and 630 nm indicates that both the brightness and altitude of the green line emission respond to seasons. The peak altitude of the green line emission increases seasonally when the Sun-Mars distance decreases. The lower peak of the green line statistically drops by 15-20 km between perihelion and aphelion at mid- to high altitude. It is significantly brighter and more pronounced in the southern hemisphere than in the north in response to the stronger Lyman-alpha solar flux near perihelion. These seasonal effects will be compared with the 297.2 nm characteristics observed the IUVS instrument on board the MAVEN orbiter. Results from a photochemical model simulating the variations of the oxygen dayglow observed will be compared with observations. Model fits to the OI 557.7 nm limb profiles are also a tool to determine the CO_2 density and its seasonal variations. MUV UVIS spectra will be compared with Mariner and MAVEN/IUVS limb observation and with the visible component of the UVIS spectra