Observations of the solar corona at the Pic du Midi began with Bernard Lyot and his spectro coronagraph installed on the multi-purpose equatorial mount of the Baillaud cupola. It was not until 1956 that domes and instruments specifically dedicated to observations of the photosphere and the solar chromosphere appeared. On the occasion of the International Geophysical Year, a solar spectroscopy laboratory was created to the west of the Pic du Midi, based on two spectrographs of 4 m and 9 m focal length. In 1961 the turret dome appeared to the east of the Pic, later equipped with an 8 m spectrograph. Around 1965, the Baillaud dome finally specialized in the corona with a new table and new spectrographs. At the same time, a revolution in infrastructure took place at the Pic in a few years, which we present as well as the solar spectrographs and their goal.
The sensitivities of STIS first-order, medium resolution modes were redetermined from on-orbit observations and CALSPEC models (version 11) of the primary white-dwarf spectrophotometric standard stars G191-B2B, GD 71, and GD 153. The sensitivity of an additional configuration was updated by comparing observations of the secondary standard BD +75 325 with the STIS low-resolution spectrum that has been calibrated consistently with the version 11 models. The procedures used to derive the sensitivities and verify the PHOTTAB reference files prior to their activation in CRDS (on May 1, 2025) are described. Results are presented in graphical form in an extensive appendix. Issues and uncertainties are discussed briefly, along with recommendations for future work.
Abstract We consider a quintessence scalar field with a class of hyperbolic potential. This potential effectively introduces matter-like components into the cosmological fluid, contributing to the dark sector of the universe. For the observational analysis, we employ the PantheonPlus and Union3.0 catalogues, Cosmic Chronometers, and Baryon Acoustic Oscillations from the DESI DR2 collaboration. We test the hypothesis that quintessence can unify the dark sector. Our results reveal that, although the quintessence field provides a minor contribution to the matter component, the data do not show any support for the unification scenario.
We report that HD 110067, the recently announced host star of a resonant sextuplet of transiting sub-Neptunes, is not a single star as claimed in the discovery paper, but a wide hierarchical triple. The K0 V planet hosting star (V = 8.4 mag, d = 32 pc) has a companion at a wide projected separation of 13400 au. This companion, namely HD 110106, is a slightly fainter (V = 8.8 mag) K3 V type 8-year period double-lined spectroscopic binary. The secondary in this spectroscopic binary is contributing a significant amount of flux and has a measured high mass ratio.
Este texto (revisto e atualizado) é baseado em aulas do curso ``Diferentes Aspectos da Relatividade Geral'', ministrado pelo autor no programa de doutorado da Universidade da Côte d’Azur, como parte do projeto de integração da equipe VIRGO em Nice (anteriormente localizada em Saclay), ocorrido em 1996. O presente artigo aborda o efeito Fulling-Davies-Unruh e sua conexão com a radiação Hawking, embora sejam processos distintos. A compreensão do efeito Fulling-Davies-Unruh é essencial na quantização de campos em espaços curvos, objetivo maior deste artigo.
Measuring the amount of gas and dust in protoplanetary disks is a key challenge in planet formation studies. Here we provide a new set of dust depletion factors and relative mass surface densities of gas and dust for the innermost regions of a sample of protoplanetary disks. We do this by combining stellar theory with observed refractory element abundances in both disk hosts and open cluster stars. Our results are independent of, and complementary to, those obtained from spatially resolved disk observations.
The 39-meter European Extremely Large Telescope (E-ELT) is expected to have very low throughput in the blue part of the visible spectrum. Because of that, a blue-optimised spectrograph at the 8-meter Very Large Telescope could potentially be competitive against the E-ELT at wavelengths shorter than 400 nm. A concept study for such an instrument was concluded in 2012. This would be a high-throughput, medium resolution (R $\sim$ 20\,000) spectrograph, operating between 300 and 400 nm. It is currently expected that construction of this instrument will start in the next few years. In this contribution, I present a summary of the instrument concept and of some of the possible Galactic and extragalactic science cases that motivate such a spectrograph.
The long-term dynamics of planetesimals in debris discs in models with parameters of binary star systems Kepler-16, Kepler-34 and Kepler-35 with planets is investigated. Our calculations have shown the formation of a stable coorbital with the planet ring is possible for Kepler-16 and Kepler-35 systems. In Kepler-34 system, significant eccentricities of the orbits of the binary and planets can to prevent the formation of such a structure. Detection circumbinary annular structures in observations of systems binary stars can be evidence of the existence of planets, retaining coorbital rings from dust and planetesimals.
Jan Jurcak, Manuel Collados, Jorrit Leenaarts
et al.
The European Solar Telescope (EST) is a project of a new-generation solar telescope. It has a large aperture of 4~m, which is necessary for achieving high spatial and temporal resolution. The high polarimetric sensitivity of the EST will allow to measure the magnetic field in the solar atmosphere with unprecedented precision. Here, we summarise the recent advancements in the realisation of the EST project regarding the hardware development and the refinement of the science requirements.
We present Magnetohydrodynamic (MHD) simulations of the magnetic interactions between a solar type star and short period hot Jupiter exoplanets, using the publicly available MHD code PLUTO. It has been predicted that emission due to magnetic interactions such as the electron cyclotron maser instability (ECMI) will be observable. In our simulations, a planetary outflow, due to UV evaporation of the exoplanets atmosphere, results in the build-up of circumplanetary material. We predict the ECMI emission and determine that the emission is prevented from escaping from the system. This is due to the evaporated material leading to a high plasma frequency in the vicinity of the planet, which inhibits the ECMI process.
Could the dips of "Boyajian's Star" (KIC 8462852) have been caused by matter in our Solar System? The interval between periods of deep dips is nearly twice the orbital period of the Kepler satellite. I consider heliocentric obscuring rings in the outer Solar System that graze the line of sight to the star once per orbit of Kepler. The hypothesis predicts that future dips may be observed from Earth during windows separated by a year, although their detailed structure depends on the distribution of particles along the ring. Dips observed at terrestrial sites separated by > 1000 km in a direction perpendicular to the Earth's orbital motion may be uncorrelated.
Mario Gennaro, Simon P. Goodwin, Richard J. Parker
et al.
We examine the level of substructure and mass segregation in the massive, young cluster Westerlund 1. We find that it is relatively smooth, with little or no mass segregation, but with the massive stars in regions of significantly higher than average surface density. While an expanding or bouncing-back scenario for the evolution of Westerlund 1 cannot be ruled out, we argue that the most natural model to explain these observations is one in which Westerlund 1 formed with no primordial mass segregation and at a similar or larger size than we now observe.
Variable star analysis and classification is an important task in the understanding of stellar features and processes. While historically classifications have been done manually by highly skilled experts, the recent and rapid expansion in the quantity and quality of data has demanded new techniques, most notably automatic classification through supervised machine learning. We present an expansion of existing work on the field by analyzing variable stars in the {\em Kepler} field using an ensemble approach, combining multiple characterization and classification techniques to produce improved classification rates. Classifications for each of the roughly 150,000 stars observed by {\em Kepler} are produced separating the stars into one of 14 variable star classes.
In massive numerical experiments we show that a planet embedded in a planetesimal disk induces a characteristic multi-lane "planetosignature" representing a pattern of several stellar-centric rings. If the planet's mass is large enough, the multi-lane signature degenerates to a three-lane one: then it consists of three rings, one bright coorbital with the planet, and two dark gaps in the radial distribution of the particles. The gaps correspond to orbital resonances 2:1 and 1:2 with the planet. This theoretical prediction may explain recent ALMA observations of the disk of HL Tau.
A program to generate codes in Fortran and C of the full Magnetohydrodynamic equations is shown. The program used the free computer algebra system software REDUCE. This software has a package called EXCALC, which is an exterior calculus program. The advantage of this program is that it can be modified to include another complex metric or spacetime. The output of this program is modified by means of a LINUX script which creates a new REDUCE program to manipulate the MHD equations to obtain a code that can be used as a seed for a MHD code for numerical applications. As an example, we present part of output of our programs for Cartesian coordinates and how to do the discretization.
In this paper we answer a simple question: can a misaligned circumbinary planet induce Kozai-Lidov cycles on an inner stellar binary? We use known analytic equations to analyse the behaviour of the Kozai-Lidov effect as the outer mass is made small. We demonstrate a significant departure from the traditional symmetry, critical angles and amplitude of the effect. Aside from massive planets on near-polar orbits, circumbinary planetary systems are devoid of Kozai-Lidov cycles. This has positive implications for the existence of highly misaligned circumbinary planets: an observationally unexplored and theoretically important parameter space.
We present simulations of star forming filaments incorporating - to our knowledge - the largest chemical network used to date on-the-fly in a 3D-MHD simulation. The network contains 37 chemical species and about 300 selected reaction rates. For this we use the newly developed package KROME (Grassi et al. 2014). Our results demonstrate the feasibility of using such a complex chemical network in 3D-MHD simulations on modern supercomputers. We perform simulations with different strengths of the interstellar radiation field and the cosmic ray ionisation rate and find chemical and physical results in accordance with observations and other recent numerical work.
We present results of time series photometry to search for variable stars in the field of metal-poor globular cluster NGC 4590 (M68). Periods have been revised for 40 known variables and no significant changes were found. A considerable change in Blazhko effect for V25 has been detected. Among nine newly discovered variable candidates, 5 stars are of RRc Bailey type variables while 4 stars are unclassified. The variable stars V10, V21, V50 and V51 are found to be cluster members based on the radial velocity data taken from literature.