Eduardo Janot-Pacheco | Universidade de São Paulo (original) (raw)

Papers by Eduardo Janot-Pacheco

Publications of the Astronomical Society of the Pacific, 2022

Observation of planetary transits and other cutting-edge scientific missions can take advantage o... more Observation of planetary transits and other cutting-edge scientific missions can take advantage of affordable nanosatellites to probe interesting stellar targets. PicSat, a CubeSat dedicated to observing the Beta Pictoris star system, was designed to provide high-precision star pointing, a critical requirement for planetary transit detection. PicSat’s Attitude Determination and Control System, responsible for delivering high-accuracy spacecraft pointing, requires dedicated development based on dynamic simulators. This paper presents a dynamic attitude and orbit propagation simulator for CubeSats in low Earth orbit, as well as for its de-tumbling mode. Validation has been performed through PicSat’s in-flight data. High-precision dynamic models have been obtained for both attitude and orbit. Such models are well suited to the different mission phases, from spacecraft design to data exploitation. It is, therefore, a crucial tool to minimize the chance of failure of both the platform an...

Http Www Theses Fr, 1987

Analyse d'un grand nombre de donnees d'observation, visant quelques objets-cibles, de plu... more Analyse d'un grand nombre de donnees d'observation, visant quelques objets-cibles, de plusieurs types (photometrie visible, ir et rx, spectrometrie visible) afin de mieux comprendre les phenomenes physiques conduisant a l'existence des systemes binaires be/rx. Recherche du mecanisme d'accretion utilisant un modele d'enveloppe equatoriale pour les etoiles be. Utilisation des compagnons compacts comme sondes des enveloppes des etoiles be permettant de determiner differents parametres physiques

The Stellar Populations of Galaxies, 1992

The group of known X-ray sources associated with a Be star in a binary system consists of about 4... more The group of known X-ray sources associated with a Be star in a binary system consists of about 40 objects. They are the most abundant type of massive X-ray binary in the Galaxy. In this contribution we present an up-to-date picture of the main physical characteristics of these objects, including their evolutionary history, mass transfer mechanism, an interpretation of their behaviour in the orbital versus spin period diagram and the use of Be/X-ray sources as galactic tracers.

Light curve parameters and classification results are presented for all the objects measured in t... more Light curve parameters and classification results are presented for all the objects measured in the first four CoRoT observing runs: IRa01, SRc01, LRc01, and LRa01. The information presented here should allow scientists to make candidate lists of their objects of study and to obtain some basic light curve information. We recall that we did not perform detailed light curve modelling, only a basic one, sufficient for producing variability class memberships for each target. We refer to the paper for a detailed description of the light curve parameters, and the classification results. It is strongly advised to read the paper prior to using the results presented here. (4 data files).

A growing number of early Be stars discovered in X-ray surveys exhibit X-ray luminosities interme... more A growing number of early Be stars discovered in X-ray surveys exhibit X-ray luminosities intermediate between those of normal stars and those of most Be/X-ray binaries in quiescence. Their X-ray spectra are also much harder than those of shocked wind OB stars and can be best fitted by a thin thermal plasma with T ˜ 10^{8} K, added to a

Proceedings of the International Astronomical Union, 2010

Guillaume Dubus: As far as I can tell your model is exactly the same as standard models for high-... more Guillaume Dubus: As far as I can tell your model is exactly the same as standard models for high-mass x-ray binaries, the on difference is that you have a mechanism for generating γ rays. My question is, we know that there are dozens of other systems that are just LS 5039, so why are they not emitting γ rays?

Planetary and Space Science, 2010

The radiation-resistant bacterium Deinococcus radiodurans was exposed to a simulated interplaneta... more The radiation-resistant bacterium Deinococcus radiodurans was exposed to a simulated interplanetary UV radiation at the Brazilian Synchrotron Light Laboratory (LNLS). Bacterial samples were irradiated on different substrates to investigate the influence of surface relief on cell survival. The effects of cell multi-layers were also investigated. The ratio of viable microorganisms remained virtually the same (average 2%) for integrated doses from 1.2 to 12 kJ m À 2 , corresponding to 16 h of irradiation at most. The asymptotic profiles of the curves, clearly connected to a shielding effect provided by multi-layering cells on a cavitary substrate (carbon tape), means that the inactivation rate may not change significantly along extended periods of exposure to radiation. Such high survival rates reinforce the possibility of an interplanetary transfer of viable microbes.

The Astrophysical Journal, 1991

... 4769 Dachs, J., Hanuschik, R., Kaiser, D., &amp; Rohe, D. 1986, A&amp;A, 159,... more ... 4769 Dachs, J., Hanuschik, R., Kaiser, D., &amp; Rohe, D. 1986, A&amp;A, 159, 276 Dal Fiume, D., Frontera, F., &amp; Morelli, E. 1988, ApJ, 331, 313 Davelaar, J., White, N., Stella, L., Parmar, A., Blisset, RJ, van der Klis, M., &amp; Schrijver, H. 1985, in X-Ray Astronomy `84, ed. M. Oda &amp; R ...

International Journal of Astrobiology, 2012

This review reports the Brazilian history in astrobiology, as well as the first delineation of a ... more This review reports the Brazilian history in astrobiology, as well as the first delineation of a vision of the future development of the field in the country, exploring its abundant biodiversity, highly capable human resources and state-of-the-art facilities, reflecting the last few years of stable governmental investments in science, technology and education, all conditions providing good perspectives on continued and steadily growing funding for astrobiology-related research. Brazil is growing steadily and fast in terms of its worldwide economic power, an effect being reflected in different areas of the Brazilian society, including industry, technology, education, social care and scientific production. In the field of astrobiology, the country has had some important landmarks, more intensely after the First Brazilian Workshop on Astrobiology in 2006. The history of astrobiology in Brazil, however, is not so recent and had its first occurrence in 1958. Since then, researchers carri...

Astrophysics and Space Science, 1977

A linear relation is calculated between the six-colour ultraviolet excess and superficial gravity... more A linear relation is calculated between the six-colour ultraviolet excess and superficial gravity for Cepheid variables. This excess appears to be a sensitive indicator of gravity behavi0ur for these stars. Six-colour photometry (the Lick system) has proved to be an advantageous tool for studying cepheid stars (see, for instance, Kron, 1963; Parsons and Bell, 1973; Canavaggia et al., 1975). Mianes (1963) defined an ultraviolet excess ~(U-G) with respect to a line of instrinsic indices determined with selected stars in the U-G/G-I diagram. In such a diagram, a cepheid will describe a loop in the course of a cycle. The lines corresponding to the ascending branch (that is, to increasing brightness) and to the descending branch (decreasing brightness) are clearly separated. Mianes suggested that it could be partially explained by a different effective gravity behaviour in the two branches. The ultraviolet excess was then defined with respect to the descending branch. Mianes also argued that the variations in ~(U-G) could be accounted for in terms of gravity effects. Recently, the sample of cepheids observed in the Lick system was extended to the southern hemisphere by means of UVBGR photoelectric measurements (Janot-Pacheco, 1976). New 6(U-G) values were then determined in the U-G/G-R diagrams for 61 stars. They are in the average greater than the previous ones, deduced from the U-G/G-I plots (Mianes, 1963). Parsons and Bouw (1971) calculated average superficial gravities for a number of population I cepheids using a six-colour fitting method. In Figure 1 ~(U-G) is plotted against (log g} for 38 stars. Open circles represents cases where the log g averages are less reliable. Cepheids members of galactic clusters are denoted by filled triangles. The (log g} value of SU Cas was corrected for taking into account the recent conclusions of Iben and Tuggle (1975) and Gieren (1976). For the seven stars members of galactic clusters it was found by least-squares the following linear relation

ABSTRACT In a X-ray binary, epochs of accretion/X-ray production (that is, of neutron star accele... more ABSTRACT In a X-ray binary, epochs of accretion/X-ray production (that is, of neutron star acceleration) alternates with quiescent phases, when the spin period increases. The position of a binary in the Prot-Porb plane depends on the balance between these phases. We show that a simple accretion scheme can explain the location of some massive X-ray binary systems in this plane. We have tested the sensibility of the solutions to relevant parameters like neutron star mass, radius and surface magnetic field. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in text query field) Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints