Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

The gamma-ray binary LS I +61 303 is composed of a Be star and a compact companion orbiting in an eccentric orbit. Variable flux modulated with the orbital period of ~26.5 d has been detected from radio to very high-energy gamma rays. In addition, the system presents a superorbital variability of the phase and amplitude of the radio outburst with a period of ~4.6 yr. We present optical photometric observations of LS I +61 303 spanning ~1.5 yr and contemporaneous Halpha equivalent width (EW Halpha) data. The optical photometry shows, for the first time, that the known orbital modulation suffers a positive orbital phase shift and an increase in flux for data obtained 1-yr apart. This behavior is similar to that already known at radio wavelengths, indicating that the optical flux follows the superorbital variability as well. The orbital modulation of the EW Halpha presents the already known superorbital flux variability but shows, also for the first time, a positive orbital phase shift. In addition, the optical photometry exhibits a lag of ~0.1-0.2 in orbital phase with respect to the EW Halpha measurements at similar superorbital phases, and presents a lag of ~0.1 and ~0.3 orbital phases with respect noncontemperaneous radio and X-ray outbursts, respectively. The phase shifts detected in the orbital modulation of thermal indicators, such as the optical flux and the EW Halpha, are in line with the observed behavior for nonthermal indicators, such as X-ray or radio emission. This shows that there is a strong coupling between the thermal and nonthermal emission processes in the gamma-ray binary LS I +61 303. The orbital phase lag between the optical flux and the EW Halpha is naturally explained considering different emitting regions in the circumstellar disk, whereas the secular evolution might be caused by the presence of a moving one-armed spiral density wave in the disk.Comment: 4 pages, 3 figures, accepted for publication in A&A (this version matches the published version

A captorhinid-dominated assemblage from the palaeoequatorial Permian of Menorca (Balearic Islands, western Mediterranean)

Altres ajuts: CERCA Programme/Generalitat de CatalunyaMoradisaurine captorhinid eureptiles were a successful group of high-fibre herbivores that lived in the arid low latitudes of Pangaea during the Permian. Here we describe a palaeoassemblage from the Permian of Menorca (Balearic Islands, western Mediterranean), consisting of ichnites of small captorhinomorph eureptiles, probably moradisaurines (Hyloidichnus), and parareptiles (cf. Erpetopus), and bones of two different taxa of moradisaurines. The smallest of the two is not diagnostic beyond Moradisaurinae incertae sedis. The largest one, on the other hand, shows characters that are not present in any other known species of moradisaurine (densely ornamented maxillar teeth), and it is therefore described as Balearosaurus bombardensis gen. et sp. nov. Other remains found in the same outcrop are identified as cf. Balearosaurus bombardensis gen. et sp. nov., as they could also belong to the newly described taxon. This species is sister to the moradisaurine from the lower Permian of the neighbouring island of Mallorca, and is also closely related to the North American genus Rothianiscus. This makes it possible to suggest the hypothesis that the Variscan mountains, which separated North America from southern Europe during the Permian, were not a very important palaeobiogeographical barrier to the dispersion of moradisaurines. In fact, mapping all moradisaurine occurrences known so far, it is shown that their distribution area encompassed both sides of the Variscan mountains, essentially being restricted to the arid belt of palaeoequatorial Pangaea, where they probably outcompeted other herbivorous clades until they died out in the late Permian

Contribution due to clumpy winds to the non-thermal emission in microquasar jets

Powerful jets in high-mass microquasars are likely to be crossed by dense inhomogeneities(clumps) from the stellar winds, which may lead to particle acceleration and thus nonthermalemission in X-rays and gamma-rays. We characterise a typical clump-jet interactionscenario and compute the contribution to the high-energy emission of these systems. Weuse hydrodynamical simulations of a single clump-jet interaction and we use this result tocompute its non-thermal (synchrotron and inverse Compton) radiation. We present severalradiative calculations for a number of clump states, as the clump is disrupted over time,letting different parameters vary (viewing angle, magnetic field). We obtain significantamounts of non-thermal radiation from jet-clump interactions in high-mass microquasars.Fil: de la Cita, M. V.. Universidad de Barcelona. Facultad de Física; EspañaFil: del Palacio, Santiago. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Bosch Ramon, Valentí. Universidad de Barcelona. Facultad de Física; EspañaFil: Paredes Fortuny, X.. Universidad de Barcelona. Facultad de Física; EspañaFil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Khangulyan, D.. Rikkyo University; JapónXII Scientific Meeting of the Spanish Astronomical SocietyBilbaoEspañaSociedad Española de Astronomí

Usages et biodiversité dans les forêts méditerranéennes - L'exemple du massif des Albères (Pyrénées-Orientales) -

De tout temps, la forêt méditerranéenne a été pourvoyeuse de ressources pour les sociétés humaines. Ces ressources étaient exploitées selon des “droits d'usages” précis. Le pacage du bétail en forêt fait partie des usages qui se maintiennent encore localement même si cette activité a subi un fort déclin sur les rives nord de la Méditerranée occidentale depuis le milieu du XIXe siècle. Cette activité pastorale pose cependant la question de son influence sur le milieu forestier, notamment en termes de régénération forestière et de maintien de la biodiversité. Le massif des Albères, dans les Pyrénées-Orientales, fait partie de ces moyennes montagnes méditerranéennes où le sylvopastoralisme perdure. Ce massif abrite également une riche biodiversité comme en témoignent les résultats des inventaires réalisés au sein de la Réserve naturelle de la Massane, située au cœur des Albères. La présence de troupeaux domestiques et l’expression d’une riche biodiversité témoignent d’une coexistence possible entre différents enjeux au sein d’un même territoire

Deletion of Wt1 during early gonadogenesis leads to differences of sex development in male and female adult mice

Assessing the role of the WT1 transcription factor (WT1) during early gonad differentiation and its impact on adult sex development has been difficult due to the complete gonadal agenesis and embryonic lethality exhibited by Wt1KO mouse models. Here, we generated Wt1LoxP/GFP;Wt1Cre mice, the first Wt1KO mouse model that reaches adulthood with a dramatically reduced Wt1 expression during early gonadogenesis. Wt1LoxP/GFP;Wt1Cre mice lacked mature gonads and displayed genital tracts containing both male and female genital structures and ambiguous genitalia. We found that WT1 is necessary for the activation of both male and female sex-determining pathways, as embryonic mutant gonads failed to upregulate the expression of the genes specific for each genetic programme. The gonads of Wt1LoxP/GFP;Wt1Cre mice showed a lack of production of Sertoli and pre-granulosa cells and a reduced number of germ cells. NR5A1 and the steroidogenic genes expression was modulated differently in XY and XX Wt1LoxP/GFP;Wt1Cre gonads, explaining the mutant phenotypes. Further studies of the XX Wt1LoxP/GFP;Wt1Cre gonads revealed that deletion of WT1 at an early stage impaired the differentiation of several cell types including somatic cells and the ovarian epithelium. Through the characterisation of this Wt1KO mouse model, we show that the deletion of Wt1 during early gonadogenesis produces dramatic defects in adult sex development

Gamma rays from clumpy wind-jet interactions in high-mass microquasars

Context. The stellar winds of the massive stars in high-mass microquasars are thought to be inhomogeneous. The interaction of these inhomogeneities, or clumps, with the jets of these objects may be a major factor in gamma-ray production. Aims. Our goal is to characterize a typical scenario of clump-jet interaction, and calculate the contribution of these interactions to the gamma-ray emission from these systems. Methods. We use axisymmetric, relativistic hydrodynamical simulations to model the emitting flow in a typical clump-jet interaction. Using the simulation results we perform a numerical calculation of the high-energy emission from one of these interactions. The radiative calculations are performed for relativistic electrons locally accelerated at the jet shock, and the synchrotron and inverse Compton radiation spectra are computed for different stages of the shocked clump evolution. We also explore different parameter values, such as viewing angle and magnetic field strength. The results derived from one clump-jet interaction are generalized phenomenologically to multiple interactions under different wind models, estimating the clump-jet interaction rates, and the resulting luminosities in the GeV range. Results. If particles are efficiently accelerated in clump-jet interactions, the apparent gamma-ray luminosity through inverse Compton scattering with the stellar photons can be significant even for rather strong magnetic fields and thus efficient synchrotron cooling. Moreover, despite the standing nature or slow motion of the jet shocks for most of the interaction stage, Doppler boosting in the postshock flow is relevant even for mildly relativistic jets. Conclusions. For clump-to-average wind density contrasts greater than or equal to ten, clump-jet interactions could be bright enough to match the observed GeV luminosity in Cyg X-1 and Cyg X-3 when a jet is present in these sources, with required non-thermal-to-total available power fractions greater than 0.01 and 0.1, respectively.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Detection of very high energy gamma-ray emission from the gravitationally-lensed blazar QSO B0218+357 with the MAGIC telescopes

Context. QSO B0218+357 is a gravitationally lensed blazar located at a redshift of 0.944. The gravitational lensing splits the emitted radiation into two components, spatially indistinguishable by gamma-ray instruments, but separated by a 10-12 day delay. In July 2014, QSO B0218+357 experienced a violent flare observed by the Fermi-LAT and followed by the MAGIC telescopes. Aims. The spectral energy distribution of QSO B0218+357 can give information on the energetics of z ~ 1 very high energy gamma- ray sources. Moreover the gamma-ray emission can also be used as a probe of the extragalactic background light at z ~ 1. Methods. MAGIC performed observations of QSO B0218+357 during the expected arrival time of the delayed component of the emission. The MAGIC and Fermi-LAT observations were accompanied by quasi-simultaneous optical data from the KVA telescope and X-ray observations by Swift-XRT. We construct a multiwavelength spectral energy distribution of QSO B0218+357 and use it to model the source. The GeV and sub-TeV data, obtained by Fermi-LAT and MAGIC, are used to set constraints on the extragalactic background light. Results. Very high energy gamma-ray emission was detected from the direction of QSO B0218+357 by the MAGIC telescopes during the expected time of arrival of the trailing component of the flare, making it the farthest very high energy gamma-ray sources detected to date. The observed emission spans the energy range from 65 to 175 GeV. The combined MAGIC and Fermi-LAT spectral energy distribution of QSO B0218+357 is consistent with current extragalactic background light models. The broad band emission can be modeled in the framework of a two zone external Compton scenario, where the GeV emission comes from an emission region in the jet, located outside the broad line region.Comment: 11 pages, 6 figures, accepted for publication in A&

Limits to dark matter annihilation cross-section from a combined analysis of MAGIC and Fermi-LAT observations of dwarf satellite galaxies

We present the first joint analysis of gamma-ray data from the MAGIC Cherenkov telescopes and the Fermi Large Area Telescope (LAT) to search for gamma-ray signals from dark matter annihilation in dwarf satellite galaxies. We combine 158 hours of Segue 1 observations with MAGIC with 6-year observations of 15 dwarf satellite galaxies by the Fermi-LAT. We obtain limits on the annihilation cross-section for dark matter particle masses between 10 GeV and 100 TeV - the widest mass range ever explored by a single gamma-ray analysis. These limits improve on previously published Fermi-LAT and MAGIC results by up to a factor of two at certain masses. Our new inclusive analysis approach is completely generic and can be used to perform a global, sensitivity-optimized dark matter search by combining data from present and future gamma-ray and neutrino detectors.Comment: 19 pages, 3 figures. V2: Few typos corrected and references added. Matches published version JCAP 02 (2016) 03

Detection of bridge emission above 50 GeV from the Crab pulsar with the MAGIC telescopes

The Crab pulsar is the only astronomical pulsed source detected at very high energy (VHE, E>100GeV) gamma-rays. The emission mechanism of VHE pulsation is not yet fully understood, although several theoretical models have been proposed. In order to test the new models, we measured the light curve and the spectra of the Crab pulsar with high precision by means of deep observations. We analyzed 135 hours of selected MAGIC data taken between 2009 and 2013 in stereoscopic mode. In order to discuss the spectral shape in connection with lower energies, 4.6 years of {\it Fermi}-LAT data were also analyzed. The known two pulses per period were detected with a significance of $8.0 \sigma$ and $12.6 \sigma$. In addition, significant emission was found between the two pulses with $6.2 \sigma$. We discovered the bridge emission above 50 GeV between the two main pulses. This emission can not be explained with the existing theories. These data can be used for testing new theoretical models.Comment: 5 pages, 4 figure