Herschel/PACS photometry of transiting-planet host stars with candidate warm debris disks

Dust in debris disks is produced by colliding or evaporating planetesimals, remnants of the planet formation process. Warm dust disks, known by their emission at < 24 micron, are rare (4% of FGK main sequence stars) and especially interesting because they trace material in the region likely to host terrestrial planets, where the dust has a very short dynamical lifetime. Statistical analyses of the source counts of excesses as found with the mid-IR Wide Field Infrared Survey Explorer (WISE) suggest that warm-dust candidates found for the Kepler transiting-planet host-star candidates can be explained by extragalactic or galactic background emission aligned by chance with the target stars. These statistical analyses do not exclude the possibility that a given WISE excess could be due to a transient dust population associated with the target. Here we report Herschel/PACS 100 and 160 micron follow-up observations of a sample of Kepler and non-Kepler transiting-planet candidates' host stars, with candidate WISE warm debris disks, aimed at detecting a possible cold debris disk in any of them. No clear detections were found in any one of the objects at either wavelength. Our upper limits confirm that most objects in the sample do not have a massive debris disk like that in beta Pic. We also show that the planet-hosting star WASP-33 does not have a debris disk comparable to the one around eta Crv. Although the data cannot be used to rule out rare warm disks around the Kepler planet-hosting candidates, the lack of detections and the characteristics of neighboring emission found at far-IR wavelengths support an earlier result suggesting that most of the WISE-selected IR excesses around Kepler candidate host stars are likely due to either chance alignment with background IR-bright galaxies and/or to interstellar emission.Comment: 8 pages, 3 figures, accepted for publication at Astronomy & Astrophysics on 4 August 201

Opinió del professorat sobre la utilització de l'aula digital a les classes de Ciències de secundària. Projecte ADIGIC

L'article descriu l'opinió del professorat de ciències de secundària sobre la implementació del projecte EduCAT2.0 així com les potencialitats i limitacions que comporta l'ús de noves tecnologies a l'aula. Els resultats s'han obtingut a partir de l'anàlisi de les respostes recollides d'una enquesta dirigida als docents, distribuïda durant el curs 2011-2012 i principis del 2012-2013 (N=154)

Real-time evolution of a large-scale relativistic jet

Context. Astrophysical jets are ubiquitous in the Universe on all scales, but their large-scale dynamics and evolution in time are hard to observe since they usually develop at a very slow pace. Aims. We aim to obtain the first observational proof of the expected large-scale evolution and interaction with the environment in an astrophysical jet. Only jets from microquasars offer a chance to witness the real-time, full-jet evolution within a human lifetime, since they combine a 'short', few parsec length with relativistic velocities. Methods. The methodology of this work is based on a systematic recalibraton of interferometric radio observations of microquasars available in public archives. In particular, radio observations of the microquasar GRS 1758-258 over less than two decades have provided the most striking results. Results. Significant morphological variations in the extended jet structure of GRS 1758-258 are reported here that were previously missed. Its northern radio lobe underwent a major morphological variation that rendered the hotspot undetectable in 2001 and reappeared again in the following years. The reported changes confirm the Galactic nature of the source. We tentatively interpret them in terms of the growth of instabilities in the jet flow. There is also evidence of surrounding cocoon. These results can provide a testbed for models accounting for the evolution of jets and their interaction with the environment.Comment: 5 pages, 3 figures, 2 tables. Accepted for publication in Astronomy and Astrophysics Letter

Experimental study of the system Nickel(II) benzoate and 2,2´-bipyridine

El trabajo de fin de grado trata del sintesis y estudio de complejos de niquel en diferentes proporciones de bipiridina y anion benzoato.<br /

La realidad del trasplante renal en Colombia

The number of patients who suffer chronical kidney disease (CKD) in our country and the overwhelming increase reflect what is happening in the world; where this disease has a pandemic appearance. Most of the patients are diagnosed grade 5 of CKD; in this stage the recomended treatment is the renal replacement therapy (RRT) (dialysis or transplant), and due to its operating high costs may destabilize any health system in the world 1. This is why, two non-exclusive schemes emerged in response to this challenge:First one: through nephrology and complementary medical specialties, to modify or delay the history of this entity, by controlling diseases with a high incidence on their etiology, offering an excellent quality of life to the patient and coordinate all previous aspects related to stage 5; which is a very incipient scheme in Colombi