Recent Talks

This talk shows an spectrophotometric analysis of HD 209458 and 18 A type stars. We have used absolute flux spectrophotometry obtained with the Hubble Space Telescope  and Kurucz model atmospheres to ascertain the angular diameters (precision of about 1%) and effective temperatures (similar or better than 1%). The same analysis also permits the determination of other stellar parameters such as metallicity and surface gravity. The A type stars were selected from the STIS Next Generation Spectral Library because they match our criteria that their absolute fluxes in the optical are reliable to within 3 per cent by comparing their HST spectra with Kurucz theoretical models. HD 209458 harbors the first transiting planet discovered and it is one of only two systems with absolute stellar and planetary masses derived from high-resolution spectroscopy. We updated the stellar radius by combining the angular diameter with the Gaia parallax and then the planetary radius with unprecedented precision. We have also determined the stellar parameters from stellar evolution models. Finally, our results are compared with those from the literature.

During the summer of 2013, a 4-month spectroscopic campaign took place at Teide IAC 80 and other professional and amateur observatories to observe the variabilities in the wind of the Wolf-Rayet star WR 134. The spectroscopic data have been analyzed to better understand its wind and long-term periodicity, which can now be interpreted as arising from corotating interaction regions (CIRs) in the wind coming from the hidden surface of the star.

We are currently conducting a survey of 25 Galactic globular clusters with MUSE, the panoramic integral-field spectrograph at the ESO VLT.

Although the observations are still ongoing, we already secured about one million spectra for more than 300000 individual stars. This is possible thanks to a novel method for the optimal extraction of stellar spectra, which in combination with MUSE provides unique multiplexing capabilities in crowded stellar fields.

In my talk, I want to highlight some of the science cases that we pursue with the MUSE data. I will put emphasis on the internal dynamics of the clusters. They are for example key to answer the question whether massive black holes reside in the centres of some clusters. Such intermediate-mass black holes would bridge the gap from stellar-mass black holes to the supermassive ones found in the bulges of galaxies. I will also touch upon other science cases, such as binary studies, chemical analyses, or the search for peculiar stars.

EMIR, the NIR camera and multiobject spectrograph of the GTC has just completed successfully its commissioning phase in telescope, after a very long development, construction and testing at the IAC. Very recently, the call for proposals for the Scientific Verification Phase of EMIR has been launched by GRANTECAN. Hence, it is now timely to describe the instrument as a whole, its expected performances and the main results of the commissioning periods, together with its planned run at the GTC. This seminar is aimed at covering all these aspects and will include also some prescriptions of the use of the observing tools to prepare EMIR proposals. Suggestions on the optimal use of the instrument in its present status as well as known problems discovered up to now will complete the content of this talk.

As of today, we know now more than 3000 planets orbiting other stars. The detection of planets through radial velocity gathers special attention in the world of exoplanet characterization, as this technique will probably allow us to detect and characterize the first Earth-mass planet inside the habitable zone of a neighbouring star. In this talk I will discuss the ongoing efforts for developing state-of-the art spectrographs that permit the detection of an Earth twin, and discuss one of the most formidable obstacles to the detection of planetary signals: stellar activity. While for several years planetary surveys simply avoided active stars, today we know that the presence of extrasolar planets around a star might suppress stellar activity as we measure it, or even boost it. I will present the current view of the intricate relationship between exoplanets and activity, and discuss some of the latest works on the topic.

En marzo de 106 AD el Reino Nabateo fue anexado por el emperador Trajano creando la nueva provincia de Arabia (Petraea). Nabatea y su antigua capital, la ciudad rosa de Petra, ha sido uno de nuestros objetivos de investigación desde nuestra primera campaña de campo en la región en 1996, hace ahora 20 años. En 2011 se llevó a cabo una campaña intensiva que deparó resultados muy sugerentes. En diciembre de 2015 se realizó una nueva visita a la zona en coincidencia con el solsticio de invierno. Se observaron y documentaron varios efectos de iluminación e importantes hierofanías en los principales monumentos de Petra. Estos hallazgos se han contrastado a la luz de las fuentes literarias y epigráficas y del simbolismo astronómico, En este sentido, como colofón, se ha analizado en detalle una de las piezas más fascinantes y enigmáticas del mundo nabateo, el llamado zodiaco de Khirbet et-Tannur, encontrado en un templo construido en la cima del Djebel Tannur en el Siglo II d.C. posiblemente bajo gobierno romano, y que ha supuesto un cambio de paradigma en nuestra forma de ver y comprender la civilización nabatea.

The IAC is part of the  Southeastern Association for Research in Astronomy (SARA), a consortium of colleges and universities in the US partnered with Lowell Observatory, the Chilean National Telescope Allocation Committee, and the Instituto de Astrofisica de Canarias.

In this seminar I will describe the remote facilities operated by the SARA observatories that comprise a 0.96m telescope at Kitt Peak, Arizona; a 0.6m instrument on Cerro Tololo, Chile; and the 1m Jacobus Kapteyn Telescope at the ORM. All are operated using standard VNC or Radmin protocols communicating with on-site PCs. Remote operation offers considerable flexibility in scheduling, allowing long-term observational cadences difficult to achieve with classical observing at remote facilities. Multiple observers at different locations can share a telescope for training, educational use, or collaborative research programs. Each telescope has a CCD system for optical imaging, using thermoelectric cooling to avoid the need for frequent local service, and a second CCD for offset guiding. SARA Kitt Peak telescope also has a fiber-fed echelle spectrograph. Switching between imaging and spectroscopy is very rapid, so a night can easily accommodate mixed observing modes.

The IAC astronomers started to use SARA facilities since early 2016 and a new call for proposals is open. I will present some early results from IAC’s observational programs and discuss the present status of the facilities and the experience obtained by the IAC users that could help new potential observers to prepare their own proposals.

The Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes reported the discovery of the most distant gamma-ray source ever observed at very high energies, thanks to the “replay” of an enormous flare by a galactic gravitational lens as foreseen by Einstein’s General Relativity. 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 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. 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. 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. 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 source detected to date. The combined MAGIC and Fermi-LAT spectral energy distribution of QSO B0218+357 is consistent with current extragalactic background light models. The broadband 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.

Work published in A&A 595, A98 (2016) ( http://www.aanda.org/articles/aa/abs/2016/11/aa29461-16/aa29461-16.html)

https://magic.mpp.mpg.de/outsiders/results/magic-highlights-5/

http://www.iac.es/divulgacion.php?op1=16&id=1133

The seminar addresses three main topics : (1) Interpretation of astronomical content in funerary texts of the 3rd millenium BC, suggesting a division of the starry sky in a southern and northern part, divided by a canal. – (2) Comparison of two theories of the Egyptian year, i.e. the traditional theory of the Egyptian 365 day vague year as deduced from observation of the heliacal risings of Sirius and Otto Neugebauer’s alternative theory of an averaged Nile year. – (3) The absolute chronology of the 8th century B.C. on the basis of dates for a specific cultic feast and introductions of the Apis bull, both events being fixed within the lunar month. These points are basic for understanding Egyptian worldview and chronology.