Showing papers by "Royal Institute and Observatory of the Spanish Navy published in 2006"

The Calar Alto lunar occultation program: update and new results

Abstract: We present an update of the lunar occultation program which is routinely carried out in the near-IR at the Calar Alto Observatory. A total of 350 events were recorded since our last report (Fors et al. 2004). In the course of eight runs we have observed, among others, late-type giants, T-Tauri stars, and infrared sources. Noteworthy was a passage of the Moon close to the galactic center, which produced a large number of events during just a few hours in July 2004. Results include the determinations of the angular diameter of RZ Ari, and the projected separations and brightness ratios for one triple and 13 binary stars, almost all of which representing first time detections. Projected separations range from 0. '' 09 to 0. '' 007. We provide a quantitative analysis of the performance achieved in our observations in terms of angular resolution and sensitivity, which reach about 0. '' 003 and K � 8.5mag, respectively. We also present a statistical discussion of our sample, and in particular of the frequency of detection of binaries among field stars.

Geomagnetic secular variation of Bransfield Strait (Western Antarctica) from analysis of marine crossover data

Abstract: SUMMARY Tracking the secular variation of the geomagnetic field in the past is severely limited in some cases by factors relating to the remoteness of the sites. This is maximal in the Antarctic where the remote location and severe climate lead to logistic limitations that make it difficult to keep a continuous record of magnetic field variations. From the magnetic information available from historical marine expeditions, it is possible to infer this time-varying component from the comparison of readings at crossovers. This study focuses on this technique, discusses the impact of the different error sources and proposes a simple mathematical procedure to infer average secular variation rates. The result is validated by comparing it with local data from the Arctowski and Livingston magnetic observatories, sited in the area. Additionally, using a high-quality data set from a local area in the neighbourhood of Deception Island, we have detected a systematic distribution in its secular variation. This dichotomy has been interpreted in terms of a volcano-magnetic signal. This fact and the nature of its principal mechanisms are analysed and discussed.

Geodynamical Studies on Deception Island: DECVOL and GEODEC Projects

Abstract: Deception Island (63° S, 60° W) is situated in the South Shetland Islands, and it is the main active volcano in the Bransfield Strait, with recent eruptions in 1842, 1967, 1969 and 1970. Its volcanic and seismic activity has been monitored from 1986 to study the geodynamic activity on the island. In this paper we present the objectives and some results obtained in DECVOL project, a crossdisciplinary study which was planned to evaluate the volcanic status of the island after the crisis occurred during the 1998/1999 campaign, as well as the goals and activities which have been carried out in the framework of GEODEC project, a multidisciplinary project to continue with the studies on the island.

A new data analysis technique in the study of mutual event lightcurves

Abstract: The purpose of this paper is to develop a new methodology for analyzing astronomical data, in particular, one of the light curves obtained in the PHEMU campaign in 1997, where the mutual phenomena between Jupiter and its satellites were observed from the Earth due to the coincidence of the equatorial plane of Jupiter and the orbit plane of the Earth. The more specific aim of this study is to determine the times of the beginning and the end of the phenomena, and the moment when the recorded light flux was at a minimum. The techniques we applied were based on the wavelet theory, which allows us to study a signal from its approximations and details at different scales. Before applying the designed algorithm to our experimental data, we considered a synthetic light curve in order to check the reliability of our method. It should be mentioned that the results are not relevant from the astronomical point of view, since no corrections for albedo or illumination were applied to the recorded data.

BOOTES-IR: a robotic nIR astronomical observatory devoted to follow-up of transient phenomena

Abstract: "BOOTES-IR" is the extension of the BOOTES experiment, which has been operating in Southern Spain since 1998, to the near-infrared (nIR). The goal is to follow up the early stage of the gamma ray burst (GRB) afterglow emission in the nIR, as BOOTES does already at optical wavelengths. The scientific case that drives the BOOTES-IR performance is the study of GRBs with the support of spacecraft like HETE-2, INTEGRAL and SWIFT (and GLAST in the future). Given that the afterglow emission in both, the nIR and the optical, in the instances immediately following a GRB, is extremely bright (reached V = 8.9 in one case), it should be possible to detect this prompt emission at nIR wavelengths too. Combined observations by BOOTES-IR and BOOTES-1 and BOOTES-2 since 2006 can allow for real time identification of trustworthy candidates to have a ultra-high redshift (z > 6). It is expected that, few minutes after a GRB, the nIR magnitudes be H ~ 10-15, hence very high quality spectra can be obtained for objects as far as z = 10 by much larger ground-based telescopes. A significant fraction of observing time will be available for other scientific projects of interest, objects relatively bright and variable, like Solar System objects, brown dwarfs, variable stars, planetary nebulae, compact objects in binary systems and blazars.