To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
The European Southern Observatory Faint Object Spectrograph and Camera v2 is one of the workhorse instruments on ESO’s New Technology Telescope, and is one of the most popular instruments at La Silla observatory. It is mounted at a Nasmyth focus, and therefore exhibits strong, wavelength and pointing-direction-dependent instrumental polarisation. In this document, we describe our efforts to calibrate the broadband imaging polarimetry mode, and provide a calibration for broadband B, V, and R filters to a level that satisfies most use cases (i.e. polarimetric calibration uncertainty ~0.1%). We make our calibration codes public. This calibration effort can be used to enhance the yield of future polarimetric programmes with the European Southern Observatory Faint Object Spectrograph and Camera v2, by allowing good calibration with a greatly reduced number of standard star observations. Similarly, our calibration model can be combined with archival calibration observations to post-process data taken in past years, to form the European Southern Observatory Faint Object Spectrograph and Camera v2 legacy archive with substantial scientific potential.
Orphan Afterglows (OA) are slow transients produced by Gamma Ray Bursts seen off–axis that become visible on timescales of days/years at optical/NIR and radio frequencies, when the prompt emission at high energies (X and γ rays) has already ceased. Given the typically estimated jet opening angle of GRBs θjet ~ 3°, for each burst pointing to the Earth there should be a factor ~ 700 more GRBs pointing in other directions. Despite this, no secure OAs have been detected so far. Through a population synthesis code we study the emission properties of the population of OA at radio frequencies. OAs reach their emission peak on year-timescales and they last for a comparable amount of time. The typical peak fluxes (which depend on the observing frequency) are of few μJy in the radio band with only a few OA reaching the mJy level. These values are consistent with the upper limits on the radio flux of SN Ib/c observed at late times. We find that the OA radio number count distribution has a typical slope − 1.7 at high fluxes and a flatter ( − 0.4) slope at low fluxes with a break at a frequency–dependent flux. Our predictions of the OA rates are consistent with the (upper) limits of recent radio surveys and archive searches for radio transients. Future radio surveys like VAST/ASKAP at 1.4 GHz should detect ~ 3 × 10− 3 OA deg− 2 yr− 1, MeerKAT and EVLA at 8.4 GHz should see ~ 3 × 10− 1 OA deg− 2 yr− 1. The SKA, reaching the μJy flux limit, could see up to ~ 0.2 − 1.5 OA deg− 2 yr− 1. These rates also depend on the duration of the OA above a certain flux limit and we discuss this effect with respect to the survey cadence.
Over the past decade, a growing number of deep imaging surveys have started to provide meaningful constraints on the population of extrasolar giant planets at large orbital separation. Primary targets for these surveys have been carefully selected based on their age, distance and spectral type, and often on their membership to young nearby associations where all stars share common kinematics, photometric and spectroscopic properties. The next step is a wider statistical analysis of the frequency and properties of low mass companions as a function of stellar mass and orbital separation. In late 2009, we initiated a coordinated European Large Program using angular differential imaging in the H band (1.66 μm) with NaCo at the VLT. Our aim is to provide a comprehensive and statistically significant study of the occurrence of extrasolar giant planets and brown dwarfs at large (5-500 AU) orbital separation around ~150 young, nearby stars, a large fraction of which have never been observed at very deep contrast. The survey has now been completed and we present the data analysis and detection limits for the observed sample, for which we reach the planetary-mass domain at separations of ≳50 AU on average. We also present the results of the statistical analysis that has been performed over the 75 targets newly observed at high-contrast. We discuss the details of the statistical analysis and the physical constraints that our survey provides for the frequency and formation scenario of planetary mass companions at large separation.
This is brief summary of the joint discussion about GRB afterglows held in Marbella
during the Gamma-Ray Burst Symposium 2012. It is based on hints proposed by many authors
in their talks and offers a (personally biased) view of some of the open issues in the
field. No attempts have actually been applied to really cover all the discussed subjects,
and consequently only a few topics are chosen as representatives of the activities going
on in the field, admittedly with some emphasis for observational results.
Starting from the Swift sample we defined a complete sub-sample of 58
bright long Gamma Ray Bursts (GRB), 52 of them (90%) with a redshift determination, in
order to characterize their properties. This complete sample of bright long- GRBs allowed
us to investigate their evolution with cosmic time and properties. We focused in
particular on the GRB luminosity function, on the spectral-energy correlations of their
prompt emission, on the nature of dark bursts and on possible correlations between the
prompt and the X-ray afterglow properties.
Gamma-ray bursts and their afterglows are thought to be produced by an ultrarelativistic jet. One of the most important open questions is the out-flow composition: the energy may be carried out from the central source either as kinetic energy (of baryons and/or pairs), or in electromagnetic form (Poynting flux). While the total observable flux may be indistinguishable in both cases, its polarization properties are expected to differ markedly. The later time evolution of afterglow polarization is also a powerful diagnostic of the jet geometry. Again, with subtle and hardly detectable differences in the output flux, we have distinct polarization predictions.
Polarimetry is a powerful diagnostic tool to study spatially unresolved sources at cosmological distances, such as gamma-ray burst (GRB) afterglows. Radiation mechanisms that produce similar spectra can be disentangled by means of their polarization signatures. Also, polarization provides unique insights into the geometry of the source, which remains hidden in the integrated light.
Historically, essentially all interpretative studies about GRB afterglow polarimetry have been based on the cosmological fireball model, which we will also use as a reference for our discussion. Afterglow polarization studies have indeed the advantage that different models are often almost indistinguishable in terms of radiation output in the optical, but produce markedly distinct predictions about polarization.
In this proceeding, we will briefly review in Section 32.2 what we have derived by optical afterglow polarimetric observations and discuss the most recent development in the field in Section 32.3.
We compute the luminosity function (LF) and the formation rate of long gamma ray bursts (GRBs) in three different scenarios: i) GRBs follow the cosmic star formation and their LF is constant in time; ii) GRBs follow the cosmic star formation but the LF varies with redshift; iii) GRBs form preferentially in low–metallicity environments. We then test model predictions against the Swift 3-year data, showing that scenario i) is robustly ruled out. Moreover, we show that the number of bright GRBs detected by Swift suggests that GRBs should have experienced some sort of luminosity evolution with redshift, being more luminous in the past. Finally we propose to use the observations of the afterglow spectrum of GRBs at z ≥ 5.5 to constrain the reionization history, and then applied our method to the case of GRB 050904.
REM (Rapid Eye Mount) is a fully robotized fast slewing telescope equipped with a high throughput Near InfraRed (Z′, J, H, K′) camera (REMIR) and an optical slitless spectrograph (ROSS). A dedicated software for data reduction and software (AQuA) has been developed to extract scientific information from REM images without any human intervent. REM is installed in La Silla (Chile) and dedicated to detect and study the prompt optical/IR afterglow of Gamma Ray Bursts with the ambitious project of discovering objects at extremely high redshift. The synergy between REMIR camera and ROSS makes REM a powerful observing tool for any kind of fast transient phenomena.
We report the discovery of the first low–mass pre–main sequence eclipsing binary among a sample of double-lined spectroscopic binaries in the Orion star forming region found in a previous high-resolution spectroscopic investigation on ROSAT–discovered weak-T Tauri stars. Here we present the preliminary results from the combined analysis of the spectroscopic orbit and B and V light–curves, using data available till spring 2000. We then compare the fundamental stellar parameters derived from the orbital solution with those inferred from some widely used theoretical evolutionary models.
A summary of the first results of a search for Cepheids in IC 1613 is reported along with a short discussion of the adopted technique, a comparison of the characteristics of Cepheid light curves in the Galaxy, Magellanic Clouds and IC 1613, and a possible application for a P–L relation derivation. First overtone Cepheids have been identified for the first time in a galaxy farther than the Magellanic Clouds.
Over the last year we obtained X-ray (ROSAT, BeppoSAX and ASCA) and optical (at ESO and at the Astronomical Observatory of Loiano) to infra-red (AAO) observations of a sample of newly discovered X-ray pulsars. Among this sample we discovered the likely optical counterpart of three of them located in the Galactic plane: GS 0834–43, 1WGA J1958.2+3232 and AX J1820.5–1434.
We obtained X–ray (ROSAT, BeppoSAX and ASCA) and optical observations of a sample of newly discovered X–ray pulsars. We here report on the discovery of the likely optical counterpart of five of them in the Small Magellanic Cloud: 1SAXJ0103–7209, XTEJ0055–724, RXJ0052–7319, XTEJ0111–7317 and 2E0050–7247.
Microanalysis has proved crucial in developing thermal-sprayed metal coatings on the surface of reinforced concrete to serve as anodes in impressed current (ICCP) and galvanic (GCP) cathodic protection systems and in understanding their long-term performance. Corrosion of reinforcing bar in concrete bridges is the primary cause of structural deterioration in high chloride environments such as coastal locations and colder climates where roads are deiced with salt. Over 40 pet of more than 500,000 bridges surveyed in the U.S. are in need of repair or rehabilitation. Cathodic protections is the most effective method of mitigating the effects of corrosion due to chloride contaminated concrete. While a young technology, consumable thermal sprayed zinc anodes (see Figure 1 for a schematic of the process) totaling over 40,000 m2 (430,00 ft2) have been installed on the Oregon coast, primarily on the Depoe Bay, Yaquina Bay, and Cape Creek bridges.
This paper addresses the microanalysis techniques used to characterize thermal sprayed Ti coatings on concrete surfaces as anodes in impressed current cathodic protection (ICCP) systems. Thermal sprayed Ti anodes on concrete were electrochemically aged in laboratory studies of anode performance and service life. A thermal sprayed catalyzed Ti anode was installed on the Depoe Bay Bridge on the Oregon Coast in a field demonstration of the ICCP system. Both air and N were used as the atomizing gases during the study. Thermal sprayed Ti coatings are typically applied in an inert atmosphere or vacuum using shrouds or chambers to prevent reactions with the atmosphere. This was not possible with a structure as large as a bridge.
Microanalysis of Ti and N together is difficult and the effects of O add to the complexity of the analysis. The ternary Ti-O-N system has not be well studied.
A grid of synthetic spectral energy distributions, representative of old stellar populations, has been used to derive colors in different photometric systems, and to compare the theoretical predictions with observational data for galactic globular clusters.
This paper discusses experimental techniques and modelling tools used to characterize energetic solids subjected to dynamic deformation and shock. Critical experiments have been designed to study shock response and impact sensitivity of energetic materials. For example, a simplified two dimensional experiment has been developed to study the critical phenomena involved in delayed detonation reactions (XDT). In addition, wedge tests are used to obtain equation-of-state data. Coupled with hydrocodes, these experiments give us an in-depth understanding of the response of energetic materials subjected to shock loading. A coupled methodology using both experimental and modelling tools is presented. Consisting of three parts, it addresses all possible responses to fragment impact. The three parts are: (1) Fragment impact modelling (hydrocodes and empirically based codes); (2) Experiments to obtain accurate data for predicting prompt detonation; and (3) Tests with planar rocket motor models to explore mechanisms related to bum reaction thresholds and degree of violence. This methodology is currently being used in weapon design and munitions hazard assessments.
Email your librarian or administrator to recommend adding this to your organisation's collection.