Stellar abundances of beryllium and CUBES

Stellar abundances of beryllium are useful in different areas of astrophysics, including studies of the Galactic chemical evolution, of stellar evolution, and of the formation of globular clusters. Determining Be abundances in stars is, however, a challenging endeavor. The two Be II resonance lines useful for abundance analyses are in the near UV, a region strongly affected by atmospheric extinction. CUBES is a new spectrograph planned for the VLT that will be more sensitive than current instruments in the near UV spectral region. It will allow the observation of fainter stars, expanding the number of targets where Be abundances can be determined. Here, a brief review of stellar abundances of Be is presented together with a discussion of science cases for CUBES. In particular, preliminary simulations of CUBES spectra are presented, highlighting its possible impact in investigations of Be abundances of extremely metal-poor stars and of stars in globular clusters.     

Heavy-elements in metal-poor stars: an UV perspective

The site(s) of the r-process(es) is(are) not completely defined, and several models have been proposed. Observed abundances are the best clues to bring some light to this field, especially the study of the extremely metal-poor (EMP) Galactic halo stars. Many elements can be measured using ground-based facilities already available, but the ultraviolet window also presents a rich opportunity in terms of chemical abundances of heavy elements. In fact, for some elements only the UV transitions are strong enough to be useful. Focusing on the project of the Cassegrain U-Band Brazilian Spectrograph (CUBES), we discuss the science case for heavy elements in metal-poor stars, describing the useful lines of trans-Fe elements present in the UV region. Lines in the far UV are also discussed.     

The X‐shooter pipeline

The X‐shooter data reduction pipeline is an integral part of the X‐shooter project, it allows the production of reduced data in physical quantities from the raw data produced by the instrument. The pipeline is based on the data reduction library developed by the X‐shooter consortium with contributions from France, The Netherlands and ESO and it uses the Common Pipeline Library (CPL) developed at ESO. The pipeline has been developed for two main functions. The first function is to monitor the operation of the instrument through the reduction of the acquired data, both at Paranal, for a quick‐look control, and in Garching, for a more thorough evaluation. The second function is to allow an optimized data reduction for a scientific user. In the following I will first outline the main steps of data reduction with the pipeline then I will briefly show two examples of optimization of the results for science reduction (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

UV opportunities at ESO

After summarizing the UV capabilities available at the Paranal observatory, the perspectives for additional UV instruments are discussed. When considering that most likely the E-ELT will not be optimized for UV, and that HST operations will be soon discontinued, UV instruments at the VLT may represent the best capabilities for the ESO community for a few years. In particular the cases of spectroscopy close to the atmospheric cutoff and Blue diffraction limited imaging show a great scientific potential.     

GENIE – The Darwin demonstrator

Darwin is a cornerstone mission of the Horizons 2000+ program of the European Space Agency. It has the express purpose of carrying out the first direct search for terrestrial exoplanets, and to achieve unprecedented spatial resolution in the infrared wavelength region. The detection and study of terrestrial exoplanets promises to usher in a new era in science and will affect a broad spectrum of disciplines. Further, the time line for implementation of such an instrument is now likely to be of the close order of 10 years, leading to possible answers to one of mankind's most fundamental questions in the second decade of the 21st century. It has been found that in order to realize am interferometer in space in the next 10–15 years, it is necessary to prepare the way through a number of intermediary steps – both on the ground and in space. In this context, we here describe GENIE – a ground based nulling interferometry experiment to be implemented at the VLTI in a partnership between ESA and ESO. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improvements on Fresnel arrays for high contrast imaging

The Fresnel Diffractive Array Imager (FDAI) is based on a new optical concept for space telescopes, developed at Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse, France. For the visible and near-infrared it has already proven its performances in resolution and dynamic range. We propose it now for astrophysical applications in the ultraviolet with apertures from 6 to 30 meters, aimed at imaging in UV faint astrophysical sources close to bright ones, as well as other applications requiring high dynamic range. Of course the project needs first a probatory mission at small aperture to validate the concept in space. In collaboration with institutes in Spain and Russia, we will propose to board a small prototype of Fresnel imager on the International Space Station (ISS), with a program combining technical tests and astrophysical targets. The spectral domain should contain the Lyman-α line (λ =?121 nm). As part of its preparation, we improve the Fresnel array design for a better Point Spread Function in UV, presently on a small laboratory prototype working at 260 nm. Moreover, we plan to validate a new optical design and chromatic correction adapted to UV. In this article we present the results of numerical propagations showing the improvement in dynamic range obtained by combining and adapting three methods : central obturation, optimization of the bars mesh holding the Fresnel rings, and orthogonal apodization. We briefly present the proposed astrophysical program of a probatory mission with such UV optics.     

Optical variability of NGC 7469 in 1967–1987

Within the framework of a five-year campaign of coordinated multifrequency observations of the 3 Tauri star RU Lupi, we present results obtained in X-ray, UV, optical, and IR spectral regions. In five cases, simultaneous data from UV to IR were collected. Data analysis shows a large variability at different wavelengths both in the continuum and lines, stronger in the UV and weaker in the IR. Correlations among variations in the UV and optical continua have been found. Moreover flare-like events (FLEs), probably due to strong activity in the surface layers of the star and burst phenomena on large scale, were detected. No forbidden coronal lines were detected in UV and optical regions with IUE and ESO 1.4m CAT telescope, respectively. This means either the used instruments have not enough sensitivity to detect the predicted forbidden lines, or the low X-ray detected intensity — with ASTRON satellite (2–25 keV) — is due to the absorption of the X-rays in the circumstellar envelope. In this paper we will discuss these results within the framework of the current models.Based on observations with IUE satellite (VILSPA) and ESO telescopes.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain     

Stellar science from a blue wavelength range

From stellar spectra, a variety of physical properties of stars can be derived. In particular, the chemical composition of stellar atmospheres can be inferred from absorption line analyses. These provide key information on large scales, such as the formation of our Galaxy, down to the small‐scale nucleosynthesis processes that take place in stars and supernovae. By extending the observed wavelength range toward bluer wavelengths, we optimize such studies to also include critical absorption lines in metal‐poor stars, and allow for studies of heavy elements (Z ≥ 38) whose formation processes remain poorly constrained. In this context, spectrographs optimized for observing blue wavelength ranges are essential, since many absorption lines at redder wavelengths are too weak to be detected in metal‐poor stars. This means that some elements cannot be studied in the visual‐redder regions, and important scientific tracers and science cases are lost. The present era of large public surveys will target millions of stars. It is therefore important that the next generation of spectrographs are designed such that they cover a wide wavelength range and can observe a large number of stars simultaneously. Only then, we can gain the full information from stellar spectra, from both metal‐poor to metal‐rich ones, that will allow us to understand the aforementioned formation scenarios in greater detail. Here we describe the requirements driving the design of the forthcoming survey instrument 4MOST, a multi‐object spectrograph commissioned for the ESO VISTA 4 m‐telescope. While 4MOST is also intended for studies of active galactic nuclei, baryonic acoustic oscillations, weak lensing, cosmological constants, supernovae and other transients, we focus here on high‐density, wide‐area survey of stars and the science that can be achieved with high‐resolution stellar spectroscopy. Scientific and technical requirements that governed the design are described along with a thorough line blending analysis. For the high‐resolution spectrograph, we find that a sampling of ≥2.5 (pixels per resolving element), spectral resolution of 18000 or higher, and a wavelength range covering 393–436 nm, is the most well‐balanced solution for the instrument. A spectrograph with these characteristics will enable accurate abundance analysis (±0.1 dex) in the blue and allow us to confront the outlined scientific questions. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Technologies and science archives for ultraviolet astronomy

This paper summarizes 17 talks presented during the Technological sessions at the “Challenges in UV Astronomy” conference. It is based on summaries submitted by the presenters, on the slides of their talks, on notes written by the authors, and on additional material kindly submitted to the lead author. In many instances the summaries were written by the presenters themselves and are included as-submitted to the authors with just minor editorial interference. In other cases one of the editors wrote the summary based on their notes and on the files of the actual presentations. The contributions are placed in the general context of the current knowledge in the field. The sessions were devoted to: [a] detectors, [b] optics, [c] integration and verification procedures for vacuum UV instruments and [d] calibration and archival research. A cautionary note: this is not a regular article in these proceedings presenting one idea, an experiment, of a result. It is rather a distillation of what was presented at the NUVA/ESO/IAG meeting at the sessions deemed technological, therefore it will lack an overall coherence although the individual sections and subsections should be logically connected.     

The Solar Dynamics Observatory (SDO)

The Solar Dynamics Observatory (SDO) was launched on 11 February 2010 at 15:23 UT from Kennedy Space Center aboard an Atlas V 401 (AV-021) launch vehicle. A?series of apogee-motor firings lifted SDO from an initial geosynchronous transfer orbit into a circular geosynchronous orbit inclined by 28° about the longitude of the SDO-dedicated ground station in New Mexico. SDO began returning science data on 1 May 2010. SDO is the first space-weather mission in NASA’s Living With a Star (LWS) Program. SDO’s main goal is to understand, driving toward a predictive capability, those solar variations that influence life on Earth and humanity’s technological systems. The SDO science investigations will determine how the Sun’s magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere and geospace as the solar wind, energetic particles, and variations in the solar irradiance. Insights gained from SDO investigations will also lead to an increased understanding of the role that solar variability plays in changes in Earth’s atmospheric chemistry and climate. The SDO mission includes three scientific investigations (the Atmospheric Imaging Assembly (AIA), Extreme Ultraviolet Variability Experiment (EVE), and Helioseismic and Magnetic Imager (HMI)), a spacecraft bus, and a dedicated ground station to handle the telemetry. The Goddard Space Flight Center built and will operate the spacecraft during its planned five-year mission life; this includes: commanding the spacecraft, receiving the science data, and forwarding that data to the science teams. The science investigations teams at Stanford University, Lockheed Martin Solar Astrophysics Laboratory (LMSAL), and University of Colorado Laboratory for Atmospheric and Space Physics (LASP) will process, analyze, distribute, and archive the science data. We will describe the building of SDO and the science that it will provide to NASA.     

Interacting binaries: Science cases where simultaneous multicolor medium‐resolution spectroscopy makes a difference

This contribution to “The 1st year of science with X‐shooter” conference illustrates 2 different applications of the new ESO multi‐waveband spectrograph to the study of interacting binaries. In particular we present spectra collected during the late decline of U Sco 2010 outburst and during a low/hard X‐ray phase of the black hole candidate GX339‐4. In both cases the unprecedented spectral coverage and resolution offered by X‐shooter have unveiled unexpected features (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Galileo project

The Galileo project comprises the design, building, and operation of a 3.5 m Italian telescope the main elements (diameter, mechanical structure, active optics, etc.) of which consist of a duplication of the ESO New Technology Telescope (NTT). Modifications have been introduced in order to allow, beyond thef/11 Nasmyth foci, a prime focusf/2.2 station, a trappedf/6 focus, and a small Cassegrainf/20 facility. Other changes with respect to the NTT have been made to the control and data acquisition system, and to the service building. The telescope could be operational at the end of 1992.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

UVMag: stellar formation,evolution, structure and environment with space UV and visible spectropolarimetry

Important insights into the formation, structure, evolution and environment of all types of stars can be obtained through the measurement of their winds and possible magnetospheres. However, this has hardly been done up to now mainly because of the lack of UV instrumentation available for long periods of time. To reach this aim, we have designed UVMag, an M-size space mission equipped with a high-resolution spectropolarimeter working in the UV and visible spectral range. The UV domain is crucial in stellar physics as it is very rich in atomic and molecular lines and contains most of the flux of hot stars. Moreover, covering the UV and visible spectral domains at the same time will allow us to study the star and its environment simultaneously. Adding polarimetric power to the spectrograph will multiply tenfold the capabilities of extracting information on stellar magnetospheres, winds, disks, and magnetic fields. Examples of science objectives that can be reached with UVMag are presented for pre-main sequence, main sequence and evolved stars. They will cast new light onto stellar physics by addressing many exciting and important questions. UVMag is currently undergoing a Research & Technology study and will be proposed at the forthcoming ESA call for M-size missions. This spectropolarimeter could also be installed on a large UV and visible observatory (e.g. NASA’s LUVOIR project) within a suite of instruments.     

Prospects of stellar abundance studies from near‐IR spectra observed with the E‐ELT

In 2006 ESO Council authorized a Phase B study of a European AO‐telescope with a 42 m segmented primary with a 5‐mirror design, the E‐ELT. Several reports and working groups have already presented science cases for an E‐ELT, specifically exploiting the new capabilities of such a large telescope. One of the aims of the design has been to find a balance in the performances between an E‐ELT and the James Webb Space Telescope, JWST. Apart from the larger photon‐collecting area, the strengths of the former is the higher attainable spatial and spectral resolutions. The E‐ELT AO system will have an optimal performance in the near‐IR, which makes it specially advantageous. High‐resolution spectroscopy in the near‐infrared has, however, not been discussed much. This paper aims at filling that gap, by specifically discussing spectroscopy of stellar (mainly red giant), photospheric abundances. Based on studies in the literature of stellar abundances, at the needed medium to high spectral resolutions in the near‐infrared (0.8–2.4 μm), I will try to extrapolate published results to the performance of the E‐ELT and explore what could be done at the E‐ELT in this field. A discussion on what instrument characteristics that would be needed for stellar abundance analyses in the near‐IR will be given (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Orbital elements of GSC 0114401023, a new eclipsing binary

We present Strömgrenuvby photometric observations and a series of radial velocities obtained with the Coravel scanner for the 11th magnitude star catalogued in the Guide Star Catalogue as GSC 0114401023. This star was serendipitously identified on UV frames taken with the Very-Wide-Field-Camera aboard Spacelab-1. Radial velocities show the star to be binary and we have determined accurate orbital elements. Photometric data and orbital elements are consistent with the system being a previously-unrecognized eclipsing binary, with period = 33.8766 days and eccentricity = 0.262.Based on observations collected at the Observatoire de Haute Provence (OHP), CNRS, Saint-Michel l'Observatoire, France, and at the European Southern Observatory (ESO), La Silla, Chile.     

World space observatory-ultraviolet among UV missions of the coming years

Continuous access to the UV domain has been considered of importance to astrophysicists and planetary scientists since the mid-sixties. However, the future of UV missions for the post-HST era is believed by a significant part of astronomical community to be less encouraging. We argue that key science problems of the coming years will require further development of UV observational technologies. Among these hot astrophysical issues are: the search for missing baryons, revealing the nature of astronomical engines, properties of atmospheres of exoplanets as well as of the planets of the Solar System etc. We give a brief review of UV-missions both in the past and in the future. We conclude that UV astronomy has a great future but the epoch of very large and efficient space UV facilities seems to be a prospect for the next decades. As to the current state of the UV instrumentation we think that this decade will be dominated by the HST and coming World Space Observatory-Ultraviolet (WSO-UV) with a 1.7 m UV-telescope onboard. The international WSO-UV mission is briefly described. It will allow high resolution/high sensitivity imaging and high/low resolution spectroscopy from the middle of the decade.     

WSO/UV spectrographs: the expected performance of HIRDES

The World Space Observatory Ultraviolet (WSO/UV) is a multi-national project grown out of the needs of the astronomical community to have future access to the UV range. WSO/UV consists of a single UV telescope with a primary mirror of 1.7 m diameter feeding the UV spectrometer and UV imagers. The spectrometer comprises three different spectrographs, two high-resolution echelle spectrographs (the High-Resolution Double-Echelle Spectrograph, HIRDES) and a low-dispersion long-slit instrument. Within HIRDES the 102–310 nm spectral band is split to feed two echelle spectrographs covering the UV range 174–310 nm and the vacuum-UV range 102–176 nm with high spectral resolution (R>55000). The technical concept is based on the heritage of two previous ORFEUS SPAS missions. The phase-B1 development activities are described in this paper considering the performance of the instruments.