arXiv subjects

A. Pala

Publications and source records attributed to A. Pala.

3 recordsLinked to original sources

arXiv2026

ESO User Support and Observation Preparation for VLTI Science Operations

We present recent enhancements to VLTI observing capabilities from a user-oriented perspective, together with new developments in ESO's Observation Handling Tools and end-to-end operations model for VLTI. Key upgrades include GRAVITY+ Coud\'e guiding with laser guide stars at the UTs, improved limiting magnitudes for GRAVITY and MATISSE, and a new MATISSE narrow-field off-axis mode, all supported by a streamlined, uniform template structure. Phase 2 tools now enable finding-chart generation and the selection of Coud\'e guide stars and fringe-tracker targets, and will soon offer expanded preparation features and uv-coverage visualisation. We summarise usage statistics for snapshot, astrometric, imaging, and time-series observations, outline VLTI scheduling considerations, and present new video tutorials. Starting in 2026, an archive data stream of reduced GRAVITY dispersed visibilities has become available. Complementary community engagement in VLTI operations continues to grow. We close by identifying operational lessons for future interferometric facilities, including the importance of an end-to-end data-flow and user-support model, flexible scheduling, high-level observation-preparation tools, and coordinated community support to keep complex interferometric facilities usable by a broad community.

astro-ph.IM↗

arXiv2021

Unveiling the faint ultraviolet Universe

With this paper we participate to the call for ideas issued by the European Space Agency to define the Science Program and plan for space missions from 2035 to 2050. In particular we present five science cases where major advancements can be achieved thanks to space-based spectroscopic observations at ultraviolet (UV) wavelengths. We discuss the possibility to (1) unveil the large-scale structures and cosmic web in emission at redshift <~1.7; (2) study the exchange of baryons between galaxies and their surroundings to understand the contribution of the circumgalactic gas to the evolution and angular-momentum build-up of galaxies; (3) constrain the efficiency of ram-pressure stripping in removing gas from galaxies and its role in quenching star formation; (4) characterize the progenitor population of core-collapse supernovae to reveal the explosion mechanisms of stars; (5) target accreting white dwarfs in globular clusters to determine their evolution and fate. These science themes can be addressed thanks to UV (wavelength range lambda ~ 90 - 350 nm) observations carried out with a panoramic integral field spectrograph (field of view ~ 1 x 1 arcmin^2 ), and medium spectral (R = 4000) and spatial (~ 1" - 3") resolution. Such a UV-optimized instrument will be unique in the coming years, when most of the new large facilities such as the Extremely Large Telescope and the James Webb Space Telescope are optimized for infrared wavelengths.

astro-ph.IM↗

arXiv2016

GW Librae: A unique laboratory for pulsations in an accreting white dwarf

Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of HST ultraviolet spectroscopy taken in 2002, 2010 and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in May~2013, we obtained new HST/COS ultraviolet observations that displayed unexpected behaviour: besides showing variability at ~275s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhibits high-amplitude variability on a ~4.4h time-scale. We demonstrate that this variability is produced by an increase of the temperature of a region on white dwarf covering up to ~30 per cent of the visible white dwarf surface. We argue against a short-lived accretion episode as the explanation of such heating, and discuss this event in the context of non-radial pulsations on a rapidly rotating star

astro-ph.SR↗