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Concept

Astronomie amateur

Publications associées (18)

GHOST commissioning science results - II: a very metal-poor star witnessing the early galactic assembly

Pascale Jablonka

This study focuses on Pristine_180956.78-294759.8 (hereafter P180956, [Fe/H] = -1.95 +/- 0.02), a star selected from the Pristine Inner Galaxy Survey (PIGS), and followed-up with the recently commissioned Gemini High-resolution Optical SpecTrograph (GHOST) ...

Oxford Univ Press2024

Performance of the Quasar Spectral Templates for the Dark Energy Spectroscopic Instrument

Jiaxi Yu, Zheng Zheng

Millions of quasar spectra will be collected by the Dark Energy Spectroscopic Instrument (DESI), leading to a fourfold increase in the number of known quasars. High-accuracy quasar classification is essential to tighten constraints on cosmological paramete ...

IOP Publishing Ltd2023

Gravitationally lensed quasars in Gaia - IV. 150 new lenses, quasar pairs, and projected quasars

Frédéric Courbin, Aymeric Alexandre Galan, Cameron Alexander Campbell Lemon

We report the spectroscopic follow-up of 175 lensed quasar candidates selected using Gaia Data Release 2 observations following Paper III of this series. Systems include 86 confirmed lensed quasars and a further 17 likely lensed quasars based on imaging an ...

OXFORD UNIV PRESS2023

A possible dwarf galaxy satellite-of-satellite problem in ?CDM

Yves Revaz, Nick Heesters

Dark matter clusters on all scales, and it is therefore expected that even substructure should host its own substructure. Using the Extragalactic Distance Database, we searched for dwarf-galaxy satellites of dwarf galaxies, that is, satellite-of-satellite ...

EDP SCIENCES S A2023

Constraining quasar structure using high-frequency microlensing variations and continuum reverberation

Frédéric Courbin, Vivien François Bonvin, Martin Raoul Robert Millon, Hung-Hsu Chan, Georgios Vernardos, Eric Gérard Guy Paic

Gravitational microlensing is a powerful tool for probing the inner structure of strongly lensed quasars and for constraining parameters of the stellar mass function of lens galaxies. This is achieved by analysing microlensing light curves between the mult ...

EDP SCIENCES S A2022

The formation of the milky way halo and its dwarf satellites: a NLTE-1D abundance analysis. IV. Segue 1, Triangulumii, and Coma Berenices UFDs

Pascale Jablonka

We present atmospheric parameters and abundances for chemical elements from carbon to barium in metal-poor stars in Segue 1 (seven stars), Coma Berenices (three stars), and Triangulum II (one star) ultrafaint dwarf galaxies (UFDs). The effective temperatur ...

OXFORD UNIV PRESS2021

Exploiting flux ratio anomalies to probe warm dark matter in future large-scale surveys

Frédéric Courbin, David Richard Harvey, Amélie Tamone, Alexey Boyarsky, Wessel Valkenburg

Flux ratio anomalies in strong gravitationally lensed quasars constitute a unique way to probe the abundance of non-luminous dark matter haloes, and hence the nature of dark matter. In this paper, we identify double-imaged quasars as a statistically effici ...

2019

Observations of Sagittarius A* during the pericenter passage of the G2 object with MAGIC

Thomas Günther Bretz

Context. We present the results of a multi-year monitoring campaign of the Galactic center (GC) with the MAGIC telescopes. These observations were primarily motivated by reports that a putative gas cloud (G2) would be passing in close proximity to the supe ...

Edp Sciences S A2017

LEAP: Looking beyond pixels with continuous-space EstimAtion of Point sources

Martin Vetterli, Thierry Blu, Paul Hurley, Matthieu Martin Jean-André Simeoni, Hanjie Pan

Context. Two main classes of imaging algorithms have emerged in radio interferometry: the CLEAN algorithm and its multiple variants, and compressed-sensing inspired methods. They are both discrete in nature, and estimate source locations and intensities on ...

2017

The formation of the Milky Way halo and its dwarf satellites; a NLTE-1D abundance analysis II. Early chemical enrichment

Pascale Jablonka, Pierre North

We present the non-local thermodynamic equilibrium (NLTE) abundances of up to 10 chemical species in a sample of 59 very metal-poor (VMP, -4

Edp Sciences S A2017

A randomised primal-dual algorithm for distributed radio-interferometric imaging

Yves Wiaux, Jason Douglas McEwen, Rafael Eduardo Carrillo Rangel

Next generation radio telescopes, like the Square Kilometre Array, will acquire an unprecedented amount of data for radio astronomy. The development of fast, parallelisable or distributed algorithms for handling such large-scale data sets is of prime impor ...

Ieee2016

Lensed Type Ia supernovae as probes of cluster mass models

Jean-Paul Richard Kneib, Hakim Atek

Using three magnified Type Ia supernovae (SNe Ia) detected behind CLASH (Cluster Lensing and Supernovae with Hubble) clusters, we perform a first pilot study to see whether standardizable candles can be used to calibrate cluster mass maps created from stro ...

Wiley-Blackwell2014

Light-cone anisotropy in the 21 cm signal from the epoch of reionization

Yves Revaz

Using a suite of detailed numerical simulations, we estimate the level of anisotropy generated by the time evolution along the light cone of the 21 cm signal from the epoch of reionization. Our simulations include the physics necessary to model the signal ...

Wiley-Blackwell2014

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses X. Modeling based on high-precision astrometry of a sample of 25 lensed quasars: consequences for ellipticity, shear, and astrometric anomalies

Frédéric Courbin, Georges Meylan

Gravitationally lensed quasars can be used as powerful cosmological and astrophysical probes. We can (i) infer the Hubble constant H-0 based on the so-called time-delay technique, (ii) unveil substructures along the line-of-sight toward distant galaxies, a ...

2012

Large Micromirror Array Based on a Scalable Technology for Astronomical Instrumentation

Michael David Canonica

Understanding the formation of galaxies and studying the expansion of the Universe, need the spectral characterization of faint astronomical objects such as stars or galaxies. From these spectra, the distance, the velocity and the chemical composition of t ...

EPFL2012

Zooming into the broad line region of the gravitationally lensed quasar QSO 2237+0305 equivalent to the Einstein Cross III. Determination of the size and structure of the C-IV and C-III] emitting regions using microlensing

Frédéric Courbin, Georges Meylan, Alexander Patrick Eigenbrod

Aims. We aim to use microlensing taking place in the lensed quasar QSO 2237+0305 to study the structure of the broad line region (BLR) and measure the size of the region emitting the C-IV and C-III] lines. ...

2011

The application of Compressed Sensing Techniques in Radio Astronomy

Yves Wiaux

Radio interferometry probes astrophysical signals through incomplete and noisy Fourier measurements. The optimal reconstruction of these signals is an important topic not only for current astronomical imaging but also that of the next generation of radio t ...

IEEE2011

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Frédéric Courbin, Georges Meylan, Yves Revaz, Malte Tewes

We present accurate time delays for the quadruply imaged quasar HE 0435-1223. The delays were measured from 575 independent photometric points obtained in the R-band between January 2004 and March 2010. With seven years of data, we clearly show that quasar ...

2011