Publications (75)
Zeeman tomography of magnetic white dwarfs III. The 70-80 Megagauss magnetic field of PG 1015+014
F. Euchner, S. Jordan, K. Beuermann +2
<b>Aims:</b> We analyse the magnetic field geometry of the magnetic DA white dwarf PG 1015+014 with our Zeeman tomography method.<br> <b>Methods:</b> This study is based on rotatio…
The First Look of Gaia: Daily data quality and instrument health assessment with automated early warnings
M. Altmann, Z. Balog, W. Löffler +15
The ESA Gaia mission is a 10+ year astrometric whole-sky scan, demanding consistent data quality over the whole timespan of operations Aims. The Gaia First Look (FL) is a system wh…
Gaia Data Release 1: The archive visualisation service
A. Moitinho, A. Krone-Martins, H. Savietto +31
Context: The first Gaia data release (DR1) delivered a catalogue of astrometry and photometry for over a billion astronomical sources. Within the panoply of methods used for data e…
white dwarfs within 40 pc III: spectroscopic observations of new candidates in the southern hemisphere
Mairi W. O'Brien, P. -E. Tremblay, N. P. Gentile Fusillo +31
We present a spectroscopic survey of 248 white dwarf candidates within 40 pc of the Sun; of these 244 are in the southern hemisphere. Observations were performed mostly with the Ve…
On the circularly polarized optical emission from AE Aquarii
N. R. Ikhsanov, S. Jordan, N. G. Beskrovnaya
The reported nightly mean value of the circular polarization of optical emission observed from the close binary system AE Aqr is 0.06% (+-) 0.01%. We discuss a possibility that the…
Gaia Focused Product Release: Sources from Service Interface Function image analysis -- Half a million new sources in omega Centauri
Gaia Collaboration, K. Weingrill, A. Mints +400
Gaia's readout window strategy is challenged by very dense fields in the sky. Therefore, in addition to standard Gaia observations, full Sky Mapper (SM) images were recorded for ni…
Phase-resolved far-ultraviolet HST spectroscopy of the peculiar magnetic white dwarf RE J0317-853
M. R. Burleigh, S. Jordan, W. Schweizer
We present phase resolved FUV HST FOS spectra of the rapidly rotating, highly magnetic white dwarf RE J0317-853. Using these data, we construct a new model for the magnetic field m…
Gaia Data Release 3: Reflectance spectra of Solar System small bodies
Gaia Collaboration, L. Galluccio, M. Delbo +444
The Gaia mission of the European Space Agency (ESA) has been routinely observing Solar System objects (SSOs) since the beginning of its operations in August 2014. The Gaia data rel…
Gaia Early Data Release 3: Acceleration of the solar system from Gaia astrometry
Gaia Collaboration, S. A. Klioner, F. Mignard +414
Context. Gaia Early Data Release 3 (Gaia EDR3) provides accurate astrometry for about 1.6 million compact (QSO-like) extragalactic sources, 1.2 million of which have the best-quali…
Gaia Data Release 2: The astrometric solution
L. Lindegren, J. Hernandez, A. Bombrun +87
Gaia Data Release 2 (Gaia DR2) contains results for 1693 million sources in the magnitude range 3 to 21 based on observations collected by the European Space Agency Gaia satellite…
Swift heavy ion irradiation of GaSb: from ion tracks to nano-porous networks
C. Notthoff, S. Jordan, A. Hadley +5
Ion track formation, amorphisation, and the formation of porosity in crystalline GaSb induced by 185 MeV Au swift heavy ion irradiation is investigated as a function of flu…
The fraction of DA white dwarfs with kilo-Gauss magnetic fields
S. Jordan, R. Aznar Cuadrado, R. Napiwotzki +2
Weak magnetic field has been searched for on only a small number of white dwarfs. Current estimates for white dwarfs with fields in excess of 1MG are about 10%; according to previo…
Discovery of kilogauss magnetic fields in three DA white dwarfs
R. Aznar Cuadrado, S. Jordan, R. Napiwotzki +3
We have detected longitudinal magnetic fields between 2 and 4 kG in three (WD 0446790, WD 1105048, WD 2359434) out of a sample of 12 normal DA white dwarfs by using optica…
The fraction of DA white dwarfs with kilo-Gauss magnetic fields
S. Jordan, R. Aznar Cuadrado, R. Napiwotzki +2
Current estimates for white dwarfs with fields in excess of 1MG are about 10%; according to our first high-precision circular-polarimetric study of 12 bright white dwarfs with the…
Kilo-gauss Magnetic Fields in three DA White Dwarfs
R. Aznar Cuadrado, S. Jordan, R. Napiwotzki +3
We have detected longitudinal magnetic fields between 2 and 4kG in three normal DA white dwarfs (WD0446-790, WD1105-048, WD2359434) out of a sample of 12 by using optical spectr…
Gaia Data Release 3: Pulsations in main sequence OBAF-type stars
Gaia Collaboration, J. De Ridder, V. Ripepi +445
The third Gaia data release provides photometric time series covering 34 months for about 10 million stars. For many of those stars, a characterisation in Fourier space and their v…
Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
L. Lindegren, U. Lammers, U. Bastian +80
Gaia Data Release 1 (Gaia DR1) contains astrometric results for more than 1 billion stars brighter than magnitude 20.7 based on observations collected by the Gaia satellite during…
Surface Magnetic Field Distributions of the White Dwarfs PG 1015+014 and HE 1045-0908
F. Euchner, S. Jordan, K. Reinsch +2
We have applied the method of Zeeman tomography to analyze the surface magnetic field structures of the white dwarfs PG 1015+014 and HE 1045-0908 from spin-phase resolved flux and…
Quantum Spacetime, from a Practitioner's Point of View
J. Ambjorn, S. Jordan, J. Jurkiewicz +1
We argue that theories of quantum gravity constructed with the help of (Causal) Dynamical Triangulations have given us the most informative, quantitative models to date of quantum…
Zeeman tomography of magnetic white dwarfs: General method and application to EF Eridani
F. Euchner, K. Beuermann, K. Reinsch +3
We have developed a new method to derive the magnetic field distribution on the surfaces of rotating magnetic white dwarfs from phase-resolved flux and circular polarization spectr…
A catalogue of white dwarfs in Gaia EDR3
N. P. Gentile Fusillo, P. -E. Tremblay, E. Cukanovaite +7
We present a catalogue of white dwarf candidates selected from Gaia early data release three (EDR3). We applied several selection criteria in absolute magnitude, colour, and Gaia q…
Gaia Data Release 1. Testing the parallaxes with local Cepheids and RR Lyrae stars
Gaia Collaboration, G. Clementini, L. Eyer +588
Parallaxes for 331 classical Cepheids, 31 Type II Cepheids and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release…
Discovery of magnetic fields in hot subdwarfs
S. J. O'Toole, S. Jordan, S. Friedrich +1
We present initial results of a project to measure mean longitudinal magnetic fields in a group of sdB/OB/O stars. The project was inspired by the discovery of three super-metal-ri…
Quantum Approximate Optimization of the Long-Range Ising Model with a Trapped-Ion Quantum Simulator
G. Pagano, A. Bapat, P. Becker +13
Quantum computers and simulators may offer significant advantages over their classical counterparts, providing insights into quantum many-body systems and possibly improving perfor…
Gaia Data Release 2: Observational Hertzsprung-Russell diagrams
Gaia Collaboration, C. Babusiaux, F. van Leeuwen +450
We highlight the power of the Gaia DR2 in studying many fine structures of the Hertzsprung-Russell diagram (HRD). Gaia allows us to present many different HRDs, depending in partic…
White paper: Gaia and the end states of stellar evolution
M. A Barstow, S. L. Casewell, S. Catalan +18
This is the product of a Gaia GREAT workshop on "Gaia and the end states of stellar evolution" held at the University of Leicester in April 2011.
Large Interferometer For Exoplanets (LIFE): IX. Assessing the Impact of Clouds on Atmospheric Retrievals at Mid-Infrared Wavelengths with a Venus-Twin Exoplanet
B. S. Konrad, E. Alei, S. P. Quanz +10
The Large Interferometer For Exoplanets (LIFE) initiative aims to develop a space based mid-infrared (MIR) nulling interferometer to measure the thermal emission spectra of tempera…
Zeeman tomography of magnetic white dwarfs IV. The complex field structure of the polars EF Eri, BL Hyi, and CP Tuc
K. Beuermann, F. Euchner, K. Reinsch +2
The magnetic fields of the accreting white dwarfs (WDs) in magnetic cataclysmic variables (mCVs) determine the accretion geometries, the emission properties, and the secular evolut…
The progenitors of magnetic white dwarfs in open clusters
B. Külebi, J. Kalirai, S. Jordan +1
According to the fossil-field hypothesis magnetic fields are remnants of the previous stages of evolution. However, population synthesis calculations are unable to reproduce the ma…
Gaia Early Data Release 3: The astrometric solution
L. Lindegren, S. A. Klioner, J. Hernández +94
Gaia Early Data Release 3 (Gaia EDR3) contains results for 1.812 billion sources in the magnitude range G = 3 to 21 based on observations collected by the European Space Agency Gai…
Spectroscopic and photometric studies of white dwarfs in the Hyades
P. -E. Tremblay, E. Schilbach, S. Röser +3
The Hyades cluster is known to harbour ten so-called classical white dwarf members. Numerous studies through the years have predicted that more than twice this amount of degenerate…
Gaia Focused Product Release: Radial velocity time series of long-period variables
Gaia Collaboration, M. Trabucchi, N. Mowlavi +403
The third Gaia Data Release (DR3) provided photometric time series of more than 2 million long-period variable (LPV) candidates. Anticipating the publication of full radial-velocit…
PG 1258+593 and its common proper motion magnetic white dwarf counterpart
J. Girven, B. T. Gänsicke, B. Külebi +4
We identify SDSS J130033.48+590407.0 as a common proper motion companion to the well-studied DA white dwarf PG 1258+593 (GD322). The system lies at a distance of 68 +/- 3 pc, where…
Zeeman tomography of magnetic white dwarfs, I. Reconstruction of the field geometry from synthetic spectra
F. Euchner, S. Jordan, K. Beuermann +2
We have computed optical Zeeman spectra of magnetic white dwarfs for field strengths between 10 and 200MG and effective temperatures between 8000 and 40000K. They form a database c…
Discovery of magnetic fields in hot subdwarfs
S. J. O'Toole, S. Jordan, S. Friedrich +1
We present polarisation measurements of sdB and sdO stars using FORS1 on the VLT. The observations were made as part of a project to determine whether magnetic fields in two super-…
Second- and First-Order Phase Transitions in CDT
J. Ambjorn, S. Jordan, J. Jurkiewicz +1
Causal Dynamical Triangulations (CDT) is a proposal for a theory of quantum gravity, which implements a path-integral quantization of gravity as the continuum limit of a sum over p…
Gaia Data Release 3: Chemical cartography of the Milky Way
Gaia Collaboration, A. Recio-Blanco, G. Kordopatis +447
Gaia DR3 opens a new era of all-sky spectral analysis of stellar populations thanks to the nearly 5.6 million stars observed by the RVS and parametrised by the GSP-spec module. The…
Catalog of magnetic white dwarfs with hydrogen dominated atmospheres
L. L. Amorim, S. O. Kepler, Baybars Külebi +2
White dwarfs are excellent research laboratories as they reach temperatures, pressures, and magnetic fields that are unattainable on Earth. To better understand how these three phy…
Gaia Early Data Release 3: The Galactic anticentre
Gaia Collaboration, T. Antoja, P. McMillan +417
We aim to demonstrate the scientific potential of the Gaia Early Data Release 3 (EDR3) for the study of the Milky Way structure and evolution. We used astrometric positions, proper…
Gaia Data Release 3: A Golden Sample of Astrophysical Parameters
Gaia Collaboration, O. L. Creevey, L. M. Sarro +445
Gaia Data Release 3 (DR3) provides a wealth of new data products for the astronomical community to exploit, including astrophysical parameters for a half billion stars. In this wor…
The Gaia DR1 Mass-Radius Relation for White Dwarfs
P. -E. Tremblay, N. Gentile-Fusillo, R. Raddi +8
The Gaia Data Release 1 (DR1) sample of white dwarf parallaxes is presented, including 6 directly observed degenerates and 46 white dwarfs in wide binaries. This data set is combin…
A second-order phase transition in CDT
J. Ambjorn, S. Jordan, J. Jurkiewicz +1
Causal Dynamical Triangulations (CDT) are a concrete attempt to define a nonperturbative path integral for quantum gravity. We present strong evidence that the lattice theory has a…
Classification and parameterisation of a large Gaia sample of white dwarfs using XP spectra
O. Vincent, M. A. Barstow, S. Jordan +3
The latest Gaia data release in July 2022, DR3, added a number of important data products to those available in earlier releases, including radial velocity data, information on ste…
Gaia Data Release 3: The extragalactic content
Gaia Collaboration, C. A. L. Bailer-Jones, D. Teyssier +444
The Gaia Galactic survey mission is designed and optimized to obtain astrometry, photometry, and spectroscopy of nearly two billion stars in our Galaxy. Yet as an all-sky multi-epo…
Discovery of magnetic fields in CPNs
S. Jordan, K. Werner, S. J. O'Toole
For the first time we have directly detected magnetic fields in central stars of planetary nebulae by means of spectro-polarimetry with FORS1 at the VLT. In all four objects of our…
De Sitter Universe from Causal Dynamical Triangulations without Preferred Foliation
S. Jordan, R. Loll
We present a detailed analysis of a recently introduced version of Causal Dynamical Triangulations (CDT) that does not rely on a distinguished time slicing. Focussing on the case o…
Discovery of four white dwarfs with strong magnetic fields by the Hamburg/ESO Survey
D. Reimers, S. Jordan, D. Koester +3
Four magnetic white dwarfs have been found in the course of the Hamburg/ESO Survey for bright QSOs. The objects have been selected as QSO candidate on the basis of its blue continu…
Four magnetic DB white dwarfs discovered by the Hamburg/ESO survey
D. Reimers, S. Jordan, V. Beckmann +2
We report on seven peculiar faint blue stars found in the course of the Hamburg/ESO survey (HES) which appear to be magnetic white dwarfs (WDs) with non-hydrogen spectra. We show i…
A 150MG magnetic white dwarf in the cataclysmic variable RX J1554.2+2721
B. T. Gaensicke, S. Jordan, K. Beuermann +4
We report the detection of Zeeman-split Lalpha absorption pi and sigma+ lines in the far-ultraviolet Hubble Space Telescope/Space Telescope Imaging Spectrograph spectrum of the mag…
Magnetic white dwarfs in the Early Data Release of the Sloan Digital Sky Survey
B. T. Gaensicke, F. Euchner, S. Jordan
We have identified 7 new magnetic DA white dwarfs in the Early Data Release of the Sloan Digital Sky Survey. Our selection strategy has also recovered all the previously known magn…
The Structure and Origin of Magnetic Fields on Accreting White Dwarfs
K. Reinsch, F. Euchner, K. Beuermann +2
We have started a systematic study of the field topologies of magnetic single and accreting white dwarfs using Zeeman tomography. Here we report on our analysis of phase-resolved f…
Gaia Data Release 3: Summary of the content and survey properties
Gaia Collaboration, A. Vallenari, A. G. A. Brown +453
We present the third data release of the European Space Agency's Gaia mission, GDR3. The GDR3 catalogue is the outcome of the processing of raw data collected with the Gaia instrum…
Zeeman tomography of magnetic white dwarfs II. The quadrupole-dominated magnetic field of HE 1045-0908
F. Euchner, K. Reinsch, S. Jordan +2
We report time-resolved optical flux and circular polarization spectroscopy of the magnetic DA white dwarf HE 1045-0908 obtained with FORS1 at the ESO VLT. Considering published re…
Stationary components of HeI in strong magnetic fields - a tool to identify magnetic DB white dwarfs
S. Jordan, P. Schmelcher, W. Becken
In only three of the 61 known magnetic white dwarfs helium has been identified unambiguously while about 20% of all non-magnetic stars of this class are known to contain HeI or HeI…
Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)
Gaia Collaboration, S. A. Klioner, L. Lindegren +448
Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3…
Causal Dynamical Triangulations without Preferred Foliation
S. Jordan, R. Loll
We introduce a generalized version of the Causal Dynamical Triangulations (CDT) formulation of quantum gravity, in which the regularized, triangulated path integral histories retai…
Evidence for helium in the magnetic white dwarf GD229
S. Jordan, P. Schmelcher, W. Becken +1
The nature of the strong absorption features in the white dwarf GD229 has been a real mystery ever since it was found to be magnetic in 1974. All attempts to explain the spectrum b…
Gaia Data Release 3: Mapping the asymmetric disc of the Milky Way
Gaia Collaboration, R. Drimmel, M. Romero-Gomez +453
With the most recent Gaia data release the number of sources with complete 6D phase space information (position and velocity) has increased to well over 33 million stars, while ste…
CDT meets Horava-Lifshitz gravity
J. Ambjorn, A. Gorlich, S. Jordan +2
The theory of causal dynamical triangulations (CDT) attempts to define a nonperturbative theory of quantum gravity as a sum over space-time geometries. One of the ingredients of th…
Gaia Early Data Release 3: The Gaia Catalogue of Nearby Stars
Gaia Collaboration, R. L. Smart, L. M. Sarro +420
We produce a clean and well-characterised catalogue of objects within 100\,pc of the Sun from the \G\ Early Data Release 3. We characterise the catalogue through comparisons to the…
white dwarfs within 40 pc I: spectroscopic observations of new candidates
P. -E. Tremblay, M. A. Hollands, N. P. Gentile Fusillo +30
We present a spectroscopic survey of 230 white dwarf candidates within 40 pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were select…
Gaia First Look
S. Jordan, U. Bastian, H. Lenhardt +3
A complicated and ambitious space mission like Gaia needs a careful monitoring and evaluation of the functioning of all components of the satellite. This has to be performed on dif…
Gaia Early Data Release 3: Structure and properties of the Magellanic Clouds
Gaia Collaboration, X. Luri, L. Chemin +417
We compare the Gaia DR2 and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show…
Phase-resolved HST/STIS spectroscopy of the exposed white dwarf in the high-field polar AR UMa
B. T. Gaensicke, G. D. Schmidt, S. Jordan +1
Phase-resolved HST/STIS ultraviolet spectroscopy of the high-field polar AR UMa confirms that the WD photospheric Ly alpha Zeeman features are formed in a magnetic field of ~200 MG…
Gaia Data Release 3: Stellar multiplicity, a teaser for the hidden treasure
Gaia Collaboration, F. Arenou, C. Babusiaux +447
The Gaia DR3 Catalogue contains for the first time about eight hundred thousand solutions with either orbital elements or trend parameters for astrometric, spectroscopic and eclips…
Detecting short period variable stars with Gaia
M. Varadi, L. Eyer, S. Jordan +2
We analyzed the frequency domain of time series of simulated ZZ Ceti light-curves to investigate the detectability and period recovery performance of short period variables (period…
Gaia Focused Product Release: A catalogue of sources around quasars to search for strongly lensed quasars
Gaia Collaboration, A. Krone-Martins, C. Ducourant +398
Context. Strongly lensed quasars are fundamental sources for cosmology. The Gaia space mission covers the entire sky with the unprecedented resolution of " in the optical, ma…
Gaia Early Data Release 3: Summary of the contents and survey properties
Gaia Collaboration, A. G. A Brown, A. Vallenari +423
We present the early installment of the third Gaia data release, Gaia EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented…
Weak magnetic fields in white dwarfs and their direct progenitors?
S. Jordan, S. Bagnulo, J. Landstreet +6
We have carried out a re-analysis of polarimetric data of central stars of planetary nebulae, hot subdwarfs, and white dwarfs taken with FORS1 (FOcal Reducer and low dispersion Spe…
On the incidence of weak magnetic fields in DA white dwarfs
J. D. Landstreet, S. Bagnulo, G. G. Valyavin +4
Context: About 10% of white dwarfs have magnetic fields with strength in the range between about 10^5 and 3x10^8 G. It is not known whether the remaining white dwarfs are not magne…
Analysis of hydrogen-rich magnetic white dwarfs detected in the Sloan Digital Sky Survey
B. Kulebi, S. Jordan, F. Euchner +2
We model the structure of the surface magnetic fields of the hydrogen-rich white dwarfs in the SDSS. We have calculated a grid of state-of-the-art theoretical optical spectra of hy…
Do Magnetic Fields Prevent Hydrogen from Accreting onto Cool Metal-line White Dwarf Stars?
S. Friedrich, S. Jordan, D. Koester
It is generally assumed that metals detected in the spectra of a few cool white dwarfs cannot be of primordial origin and must be accreted from the interstellar medium. However, th…
Temperature determination of the cool DO white dwarf HD149499B from EUVE observations
S. Jordan, R. Napiwotzki, D. Koester +1
We present a LTE model atmosphere analysis of the medium and long wavelength spectrum of the cool DO white dwarf HD149499B. This observation in the spectral range 230-700 A supplem…
Gaia Data Release 1. Open cluster astrometry: performance, limitations, and future prospects
Gaia Collaboration, F. van Leeuwen, A. Vallenari +589
Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry,…
Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry
Gaia Collaboration, P. Panuzzo, T. Mazeh +412
Gravitational waves from black-hole merging events have revealed a population of extra-galactic BHs residing in short-period binaries with masses that are higher than expected base…