Rudolf Le Poole

• Leiden University

We present radio coverage of the 2019 outburst of the accreting millisecond X-ray pulsar (AMXP) SAX J1808.4–3658, obtained with MeerKAT. We compare these data to contemporaneous X-ray and optical measurements in order to investigate the coupling between accretion and jet formation in this system, while the optical light curve provides greater detai...

We present radio coverage of the 2019 outburst of the accreting millisecond X-ray pulsar SAX J1808.4-3658, obtained with MeerKAT. We compare these data to contemporaneous X-ray and optical measurements in order to investigate the coupling between accretion and jet formation in this system, while the optical lightcurve provides greater detail of the...

Context. Colour–magnitude diagrams reveal a population of blue (hot) sub-luminous objects with respect to the main sequence. These hot sub-luminous stars are the result of evolutionary processes that require stars to expel their obscuring, hydrogen-rich envelopes to reveal the hot helium core. As such, these objects offer a direct window into the h...

Colour-magnitude diagrams reveal a population of blue (hot) sub-luminous objects with respect to the main sequence. These hot sub-luminous stars are the result of evolutionary processes that require stars to expel their obscuring, hydrogen-rich envelopes to reveal the hot helium core. As such, these objects offer a direct window into the hearts of...

SXP 15.6 is a recently established Be star X-ray binary system (BeXRB) in the Small Magellanic Cloud (SMC). Like many such systems the variable X-ray emission is driven by the underlying behaviour of the mass donor Be star. It is shown here that the neutron star in this system is exceptionally close to spin equilibrium averaged over several years,...

SXP 15.6 is a recently established Be star X-ray binary system (BeXRB) in the Small Magellanic Cloud (SMC). Like many such systems the variable X-ray emission is driven by the underlying behaviour of the mass donor Be star. It is shown here that the neutron star in this system is exceptionally close to spin equilibrium averaged over several years,...

Astronomers require efficient automated detection and classification pipelines when conducting large-scale surveys of the (optical) sky for variable and transient sources. Such pipelines are fundamentally important, as they permit rapid follow-up and analysis of those detections most likely to be of scientific value. We therefore present a deep lea...

Astronomers require efficient automated detection and classification pipelines when conducting large-scale surveys of the (optical) sky for variable and transient sources. Such pipelines are fundamentally important, as they permit rapid follow-up and analysis of those detections most likely to be of scientific value. We therefore present a deep lea...

Magnetars are a promising candidate for the origin of Fast Radio Bursts (FRBs). The detection of an extremely luminous radio burst from the Galactic magnetar SGR J1935+2154 on 2020 April 28 added credence to this hypothesis. We report on simultaneous and non-simultaneous observing campaigns using the Arecibo, Effelsberg, LOFAR, MeerKAT, MK2 and Nor...

Context. The Advanced LIGO and Virgo gravitational wave observatories detected a signal on 2019 August 14 during their third observing run, named GW190814. A large number of electromagnetic facilities conducted follow-up campaigns in the search for a possible counterpart to the gravitational wave event, which was made especially promising given the...

Magnetars are a promising candidate for the origin of Fast Radio Bursts (FRBs). The detection of an extremely luminous radio burst from the Galactic magnetar SGR J1935+2154 on 2020 April 28 added credence to this hypothesis. We report on simultaneous and non-simultaneous observing campaigns using the Arecibo, Effelsberg, LOFAR, MeerKAT, MK2 and Nor...

The Advanced LIGO and Virgo gravitational wave observatories detected a signal on 2019 August 14 during their third observing run, named GW190814. A large number of electromagnetic facilities conducted follow-up campaigns in the search for a possible counterpart to the gravitational wave event, which was made especially promising given the early so...

ESO 149-G003 is a close-by, isolated dwarf irregular galaxy. Previous observations with the ATCA indicated the presence of anomalous neutral hydrogen (H i) deviating from the kinematics of a regularly rotating disc. We conducted follow-up observations with the MeerKAT radio telescope during the 16-dish Early Science programme as well as with the Me...

Context. The inner few au region of planet-forming disks is a complex environment. High angular resolution observations have a key role in understanding the disk structure and the dynamical processes at work. Aims. In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-mass star HD...

ESO 149-G003 is a close-by, isolated dwarf irregular galaxy. Previous observations with the ATCA indicated the presence of anomalous neutral hydrogen (HI) deviating from the kinematics of a regularly rotating disc. We conducted follow-up observations with the MeerKAT radio telescope during the 16-dish Early Science programme as well as with the Mee...

Aims. We present the results of three commissioning H I observations obtained with the MeerKAT radio telescope. These observations make up part of the preparation for the forthcoming MHONGOOSE nearby galaxy survey, which is a MeerKAT large survey project that will study the accretion of gas in galaxies and the link between gas and star formation. M...

We present the results of three commissioning HI observations obtained with the MeerKAT radio telescope. These observations make up part of the preparation for the forthcoming MHONGOOSE nearby galaxy survey, which is a MeerKAT large survey project that will study the accretion of gas in galaxies and the link between gas and star formation. We used...

We present phase-resolved spectroscopy, photometry, and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the inside-out projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and...

We present phase-resolved spectroscopy, photometry and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the inside-out projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and...

accepted for publication in A&A

Preliminary results are shown of our study on the metallicities and ages of the stellar populations present in different components along the line of sight to field #3 of the Palomar-Groningen Variable Star Survey (PG3) with synthetic Hertzsprung-Russell Diagrams (HRDs).

Twenty - two Wolf-Rayet stars (12 of type WN and 10 of type UC) were observed in the years 1986-1990 with the VBLUW photometer of Walraven. Eight (WC and WN) objects appeared to be constant. Five of the in total 14 variable objects will be discussed in the present paper: UR46 (WN3 pec), WR50 (WC6+a), WR55 (WN8), WR86 (WC7) and WR123 (WN8). Simultan...

The Multi-site All-Sky CAmeRA, MASCARA, is an instrument currently in the design phase, that is aimed to find the brightest transiting planet systems in the sky. It will consist of several stations across the globe, each monitoring the near-entire sky using a battery of CCD-detectors plus wide-field lenses, targeting stars in the V = 4 - 8 magnitud...

Exoplanet observations promise one day to unveil the presence of extraterrestrial life. Atmospheric compounds in strong chemical disequilibrium would point to large-scale biological activity just as oxygen and methane do in the Earth's atmosphere. The cancellation of both the Terrestrial Planet Finder and Darwin missions means that it is unlikely t...

The Multi-site All-sky CAmeRA MASCARA is an instrument concept consisting of several stations across the globe, with each station containing a battery of low-cost cameras to monitor the near-entire sky at each location. Once all stations have been installed, MASCARA will be able to provide a nearly 24-hr coverage of the complete dark sky, down to m...

The NOVA Fringe Tracker (NFT) is a proposed solution to the call by ESO for a second generation fringe tracking facility. This instrument at the VLTI will enable the cophasing of up to 6 telescopes simultaneously. Using broad band optics with detection from 1.2 to 2.4 microns, a unique configuration is employed that eliminates so-called “photometri...

After many unsuccessful attempts, ground-based transmission spectroscopy has finally yielded its first detections of planetary atmospheres. Redfield et al. (2008) have presented successful observations of sodium in HD 189733b using the Hobby-Eberly Telescope, and our group have detected the same chemical element in HD 209458b using archival Subaru...

The Polarization-Based Collimated Beam Combiner efficiently produces pairwise interference between beams from mul-tiple telescopes. An important feature is achieving "Photometric Symmetry" whereby interference measurements have no first-order sensitivity to wavefront perturbations (or photometric variations following spatial filtering) which otherw...

[Context] The first detection of an atmosphere around an extrasolar planet was presented by Charbonneau and collaborators in 2002. In the optical transmission spectrum of the transiting exoplanet HD209458b, an absorption signal from sodium was measured at a level of 0.023+-0.006%, using the STIS spectrograph on the Hubble Space Telescope. Despite s...

We present two separate ground-based detections of sodium in the transmission spectrum of HD 209458b. First we reanalyzed an archival data set from the HDS spectrograph on Subaru, which shows sodium at a >5σ level. Secondly, our preliminary results of a UVES/VLT data set indicate sodium absorption at a similar level, although the data cover the ecl...

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The start of NEVEC was initiated by the opportunity in the Netherlands to reinstate instrumental efforts in astronomy through a funding program for Top Research Schools', which brought about the creation of NOVA. The fact that considerable experience exists in Radio Astronomical imaging through interferometry (the Westerbork Synthesis Radio Telesco...

A search for extrasolar planets using the ESO VLTI PRIMA facility will become feasible in 2007. An astrometric accuracy of 10 micro-arcseconds will allow us to detect sub-Uranus mass planets (MUranus=14.5 MEarth) around the most nearby stars, as well as to conduct a planet search around stars of different ages. Most of the PRIMA hardware subsystems...

The PRIMA facility will implement dual-star astrometry at the VLTI. We have formed a consortium that will build the PRIMA differential delay lines, develop an astrometric operation and calibration plan, and deliver astrometric data reduction software. This will enable astrometric planet surveys with a target precision of 10μas. Our scientific goals...

Homothetic mapping is an aperture synthesis technique that allows interferometric imaging over a wide field-of-view. A laboratory experiment was set up to demonstrate the feasibility of this technique. Here, we present the first static experiments on homothetic mapping that have been done on the Delft Testbed for Interferometry (DTI). Before a chan...

A search for extrasolar planets using the ESO VLTI PRIMA facility will become feasible in 2007. An astrometric accuracy of 10 micro-arcseconds will allow us to detect sub-Uranus mass planets around the most nearby stars, as well as to conduct a planet search around stars of different ages. Most of the PRIMA hardware subsystems are currently being d...

Knowledge of the dispersion due to (humid) air in the light path of the Very Large Telescope Interferometer (VLTI) is crucial to obtaining good science data from MIDI, PRIMA and GENIE. To calculate the refraction due to air at infra red wavelengths in the ducts and delay line tunnel, the temperature and humidity has to be monitored during observati...

With ESO's Phase Referenced Imaging and Micro-arcsecond Astrometry (PRIMA) facility well into its procurement phase expectations are made about the astrometric performance. It appears that in almost all respects the instrumentally induced errors are expected to have Power Spectral densities well below those due to the atmosphere. However for the ta...

A special case of optical aperture synthesis, homothetic mapping, is the topic of this paper. It allows for a wide field of view for interferometric instruments. This paper describes a testbed constructed and tested in TNO-TPD in Delft (the Netherlands). This testbed is intended as a tool to investigate the ins and outs of homothetic mapping. The h...

The PRIMA facility will implement dual-star astrometry at the VLTI. We have formed a consortium that will build the PRIMA differential delay lines, develop an astrometric operation and calibration plan, and deliver astrometric data reduction software. This will enable astrometric planet surveys with a target precision of 10 μas. Our scientific goal...

Homothetic mapping is an aperture synthesis technique that allows interferometric imaging over a wide fieldof-view. A laboratory experiment was set up to demonstrate the feasibility of this technique. Here, we present the first static experiments on homothetic mapping that have been done on the Delft Testbed for Interferometry (DTI). Before a chang...

Darwin will spend part of the mission lifetime carrying out aperture synthesis imaging of star- and planet-forming regions, quasars and very distant galaxies in the 6-18 micron wavelength range. A wide field of view of at least 1" is highly desirable to fully exploit the scientific potential of the mission. This could be achieved by configuring Dar...

ESA's DARWIN will be an interferometric mission carrying out high-resolution astrophysical observations as well as the detection/characterization of earthlike exoplanets. In this paper, the current status and development perspectives of the Darwin imaging mode are discussed. First, overall system aspects are addressed including expected sensitivity...

A wideband interferometer is sensitive to the effects of longitudinal dispersion which affect the interfering light beams unequally. At shorter wavelengths the major effect of dispersion is from dry air itself, while at mid infrared wavelengths the effect of water vapor is dominant. MIDI, the future 10 micron instrument of the VLTI, will experience...

With the imaging and astrometric facilities coming up as the next major leaps forward in interferometry at the VLT we examine options for beam combination of multiple beams, both in the Science Channel and in the Reference Channel. We look at the science we expect to become feasible as soon as phase referencing becomes available, and the hopes for...

The field of view for the first generation VLTI instruments (VINCI, MIDI, AMBER etc.) is limited to the diffraction limited beam of a single telescope (for a 8.2-meter telescope at 2-micron this is 0.6 arcseconds). However, the VLTI infrastructure with its main delay lines, transfers a 2 arcseconds beam from the telescopes to the interferometric la...

A wideband interferometer is sensitive to the effects of longitudinal dispersion which affect the interfering light beams unequally. At shorter wavelengths the major effect of dispersion is from dry air itself, while at mid infrared wavelengths the effect of water vapor is dominant. MIDI, the future 10 micron instrument of the VLTI, will experience...

ESA's DARWIN will be an interferometric mission carrying out high-resolution astrophysical observations as well as the detection/characterization of earthlike exoplanets. In this paper, the current status and development perspectives of the Darwin imaging mode are discussed. First, overall system aspects are addressed including expected sensitivity...

A wideband interferometer is sensitive to the eects of longitudinal dispersion which aect the interfering light beams unequally. At shorter wavelengths the major eect of dispersion is from dry air itself, while at mid infrared wavelengths the eect of water vapor is dominant. MIDI, the future 10 micron instrument of the VLTI, will experience signi c...

We publish 622 CCD photometric sequences in the Johnson-Kron-Cousins standard system, distributed both in the northern and southern hemispheres, useful for the calibration of photographic photometry of Schmidt survey plates. The collection and reduction of the CCD data presented here are part of a long-term program devoted to the construction of th...

A proper motion study is presented of the globular cluster omega Centauri. Based on 100 plates obtained with the Yale-Columbia 66 cm (26 inch) refractor, and ranging in epoch from 1931 till 1935 and 1978 till 1983, differential proper motions are obtained for 9847 stars. The limiting magnitude (photographic) is 16.0 for the centre of the cluster, 1...

The tables present the photometric and astrometric results of an extensive proper motion study of the globular cluster omega Centauri: information on the photographic plates used, variability analysis, astrometric data for 9847 stars, membership determination and surface density profile, cluster proper motion dispersions and systematics and cross-r...

A proper motion study is presented of the globular cluster ω Centauri. Based on 100 plates obtained with the Yale-Columbia 66 cm (26 inch) refractor, and ranging in epoch from 1931 till 1935 and 1978 till 1983, differential proper motions are obtained for 9847 stars. The limiting magnitude (photographic) is 16.0 for the centre of the cluster, 16.5...

Our goal is to fly a diffraction limited 2.5-m optical telescope and coronagraph on long duration balloon flights at an altitudes of 35 km above 99.99% of the Earth's atmosphere to search for Jupiter-like planets around nearby stars. Analysis of radiosonde data from Mauna Kea and the South Pole suggests that at optical wavelengths and altitudes abo...

In order to improve the efficiency with which SCUBA (see elsewhere in this conference) operates on the JCMT, a new and innovative data acquisition system has been developed and will be implemented shortly. The fundamental innovation is in the operation of the telescope secondary mirror, merging the function of chopping for sky-elimination, and 'jig...

b DESPA / Observatoire de Paris; 5 Place Jules Janssen; F-92195 Meudon; France c Observatoire de Bordeaux; BP 89; Avenue P. Semirot; F-33270 Floriac; France d Max-Planck-Institut f ur Radioastronomie; Auf dem H ugel 69; D-53121 Bonn; Germany e Max-Planck-Institut f ur Extraterrestrische Physik; Giessenbachstr.; Postfach 1603; D-85470 Garching; Germ...

In order to improve the efficiency with which SCUBA (see elsewhere in this conference) operates on the JCMT, a new and innovative data acquisition system has been developed and will be implemented shortly. The fundamental innovation is in the operation of the telescope secondary mirror, merging the function of chopping for sky-elimination, and 'jig...

In order to improve the efficiency with which SCUBA (see elsewhere in this conference) operates on the JCMT , a new and innovative data acquisition system has been developed and will be implemented shortly. The fundamental innovation is in the operation of the telescope secondary mirror, merging the function of chopping for sky-elimination, and 'ji...

We present results from the analysis of spectra of the fast rotating active giant star FK Comae Berenices. The extended emission is interpreted as arising in giant active loops and prominences. The absorption is due to a shell of cold and dense gas (like solar filaments).

We present results from the analysis of spectra of the fast rotating giant FK Comae Berenices, obtained with the recently commissioned ESA-MUSICOS spectrograph at the INT and with the Aurelie spectrograph at the OHP. The Balmer lines broad emission is modelled as arising from structures extending up to 4 stellar radii. The absorption is modelled du...

We present the first results of a comprehensive census of the stellar content of the nearby OB associations based on Hipparcos positions, proper motions and parallaxes for 12842 candidate member stars distributed over 21 fields on the sky. We use a new method to identify moving groups in these fields (see de Bruijne et al., these proceedings). Prev...

This is the first paper in a series in which we study the kinematical structure and dynamical evolution of OB associations and young stellar clusters. By means of high-resolution high-S/N spectroscopic observations, we aim at obtaining accurate stellar radial and rotational velocities and information on binarity in a selected number of such systems...

The principal observational characteristics of the Hipparcos Catalogue, and a summary of its main astrometric and photometric properties, are presented. Median astrometric standard errors (in position, parallax, and annual proper motion) are in the range 0.7-0.9 milliarcsec (mas) for stars brighter than 9 mag at the catalogue epoch (J1991.25). The...

Distances to the recently-discovered planetary system candidates, 47 UMa, 70 Vir and 51 Peg, are presented, based on absolute trigonometric parallaxes from the global reduction of the ESA Hipparcos astrometry satellite data. Standard errors of the parallaxes are in the range 0.66-0.76mas (milliarcsec), with resulting distances accurate to around 1...

We outline the principles by which absolute trigonometric parallaxes have been derived from the first 30 months of data acquired by the Hipparcos astrometry satellite. Distributions of the parallaxes and formal errors of more than one hundred thousand stars are presented, indicating median standard errors of about 1.5milliarcsec (mas). Tests which...

New reductions of Schmidt plate measurements have been performed, using preliminary Hipparcos and Tycho data for the astrometric reference stars. The measurements reported here have been obtained with the MAMA automatic measuring machine of the Centre d'Analyse des Images in Paris. The Hipparcos data considered, the `combined 30-month solution', or...

We describe a concept for an interferometric space mission dedicated to global (wide-angle) astrometry. The GAIA satellite contains two small (baseline APEQ 3 m) optical interferometers of the Fizeau type, mechanically set at a large and fixed angle to each other. Each interferometer has a field of view of about one degree. Continuous rotation of t...

Preliminary results are shown of our study on the metallicities and ages of the stellar populations present in different components along the line of sight to field #3 of the Palomar- Groningen Variable Star Survey (PG3) with synthetic Hertzsprung-Russell Diagrams (HRDs).

A simple geometrical model of the Hipparcos telescope is described whereby the relative positions and orientations of critical optical elements can be derived from the field-to-grid transformation determined as part of the normal data processing. The instrument is very stable on time scales of hours, but secular drifts of the order of 0.1 micron/d...

A positional accuracy of 1.5 arcsec rms at the epoch of observation was required for the stars proposed for observation by the Hipparcos satellite. How this was achieved by collecting and investigating already available positions and proper motions in a special compilation catalog, carrying out new ground-based measurements, and a detailed analysis...

Vol. 1 - 5: The Hipparcos Input Catalogue. Vol. 6: Annex 1. Double and multiple stars. Vol. 7: Annex 2. The atlas of identification charts for faint stars. Annex 3. Identification charts for stars in galactic open clusters. Annex 4. Identification charts for stars in the Magellanic Clouds. The Hipparcos Input Catalogue was constructed as the observ...

An investigation into the achieved fidelity of copies of a large Schmidt telescope plate is reported. Atlas quality copies both on glass and film and the original are compared. Two glass copies made through different intermediate positives are used to look at the fidelity of the separate positives. The general belief that glass copies are capable o...

The main features of the data analysis methods adopted by FAST in the calibration and processing of the Hipparcos data are discussed. The structure of the data reduction software is examined, and the actual processing and evaluation are presented. Attention is given to the first look task, the calibration task, data preparation, attitude determinat...

A procedure for an automatic search and measurement of artificial targets in digital images for elose-range photogrammetric applications is presented. Photographs taken with a sem i metric 6x6 camera were digitized by the "ASTROSCAN" at the Sterrewacht Leiden. The especially designed targets contain a circular barcode for automatic identification....

A sample of IRAS sources is examined to determine whether the OH 1612 MHz double-peaked spectra characteristic of OH/IR stars can be found in the Galaxy's bulge. Reviews of several surveys are presented with reference to corresponding theoretical investigations. The survey includes a complete list of relevant IRAS colors F(12) greater than 3Jy with...

The origin and state of evolution of the Galactic bulge is studied using all stars present in Baade-Plaut field 3. This 6.5 x 6.5-deg field is centered at l = 0 deg and b = -10 deg. Preliminary results are shown for a blue and red plate pair. For a small 1-deg x 1-deg field near the plate center an uncalibrated color-magnitude diagram is presented...

3′×3′ pictures centered onHipparcos Input Catalog Objects (L3-2 INCA) have been produced in Leiden from measuring 87 plates of the Dutch glass copy of the ESO Quick Blue Survey by use of astroscan. We extract from this material our studied sample, consisting of 19825 regions around INCA objects brighter than 11 mag and outside open clusters. It ena...

In the context of task 4000 (Astrometric measurements) the authors have measured at Leiden Observatory some 87 glass copy plates of the ESO Quick Blue survey in an area near the galactic plane. The coverage was (incomplete) between 260° and 350° in longitude and latitude between -20° and +20°.

A multiaperture optical interferometer, mounted on a single structure in space is proposed. The design is guided by radio aperture synthesis experience. The essential element is the use of a bright nearby reference object to equalize optical pathlengths in the array during long integrations on faint objects. The instrument has to be operated on an...

The extended 100 micron emission discovered by IRAS and called "interstellar cirrus" is also visible on modern sky survey Schmidt plates as faint, blue emission. In this paper the infrared emission and optical appearance for two "cirrus" clouds are compared. A dust temperature of about 20K is derived and a luminosity at 100 micron of about 9 MJy/Sr...

A means of calibrating the HIPPARCOS grid optically is proposed. The technique uses the demagnified image of a detector array as "reference ruler", and is expected to be capable of such accuracy, that errors in gridgeometry can be eliminated from the total HIPPARCOS error budget.

The Westerbork Synthesis Radio Telescope (WSRT) has now been used to make source surveys at frequencies of 610 and 1415 MHz. This paper summarizes the results concerning source counts and anisotropies in the distribution of sources from those surveys not concerned with clusters of galaxies.

The Westerbork Synthesis Radio Telescope (WSRT) has now been used to make source surveys at frequencies of 610 and 1415 MHz. This paper summarizes the results concerning source counts and anisotropies in the distribution of sources from those surveys not concerned with clusters of galaxies.