Thomas Augusteijn worked on data of the soft X-ray transient and black-hole candidate 4U1630-47. From IR photometry of this `micro-quasar' taken during its 1998 outburst the counterpart was identified. The properties of this source are similar to several other recently detected Soft X-ray transients which have relatively long-orbital periods (~few days) and early (B-F) type secondaries. He has also been involved in an extensive photometric study of the cataclysmic variable TV Columbae which resulted in the detection of the longest known superhump period. Theoretical models predict that these superhumps can only occur in systems where the secondary is at least three times lighter than the primary white dwarf. Given the 5.5-hr orbital period of the system, the secondary would have to be under-massive for its size even if the mass of the white dwarf is equal to the Chandrasekhar mass. He also continued his work on the identification of cataclysmic variables from the Calán-Tololo and Hamburg-ESO objective prism-plate surveys. The final aim of this project is to derive the true space density and study the period distribution of a well-defined sample of cataclysmic variables, which is essential for a proper understanding of the formation and evolution of these sources.
Chris Benn had great success with his discovery of 5 QSOs at redshifts greater than 3.8, from pilot observations of QSO candidates from the FIRST radio survey. He has subsequently been awarded more telescope time for a full-scale survey. He also worked on a project using standard-candle radio galaxies behind foreground spirals to directly measure the dust extinction at large radii. In this project he supervised the placement student Rachel Curran. He has also constructed a sample of QSOs lying near bright stars for adaptive-optics study using NAOMI and has already observed a subset of these with the TNG's tip-tilt system, and is PI on a proposal awarded WHT NAOMI time in 2001. His other research projects include: use of microJy radio sources to measure the star-formation rate as a function of redshift (PI on proposal awarded 4 WHT AF2 nights in 2001, with Treyer, Mobasher), investigation of dust extinction in QSOs (coI on 2001 allocations on the JKT and INT, with Vigotti, Sanchez, Gonzalez-Serrano), and investigation of the lunar atmosphere (with Verani, Barbieri). Finally Chris made a citation-based analysis of the relative impact of telescopes worldwide, now published in PASP.
Romano Corradi focused on several aspects of the late stages of stellar evolution in single and binary (symbiotic) stars, in particular the formation of small-scale, low-ionization microstrucutres in planetary nebulae (PNe). In addition he worked on observations and hydrodynamical modelling of PNe, with the aim of understanding their dynamical evolution and recovering the mass loss history from their stellar progenitors, and studied the outflows from symbiotic stars, which are ideal laboratories to investigate the effects of binary interactions on the mass loss history and geometry of red giants in detached binary systems. He also led a search and study of extragalactic PNe in the nearby galaxy M 33. One of the main highlights from his work is that hydrodynamical modelling of the PN NGC2438 lead to the discovery of `false' haloes in PNe, i.e. of ionised shells which are not the signature of mass loss variations during the AGB phase of the progenitor. They are instead the dynamical effect of the recombination front produced by a sudden drop of the luminosity of the PN central star on its way to a white dwarf.
Begoña Garcia-Lorenzo has studied the circumnuclear regions of Seyfert galaxies, concentrating in NGC2992, where evidence has been found for a rapidly rotating disk within the more slowly rotating bulge. The dynamical centres of these components are also found to be non-coincident and the first evidence for an optical counterpart to the radio emission from this galaxy has been found. She has also started work on an atlas of Starburst Galaxies and is carrying out a multi-wavelength study of Blue Compact Dwarf galaxies.
Johan Knapen worked mainly on the morphology and dynamics of disk galaxies, and the interrelations between the disk and bar regions with the circumnuclear and nuclear regions. He made a kinematical analysis of the circumnuclear region of the barred spiral M100 based upon high-quality WHT TAURUS data, proving that this is a resonant region, dynamically related directly to the disk which hosts it. The data also led to confirmation and refinement of results obtained from SPH modelling done previously by the same team. As a result of a large NIR imaging programme of Seyfert and non-active galaxies, Knapen found that Seyfert hosts are indeed, as long suspected but never proven, preferentially barred as compared to a matched but non-active control sample. However, the bars in Seyferts are statistically thicker, or weaker, than those on non-active galaxies, which was explained as a potential effect of the central mass concentration upon the elongated bar orbits. Knapen also published first results from a NIR imaging survery of central regions of barred galaxies, showing that spiral structure is ubiquitous in the central kpc. Knapen also continued work on the ages of stellar populations in the circumnuclear regions of galaxies, as based upon a combination of NIR imaging and spectroscopy with modelling, and spent considerable effort on completing a large optical broad-band and Halpha and NIR imaging survey of a complete sample of 57 large face-on spiral galaxies.
Danny Lennon worked on data resulting from a definitive high resolution spectroscopic survey of metal poor massive O-type stars in the Small Magellanic Cloud using HST/STIS, the ESO 3.6m and AAT telescopes. This survey is ultimately aimed at better understanding the spectra of high-redshift star forming galaxies and starburst galaxies, with important collatoral aims of investigating the poorly understood metallicity dependence of massive star evolution and mass-loss. First results indicate that rotation plays a crucial role in the evolution of massive stars and spectral synthesis of the high redshift lensed galaxy M1512-cB58 is more accurate with the new low metallicity spectral library. Important developments were the realization that B-stars contribute significantly to continuous star-forming models leading to the successful application for HST/STIS time in Cycle 10 (64 orbits; PI Lennon) and FUSE time (40 kseconds; CoI Lennon) in order to extend this work to B-stars and increase wavelength coverage. Lennon also worked on projects using supergiant stars as direct probes of metallicity in Local Group galaxies, producing the first results for the galaxies M31, M33 and NGC6822, as well as continuing investigations into the Magellanic Clouds and the central regions of the Milky Way. He has also worked on problems related to the influence of rotation on B-star evolution.
Chris Packham departed the ING in the summer of 2000. He worked on near-IR polarimetry of AGN, studying the structure in the nuclear or near-nuclear regions these objects. He was involved in detailed studies of studies of Cyg A in particular.
John Telting has continued his research on non-radial pulsations in early type stars, with case studies, and an ongoing observational project to establish the number of bright early-B type stars that show non-radial pulsations. One important case study was the pulsational behaviour of the primary in the close binary psi 2 Ori, which consists of two early-B type stars that orbit each other in 2.5 days. He discovered that the primary shows non-radial pulsations that are similar to that of other single, rotating stars in the spectral class region of the Beta Cephei stars. For this primary the question is whether the pulsations are induced by tidal effects or are due to the possible Beta Cephei nature of the star. This binary is the closest of its kind that shows such pulsational behaviour, and so is the most likely candidate for tidal excitation of pulsations in Beta Cephei stars, possibly leading to loss of orbital angular momentum. The answer to the above question has therefore implications for close binary evolution and for tidal capture in the central parts of globular clusters, as theorists assume that orbital angular momentum can be effectively dissipated through non-radial pulsations. Additionally, he has published a review article on the observational aspects of long-term variability in disks around Be stars.
Nic Walton has continued his work in the area of wide field surveys, both in his operational role as project scientist on the ING Wide Field Survey and as Co-PI on the Wide Angle Survey component. He is also the PI of a major new Wide Field Survey programme, The Local Group Census, which was one of the top rated survey programmes accepted in the second call for proposals. This survey, which has a strong ING representation among the CoIs (Corradi, Lennon, Skillen, Greimel) concentrates mainly on deep narrow-band imaging of all northern Local Group galaxies in order to uncover the populations of emission line objects such as planetary nebulae, Wolf-Rayet stars, luminous blue variables and HII regions. Evolutionary processes among a wide range of galaxy types will be investigated. Walton has used supernovae (SN) both to study physical processes and as cosmological probes. In collaboration with the Imperial College group led by Meikle he has continued to obtain high quality observational data on nearby bright SN. For the Type IIn SN 1998S, Fassia et al (2000), from analysis of IR and optical data, explain this SN's high IR excess as resulting from excited dust pre-existing in the circumstellar medium of the progenitor. In collaboration with colleagues in Paris, Cambridge, Stockholm and Barcelona, Walton led an observational campaign to search (based on EROS data) for, and followup, Type Ia SN at intermediate red shifts (see IAUC 7406). This data, together with SN resulting from 1999 searches, is now being analyzed. Walsh and Walton used the VLT to obtain deep spectra of planetary nebulae in Centaurus-A. The PN were used to probe the variation of chemical abundances. Walsh et al (2000) found a discrepancy between the metallicities found from PN and those found from stellar indices (which generally gave higher abundances).
In addition to the above, a number of ING scientific and technical staff in zero research time posts contribute to the research astmophere of the ING through their own interests. Such staff include Ian Skillen (ING Scheduler & Technical Secretary; the distance scale), Robert Greimel (Astronomy Software; high precision radial velocity measurement), Peter Sorensen (Telescope Operator; planetary nebulae), Javier Mendez (Librarian & Publicity Officer; Type Ia supernovae), Marco Azzaro (Telescope Operator; Galaxy evolution and mergers), Neil O'Mahoney (Telescope Operator; Adaptive optics), Sebastian Sanchez (Astronomy Administration; QSOs and galaxy clusters).
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Last Updated: March 22, 2001 S. Prins stp@ing.iac.es |