Search Publications
Mid-infrared imaging and spectroscopy of the enigmatic cocoon stars in the Quintuplet Cluster
Blommaert, J. A. D. L.; Moneti, A.; Najarro, F. +2 more
In an attempt to determine the nature of the enigmatic cocoon stars in the Quintuplet Cluster, we have obtained mid-infrared imaging and spectrophotometry of the cluster, using the CAM and SWS instruments on ISO, using SpectroCam-10 on the Palomar 5 m telescope, and NICMOS on HST. The spectra show smooth continua with various dust and ice absorpti…
Infrared optical properties of spinels. A study of the carrier of the 13, 17 and 32 mu m emission features observed in ISO-SWS spectra of oxygen-rich AGB stars
Mutschke, H.; Posch, Th.; Kerschbaum, F. +2 more
In a previous paper, we have proposed magnesium aluminium spinel to be the carrier of the 13 and 17 mu m band features observed in the ISO spectra of some red giants. The IR optical properties of spinel strongly depend on its chemistry and its internal structure. To study the dependence of spinel's IR-spectra on its aluminium content, we have synt…
Infrared dark clouds from the ISOGAL survey. Constraints on the interstellar extinction curve
Ganesh, S.; Teyssier, D.; Pérault, M. +1 more
The ISO galactic survey provides images of the inner disk in two broad filters (around 7 and 15 mu m) over some 15 square degrees, away from the brightest star forming regions. A multiresolution analysis of the images leads to a catalogue of infrared dark clouds, most of which are condensed cores of large molecular clouds, several kpc away from th…
Structure and Mass of a Young Globular Cluster in NGC 6946
Brodie, Jean P.; Elmegreen, Bruce G.; Hodge, Paul W. +3 more
Using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we have imaged a luminous young star cluster in the nearby spiral galaxy NGC 6946. Within a radius of 65 pc, the cluster has an absolute visual magnitude, MV=-13.2, comparable to the most luminous young ``super star clusters'' in the Antennae merger galaxy. UBV…
The MACHO Project: Microlensing Detection Efficiency
Alcock, C.; Allsman, R. A.; Alves, D. R. +21 more
The MACHO project is a search for dark matter in the form of massive compact halo objects (MACHOs). The project has photometrically monitored over forty million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and Galactic bulge in search of rare gravitational microlensing events caused by these otherwise invisible objects.…
Hubble Space Telescope Optical-Near-Infrared Colors of Nearby R1/4 and Exponential Bulges
Stiavelli, Massimo; de Zeeuw, P. Tim; Carollo, C. Marcella +2 more
We have analyzed V, H, and J Hubble Space Telescope (HST) images for a sample of early- to late-type spiral galaxies and have reported elsewhere the statistical frequency of R1/4-law and exponential bulges in our sample as a function of Hubble type and the frequency of occurrence and structural properties of the resolved central nuclei …
An XMM-Newton study of the X-ray binary MXB 1659-298 and the discovery of narrow X-ray absorption lines
Parmar, A. N.; Sidoli, L.; Oosterbroek, T. +2 more
We report the discovery of narrow X-ray absorption lines from the low-mass X-ray binary MXB 1659-298 during an XMM-Newton observation in 2001 February. The 7.1 hr orbital cycle is clearly evident with narrow X-ray eclipses preceded by intense dipping activity. A sinusoid-like OM B-band modulation with a peak-to-peak modulation of ~ 0.5 mag and a m…
Evidence for Dust Grain Growth in Young Circumstellar Disks
Throop, Henry B.; Bally, John; Esposito, Larry W. +1 more
Hundreds of circumstellar disks in the Orion nebula are being rapidly destroyed by the intense ultraviolet radiation produced by nearby bright stars. These young, million-year-old disks may not survive long enough to form planetary systems. Nevertheless, the first stage of planet formation-the growth of dust grains into larger particles-may have b…
Unusual Depletions toward the SMC Star SK 155-Differences in Dust Composition in the SMC Interstellar Medium?
York, Donald G.; Blades, J. Chris; Welty, Daniel E. +2 more
We report initial results from an analysis of Hubble Space Telescope/Space Telescope Imaging Spectrograph echelle spectra of interstellar absorption toward Sk 155, located in the ``wing'' region of the SMC. There are at least 12 Milky Way (disk and halo) and at least 25 SMC components discernible in the profiles of various neutral and singly ioniz…
The Proper Motion of the Globular Cluster NGC 6553 and of Bulge Stars with the Hubble Space Telescope
Zoccali, M.; Bica, E.; Barbuy, B. +2 more
WFPC2 images obtained with the Hubble Space Telescope (HST) 4.16 years apart have allowed us to measure the proper motion of the metal-rich globular cluster NGC 6553 with respect to the background bulge stars. With a space velocity of (Π, Θ, W)=(-3.5, 230, -3) km s-1, NGC 6553 follows the mean rotation of both disk and bulge stars at a …