Search Publications
Hubble Space Telescope spectroscopy of the Balmer lines in Sirius B*
Bond, Howard E.; Barstow, M. A.; Koester, D. +3 more
Sirius B is the nearest and brightest of all white dwarfs, but it is very difficult to observe at visible wavelengths due to the overwhelming scattered light contribution from Sirius A. However, from space we can take advantage of the superb spatial resolution of the Hubble Space Telescope (HST) to resolve the A and B components. Since the closest…
Predicting QSO Continua in the Lyα Forest
O'Meara, John M.; Tytler, David; Lubin, Dan +2 more
We present a method to make predictions with sets of correlated data values, in this case QSO flux spectra. We predict the continuum in the Lyα forest of a QSO, from 1020 to 1216 Å, using the spectrum of that QSO from 1216 to 1600 Å. We find correlations between the unabsorbed flux in these two wavelength regions in the Hubble Space Telescope (HST…
Integrated spectrum of the planetary nebula NGC 7027
Barlow, M. J.; Zhang, Y.; Liu, X. -W. +2 more
We present deep optical spectra of the archetypal young planetary nebula (PN)
Automated Detection Of Eit Waves And Dimmings
Berghmans, David; Podladchikova, Olena
Studies of the onset of Earth-directed coronal mass ejections (CMEs) rely on solar disk observations where CME structures are difficult to disentangle because of the diversity and transient character of the phenomena involved. Dimmings and coronal waves are among the best evidence of the large-scale reorganization of coronal magnetic fields associ…
The Fundamental Plane of Cluster Elliptical Galaxies at z=1.25
Rosati, P.; Rix, H. -W.; van der Wel, A. +8 more
Using deep Hubble Space Telescope Advanced Camera for Surveys imaging and Very Large Telescope FOcal Reducer/low dispersion Spectrograph 2 spectra, we determined the velocity dispersions, effective radii, and surface brightnesses for four early-type galaxies in the z=1.237 cluster RDCS 1252.9-2927. All four galaxies are massive, greater than 10
The evolution of planetary nebulae. III. Internal kinematics and expansion parallaxes
Steffen, M.; Schönberner, D.; Jacob, R.
A detailed theoretical study of the basic internal kinematics of planetary nebulae is presented, based on 1D radiation-hydrodynamics simulations of circumstellar envelopes around central stars of 0.595 and 0.696 M⊙. By means of observable quantities like radial surface-brightness distributions and emission-line profiles computed from th…
Optical novae: the major class of supersoft X-ray sources in M 31
Pietsch, W.; Haberl, F.; Greiner, J. +4 more
We searched for X-ray counterparts of optical novae detected in
Magnetohydrodynamic Simulations of the Solar Corona and Solar Wind Using a Boundary Treatment to Limit Solar Wind Mass Flux
Hayashi, Keiji
Magnetohydrodynamic simulations of the solar corona and solar wind are sensitive to conditions in the sub-Alfvénic plasma at the base of the solar corona because the structure of the simulated solar corona is determined by the pressure balance of the plasma and the magnetic field. Therefore, it is important to construct an adequate boundary treatm…
Hubble Space Telescope WFPC2 Color-Magnitude Diagrams for Globular Clusters in M31
Djorgovski, S. G.; Cacciari, C.; Rich, R. M. +4 more
We report new photometry for 10 globular clusters in M31, observed to a uniform depth of four orbits in F555W (V) and F814W (I) using WFPC2 on board the Hubble Space Telescope (HST). In addition, we have reanalyzed HST archival data of comparable quality for two more clusters. A special feature of our analysis is the extraordinary care taken to ac…
A 3-5 µm VLT spectroscopic survey of embedded young low mass stars II. Solid OCN-
van Dishoeck, E. F.; Pontoppidan, K. M.; Fraser, H. J. +1 more
The 4.62 µm (2164.5 cm-1) “XCN” band has been detected in the M-band spectra of 34 deeply embedded young stellar objects (YSO's), observed with high signal-to-noise and high spectral resolution with the VLT-ISAAC spectrometer, providing the first opportunity to study the solid OCN- abundance toward a large number of low…