Search Publications
Spectropolarimetry and Radiative Transfer Modeling of Three Proto-Planetary Nebulae
Gordon, Karl D.; Bieging, John H.; Schmidt, Gary D. +3 more
We measured the spectrum of polarization for three proto-planetary nebulae (PPNs), IRAS 17411-2411, IRAS 08005-2356, and IRAS 04296+3429, and made model calculations with the dust-scattering Monte Carlo code DIRTY and the dust emission code 2Dust. We show that high levels of polarization in these PPNs correlate with extreme asymptotic giant branch…
The Stellar Structure of Irregular Galaxies. Face-on Galaxies
Tikhonov, N. A.
Stellar photometry of nearby irregular galaxies of the Local Group is used to identify and study the young and old stellar populations of these galaxies. An analysis of the spatial distributions of stars of different ages in face-on galaxies shows that the young stellar populations in irregular galaxies are concentrated toward the center, and form…
A 2 Hour Quasi Period in an Ultraluminous X-Ray Source in NGC 628
Bregman, Joel N.; Seitzer, Patrick; Espaillat, Catherine +3 more
Quasi-periodic oscillations and X-ray spectroscopy are powerful probes of black hole masses and accretion disks, and here we apply these diagnostics to an ultraluminous X-ray source (ULX) in the spiral galaxy NGC 628 (M74). This object was observed four times over 2 years with the Chandra X-Ray Observatory and XMM-Newton, with three long observati…
Deep ALTAIR+NIRI Imaging of the Disk and Bulge of M31
Davidge, T. J.; Olsen, K. A. G.; Rigaut, F. +2 more
Deep J, H, and K' images, recorded with the ALTAIR adaptive optics system and NIRI imager on Gemini North, are used to probe the stellar content of the disk and bulge of the Local Group galaxy M31. With an FWHM near 0.08" in K, these are the highest angular resolution near-infrared images yet obtained of this galaxy. One field samples the outer di…
Generation of downshifted oscillations in the electron foreshock: A loss-cone instability
Schwartz, S. J.; Fazakerley, A.; Décréau, P. +4 more
Measurements performed aboard Cluster spacecraft near Earth's bow shock on 24 January 2001 provide convincing evidence of a loss-cone feature within the electron foreshock region. This feature is formed by suprathermal electrons with energies 15-45 eV and pitch angles 130°-150° and is always accompanied by electrostatic waves with frequencies well…
The dynamics of velocity fluctuations in the solar wind - I. Coronal mass ejections
Raga, A. C.; Lara, A.; de Gouveia Dal Pino, E. M. +3 more
In this paper we present a simple, analytic model for the dynamical evolution of supersonic velocity fluctuations at the base of the ambient solar wind. These fluctuations result in the formation of dense working surfaces that travel down the wind. It is shown how the initial parameters of the fluctuations (velocity, density and duration) are rela…
Flare-associated Coronal Disturbances Observed with the Norikura Green-Line Imaging System. I. A Coronal Mass Ejection Onset
Ichimoto, K.; Sakurai, T.; Hori, K. +2 more
We present the first detection of an onset of a coronal mass ejection (CME) in the coronal green-line emission (Fe XIV λ5303, 2 MK) by the two-dimensional Doppler coronagraph NOGIS (Norikura Green-Line Imaging System) at the Norikura Solar Observatory, National Astronomical Observatory of Japan. On 2003 June 1-2, NOGIS continuously observed the bi…
A Multiwavelength Study of IC 63 and IC 59
Martin, P. G.; Noriega-Crespo, A.; Karr, J. L.
IC 63 and IC 59 are two nearby arc-shaped nebulae with relatively simple geometries and minimal obscuring material. The two regions, in spite of a similar projected distance from their ionizing star, have very different observational properties, both in continuum emission and in the presence and strength of line emission from molecular species. Th…
Discovery of Ne VII in the Winds of Hot Evolved Stars
Hillier, D. J.; Bianchi, L.; Herald, J. E.
We show that a strong P Cygni feature seen in the far-UV spectra of some very hot (Teff>~85 kK) central stars of planetary nebulae (CSPN), which has been previously identified as C III λ977, actually originates from Ne VII λ973. Using stellar atmosphere models, we reproduce this feature seen in the spectra of two [WR] PG 1159-type CS…
Orbits of new Hipparcos binaries. I
Weigelt, G.; Hofmann, K. -H.; Schertl, D. +4 more
We present first orbits for 6 new Hipparcos binaries. The orbits were determined from speckle interferometric measurements collected mainly at the6m BTAtelescope of the Special Astrophysical Observatory in Zelenchuk. Three of the systems, HIP 11352, HIP 14075 and HIP 14230, have late G- or early K-type components, while HIP 14669 = GJ 125, HIP 106…