Search Publications
Oscillations in the Magnetic Field of the Solar Corona in Response to Flares near the Photosphere
Schrijver, Carolus J.; Brown, Daniel S.
The magnetic field in the outer solar atmosphere is frequently distorted by flares. In some cases, a fraction of the field exhibits a rapidly damped oscillation (Schrijver et al.; Aschwanden et al.). If this is a resonating wave trapped in the field, then the rapid damping requires a viscosity or resistivity that is at least 108 times l…
Chandra X-Ray Observatory Detection of Extended X-Ray Emission from the Planetary Nebula BD +30°3639
Soker, Noam; Kastner, Joel H.; Vrtilek, Saeqa D. +1 more
We report the detection of well-resolved, extended X-ray emission from the young planetary nebula BD +30°3639 using the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-ray Observatory. The X-ray emission from BD +30°3639 appears to lie within, but is concentrated to one side of, the interior of the shell of ionized gas seen in high-r…
Drive Mechanisms of Erupting Solar Magnetic Flux Ropes
Chen, J.; Krall, J.; Santoro, R.
The dynamics of magnetic flux ropes near the Sun and in interplanetary space are studied using a magnetohydrodynamic model of erupting magnetic flux ropes. In this model, the magnetic structure of a coronal mass ejection (CME) corresponds to a flux rope with footpoints that remain anchored below the photosphere. The model flux rope eruption can be…
Heating and Acceleration of Protons and Minor Ions by Fast Shocks in the Solar Corona
Lee, L. C.; Wu, B. H.
We propose a new mechanism of coronal heating, in which protons and minor ions are heated and accelerated by fast shocks. The interaction between network magnetic fields and emerging intranetwork fields may lead to the formation of thin current sheets, which triggers magnetic reconnection and microflares. The disruption of current sheet leads to f…
How Young are Early-type Cluster Galaxies? Quantifying the Young Stellar Component in a Rich Cluster at z=0.41
Ferreras, Ignacio; Silk, Joseph
We present a new method of quantifying the mass fraction of young stars in galaxies by analyzing near-ultraviolet (NUV)-optical colors. We focus our attention on early-type cluster galaxies, whose star formation history is at present undetermined. Rest-frame NUV (F300W) and optical (F702W) images of cluster Abell 851 (z=0.41) using Hubble Space Te…
Intensive HST, RXTE, and ASCA Monitoring of NGC 3516: Evidence against Thermal Reprocessing
Nandra, Kirpal; Peterson, Bradley M.; Maoz, Dan +10 more
During 1998 April 13-16, the bright, strongly variable Seyfert 1 galaxy NGC 3516 was monitored almost continuously with HST for 10.3 hr at ultraviolet wavelengths and 2.8 days at optical wavelengths, and simultaneous RXTE and ASCA monitoring covered the same period. The X-ray fluxes were strongly variable with the soft (0.5-2 keV) X-rays showing s…
Resolved Spectroscopy of the Narrow-Line Region in NGC 1068. II. Physical Conditions near the NGC 1068 ``Hot Spot''
Crenshaw, D. Michael; Kraemer, Steven B.
The physical conditions near the optical continuum peak (``hot spot'') in the inner narrow-line region of the Seyfert 2 galaxy NGC 1068 are examined using ultraviolet and optical spectra and photoionization models. The spectra were taken with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (STIS) through the 0.1"x52.0" slit, coveri…
Heliospheric, Astrospheric, and Interstellar Lyα Absorption toward 36 Ophiuchi
Zank, Gary P.; Wood, Brian E.; Linsky, Jeffrey L.
We use high-resolution UV spectra taken by the Space Telescope Imaging Spectrograph instrument on board the Hubble Space Telescope to study the 5.5 pc line of sight to the K0 V star 36 Oph A. The one interstellar component detected for this line of sight has a velocity inconsistent with the local interstellar cloud (LIC) flow vector but consistent…
Space Telescope Imaging Spectrograph Long-Slit Spectroscopy of the Narrow-Line Region of NGC 4151. II. Physical Conditions along Position Angle 221 deg
Gull, T. R.; Kraemer, S. B.; Crenshaw, D. M. +4 more
We have examined the physical conditions in the narrow-line region of the well-studied Seyfert galaxy NGC 4151, using long-slit spectra obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph. The data were taken along a position angle of 221 deg, centered on the optical nucleus. We have generated photoionization models for a…
3C 48: Stellar Populations and the Kinematics of Stars and Gas in the Host Galaxy
Stockton, Alan; Canalizo, Gabriela
We present deep Keck LRIS spectroscopy of the host galaxy of 3C 48. Our observations at various slit positions sample the different luminous components near the quasar, including the apparent tidal tail to the northwest and several strong emission line regions. By fitting Bruzual & Charlot population synthesis models to our spectra, we obtain …