Search Publications
Magnetic Field-line Lengths in Interplanetary Coronal Mass Ejections Inferred from Energetic Electron Events
Richardson, I. G.; Kahler, S. W.; Haggerty, D. K.
About one quarter of the observed interplanetary coronal mass ejections (ICMEs) are characterized by enhanced magnetic fields that smoothly rotate in direction over timescales of about 10-50 hr. These ICMEs have the appearance of magnetic flux ropes and are known as "magnetic clouds" (MCs). The total lengths of MC field lines can be determined usi…
Molecular Environment and an X-Ray Spectroscopy of Supernova Remnant Kesteven 78
Zhou, Ping; Chen, Yang
We investigate the molecular environment of the Galactic supernova remnant (SNR) Kesteven 78 and perform an XMM-Newton X-ray spectroscopic study for the northeastern edge of the remnant. SNR Kes 78 is found to interact with the molecular clouds (MCs) at a systemic local standard of rest velocity of 81 km s-1. At around this velocity, th…
History and Modes of Star Formation in the Most Active Region of the Small Magellanic Cloud, NGC 346
Cignoni, M.; Tosi, M.; Sabbi, E. +2 more
We discuss the star formation history of the Small Magellanic Cloud (SMC) region NGC 346 based on Hubble Space Telescope images. The region contains both field stars and cluster members. Using a classical synthetic color-magnitude diagram (CMD) procedure applied to the field around NGC 346 we find that the star formation pace there has been rising…
Revealing O VII from stacked X-ray grating spectra of clusters, groups and elliptical galaxies
Fabian, A. C.; Sanders, J. S.
We stack 4.6 Ms of high spectral resolution XMM-Newton Reflection Grating Spectrometer spectra from galaxy clusters, groups of galaxies and elliptical galaxies. For those objects with a central temperature of less than 1 keV, we detect O VII for the first time, with a probability of false detection of 2.5 × 10-4. The flux ratio of the O…
The Far-ultraviolet "Continuum" in Protoplanetary Disk Systems. I. Electron-impact H2 and Accretion Shocks
France, Kevin; Yang, Hao; Linsky, Jeffrey L.
We present deep spectroscopic observations of the classical T Tauri stars DF Tau and V4046 Sgr in order to better characterize two important sources of far-ultraviolet continuum emission in protoplanetary disks. These new Hubble Space Telescope-Cosmic Origins Spectrograph observations reveal a combination of line and continuum emission from collis…
X-ray spectral properties of Seyfert galaxies and the unification scheme
Singh, V.; Risaliti, G.; Shastri, P.
Context. The unification scheme of Seyfert galaxies predicts that the observed differences between types 1 and 2 Seyfert galaxies are solely due to the differing orientations of the toroidal-shaped obscuring material around AGN. The observed X-ray spectra of Seyfert type 2s compared to type 1s are expected to be affected by higher absorbing column…
Observations of Binary Stars with the Differential Speckle Survey Instrument. III. Measures below the Diffraction Limit of the WIYN Telescope
Howell, Steve B.; Ciardi, David R.; Horch, Elliott P. +2 more
In this paper, we study the ability of CCD- and electron-multiplying-CCD-based speckle imaging to obtain reliable astrometry and photometry of binary stars below the diffraction limit of the WIYN 3.5 m Telescope. We present a total of 120 measures of binary stars, 75 of which are below the diffraction limit. The measures are divided into two group…
The Acoustic Cutoff Frequency of the Sun and the Solar Magnetic Activity Cycle
García, R. A.; Pallé, P. L.; Jiménez, A.
The acoustic cutoff frequency—the highest frequency for acoustic solar eigenmodes—is an important parameter of the solar atmosphere as it determines the upper boundary of the p-mode resonant cavities. At frequencies beyond this value, acoustic disturbances are no longer trapped but are traveling waves. Interference among them gives rise to higher-…
Hinode extreme-ultraviolet imaging spectrometer observations of a limb active region
Young, P. R.; Mason, H. E.; Del Zanna, G. +3 more
Aims: We investigate the electron density and temperature structure of a limb active region.
Methods: We have carried out a study of an active region close to the solar limb using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) and the X-ray telescope (XRT) on board Hinode. The electron density and temperature distri…
High-resolution wave number spectrum using multi-point measurements in space - the Multi-point Signal Resonator (MSR) technique
Glassmeier, K. -H.; Narita, Y.; Motschmann, U.
A new analysis method is presented that provides a high-resolution power spectrum in a broad wave number domain based on multi-point measurements. The analysis technique is referred to as the Multi-point Signal Resonator (MSR) and it benefits from Capon's minimum variance method for obtaining the proper power spectral density of the signal as well…