Search Publications
Spectral and Timing Properties of the Magnetar CXOU J164710.2-455216
An, Hongjun; Kaspi, Victoria M.; Archibald, Robert +1 more
We report on spectral and timing properties of the magnetar CXOU J164710.2-455216 in the massive star cluster Westerlund 1. Using 11 archival observations obtained with Chandra and XMM-Newton over approximately 1000 days after the source's 2006 outburst, we study the flux and spectral evolution of the source. We show that the hardness of the sourc…
Hubble Space Telescope Fine Guidance Sensor Parallaxes for Four Classical Novae
Harrison, Thomas E.; Benedict, G. Fritz; McArthur, Barbara E. +1 more
We have used data obtained with the Fine Guidance Sensors on the Hubble Space Telescope to derive precise astrometric parallaxes for four classical novae: V603 Aql, DQ Her, GK Per, and RR Pic. All four objects exceeded the Eddington limit at visual maximum. Re-examination of the original light curve data for V603 Aql and GK Per has led us to concl…
A Study of Fast Flareless Coronal Mass Ejections
Chen, Y.; Song, H. Q.; Zhang, J. +5 more
Two major processes have been proposed to convert coronal magnetic energy into the kinetic energy of a coronal mass ejection (CME): resistive magnetic reconnection and the ideal macroscopic magnetohydrodynamic instability of a magnetic flux rope. However, it remains elusive whether both processes play a comparable role or one of them prevails duri…
Kelvin-Helmholtz Instability of a Coronal Streamer
Feng, L.; Inhester, B.; Gan, W. Q.
Shear-flow-driven instability can play an important role in energy transfer processes in coronal plasma. We present for the first time the observation of a kink-like oscillation of a streamer that is probably caused by the streaming kink-mode Kelvin-Helmholtz instability (KHI). The wave-like behavior of the streamer was observed by the Large Angle…
Toward a Removal of Temperature Dependencies from Abundance Determinations: NGC 628
Armus, L.; Hunt, L. K.; Pellegrini, E. +16 more
The metal content of a galaxy, a key property for distinguishing between viable galaxy evolutionary scenarios, strongly influences many of the physical processes in the interstellar medium. An absolute and robust determination of extragalactic metallicities is essential in constraining models of chemical enrichment and chemical evolution. Current …
The High-ion Content and Kinematics of Low-redshift Lyman Limit Systems
Tripp, Todd M.; Prochaska, J. Xavier; Davé, Romeel +9 more
We study the high-ion content and kinematics of the circumgalactic medium around low-redshift galaxies using a sample of 23 Lyman limit systems (LLSs) at 0.08 < z < 0.93 observed with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. In Lehner et al., we recently showed that low-z LLSs have a bimodal metallicity distributi…
A Direct Stellar Metallicity Determination in the Disk of the Maser Galaxy NGC 4258
Hosek, Matthew W., Jr.; Bresolin, Fabio; Kudritzki, Rolf-Peter +4 more
We present the first direct determination of a stellar metallicity in the spiral galaxy NGC 4258 (D = 7.6 Mpc) based on the quantitative analysis of a low-resolution (~5 Å) Keck Low Resolution Imaging Spectrograph spectrum of a blue supergiant star located in its disk. A determination of stellar metallicity in this galaxy is important for the abso…
A Study of a Failed Coronal Mass Ejection Core Associated with an Asymmetric Filament Eruption
Joshi, Navin Chandra; Filippov, Boris; Srivastava, Abhishek K. +3 more
We present multi-wavelength observations of an asymmetric filament eruption and associated coronal mass ejection (CME) and coronal downflows on 2012 June 17 and 18 from 20:00-05:00 UT. We use SDO/AIA and STEREO-B/SECCHI observations to understand the filament eruption scenario and its kinematics, while LASCO C2 observations are analyzed to study t…
Dancing in the Dark: New Brown Dwarf Binaries from Kernel Phase Interferometry
Martinache, Frantz; Tuthill, Peter; Pope, Benjamin
This paper revisits a sample of ultracool dwarfs in the solar neighborhood previously observed with the Hubble Space Telescope's NICMOS NIC1 instrument. We have applied a novel high angular resolution data analysis technique based on the extraction and fitting of kernel phases to archival data. This was found to deliver a dramatic improvement over…
The ACS Nearby Galaxy Survey Treasury. XI. The Remarkably Undisturbed NGC 2403 Disk
Skillman, Evan D.; Williams, Benjamin F.; Dolphin, Andrew +3 more
We present detailed analysis of color-magnitude diagrams of NGC 2403, obtained from a deep (m <~ 28) Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observation of the outer disk of NGC 2403, supplemented by several shallow (m <~ 26) HST Advanced Camera for Surveys fields. We derive the spatially resolved star formation history of…