Search Publications
Proto-Planetary Nebulae as Explosions: Bullets versus Jets and Nebular Shaping
Frank, Adam; Balick, Bruce; Blackman, Eric G. +3 more
Many proto-planetary nebulae (PPNs) appear as narrow collimated structures sometimes showing multiple, roughly aligned lobes. In addition, many PPN flows have been shown to have short acceleration times. In this paper we explore whether jet or "bullet" (a massive clump) models fit the observations of individual collimated lobes adequately by compa…
The Spectral Lag of GRB 060505: A Likely Member of the Long-Duration Class
McGlynn, S.; McBreen, S.; Foley, S. +7 more
Two long γ-ray bursts, GRB 060505 and GRB 060614, occurred in nearby galaxies at redshifts of 0.089 and 0.125, respectively. Due to their proximity and durations, deep follow-up campaigns to search for supernovae (SNe) were initiated. However, none were found in either case, to limits more than 2 orders of magnitude fainter than the prototypical G…
Submillimeter Structure of the Disk of the Butterfly Star
Stapelfeldt, K. R.; Wolf, S.; Beuther, H. +2 more
We present a spatially resolved 894 µm map of the circumstellar disk of the Butterfly Star in Taurus (IRAS 04302+2247), obtained with the Submillimeter Array (SMA). The predicted and observed radial brightness profiles agree well in the outer disk region but differ in the inner region with an outer radius of ~80-120 AU. In particular, we fin…
Unveiling the Important Role of Groups in the Evolution of Massive Galaxies: Insights from an Infrared Passive Sequence at Intermediate Redshift
Wilman, D. J.; Mulchaey, J. S.; Balogh, M. L. +6 more
The most massive galaxies in the universe are also the oldest. To overturn this apparent contradiction with hierarchical growth models we focus on the group-scale halos that host most of these galaxies. Our z ~ 0.4 group sample is selected in redshift space from the CNOC2 redshift survey. A stellar mass-selected M*gtrsim 2 × 1010
The Long-Term Radiative Evolution of Anomalous X-Ray Pulsar 1E 2259+586 After Its 2002 Outburst
Zhu, Weiwei; Kaspi, Victoria M.; Woods, Peter M. +3 more
We present an analysis of five XMM-Newton observations of the anomalous X-ray pulsar (AXP) 1E 2259+586 taken in 2004 and 2005 during its relaxation following its 2002 outburst. We compare these data with those of five previous XMM-Newton observations taken in 2002 and 2003, and find the observed flux decay is well described by a power law of index…
A Statistical Study on Rotating Sunspots: Polarities, Rotation Directions, and Helicities
Yan, X. L.; Qu, Z. Q.; Xu, C. L.
Observations of white-light images from SOHO MDI, TRACE, Hinode, SOHO MDI magnetograms, and Hinode SP vector magnetograms show sufficient samples of rotating sunspots on the solar photosphere for a statistical study. During the period from 1996 December to 2007 December, after individually checking the active regions in detail, we found 182 measur…
Magnetic Flux Loss and Flux Transport in a Decaying Active Region
Kubo, M.; Lites, B. W.; Ichimoto, K. +1 more
We estimate the temporal change of magnetic flux normal to the solar surface in a decaying active region by using a time series of the spatial distribution of vector magnetic fields in the photosphere. The vector magnetic fields are derived from full spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode. We compare a magn…
Small-Scale Behavior of the Physical Conditions and the Abundance Discrepancy in the Orion Nebula
Mesa-Delgado, Adal; Esteban, César; García-Rojas, Jorge
We present the results of long-slit spectroscopy, in several positions, of the Orion Nebula. Our goal is to study the spatial distributions of a large number of nebular quantities, including line fluxes, physical conditions, and ionic abundances, at a spatial resolution of about 1''. In particular, we have compared the O++ abundance det…
Probing the Nature of the Vela X Cocoon
Slane, Patrick O.; LaMassa, Stephanie M.; de Jager, Okkie C.
Vela X is a pulsar wind nebula (PWN) associated with the active pulsar B0833-45 and contained within the Vela supernova remnant (SNR). A collimated X-ray filament ("cocoon") extends south-southwest from the pulsar to the center of Vela X. VLA observations uncovered radio emission coincident with the eastern edge of the cocoon, and H.E.S.S. has det…
A Broadband Microwave Burst Produced by Electron Beams
Melnikov, V. F.; Fleishman, G. D.; Huang, G. -L. +1 more
The theoretical and experimental study of fast electron beams attracts much attention in astrophysics and the laboratory. In the case of solar flares, the problem of reliable beam detection and diagnostics is of exceptional importance. This paper explores the fact that electron beams moving obliquely to the magnetic field or along the field with s…