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A faint red stellar halo around an edge-on disc galaxy in the Hubble Ultra Deep Field
Zibetti, Stefano; Ferguson, Annette M. N.
We analyse the detailed structure of a highly-inclined (i>~ 80°) disc galaxy that lies within the Hubble Ultra Deep Field (UDF). The unprecedented depth of the UDF data allow disc and extraplanar emission to be traced reliably to surface brightness levels of µV,i,z~ 29-30 mag arcsec-2 (corresponding to rest-frame equ…
X-Ray Observations of the Compact Source in CTA 1
Hughes, John P.; Slane, Patrick; Gaensler, Bryan M. +3 more
We have studied the point source RX J0007.0+7302, at the center of supernova remnant CTA 1, using the X-Ray Multi-mirror Mission (XMM-Newton). The X-ray spectrum of the source is consistent with that of a neutron star and is well described by a power law with the addition of a soft thermal component that may correspond to emission from hot polar c…
A Multiwavelength Perspective of Flares on HR 1099: 4 Years of Coordinated Campaigns
Ayres, Thomas R.; Brown, Alexander; Skinner, Stephen L. +7 more
We report on four years of multiple wavelength observations of the RS CVn system V711 Tau (HR 1099) from 1993, 1994, 1996, and 1998. This combination of radio, ultraviolet, extreme ultraviolet, and X-ray observations allows us to view, in the most comprehensive manner currently possible, the coronal and upper atmospheric variability of this active…
Counterstreaming electrons in magnetic clouds near 5 AU
Forsyth, R.; Crooker, N. U.; Gosling, J. T. +2 more
Suprathermal electron pitch angle spectrograms were searched for counterstreaming signatures in 31 magnetic clouds identified in Ulysses data when the spacecraft was located ∼5 AU from the Sun. Under the assumption that counterstreaming indicates closed field lines, that is, field lines attached to the Sun at both ends, we find that the clouds ran…
HST/STIS high resolution echelle spectra of α Centauri A (G2 V)
Pagano, I.; Linsky, J. L.; Valenti, J. +1 more
We describe and analyze HST/STIS observations of the G2 V star α Centauri A (
Ultracompact Dwarf Galaxies in Abell 1689: A Photometric Study with the Advanced Camera for Surveys
Ford, H. C.; Infante, L.; Zheng, W. +37 more
The properties of ultracompact dwarf (UCD) galaxy candidates in Abell 1689 (z=0.183) are investigated, based on deep high-resolution images from the Hubble Space Telescope Advanced Camera for Surveys. A UCD candidate has to be unresolved, have i<28 mag (MV<-11.5 mag), and satisfy color limits derived from Bayesian photometric reds…
On the deep minimum state in the Seyfert galaxy MCG-6-30-15
Staubert, Rüdiger; Wilms, Jörn; Reynolds, Christopher S. +2 more
We present a detailed spectral analysis of the first observation of the Seyfert 1 galaxy MCG-6-30-15 by the European Photon Imaging Camera on board the XMM-Newton observatory, together with contemporaneous data from the Proportional Counter Array on the Rossi X-ray Timing Explorer. Confirming our previously published result, we find that the prese…
Internal Velocities in the Orion Nebula: Large Radial Velocity Features
Hartigan, Patrick; O'Dell, C. R.; Doi, Takao
A map of high-velocity features in the 3'×5' central region of the Orion Nebula was created from slit spectra with a velocity resolution of 8 km s-1. We identified two new bipolar flows, Herbig-Haro (HH) 725 and HH 726, as well as a highly redshifted flow, HH 512. We also found multiple new high-velocity co-moving …
New Perspectives on the X-Ray Emission of HD 104237 and Other Nearby Herbig Ae/Be Stars from XMM-Newton and Chandra
Skinner, Stephen L.; Güdel, Manuel; Audard, Marc +1 more
The origin of the X-ray emission from Herbig Ae/Be stars is not yet known. These intermediate-mass pre-main-sequence stars lie on radiative tracks and are not expected to emit X-rays via solar-like magnetic processes, nor are their winds powerful enough to produce X-rays by radiative wind shocks as in more massive O-type stars. The emission could …
High-amplitude, long-term X-ray variability in the solar-type star HD 81809: The beginning of an X-ray activity cycle?
Schmitt, J. H. M. M.; Güdel, M.; Harnden, F. R., Jr. +5 more
We present the initial results from our XMM-Newton program aimed at searching for X-ray activity cycles in solar-type stars. HD 81809 is a G2-type star (somewhat more evolved than the Sun, and with a less massive companion) with a pronounced 8.2 yr chromospheric cycle, as evident from from the Mt. Wilson program data. We present here the results f…