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Hubble Space Telescope Multiepoch Imaging of the PSR B0540-69 System Unveils a Highly Dynamic Synchrotron Nebula
Caraveo, P. A.; Bignami, G. F.; De Luca, A. +1 more
PSR B0540-69 is the Crab twin in the Large Magellanic Cloud. The age and energetic and overall behavior of the two pulsars are very similar. The same is true for the general appearance of their pulsar wind nebulae (PWNe). Analysis of Hubble Space Telescope images spanning 10 yr unveiled significant variability in the PWN surrounding PSR B0540-69, …
Hubble Space Telescope Observations of Chromospheres in Metal-Deficient Field Giants
Smith, Graeme H.; Dupree, A. K.; Li, Timothy Q.
Hubble Space Telescope high-resolution spectra of metal-deficient field giants more than double the stars in previous studies, span ~3 mag on the red giant branch, and sample an abundance range [Fe/H] = -1 to -3. These stars, in spite of their age and low metallicity, possess chromospheric fluxes of Mg II (λ2800) that are within a factor of 4 of P…
The Post-Coronal Mass Ejection Solar Atmosphere and Radio Noise Storm Activity
Ramesh, R.; Kathiravan, C.; Nataraj, H. S.
We carried out a statistical study of solar radio noise storms whose onset was in the aftermath of coronal mass ejections (CMEs) that occurred during 1997-2004, the first half of present solar cycle 23. The work is an attempt to understand the post-CME corona through observations of noise storms since the latter are considered to be closely relate…
An XMM-Newton observation of the neutron star X-ray transient 2S 1803-245 in quiescence
Wijnands, R.; Homan, J.; Cornelisse, R.
We observed the neutron star X-ray transient 2S 1803-245 in quiescence with the X-ray satellite XMM-Newton, but did not detect it. An analysis of the X-ray bursts observed during the 1998 outburst of 2S 1803-245 gives an upper limit to the distance of <=7.3 kpc, leading to an upper limit on the quiescent 0.5-10 keV X-ray luminosity of <=2.8 …
Hard X-Rays and Fluorescent Iron Emission from the Embedded Infrared Cluster in NGC 2071
Skinner, Stephen L.; Güdel, Manuel; Audard, Marc +1 more
We present first results of XMM-Newton X-ray observations of the infrared cluster lying near the NGC 2071 reflection nebula in the Orion B region. This cluster is of interest because it is one of the closest regions known to harbor embedded high-mass stars. We report the discovery of hard X-ray emission from the dense central NGC 2071-IR subgroup,…
The X-ray spectra of the flaring and quiescent states of YZ CMi observed by XMM-Newton
Raassen, A. J. J.; Güdel, M.; Mitra-Kraev, U.
We analyse the X-ray spectrum of the active late-type star YZ CMi (M4.5V); for quiescent as well as active stages, we derive emission measure (EM) distributions, elemental abundances, and electron temperatures and densities, which are in turn used to estimate flare loop lengths as well as coronal magnetic field strengths.
YZ CMi was observed …Surface roughness and geological mapping at subhectometer scale from the High Resolution Stereo Camera onboard Mars Express
Greeley, Ronald; Mangold, Nicolas; Martin, Patrick +7 more
The quantitative measurement of surface roughness of planetary surfaces at all scales provides insights into geological processes. A characterization of roughness variations at the scale of a few tens of meters is proposed that complements the analysis of local topographic data of the martian surface at kilometer scale, as achieved from the Mars O…
Optical Variability of Infrared Power-Law-Selected Galaxies and X-Ray Sources in the GOODS-South Field
Sarajedini, Vicki; Klesman, Alison
We investigate the use of optical variability to identify and study active galactic nuclei (AGNs) in the GOODS-South field. A sample of 22 mid-IR power-law sources and 102 X-ray sources with optical counterparts in the HST ACS images were selected. Each object is classified with a variability significance value related to the standard deviation of…
A Robust Test of Evolution near the Tip of the Red Giant Branch and Missing Giants in NGC 2808
Martel, André R.; Sandquist, Eric L.
We describe a new method for robustly testing theoretical predictions of red giant evolution near the tip of the giant branch. When theoretical cumulative luminosity functions are shifted to align the tip in the I band and normalized at a luminosity level slightly brighter than the red giant bump, virtually all dependence on age and composition (h…
On the artificial nature of aperiodic variability in XMM-Newton observations of M 31 X-ray sources and the ultraluminous X-ray source NGC 4559 ULX-7
Osborne, J. P.; Barnard, R.; Kolb, U. C. +3 more
Context: Power density spectra (PDS) that are characteristic of low mass X-ray binaries (LMXBs) have been previously reported for M 31 X-ray sources, observed by XMM-Newton. However, we have recently discovered that these PDS result from the improper addition/subtraction of non-simultaneous lightcurves.
Aims: To understand the properties and o…