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Noise characteristics of full-disc helioseismic observations made by resonant scattering spectrometers
Chaplin, W. J.; Elsworth, Y.; Isaak, G. R. +3 more
Resonant scattering spectrometers (RSSs) have been used to make high-precision full-disc helioseismic observations since the 1970s. They are capable of very high-precision determinations of line-shift, meaning that they are used to obtain precise velocity measurements, and, for suitably configured RSSs, the disc-averaged longitudinal magnetic fiel…
XMM-Newton observations of the interacting galaxy pairs NGC 7771/0 and NGC 2342/1
Zezas, A.; Roberts, T. P.; Ward, M. J. +1 more
We present XMM-Newton X-ray observations of the interacting galaxy pairs NGC 7771/7770 and NGC 2342/2341. In NGC 7771, for the first time we are able to resolve the X-ray emission into a bright central source plus two bright (LX > 1040 erg s-1) ultraluminous X-ray sources (ULXs) located either end of the bar. In…
Supersolar N/C in the Narrow-Line Seyfert 1 Galaxy Markarian 1044
Pogge, Richard W.; Nicastro, Fabrizio; Mathur, Smita +2 more
Narrow-line Seyfert 1 galaxies (NLS1s) are known to have extreme values of a number of properties compared to active galactic nuclei (AGNs) as a class. In particular, previous emission-line studies have suggested that NLS1s are unusually metal-rich compared to broad-line AGNs of comparable luminosity. We present low- and medium-resolution spectros…
HST/NICMOS observations of a proto-brown dwarf candidate
Henning, T.; Apai, D.; Lemke, D. +3 more
We present deep HST/NICMOS observations peering through the outflow cavity of the protostellar candidate IRAS 04381+2540 in the Taurus Molecular Cloud-1. A young stellar object as central source, a jet and a very faint and close (0.6'') companion are identified. The primary and the companion have similar colours, consistent with strong reddening. …
Cluster electron observations of the separatrix layer during traveling compression regions
Balogh, A.; Fazakerley, A. N.; Owen, C. J. +2 more
We present Cluster 4-point observations of electrons during traveling compression regions (TCRs) on 19 September 2001. The electron and |B| signatures vary with distance from the plasma sheet, confirming that transient plasma sheet bulges propagate past Cluster. TCRs with |B| increases have either no electron signature, or unidirectional ~1 keV el…
Dissipation scales in the Earth's plasma sheet estimated from Cluster measurements
Balogh, A.; Nakamura, R.; Baumjohann, W. +5 more
In order to estimate the dissipation time-scale in magnetic turbulence in the plasma sheet a novel method is introduced for classification of velocity dependent patterns of two-point probability density functions' shapes near their maxima. For the first time, we provide evidence for Reynolds number (velocity) dependent widening of the inertial ran…
Polarization Measurements of Post-Asymptotic Giant Branch Candidates and Related Stars
Parthasarathy, M.; Jain, S. K.; Sarkar, G.
We have obtained UBVRI polarization measurements of 26 post-asymptotic giant branch (post-AGB) candidates and related stars. The extremely metal-poor post-AGB star HR 4049 has been observed several times. In most cases we find the objects to be intrinsically polarized. The polarization measurements presented in this paper indicate asymmetric circu…
Fractal-Based Fuzzy Technique For Detection Of Active Regions From Solar Images
Revathy, K.; Lekshmi, S.; Nayar, S. R. Prabhakaran
Fractal concepts are used to describe the irregular structures and regions of interest of solar images. The most common and easiest way to extract regions of interest from an image is through segmentation. Segmentation techniques vary from conventional edge-detection mechanism to fuzzy c-means clustering. In this study, the pixelwise local fractal…
Properties of solar wind turbulence near the Sun as deduced from coronal radio sounding experiments
Plettemeier, D.; Bird, M. K.; Efimov, A. I. +2 more
The characteristics of plasma turbulence in the inner solar wind, as deduced from radio frequency fluctuation measurements recorded during solar conjunction, are reviewed. Special emphasis is placed on results from the radio occultation experiments performed with the Galileo and Ulysses spacecraft in the interval 1991-2000. Estimates of the power …
On the Ga II and Ga III Resonance Lines and the Implication for Chemical Stratification in HgMn Stars
Nielsen, K. E.; Leckrone, D. S.; Wahlgren, G. M. +2 more
The gallium abundance in HgMn stars has been reported to be different for analyses conducted from spectral lines in the optical versus those from the ultraviolet. We pursue this ultraviolet-optical discrepancy from a line-blending perspective by investigating the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) spectrum of …