Search Publications
Physical Structure of the Protoplanetary Nebula CRL 618. II. Interferometric Mapping of Millimeter-Wavelength HCN J = 1-0, HCO+ J = 1-0, and Continuum Emission
Sahai, R.; Sánchez Contreras, C.
We present interferometric maps with high angular resolution, 1.1" to 1.9", of the HCO + J=1-0 and HCN J=1-0 emission lines in the protoplanetary nebula CRL 618. These molecules are present in both the slowly (~10-20 km s-1) and rapidly (~200 km s-1) outflowing components of the molecular envelope of CRL 618. The …
Hubble Space Telescope Imaging of Extraplanar Dust Structures in the Edge-On Spiral NGC 4217
Savage, Blair D.; Howk, J. Christopher; Thompson, Thomas W. J.
We present high-resolution (~ 0.1") B, V, and I images of the edge-on Sb galaxy NGC 4217 obtained with the Wide Field Planetary Camera 2 (WFPC2) on-board the Hubble Space Telescope (HST). We make use of these images to study extraplanar (z>0.4 kpc) dust structures visible in absorption against the background stellar light of the galaxy, similar…
Waiting in the Wings: Reflected X-Ray Emission from the Homunculus Nebula
Weis, K.; Davidson, K.; Smith, N. +14 more
We report the first detection of X-ray emission associated with the Homunculus nebula that surrounds the supermassive star η Car. The emission is characterized by a temperature in excess of 100 MK and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and n…
Pronounced Long-Term Flux Variability of the Anomalous X-Ray Pulsar 1E 1048.1-5937
Tiengo, A.; Mereghetti, S.; Stella, L. +4 more
We present XMM-Newton and Chandra observations of 1E 1048.1-5937, being the first to show evidence for a significant variation in the X-ray luminosity of this anomalous X-ray pulsar (AXP). While during the first XMM-Newton (2000 December) and Chandra (2001 July) observations the source had a flux consistent with that measured on previous occasions…
Magnetic Field-Minimum Intensity Correlation in Sunspots: A Tool for Solar Dynamo Diagnostics
Norton, Aimee A.; Gilman, Peter A.
Within a sunspot umbra, the continuum intensity is known to be inversely proportional to the magnetic field strength. Studied less is the relationship between the minimum continuum intensity and the maximum field strength of different sunspots. We conduct a test of this global relationship, using brightness ratios and magnetic field data from the …
Geoeffectiveness of interplanetary shocks during solar minimum (1995 1996) and solar maximum (2000)
Echer, E.; Gonzalez, W. D.; Alves, M. V.
Plasma and magnetic field parameter variations across fast forward interplanetary shocks are analyzed during the last solar cycle minimum (1995-1996, 15 shocks), and maximum year 2000 (50 shocks). It was observed that the solar wind velocity and magnetic field strength variation across the shocks were the parameters better correlated with Dst. Sup…
A Chandra observation of the old open cluster M 67
Tagliaferri, G.; Belloni, T.; van den Berg, M. +1 more
We present the results of a 47-ks Chandra-ACIS observation of the old open cluster
Balltracking: An highly efficient method for tracking flow fields
Potts, H. E.; Barrett, R. K.; Diver, D. A.
We present a method for tracking solar photospheric flows that is highly efficient, and demonstrate it using high resolution MDI continuum images. The method involves making a surface from the photospheric granulation data, and allowing many small floating tracers or balls to be moved around by the evolving granulation pattern. The results are tes…
I Zw 1 observed with XMM-Newton . Low-energy spectral complexity, iron lines, and hard X-ray flares
Brandt, W. N.; Vaughan, S.; Fabian, A. C. +2 more
We present a 20 ks XMM-Newton observation of the prototypical Narrow-Line Seyfert 1 galaxy I Zw 1. The best-fit model to the data is a double blackbody plus a dominant power-law, on which complex soft absorption (possibly a blended edge or absorption lines) and/or OVII emission are superimposed, as well as strong Fe Kα emission. The iron feature i…
The complex X-ray spectrum of NGC 4507
Bianchi, S.; Matt, G.; D'Ammando, F. +1 more
XMM-Newton and Chandra/HETG spectra of the Compton-thin (NH∼4×1023 cm-2) Seyfert 2 galaxy, NGC 4507, are analyzed and discussed. The main results are: a) the soft X-ray emission is rich in emission lines; an (at least) two-zone photoionization region is required to explain the large range of ionization states; b) t…