Search Publications
Periodic variability during the X-ray decline of 4U 1636-53
Charles, P. A.; Bird, A. J.; Cornelisse, R. +2 more
We report the onset of a large amplitude, statistically significant periodicity (~46 d) in the Rossi X-ray Timing Explorer/All Sky Monitor (RXTE/ASM) data of the prototype X-ray burster 4U 1636-53, the X-ray flux of which has been gradually declining over the last 4 yr. This behaviour is remarkably similar to that observed in the neutron star low …
Stellar Populations in the Wing of the Small Magellanic Cloud from Hubble Space Telescope Photometry
Garnett, Donald R.; Dufour, Reginald J.; McCumber, Michael P.
We have used the Wide Field Planetary Camera 2 on the Hubble Space Telescope to image a star field in the wing of the Small Magellanic Cloud (SMC), near the H II region N81. The images were taken in the F336W, F547M, F675W, and F814W filters. From photometry of stars in this field, we construct color-magnitude diagrams (CMDs) for about 4200 stars …
The Nuclear Disk in the Dwarf Elliptical Galaxy NGC 4486A
Gebhardt, Karl; Kormendy, John; Sparks, W. B. +3 more
Many ellipticals contain nuclear disks of dust and gas. Some ellipticals contain nuclear disks of stars that are distinct from the rest of the galaxy. We show that the dwarf E2 galaxy NGC 4486A contains both-it is a ``Rosetta stone'' object that tells us how nuclear disks evolve. Its properties suggest that, as accreted gas dissipates and settles …
On the 3-dimensional structure of the streamer belt of the solar corona
Llebaria, A.; Zhukov, A. N.; Lamy, P. +1 more
We investigate the three-dimensional structure of the streamer belt of the solar corona using a model that allows us to simulate its quasi-stationary configuration. Starting from the National Solar Observatory photospheric magnetograms, the position of the neutral line at the source surface (2.5 ~R_⊙) is determined using the potential field source…
Enhanced X-ray variability from V1647 Ori, the young star in outburst illuminating McNeil's Nebula
Hamaguchi, K.; Grosso, N.; Kastner, J. H. +5 more
We report a 38 ks X-ray observation of McNeil's Nebula obtained with XMM-Newton on 2004 April 4. V1647 Ori, the young star in outburst illuminating McNeil's Nebula, is detected with XMM-Newton and appears variable in X-rays. We investigate the hardness ratio variability and time variations of the event energy distribution with quantile analysis, a…
Multialtitude Observations of a Coronal Jet during the Third Whole Sun Month Campaign
Mason, H. E.; Thompson, B. J.; Raymond, J. C. +11 more
On 1999 August 26, a coronal jet occurred at the northwest limb near a sigmoid active region (AR 8668) that was the target for a joint observation plan (SOHO joint observing program 106) during the third Whole Sun Month Campaign. This jet was observed by several instruments at the limb (SOHO/CDS, SOHO/EIT, TRACE, and Mauna Loa Solar Observatory CH…
Jupiter's cyclones and anticyclones vorticity from Voyager and Galileo images
Sánchez-Lavega, A.; Legarreta, J.
We have measured the internal velocity field in jovian synoptic-scale cyclones and anticyclones by tracking cloud elements in very high spatial resolution images obtained by the Voyager 1 and 2 (in 1979) and Galileo (1996-2000) spacecrafts. In total we have studied 24 different closed vortices (6 cyclones, 18 anticyclones) spanning a latitude rang…
On the formation of the He I 10 830 Å line in a flaring atmosphere
Ding, M. D.; Li, H.; Fang, C.
We explore the formation of the He i 10 830 Å line in a flaring atmosphere, with special attention to the nonthermal effects of an electron beam. Using non-LTE calculations we obtain the line profiles from different model atmospheres. Without the nonthermal effects, the line changes from weak absorption in a cool atmosphere to emission in a hot an…
Temporal deconvolution of the hydrogen coma. II. Pre- and post-perihelion activity of Comet Hyakutake (1996 B2)
Bertaux, J. -L.; Combi, M. R.; Mäkinen, J. T. T. +1 more
Comet 1996 B2 (Hyakutake) displayed strong evidence for break-up, with a prominent antisunward dust spike and fragments traveling antisunward for many days after an eruptive event in late March 1996. Because of its high orbital inclination and rapid southward motion after perihelion, its post-perihelion activity was not well monitored from the gro…
Correlation Heights of the Sources of Solar Ultraviolet Emission Lines in a Quiet-Sun Region
Wilhelm, Klaus; Marsch, Eckart; Wang, Jing-Xiu +4 more
The radiance and Doppler-velocity maps of the emission lines of Si II, C IV, and Ne VIII obtained in a quiet region of the Sun by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) are correlated with the vertical component, Bz, of the magnetic field vector as extrapolated, by means of a force-free field model, from the photosp…