arXiv subjects

David C. Morris

Publications and source records attributed to David C. Morris.

4 recordsLinked to original sources

arXiv2018

From a computer controlled telescope to a robotic observatory: the history of the VIRT

The Virgin Island Robotic Telescope is located at the Etelman Observatory, St Thomas, since 2002. We will present its evolution since that date with the changes we have performed in order to modify an automated instrument, needing human supervision, to a fully robotic observatory. The system is based on ROS (Robotic Observatory Software) developed for TAROT and now installed on various observatories across the world (Calern, La Silla, Zadko, Les Markes, Etelman Observatory).

astro-ph.IM↗

arXiv2016

Solar Atmospheric Magnetic Energy Coupling: Broad Plasma Conditions and Spectrum Regimes

Solar variability investigations that include magnetic energy coupling are paramount to solving many key solar/stellar physics problems, particularly for understanding the temporal variability of magnetic energy redistribution and heating processes. Using three years of observations from the {\it Solar Dynamics Observatory's} Atmospheric Imaging Assembly and Heliosemic Magnetic Imager; radiative and magnetic fluxes were measured from gross features and at full-disk scales, respectively. Magnetic energy coupling analyses support radiative flux descriptions via a plasma heating connectivity of dominant (magnetic) and diffuse components, specifically of the predominantly closed field corona. Our work shows that this relationship favors an energetic redistribution efficiency across large temperature gradients, and potentially sheds light on the long withstanding issue of diffuse unresolved low corona emission. The intimacy of magnetic energy redistribution and plasma conditions revealed by this work holds significant insight for the field of stellar physics, as we have provided possible means for probing distant sources in currently limited and/or undetectable radiation distributions.

astro-ph.SR↗

arXiv2006

The Swift X-ray flaring afterglow of GRB 050607

The unique capability of the Swift satellite to perform a prompt and autonomous slew to a newly detected Gamma-Ray Burst (GRB) has yielded the discovery of interesting new properties of GRB X-ray afterglows, such as the steep early lightcurve decay and the frequent presence of flares detected up to a few hours after the GRB trigger. We present observations of GRB 050607, the fourth case of a GRB discovered by Swift with flares superimposed on the overall fading X-ray afterglow. The flares of GRB 050607 were not symmetric as in previously reported cases, showing a very steep rise and a shallower decay, similar to the Fast Rise, Exponential Decay that are frequently observed in the gamma-ray prompt emission. The brighter flare had a flux increase by a factor of approximately 25,peaking for 30 seconds at a count rate of approximately 30 counts s-1, and it presented hints of addition short time scale activity during the decay phase. There is evidence of spectral evolution during the flares. In particular, at the onset of the flares the observed emission was harder, with a gradual softening as each flare decayed. The very short time scale and the spectral variability during the flaring activity are indicators of possible extended periods of energy emission by the GRB central engine. The flares were followed by a phase of shallow decay, during which the forward shock was being refreshed by a long-lived central engine or by shells of lower Lorentz factors, and by a steepening after approximately 12 ks to a decay slope considered typical of X-ray afterglows.

astro-ph↗

arXiv2005

Swift XRT and VLT Observations of the Afterglow of GRB 041223

The Swift Gamma-Ray Burst Explorer, launched on 2004 November 20, is a multiwavelength, autonomous, rapid-slewing observatory for gamma-ray burst (GRB) astronomy. On 2004 December 23, during the activation phase of the mission, the Swift X-Ray Telescope (XRT) was pointed at a burst discovered earlier that day by the Swift Burst Alert Telescope. A fading, uncataloged X-ray source was discovered by the XRT and was observed over a period of about 3 hours, beginning 4.6 hours after the burst. The X-ray detection triggered a VLT observation of the optical/NIR counterpart, located about 1.1 arcseconds from the XRT position. The X-ray counterpart faded rapidly, with a power law index of -1.72 +/- 0.20. The average unabsorbed X-ray flux 4.6-7.9 hours after the burst was 6.5 x 10^{-12} erg cm^{-2} s^{-1} in the 0.5-10 keV band, for a power-law spectrum of photon index 2.02 +/- 0.13 with Galactic absorption. The NIR counterpart was observed at three epochs between 16 and 87 hours after the burst, and faded with a power-law index of -1.14 +/- 0.08 with a reddening-corrected SED power-law slope of -0.40 +/- 0.03. We find that the X-ray and NIR data are consistent with a two-component jet in a wind medium, with an early jet break in the narrow component and an underlying electron index of 1.8-2.0.

astro-ph↗