No Arabic abstract
We report on the current operating status of the ROTSE-IIIa telescope, currently undergoing testing at Los Alamos National Laboratories in New Mexico. It will be shipped to Siding Spring Observatory, Australia, in first quarter 2002. ROTSE-IIIa has been in automated observing mode since early October, 2001, after completing several weeks of calibration and check-out observations. Calibrated lists of objects in ROTSE-IIIa sky patrol data are produced routinely in an automated pipeline, and we are currently automating analysis procedures to compile these lists, eliminate false detections, and automatically identify transient and variable objects. The manual application of these procedures has already led to the detection of a nova that rose over six magnitudes in two days to a maximum detected brightness of m_R~13.9 and then faded two magnitudes in two weeks. We also readily identify variable stars, includings those suspected to be variables from the Sloan Digital Sky Survey. We report on our system to allow public monitoring of the telescope operational status in real time over the WWW.
The observation of a prompt optical flash from GRB990123 convincingly demonstrated the value of autonomous robotic telescope systems. Pursuing a program of rapid follow-up observations of gamma-ray bursts, the Robotic Optical Transient Search Experiment (ROTSE) has developed a next-generation instrument, ROTSE-III, that will continue the search for fast optical transients. The entire system was designed as an economical robotic facility to be installed at remote sites throughout the world. There are seven major system components: optics, optical tube assembly, CCD camera, telescope mount, enclosure, environmental sensing & protection and data acquisition. Each is described in turn in the hope that the techniques developed here will be useful in similar contexts elsewhere.
The X-ray nova XTE J1118+480 exhibited two outbursts in the early part of 2000. As detected by the Rossi X-ray Timing Explorer (RXTE), the first outburst began in early January and the second began in early March. Routine imaging of the northern sky by the Robotic Optical Transient Search Experiment (ROTSE) shows the optical counterpart to XTE J1118+480 during both outbursts. These data include over 60 epochs from January to June 2000. A search of the ROTSE data archives reveal no previous optical outbursts of this source in selected data between April 1998 and January 2000. While the X-ray to optical flux ratio of XTE J1118+480 was low during both outbursts, we suggest that they were full X-ray novae and not mini-outbursts based on comparison with similar sources. The ROTSE measurements taken during the March 2000 outburst also indicate a rapid rise in the optical flux that preceded the X-ray emission measured by the RXTE by approximately 10 days. Using these results, we estimate a pre-outburst accretion disk inner truncation radius of 1.2 x 10^4 Schwarzschild radii.
The ANTARES telescope has the capability to detect neutrinos produced in astrophysical transient sources. Potential sources include gamma-ray bursts, core collapse supernovae, and flaring active galactic nuclei. To enhance the sensitivity of ANTARES to such sources, a new detection method based on coincident observations of neutrinos and optical signals has been developed. A fast online muon track reconstruction is used to trigger a network of small automatic optical telescopes. Such alerts are generated for special events, such as two or more neutrinos, coincident in time and direction, or single neutrinos of very high energy.
The Gravitational-wave Optical Transient Observer (GOTO) is a wide-field telescope project focused on detecting optical counterparts to gravitational-wave sources. The GOTO Telescope Control System (G-TeCS) is a custom robotic control system which autonomously manages the GOTO telescope hardware and nightly operations. Since the commissioning the GOTO prototype on La Palma in 2017, development of the control system has focused on the alert handling and scheduling systems. These allow GOTO to receive and process transient alerts and then schedule and carry out observations, all without the need for human involvement. GOTO is ultimately anticipated to include multiple telescope arrays on independent mounts, both on La Palma and at a southern site in Australia. When complete these mounts will be linked to form a single multi-site observatory, requiring more advanced scheduling systems to best optimise survey and follow-up observations.
We present several cases of optical observations during gamma-ray bursts (GRBs) which resulted in prompt limits but no detection of optical emission. These limits constrain the prompt optical flux densities and the optical brightness relative to the gamma-ray emission. The derived constraints fall within the range of properties observed in GRBs with prompt optical detections, though at the faint end of optical/gamma flux ratios. The presently accessible prompt optical limits do not require a different set of intrinsic or environmental GRB properties, relative to the events with prompt optical detections.