Sergey Bondar

From TORTORA to MegaTORTORA—Results and Prospects of Search for Fast Optical Transients

To study short stochastic optical flares of different objects (GRBs, SNs, etc.) of unknown localizations as well as NEOs it is necessary to monitor large regions of sky with high-time resolution. We developed a system consisting of widefield camera with field of view of 400–600 sq.deg. which uses TV-CCD with 0.13 s temporal resolution to record and classify optical transients, and a fast robotic telescope aimed to perform their spectroscopic and photometric investigation just after detection. Such two-telescope complex, combining wide-field camera TORTORA and robotic telescope REM, operated from May 2006 at La Silla ESO observatory. Some results of its operation, including first high time resolution study of optical transient accompanying GRB and discovery of its fine time structure, are presented. Also, prospects for improving the efficiency of such observations are given, and a project of a next generation wide field monitoring system, the MegaTORTORA, is described.

TORTORA discovery of Naked‐Eye Burst fast optical variability

Features characterizing gamma‐ray bursts in the different spectral bands may be a clue for the nature of their inner engine. Up to now, only several bursts have been observed in optical band during the gamma activity, and the only one—GRB080319B—was covered from rise till fall with high temporal resolution. Here we discuss these data, acquired with TORTORA fast wide‐field monitoring optical camera, as well as results of its analysis.The camera observed the position of Naked‐Eye Burst, GRB080318B, before, during and after the trigger. It detected the fast rise of optical emission, which reached the peak of V 5.3 at the eighteenth second, had a complex evolution till T+43s and monotonously faded then. The brightest part of the light curve contains two 15–20 s segments with different fluxes, each having two clearly‐seen peaks of 5–8 s duration; all four peaks look quasi‐periodic with separation of 9 s. There is no clear evidence of any sub‐second variability. However, there are signs of quasi‐periodic variab...

Wide and Fast: Monitoring the Sky in Subsecond Domain with the FAVOR and TORTORA Cameras

In order to detect and investigate short stochastic optical flares from a number of variable astrophysical objects (GRBs, SNe, flare stars, CVs, X-Ray binaries) of unknown localizations as well as near-earth objects (NEOs), both natural and artificial, it is necessary to perform the systematic monitoring of large regions of the sky with high temporal resolution. Here we discuss the criteria for a system that is able to perform such a task and describe two cameras we created for wide-field monitoring with high temporal resolution—FAVOR and TORTORA. Also, we describe basic principles of real-time data processing for the high frame rates needed to achieve subsecond temporal resolution on a typical hardware.

Wide-field optical monitoring with Mini-MegaTORTORA (MMT-9) multichannel high temporal resolution telescope

We describe the properties of Mini-MegaTORTORA (MMT-9) nine-channel wide-field optical sky monitoring system with subsecond temporal resolution. This instrument can observe sky areas as large as 900 deg2, perform photometry in three filters close to Johnson BV R system and polarimetry of selected objects or areas with 100–300 deg2 sizes. The limiting magnitude of the system is up to V = 11m for 0.1 s temporal resolution, and reaches V = 15m in minute-long exposures. The system is equipped with a powerful computing facility and dedicated software pipeline allowing it to perform automatic detection, real-time classification, and investigation of transient events of different nature located both in the near- Earth space and at extragalactic distances. The objects routinely detected by MMT-9 include faint meteors and artificial Earth satellites.We discuss astronomical tasks that can be solved using MMT-9, and present the results of the first two years of its operation. In particular, we report the parameters of the optical flare detected on June 25, 2016, which accompanied the gamma-ray burst GRB160625B.

Multi-objective transforming telescope for wide-field optical monitoring of the sky with high-temporal resolution

We present the design of a MegaTORTORA telescope (and its prototype, mini-MegaTORTORA, presently in construction at Special Astrophysical Observatory) - modular, multi-purpose, scalable grid of optical cameras based on commercially available objectives and fast CCDs, able to operate with sub-second temporal resolution in both wide-field monitoring regime with all objectives observing different regions of the sky as well as in narrow-field follow-up mode with co-aligned channels and installed color and polarimetric filters for detailed investigation of selected objects, and to change the regime of operation on a sub-second time scale.

The first light of Mini-MegaTORTORA wide-field monitoring system

Abstract We describe the first light of a new 9-channel wide-field optical monitoring system with sub-second temporal resolution, Mini-MegaTORTORA, which is being tested now at the Special Astrophysical Observatory in Russian Caucasus. The system is able to observe the sky simultaneously in either wide (~900 deg2) or narrow (~100 deg2) fields of view, either in clear light or with any combination of color (Johnson B, V or R) and polarimetric filters installed, with exposure times ranging from 100 ms to 100 s. The primary goal of the system is the detection of rapid (with sub-second characteristic time scales) optical transients, but it may be also used for studying variability of sky objects over longer time scales.

Ground-based complex for detection and investigation of fast optical transients in wide field

To study short stochastic optical flares of different objects (GRBs, SNs, etc) of unknown localizations as well as NEOs it is necessary to monitor large regions of sky with high time resolution. We developed a system which consists of wide-field camera (FOW is 400-600 sq.deg.) using TV-CCD with time resolution of 0.13 s to record and classify optical transients, and a fast robotic telescope aimed to perform their spectroscopic and photometric investigation just after detection. Such two telescope complex TORTOREM combining wide-field camera TORTORA and robotic telescope REM operated from May 2006 at La Silla ESO observatory. Some results of its operation, including first fast time resolution study of optical transient accompanying GRB and discovery of its fine time structure, are presented. Prospects for improving the complex efficiency are given.

Wide Field Optical Camera for Search and Investigation of Fast Cosmic Transients

The primary purpose of the fast wide field optical camera (WFOC) is to perform continuous, alert‐independent observations of optical transients and variable astrophysical sources simultaneously with space‐born wide field X‐ and γ‐ray telescopes. In particular the camera can detect possible optical precursors and early prompt emission from cosmic Gamma‐Ray Bursts. The real‐time source identification software generates alerts that also could be sent to global alert distribution networks such as the GCN. We estimate that in one year of continuous observation with the WFOC we will observe the following numbers of GRB error boxes simultaneously with space‐ borne telescopes: 1.6 (WXM/HETE‐2), 0.5 (SPI/INTEGRAL), and 4 (BAT/SWIFT).

Untriggered search for rapid optical transients with Mini-MegaTORTORA wide-field monitoring system

Here we report an ongoing efforts for an untriggered search of rapid optical transients of various astrophysical and non-astrophysical origins on time scales down to fractions of a second with Mini-MegaTORTORA. Mini-MegaTORTORA is a novel 9-channel wide-field optical monitoring system in operation since 2014 at Special Astrophysical Observatory on Russian Caucasus.

Status and Perspectives of the Mini-MegaTORTORA Wide-field Monitoring System with High Temporal Resolution

Here we briefly summarize our long-term experience of constructing and operating wide-field monitoring cameras with sub-second temporal resolution to look for optical components of GRBs, fast-moving satellites and meteors. The general hardware requirements for these systems are discussed, along with algorithms for real-time detection and classification of various kinds of short optical transients. We also give a status report on the next generation, the MegaTORTORA multi-objective and transforming monitoring system, whose 6-channel (Mini-MegaTORTORA-Spain) and 9-channel prototypes (Mini-MegaTORTORA-Kazan) we have been building at SAO RAS. This system combines a wide field of view with subsecond temporal resolution in monitoring regime, and is able, within fractions of a second, to reconfigure itself to follow-up mode, which has better sensitivity and simultaneously provides multi-color and polarimetric information on detected transients.