Detection Of Optical Transients Research Articles

Up-converted photorefractive optical transient detection with femtosecond laser pulses.

We report on experimental demonstration of optical transient detection (OTD) based on photorefractive two-wave mixing of femtosecond pulses. The demonstrated technique also combines nonlinear-crystal-based OTD with up-conversion from infrared into the visible range. The approach enables measurement of phase changes of a dynamic signal in the infrared using GaP- or Si-based detectors while suppressing stationary background. Experimental results reveal existence of the relation between input phases in the infrared and output phases in the visible wavelength range. We further present experimental evidence of additional merits of up-converted transient phase analysis under noisy conditions, such as residual continuous-wave emission affecting the ultrashort pulses from the laser.

Vetting the optical transient candidates detected by the GWAC network using convolutional neural networks

ABSTRACT The observation of the transient sky through a multitude of astrophysical messengers has led to several scientific breakthroughs in the last two decades, thanks to the fast evolution of the observational techniques and strategies employed by the astronomers. Now, it requires to be able to coordinate multiwavelength and multimessenger follow-up campaigns with instruments both in space and on ground jointly capable of scanning a large fraction of the sky with a high-imaging cadency and duty cycle. In the optical domain, the key challenge of the wide field-of-view telescopes covering tens to hundreds of square degrees is to deal with the detection, identification, and classification of hundreds to thousands of optical transient (OT) candidates every night in a reasonable amount of time. In the last decade, new automated tools based on machine learning approaches have been developed to perform those tasks with a low computing time and a high classification efficiency. In this paper, we present an efficient classification method using convolutional neural networks (CNNs) to discard many common types of bogus falsely detected in astrophysical images in the optical domain. We designed this tool to improve the performances of the OT detection pipeline of the Ground Wide field Angle Cameras (GWAC) telescopes, a network of robotic telescopes aiming at monitoring the OT sky down to R = 16 with a 15 s imaging cadency. We applied our trained CNN classifier on a sample of 1472 GWAC OT candidates detected by the real-time detection pipeline.

Open-source, cost-effective system for low-light in vivo fiber photometry.

Fiber photometry uses genetically encoded optical reporters to link specific cellular activity in stereotaxically targeted brain structures to specific behaviors. There are still a number of barriers that have hindered the widespread adoption of this approach. This includes cost, but also the high-levels of light required to excite the fluorophore, limiting commercial systems to the investigation of short-term transients in neuronal activity to avoid damage of tissue by light. Here, we present a cost-effective optoelectronic system for in vivo fiber photometry that achieves high-sensitivity to changes in fluorescence intensity, enabling detection of optical transients of a popular calcium reporter with excitation powers as low as 100nW. By realizing a coherent detection scheme and by using a photomultiplier tube as a detector, the system demonstrates reliable study of in vivo neuronal activity, positioning it for future use in the experiments inquiring into learning and memory processes. The system was applied to study stress-evoked calcium transients in corticotropin-releasing hormone neurons in the mouse hypothalamus.

Detection of GRBs and OTs by All‐Sky Optical and SID Monitors

We report on two alternative simple methods to detect counterparts of cosmic gamma‐ray bursts (GRBs) and optical transients (OTs). We report on the development and tests of an alternative optical all‐sky monitor recently tested at the Karlovy Vary Observatory. The monitor is based on a Peleng 8 mm fish‐eye lens (1 : 3,5–1 : 16) and CANON EOS 350D digital CCD camera. This type of monitor represents a low‐cost device suitable for easy replication and still able to detect brighter optical transients simultaneously to GRB triggers. Such OTs have been observed for some of the GRBs such as GRB990123, GRB060117, or recently GRB080319 indicating that some fraction of GRBs can generate optical transient emission accessible by simple small aperture instrumentation as described here. These efforts are accompanied by development of dedicated programmes to access and to evaluate all‐sky images; these efforts will be also briefly described. The All‐Sky Monitor is a space variant optical system and its point spread function (PSF) has not uniform shape in the field of view. The processing and measuring of image data is complicated, and sophisticated deconvolution algorithms are used for image restoration. The second method is the GRB detection based on their ionospheric response.

OT 060420: A Seemingly Optical Transient Recorded by All‐Sky Cameras

ABSTRACTWe report on a ∼5th magnitude flash detected for approximately 10 minutes by two CONCAM all‐sky cameras located in Cerro Pachón, Chile, and La Palma, Spain. A third all‐sky camera, located in Cerro Paranal, Chile, did not detect the flash, and therefore we suggest that the flash was a series of cosmic‐ray hits, meteors, or satellite glints. Another proposed hypothesis is that the flash was an astronomical transient with variable luminosity. In this paper, we discuss bright optical transient detection using fish‐eye all‐sky monitors, analyze the apparently false‐positive optical transient, and propose possible causes to false optical transient detection in all‐sky cameras.

Transient Detection Using Panoramic All-Sky Cameras

A method of using on-going panoramic all-sky monitors for the purpose of bright optical transient detection is described. The detection is performed by comparing all-sky images to canonical images taken at the same sidereal time. The described approach has been implemented and tested using the infrastructure of the Night Sky Live network of panoramic all-sky cameras. Preliminary results of detected bright flashes are presented in the paper.

Software for detection of optical transients in observations with rapid wide‐field camera

Astronomische NachrichtenVolume 325, Issue 6-8 p. 676-676 Original Paper Software for detection of optical transients in observations with rapid wide-field camera A. Biryukov, A. Biryukov [email protected] Sternberg Astronomical Institute of Moscow State University, 13 Universitetskij pr., 117415 Moscow, Russia SAO RAS, 369167 Nizhnij Arkhyz, Karachai-Cherkessia, RussiaSearch for more papers by this authorG. Beskin, G. Beskin SAO RAS, 369167 Nizhnij Arkhyz, Karachai-Cherkessia, RussiaSearch for more papers by this authorS. Bondar, S. Bondar Russian Institute of Precision Instruments, 53 Aviamotornaya st., 111250 Moscow, RussiaSearch for more papers by this authorK. Hurley, K. Hurley Space Science Labolatory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450, USASearch for more papers by this authorE. Ivanov, E. Ivanov Russian Institute of Precision Instruments, 53 Aviamotornaya st., 111250 Moscow, RussiaSearch for more papers by this authorS. Karpov, S. Karpov SAO RAS, 369167 Nizhnij Arkhyz, Karachai-Cherkessia, RussiaSearch for more papers by this authorE. Katkova, E. Katkova Russian Institute of Precision Instruments, 53 Aviamotornaya st., 111250 Moscow, RussiaSearch for more papers by this authorA. Pozanenko, A. Pozanenko Space Research Institute, 84/32 Profsojuznaja st., 117997 Moscow, RussiaSearch for more papers by this authorI. Zolotukhin, I. Zolotukhin Sternberg Astronomical Institute of Moscow State University, 13 Universitetskij pr., 117415 Moscow, Russia SAO RAS, 369167 Nizhnij Arkhyz, Karachai-Cherkessia, RussiaSearch for more papers by this author A. Biryukov, A. Biryukov [email protected] Sternberg Astronomical Institute of Moscow State University, 13 Universitetskij pr., 117415 Moscow, Russia SAO RAS, 369167 Nizhnij Arkhyz, Karachai-Cherkessia, RussiaSearch for more papers by this authorG. Beskin, G. Beskin SAO RAS, 369167 Nizhnij Arkhyz, Karachai-Cherkessia, RussiaSearch for more papers by this authorS. Bondar, S. Bondar Russian Institute of Precision Instruments, 53 Aviamotornaya st., 111250 Moscow, RussiaSearch for more papers by this authorK. Hurley, K. Hurley Space Science Labolatory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450, USASearch for more papers by this authorE. Ivanov, E. Ivanov Russian Institute of Precision Instruments, 53 Aviamotornaya st., 111250 Moscow, RussiaSearch for more papers by this authorS. Karpov, S. Karpov SAO RAS, 369167 Nizhnij Arkhyz, Karachai-Cherkessia, RussiaSearch for more papers by this authorE. Katkova, E. Katkova Russian Institute of Precision Instruments, 53 Aviamotornaya st., 111250 Moscow, RussiaSearch for more papers by this authorA. Pozanenko, A. Pozanenko Space Research Institute, 84/32 Profsojuznaja st., 117997 Moscow, RussiaSearch for more papers by this authorI. Zolotukhin, I. Zolotukhin Sternberg Astronomical Institute of Moscow State University, 13 Universitetskij pr., 117415 Moscow, Russia SAO RAS, 369167 Nizhnij Arkhyz, Karachai-Cherkessia, RussiaSearch for more papers by this author First published: 13 October 2004 https://doi.org/10.1002/asna.200410329Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume325, Issue6-8October 2004Pages 676-676 RelatedInformation

BeppoSAX observation of the X-ray emission of gamma-ray bursts

For more than 20 years the difficulty, to locate the direction of a beam, intrinsic to the γ ray detection techniques, and the rapidity of the phenomenon itself has been the insurmountable limit to the association of Gamma-Ray Bursts with an already established class of sources. The combination of different instruments aboard BeppoSAX has turned out to be a real breakthrough for the study of this outstanding phenomenon. From January to May 1997 four gamma ray bursts were detected with Wide Field Instruments and a rapidly pointed with Narrow Field Instruments. In the direction of three of these burst (and likely also of the fourth one) faint, fading sources, have been found. These fading sources decay according to a power law but with the evidence of a flaring activity. The spectra are hard and non-thermal. Some data suggest that the burst itself continuously evolves into the decaying source and the energy associated to the source is comparable to that of the burst itself. This discovery, followed by the detection of optical transients associated with two of the X-ray sources, one with a nebulosity ad another with redshifted absorption features and a scintillating radio source, has substantially enriched the phenomenological landscape of orders of magnitude in wavelength, positioning and time starting a new season of theoretical interpretations. The perspectives of this research of BeppoSAX and the new contribution of other missions, with particular regard to RossiXTE, are also discussed.

Ground-based optical CCD experiments for GRB and optical transient detection

We present details of one operational ground-based experiment for optical detection of GRBs and two which are under consideration/development. The wide-field CCD camera is already in manual burst alert operation with promising results. The Optical Transient Monitor is a CCD-based double monitor suitable for network use for reliable detection of short-lived phenomena in the sky. The system is well suited for correlated efforts with GRB projects. The third experiment is a robotic telescope with automatic response to GRB burst alert messages received via the Internet link. It is expected to get CCD frames with a FOV of 20 deg (needed for BACODINE triggers) of positions of newly detected GRBs within 1 minute.