The purpose of this article is to present novel algorithm for searching variable stars in the Pi of the Sky data, based on Multivariate Analysis (MVA). Pi of the Sky is a system of wide field-of-view robotic telescopes, which search for short timescale astrophysical phenomena, especially for prompt optical emission from GRB. The system was designed for autonomous operation, monitoring a large fraction of the sky with 12m -13m range and time resolution of the order of 1 - 100 seconds.
Dedicated photometric algorithm was implemented in the LUIZA framework and optimized on a sample of test sky images. It was then used on a ”training” image sample, which was obtained by modifying the test sample of images, using different patterns of variability to selected constant stars. Different statistical estimators were considered to find the most efficient algorithm, based on MVA method, for variable star identification. Analysis of the test results indicated that most efficient candidate star selection can be based on the so called Boosted Decision Tree (BDT) approach. The algorithm is then used to search for variable star candidates in the actual data. New results of the analysis and three candidate stars found are presented.
Pi of the Sky is a system of wide field of view robotic telescopes, which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system was designed for autonomous operation, monitoring a large fraction of the sky to a depth of 12m−13m and with time resolution of the order of 10 seconds. Custom designed CCD cameras are equipped with Canon lenses f = 85 mm, f/d = 1.2 and cover 20° × 20° of the sky each. The final system with 16 cameras on 4 equatorial mounts was completed in 2014 at the INTA El Arenosillo Test Centre in Spain.
GRB160625B was an extremely bright GRB with three distinct emission episodes. Cameras of the Pi of the Sky observatory in Spain were not observing the position of the GRB160625B prior to the first emission episode. Observations started only after receiving Fermi/GBM trigger, about 140 seconds prior to the second emission. As the position estimate taken from the Fermi alert and used to position the telescope was not very accurate, the actual position of the burst happened to be in the overlap region of two cameras, resulting in two independent sets of measurements. Light curves from both cameras were reconstructed using the Luiza framework. No object brighter than 12.4m (3σ limit) was observed prior to the second GRB emission. An optical flash was identified on an image starting -5.9s before the time of the Fermi/LAT trigger, brightening to about 8m on the next image and then becoming gradually dimmer, fading below our sensitivity after about 400s.
Emission features as measured in different spectral bands indicate that the three emission episodes of GRB160625B were dominated by distinct physics process. Simultaneously observations in gamma-rays and optical wavelengths support the hypothesis that this was the first observed transition from thermal to non-thermal radiation in a single GRB. Main results of the combined analysis are presented.
The presentation focuses on plans of the Pi of the Sky collaboration to participate in the future LSC-Virgo's Electromagnetic (EM) Follow-up campaigns. Pi of the Sky telescope participated in the first "EM Follow-up project", called Looc-Up1-3 2009-2010 organized by LSC-Virgo collaboration. Pi of the Sky brought to the project an instrument with the biggest field of view and with a very high time resolution. Recently Pi of the Sky has signed an Memorandum of Understanding (MOU) with LSC-Virgo for EM Follow-up observations in the Advanced Detector Era (ADE). Plans of the Pi of the Sky telescope for joint observations with advanced LIGO and Virgo detectors will be also outlined.
"Pi of the Sky" is a system of wide field of view robotic telescopes, which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system was designed for autonomous operation, monitoring a large fraction of the sky with 12m-13m range and time resolution of the order of 1 - 10 seconds. For now there are two working "Pi of the Sky" observatories: in San Pedro de Atacama (Chile) and near Mazagón in Southern Spain. In this paper we report on the status of the project, as well as recent observation of asteroid 2004BL86, which passed the Earth in late January 2015, DG CVn outburst in 2014, satellites observations and our future plans.
Pi of the Sky is a system of wide field-of-view robotic telescopes, which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system was designed for autonomous operation, monitoring a large fraction of the sky with 12m-13m range and time resolution of the order of 1 - 100 seconds. LUIZA is a dedicated framework developed for efficient off-line processing of the Pi of the Sky data, implemented in C++.
The photometric algorithm based on ASAS photometry was implemented in LUIZA and compared with the algorithm based on the pixel cluster reconstruction and simple aperture photometry algorithm. Optimized photometry algorithms were then applied to the sample of test images, which were modified to include different patterns of variability of the stars (training sample). Different statistical estimators are considered for developing the general variable star identification algorithm. The algorithm will then be used to search for short-period variable stars in the real data.
Pi of the Sky is a system of wide field-of-view robotic telescopes, which search for short timescale astrophysical phenomena, especially for prompt optical GRB emission. The system was designed for autonomous operation, monitoring a large fraction of the sky with 12m-13m range and time resolution of the order of 1 - 100 seconds. System design and observation strategy were successfully tested with a prototype detector in Chile, operational since 2004. In July 2013 the final Pi of the Sky detector system, with 16 CCD cameras on 4 mounts, was comissioned at the INTA El Arenosillo Test Centre in Spain, resulting in a total coverage of about 6000 square degrees. LUIZA is a dedicated framework developed for efficient image processing, implemented in C++. Data analysis is divided into small, well-defined steps, which are implemented as so called processors. The framework allows to define the processor selection and their order, as well as all the required parameters at runtime, in a simple XML steering file. It was used in the presented study to compare three different photometric algorithms considered in analysis of the Pi of the Sky data. The algorithm based on the ASAS photometry was implemented in LUIZA as a sequence of three processors. First processor searches for stars in the considered images and extracts parameters of the Gaus profile describing star pointoint spread function (PSF) best. The next processor uses the PSF parameters to convolute the image with the Gaussian kernel and used to identify stars on the resulting image. In the last step the actual photometry is peformed, i.e. object brightnesses are calculated. In the presented study, results obtained from the ASAS photometry were compared with the new photometry algorithm developed within LUIZA and with the simple aperture photometry implemented previoulsly Results are presented for analysis of single images with different exposure times, as well as for stacked frames.
Pi of the Sky telescope have taken part in gravitational wave EM follow-up project, runned by LSC-Virgo Collaboration, in its initial run in 2009-2010. Since than gravitational wave detectors are being upgraded and become operation in 2015, when the next science run is planned. The paper focuses on Pi of the Sky preparations to LSC-Virgo EM Follow-up project of gravitational wave transient candidates in 2015+ and on Pi of the Sky results of previous science run 2009-2010.
The aim of the paper is to show methods used by Pi of the Sky team to search for optical counterparts of GW event candidates during Looc-Up science run1 and methods that we are planning to develop as part of the future Looc-Up. During the future joint GW-EM observations a new Pi of the Sky telescope unit could image more than 1/3 of GW candidate probability maps in less than 10 minutes, taking many pictures of the same observation eld. The system could automatically recognize optical transients and perform follow-ups of interesting events.
Pi of the Sky is a system of wide field-of-view robotic telescopes designed for observations of short timescale astrophysical phenomena, especially for prompt optical GRB emission. The apparatus was designed for autonomous operation, follows the predefined observing strategy and adopts it to the actual conditions, monitoring a large part of the sky with time resolution of the order of 1 - 10 seconds and range 12m-13m.
Observation strategy and system design was successfully tested with a prototype detector working in 2004-2009 at Las Campanas Observatory, Chile, and moved to San Pedro de Atacama Observatory in March 2011. In October 2010 the first unit of the final Pi of the Sky detector system, with 4 CCD cameras, was successfully installed in the INTA El Arenosillo Test Centre in Spain. Simultaneous observations from locations in Chile and Spain allow a systematic search for optical transients of cosmological origin. Accurate analysis of data arising from a wide-field system like Pi of the Sky is a real challenge because of a number of factors that can influence the measurements. We have developed a set of dedicated algorithms which remove poor quality measurements, improve photometric accuracy and allow us to reach uncertainties as low as 0.015– 0.02 mag.
Three more units (12 CCD cameras) are being prepared for installation on a new platform in INTA, aiming at a total coverage of about 6400 square degrees. Status and performance of the detectors is presented.
Pi of the Sky is a system of wide field-of-view robotic telescopes, which search for short timescale astrophysic phenomena, especially for prompt optical GRB emission. The system was designed for autonomous operatio , monitoring a large fraction of the sky with 12m-13m range and time resolution of the order of 1 - 10 second , and automatic flash recognition in real time.
System design and observation stratedy was successfully tested with a prototype detector operational in 2004-
2009 at Las Campanas Observatory, Chile, and moved to San Pedro de Atacama Observatory in March 2011.
In October 2010 the first unit of the final Pi of the Sky detector system, with 4 CCD cameras, was successfully installed in the INTA El Arenosillo Test Centre in Spain. Three more units (12 CCD cameras) are being prepared for installation on a new platform in INTA, aiming at a total coverage of about 6400 square degrees. Observation strategy and background conditions are different than those in Chile. Therefore additional selection algorithm are needed to improve rejection of false flash candidates selected by the on-line selection algrithm.
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