R. Opiela

Early optical follow-up of the nearby active star DG CVn during its 2014 superflare

DG CVn is a binary system in which one of the components is an M type dwarf ultra fast rotator, only three of which are known in the solar neighborhood. Observations of DG CVn by the Swift satellite and several ground-based observatories during its super-flare event on 2014 allowed us to perform a complete hard X-ray - optical follow-up of a super-flare from the red-dwarf star. The observations support the fact that the super-flare can be explained by the presence of (a) large active region(s) on the surface of the star. Such activity is similar to the most extreme solar flaring events. This points towards a plausible extrapolation between the behaviour from the most active red-dwarf stars and the processes occurring in the Sun.

Pi of the Sky—robotic telescope

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 Telescopes in Spain and Chile

Pi of the Sky is a system of robotic telescopes designed for observations of short timescale astrophysical phenomena, e.g. prompt optical GRB emissions. The apparatus is designed to monitor a large fraction of the sky with 12–13 m range and time resolution of the order of 1–10 seconds. In October 2010 the first unit of the new Pi of the Sky detector system was successfully installed in the INTA El Arenosillo Test Centre in Spain. We also moved our prototype detector from Las Campanas Observatory to San Pedro de Atacama Observatory in March 2011. The status and performance of both detectors is presented.

Present status of Pi of the Sky telescopes

In October 2010 Pi of the Sky set up a new system, consisting of 4 cameras installed on a new mount, in El Arenosillo, in southern Spain. It was followed by moving the prototype system from Las Campanas Observatory (central Chile) to San Pedro de Atacama (northern Chile) in March 2011. In this paper our new sites, some details about observational conditions and first results in both observatories are described.

Hunting for Gamma Ray Bursts with Pi of the Sky telescopes in Chile and Spain

The 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 12 − 13 range and time resolution of the order of 1− 10 seconds. System design and observation strategy were 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 6 400 square degrees. Status and performance of the detectors is presented.

Parallax in Pi of the Sky project

Starting March 2011 the “Pi of the Sky” project has two observatories in use: in northern Chile and in southern Spain. Since then we are able to observe a parallax of objects, which pass close to the Earth. Simultaneous observations from two sites are very important to us, because this allows us to reject false flash observations, due to cosmic radiation, meteors, planes, etc. In this paper we present theoretical limitations of our parallax observations. Moreover, first results are shown.

Improving photometry of the Pi of the Sky

After brief introduction to the Pi of the Sky project standard photometry method used in the data reduction will be described. After data quality cuts uncertainty of the single measurement is of the order of 0.018-0.024 magnitudo for stars 7-10m. With new calibration algorithm taking into account the spectral type of reference stars stability of the photometry algorithm can be significantly improved. Preliminary results from the BGInd variable are presented showing than uncertainty of the order of 0.013 can be obtained.

Pi of the Sky observation of GRB160625B

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.

Comparison of the period detection algorithms based on Pi of the Sky data

The Pi of the Sky is a system of five autonomous detectors designed for continuous observation of the night sky, mainly looking for optical flashes of astrophysical origin, in particular for Gamma Ray Bursts (GRB). In the Pi of the Sky project we also study many kinds of variable stars (periods in range of 0.5d - 1000.0d) or take part in the multiwavelength observing campaigns, such as the DG Cvn outburst observations. Our wide field of view robotic telescopes are located in San Pedro the Atacama Observatory, Chile and INTA El Arenosillo Observatory, Spain and were designed for monitoring a large fraction of the sky with 12m -13m range and time resolution of the order of 1 - 10 seconds. During analysis of the variable stars observations very important is accurate determination of their variability parameters. We know a lot of algorithms which can be used to the variability analysis of the observed stars123 . In this article using Monte Carlo analysis we compare all used by us the period detection algorithms dedicated to the astronomical origin data analysis. Based on the tests performed we show which algorithm gives us the best period detection quality and try to derived approximate formula describing the period detection error. We also give some examples of this calculation based on the observed by our detectors variable stars. At the end of this article we show how removing bad measurements from the analysed light curve affect to the accuracy of the period detection.

Pi of the Sky preparations towards advanced gravitational detector era

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.