Search Publications
HILIGT, upper limit servers I-Overview
Gabriel, C.; Kretschmar, P.; Kuulkers, E. +10 more
The advent of all-sky facilities, such as the Neil Gehrels Swift observatory, the All Sky Automated Search for Supernovae (ASAS-SN), eROSITA and Gaia has led to a new appreciation of the importance of transient sources in solving outstanding astrophysical questions. Identification and catalogue cross-matching of transients has been eased over the …
HILIGT, Upper Limit Servers II - Implementing the data servers
Freyberg, M. J.; Wilms, J.; Savchenko, V. +7 more
The High-Energy Lightcurve Generator (HILIGT) is a new web-based tool which allows the user to generate long-term lightcurves of X-ray sources. It provides historical data and calculates upper limits from image data in real-time. HILIGT utilizes data from twelve satellites, both modern missions such as XMM-Newton and Swift, and earlier facilities …
The Open Universe VOU-Blazars tool
Giommi, P.; Chang, Y. -L.; Brandt, C. H.
Blazars are a remarkable type of Active Galactic Nuclei (AGN) that are playing an important and rapidly growing role in today's multi-frequency and multi-messenger astrophysics. In the past several years, blazars have been discovered in relatively large numbers in radio, microwave, X-ray and gamma-ray surveys, and more recently have been associate…
Identifying transient and variable sources in radio images
Eislöffel, J.; Wijers, R. A. M. J.; Fender, R. +16 more
With the arrival of a number of wide-field snapshot image-plane radio transient surveys, there will be a huge influx of images in the coming years making it impossible to manually analyse the datasets. Automated pipelines to process the information stored in the images are being developed, such as the LOFAR Transients Pipeline, outputting light cu…
Estimation of error on the cross-correlation, phase and time lag between evenly sampled light curves
Misra, R.; Dewangan, G.; Bora, A.
Temporal analysis of radiation from Astrophysical sources like Active Galactic Nuclei, X-ray Binaries and Gamma-ray bursts provides information on the geometry and sizes of the emitting regions. Establishing that two light-curves in different energy bands are correlated, and measuring the phase and time-lag between them is an important and frequen…
Spectral clustering for optical confirmation and redshift estimation of X-ray selected galaxy cluster candidates in the SDSS Stripe 82
Takey, A.; Mahmoud, E.; Shoukry, A.
We develop a galaxy cluster finding algorithm based on spectral clustering technique to identify optical counterparts and estimate optical redshifts for X-ray selected cluster candidates. As an application, we run our algorithm on a sample of X-ray cluster candidates selected from the third XMM-Newton serendipitous source catalog (3XMM-DR5) that a…
Mobile applications and Virtual Observatory
Schaaff, A.; Jagade, S.
Within a few years, smartphones and Internet tablets have become the devices to access Web or standalone applications from everywhere, with a rapid development of the bandwidth of the mobile networks (e.g. 4G). Internet tablets are used to take notes during meetings or conferences, to read scientific papers in public transportation, etc. A smartph…
Irregular time series in astronomy and the use of the Lomb-Scargle periodogram
Andreani, P.; Vio, R.; Diaz-Trigo, M.
Detection of a signal hidden by noise within a time series is an important problem in many astronomical searches, i.e. for light curves containing the contributions of periodic/semi-periodic components due to rotating objects and all other astrophysical time-dependent phenomena. One of the most popular tools for use in such studies is the periodog…