We present a study of the parsec-scale multifrequency properties of the quasar S4 1030+61 during a prolonged radio and {gamma}-ray activity. Observations were performed within Fermi {gamma}-ray telescope, Owens Valley Radio Observatory 40-m telescope and MOJAVE Very Long Baseline Array (VLBA) monitoring programmes, covering five years from 2009. The data are supplemented by four-epoch VLBA observations at 5, 8, 15, 24 and 43GHz, which were triggered by the bright {gamma}-ray flare, registered in the quasar in 2010. The S4 1030+61 jet exhibits an apparent superluminal velocity of (6.4+/-0.4)c and does not show ejections of new components in the observed period, while decomposition of the radio light curve reveals nine prominent flares. The measured variability parameters of the source show values typical for Fermi-detected quasars. Combined analysis of radio and {gamma}-ray emission implies a spatial separation between emitting regions at these bands of about 12pc and locates the {gamma}-ray emission within a parsec from the central engine. We detected changes in the value and direction of the linear polarization and the Faraday rotation measure. The value of the intrinsic brightness temperature of the core is above the equipartition state, while its value as a function of distance from the core is well approximated by the power law. Altogether these results show that the radio flaring activity of the quasar is accompanied by injection of relativistic particles and energy losses at the jet base, while S4 1030+61 has a stable, straight jet well described by standard conical jet theories.
This study aims to search for the existence of intraday variability (IDV) of BL Lac object S5 0716+714 at high radio frequencies for which the interstellar scintillation effect is not significant. Using the 21-m radio telescope of the Korean VLBI Network (KVN), we present results of multi-epoch simultaneous dual-frequency radio observations. Single-dish observations of S5 0716+714 were simultaneously conducted at 21.7GHz (K-band) and 42.4GHz (Q-band), with a high cadence of 30-60min intervals. We observed four epochs between December 2009 and June 2010. Over the whole set of observation epochs, S5 0716+714 showed significant inter-month variations in flux density at both the K- and Q-bands, with modulation indices of approximately 19% for the K-band and approximately 36% for the Q-band. In all epochs, no clear intraday variability was detected at either frequency. The source shows monotonic flux density increase in epochs 1 and 3 and monotonic flux density decrease in epochs 2 and 4. In the flux density increasing phases, the flux densities at the Q-band increase more rapidly. In the decreasing phase, no significant flux density difference is seen at the two frequencies. The situation could be different close to flux density peaks that we did not witness in our observations. We find an inverted spectrum with mean spectral indices, {bar}{alpha}(S_{nu}_{prop.to}{nu}^-{alpha}^), of -0.57+/-0.13 in epoch 1 and -0.15+/-0.11 in epoch 3. On the other hand, we find relatively steep indices of +0.24+/-0.14 and +0.17+/-0.18 in epochs 2 and 4, respectively. We conclude that the frequency dependence of the variability and the change of the spectral index are caused by source-intrinsic effects rather than by any extrinsic scintillation effect.
We explored the AllWISE catalogue of the Wide-field Infrared Survey Explorer mission and identified Young Stellar Object candidates. Reliable 2MASS and WISE photometric data combined with Planck dust opacity values were used to build our dataset and to find the best classification scheme. A sophisticated statistical method, the Support Vector Machine (SVM) is used to analyse the multi-dimensional data space and to remove source types identified as contaminants (extragalactic sources, main sequence stars, evolved stars and sources related to the interstellar medium). Objects listed in the SIMBAD database are used to identify the already known sources and to train our method. A new all-sky selection of 133,980 Class I/II YSO candidates is presented. The estimated contamination was found to be well below 1% based on comparison with our SIMBAD training set. We also compare our results to that of existing methods and catalogues. The SVM selection process successfully identified >90% of the Class I/II YSOs based on comparison with photometric and spectroscopic YSO catalogues. Our conclusion is that by using the SVM, our classification is able to identify more known YSOs of the training sample than other methods based on colour-colour and magnitude-colour selection. The distribution of the YSO candidates well correlates with that of the Planck Galactic Cold Clumps in the Taurus-Auriga-Perseus-California region.
The SVO EXPORT Herbig AeBe SSAP service gives access to a homogeneous spectroscopic database of HAeBe stars. It consists of 337 multi-epoch optical spectra of 38 object observed by the EXPORT consortium (Eiroa, C., Alberdi, A., Camron, A. et al. 2000, ESASP, 451, 189) in 1998/1999.The multi-epoch observation is a useful approach for understanding the origin of the CS lines and their variability, and to establish distinctions in the physical processes operating in pre-main sequence stars.
The Filter Profile Service provides standardized information, including transmission curves and calibration, about astronomical filters. The service is designed to be compliant to the VO Photometry Data Model.
The SVOM mission currently under development will carry various instruments, and in particular the coded-mask telescope ECLAIRs, with a large field of view of about 2sr, operating in the 4-150keV energy band. The main goal of ECLAIRs is to detect high-energy transients such as gamma-ray bursts. Its onboard trigger software will search for new hard X-ray sources appearing in the sky, as well as peculiar behaviour (e.g. strong outbursts) from known sources, in order to repoint the satellite to perform follow-up observations with its onboard narrow-field-of-view instruments. The presence of known X-ray sources must be disentangled from the appearance of new sources. This is done with the help of an onboard source catalogue, which we present in this paper. As an input we use catalogues of X-ray sources detected by Swift/BAT and MAXI/GSC and we study the influence of the sources on ECLAIRs' background level and on the quality of the sky-image reconstruction process. We show that the influence of the sources depends on the pointing direction on the sky, on the energy band, and on the exposure time. In the Galactic centre, the contribution from known sources largely dominates the cosmic X-ray background, which is, on the contrary, the main background in sky regions lacking strong sources. We also demonstrate the need to clean the contributions of these sources in order to maintain a low noise level in the sky images and to maintain a low threshold for the detection of new sources without introducing false triggers. We briefly describe one of our cleaning methods and its challenges. Finally, we present the overall structure of the onboard catalogue and the way it will be used to perform the source cleaning and disentangle detections of new sources from outbursts of known sources.
