Rubin-LSST

Abstract:

E-VLBI (electronic very long baseline interferometry) is a new implementation of the VLBI technique consisting in transferring the data from the radio telescopes to the correlator over the internet and correlating them in real-time. Time-wise this is a major improvement over the traditional method. e-VLBI is thus offering new opportunities for radio transient studies. Its capability of rapid response enables a more efficient decision making process with respect to potential followup observations. The rapid feedback time also permits to quickly modify the observing strategy to best track the development of the transient phenomena. The results summarized here have been obtained with the EVN (European VLBI Network) in the past few years within a transient ToO programme. The targets were XRBs (X-ray binaries) undergoing periods of enhanced activity (outbursts). The EVN observations were performed at 5 GHz and were often complemented by quasi-simultaneous (within one day) data at other wavelengths (X-ray and optical). The findings reveal a complex behaviour of the accretion/ejection phenomena in the systems investigated and offer insights into the extreme physics close to a compact object.

Abstract:

We present the results of our investigation into the stellar populations of 24 radio galaxies at z ≃ 0.5 drawn from four complete, low-frequency-selected radio surveys. We use the strength of the 4000-Å break as an indicator of recent star formation and compare this with radio luminosity, optical spectral classification and morphological classification. We find evidence of different star formation histories for high- and low-luminosity radio sources; our group of low radio luminosity sources (typically Fanaroff-Riley type I sources) has systematically older stellar populations than the higher radio luminosity group. Our sample is also fairly well divided by optical spectral classification. We find that galaxies classified as having low excitation spectra (LEGs) possess older stellar populations than high excitation line objects (HEGs), with the HEGs showing evidence for recent star formation. We also investigate the link between radio morphology, as used by Owen and Laing, and the stellar populations. We find that there is a preference for the 'fat-double' sources to have older stellar populations than the 'classical double' sources, although this is also linked to these sources lying predominantly in the LEG and HEG categories, respectively. These results are consistent with the hypothesis that HEGs are powered by accretion of cold gas, which could be supplied, for example, by recent mergers, secular instabilities or filamentary cold flows. These processes could also trigger star formation in the host galaxy. The host galaxies of the LEGs do not show evidence for recent star formation and an influx of cold gas and are consistent with being powered by the accretion of the hot phase of the interstellar medium. © 2010 The Authors. Journal compilation © 2010 RAS.

Abstract:

The 2009 November outburst of the neutron star X-ray binary Aquila X-1 (Aql X-1) was observed with unprecedented radio coverage and simultaneous pointed X-ray observations, tracing the radio emission around the full X-ray hysteresis loop of the outburst for the first time. We use these data to discuss the disk-jet coupling, finding the radio emission to be consistent with being triggered at state transitions, both from the hard to the soft spectral state and vice versa. Our data appear to confirm previous suggestions of radio quenching in the soft state above a threshold X-ray luminosity of ∼10% of the Eddington luminosity. We also present the first detections of Aql X-1 with very long baseline interferometry, showing that any extended emission is relatively diffuse and consistent with steady jets rather than arising from discrete, compact knots. In all cases where multi-frequency data were available, the source radio spectrum is consistent with being flat or slightly inverted, suggesting that the internal shock mechanism that is believed to produce optically thin transient radio ejecta in black hole X-ray binaries is not active in Aql X-1. © 2010. The American Astronomical Society. All rights reserved..

Abstract:

The radio sky is not steady on timescales below one second. Pulsars (including the rotating radio transients RRATs) and solar-system objects (e.g. solar flares, jupiter bursts, saturn lightning) give rise to sub-second pulses. Also in many known radiation processes coherent radiation can more easily occur at longer wavelengths, for which the size of the emitting region is comparable to the wavelength. This makes low frequency surveys ideally suited for the detection of new emission mechanisms caused by compact objects, such as white dwarfs, neutron stars and black holes. To detect as many of these Fast Radio Transients (FRATs) as possible, we are setting up a technique to detect and identify short single pulses with LOFAR in real-time, with unprecedented sensitivity in this frequency range, and excellent discrimination against terrestrial signals.

Abstract:

The CMS experiment uses self-triggering arrays of drift tubes in the barrel muon trigger to perform the identification of the correct bunch crossing. The identification is unique only if the trigger chain is correctly synchronized. In this paper, the synchronization performed during an extended cosmic ray run is described and the results are reported. The random arrival time of cosmic ray muons allowed several synchronization aspects to be studied and a simple method for the fine synchronization of the Drift Tube Local Trigger at LHC to be developed. © 2010 IOP Publishing Ltd and SISSA.