Constraining the duty cycle of transient low-mass X-ray binaries through simulations

We performed simulations of a large number of so-called very faint X-ray transient sources from surveys obtained using the X-ray telescope aboard the Neil Gehrels \emph{Swift} Observatory on two Galactic globular clusters, and the Galactic Center. We calculated the ratio between the duty cycle we input in our simulations and the one we measure after the simulations. We found that fluctuations in outburst duration and recurrence times affect our estimation of the duty cycle more than non detected outbursts. This biases our measures to overestimate the simulated duty cycle of sources. Moreover, we determined that compact surveys are necessary to detect outbursts with short duration because they could fall in gaps between observations, if such gaps are longer than their duration. On the other hand, long surveys are necessary to detect sources with low duty cycle because the smallest duty cycle a survey can observe is given by the ratio between the shortest outburst duration and the total length of the survey. If one has a limited amount of observing time, these two effects are competing, and a compromise is required which is set by the goals of the proposed survey. We have also performed simulations with several artificial survey strategies in order to evaluate the optimal observing campaign aimed at detecting transients as well as at having the most accurate estimates of the duty cycle. As expected, the best campaign would be a regular and dense monitoring that extends for a very long period. The closest real example of such a dataset is the monitoring of the Galactic Centre.Comment: 13 pages, 6 figures. Accepted for publication in MNRA

Stochastic and Reactive Methods for the Determination of Optimal Calibration Intervals

The length of calibration intervals of measurement instrumentations can be determined by means of several techniques. In this paper three different methods are compared for the establishment of optimal calibration intervals of atomic clocks. The first one, is based on a stochastic model, and provides the estimation of the calibration interval also in the transient situation, while the others, attain to the class of the so–called reactive methods, which determine the value of the optimal interval on the basis of the last calibration outcomes. Algorithms have been applied to experimental data and obtained results have been compared in order to determine the most effective technique. Since the analyzed reactive methods present a large transient time, a new algorithm is proposed and applied to the available data

Transient Simulations for Radio Surveys

Several new radio facilities have a field of view and sensitivity well suited for transient searches. This makes it more important than ever to accurately determine transient rates in radio surveys. The work presented here seeks to do this task by using Monte-Carlo simulations. In particular, the user inputs either a real or simulated observational setup, and the simulations code calculates transient rate as a function of transient duration and peak flux. These simulations allow for simulating a wide variety of scenarios including observations with varying sensitivities and durations, multiple overlapping telescope pointings, and a wide variety of light curve shapes with the user having the ability to easily add more. While the current scientific focus is on the radio regime, with examples given here from the MeerKAT telescope in South Africa, the simulations code can be easily adapted to other wavelength regimes.Comment: Minor updates to plot

An upper-limit on the linear polarization fraction of the GW170817 radio continuum

We present late-time radio observations of GW170817, the first binary neutron star merger discovered through gravitational waves by the advanced LIGO and Virgo detectors. Our observations, carried out with the Karl G. Jansky Very Large Array, were optimized to detect polarized radio emission, and thus to constrain the linear polarization fraction of GW170817. At an epoch of ~244 days after the merger, we rule out linearly polarized emission above a fraction of ~12% at a frequency of 2.8 GHz (99% confidence). Within the structured jet scenario (a.k.a. successful jet plus cocoon system) for GW170817, the derived upper-limit on the radio continuum linear polarization fraction strongly constrains the magnetic field configuration in the shocked ejecta. We show that our results for GW170817 are compatible with the low level of linear polarization found in afterglows of cosmological long gamma-ray bursts. Finally, we discuss our findings in the context of future expectations for the study of radio counterparts of binary neutron star mergers identified by ground-based gravitational-wave detectors.Comment: 5 pages, 2 figures, 1 tabl

miniaturized fish for screening of onco hematological malignancies

Fluorescence in situ hybridization (FISH) represents a major step in the analysis of chromosomal aberrations in cancer. It allows the precise detection of specific rearrangements, both for diagnost..

Evidence of electron wave function delocalization in CdSe/CdS asymmetric nanocrystals

Abstract We studied the delocalization of electron wave function in asymmetric CdSe/CdS nanocrystals, consisting of a spherical CdSe dot embedded in an elongated CdS shell, by means of a pump–probe technique. By comparing the transient spectra obtained upon pumping the band edge transition of the CdSe in CdSe/CdS heterostructure and in a bare CdSe dot, we observed the delocalization of electron wave function at the CdSe/CdS interface