Giuseppe Greco

Structure—affinity relationship studies on benzotriazole derivatives binding to 5-HT receptor subtypes

Summary A number of benzotriazole derivatives have been assayed in radioligand binding experiments involving the following recombinant human serotonin receptors: 5-HT 2A , 5-HT 1A , 5-HT 1Dβ and 5-HT 2C . Several of the compounds tested show interesting selectivity profiles. In particular, the affinities of 3d, 4a and 4d for teh 5-HT 2A subtype (with p K i values of 7.4, 7.4 and 8.0, respectively) are between 100 and 1000 times higher than for the other investigated receptors. Compound 51 , characterized by a p K i value of 7.4 on the 5-HT 1A receptor, binds with 100- to 1000-fold lower potencies on the other receptors. Our benzotriazole derivatives are generally weak ligands of the 5-HT 1Dβ and 5-HT 2C receptors. Structure—affinity relationship data suggest that not all the compounds exhibit the same binding mode at the 5-HT 2A and 5-HT 1A receptors.

Statistical analysis of the parameters of gamma-ray bursts with known redshifts and peaked optical light curves

We present the statistical analysis of the properties of gamma-ray bursts with measured host galaxy redshifts and peaked optical light curves in proper frames of reference. The optical transients are classified by comparing the time lag of the optical peak relative to the GRB trigger with the duration of the gamma-ray emission itself. The results of the correlation analysis of all possible pairs of energy, spectral, and temporal characteristics of both gamma-ray and optical emissions are given. We specify the pairs of the parameters with correlation coefficients greater than 50% at significance levels better than 1%. The following empirical relations, obtained for the first time, are specifically discussed: a correlation between the peak optical afterglow R band luminosity and redshift LR ∝ (z +1)5.39±0.74 and a correlation between the peak luminosity of the prompt optical emissions and the time of the peak LR ∝ Tpeak−3.85±1.22. We also analyze the similarity of the relationships between the peak optical luminosity and the isotropic equivalent of the total energy of gamma-ray bursts for afterglows (LR ∝ Eiso1.06±0.22) and for prompt optical emissions (LR ∝ Eiso1.59±0.21).

On Some Statistical Properties of GRBs with Measured Redshifts Having Peaks in Optical Light Curves

We studied the subset of optical light curves of gamma-ray bursts with measured redshifts and well-sampled R band data that have clearly detected peaks. Among 43 such events, 11 are promptoptical peaks (P), coincident with gamma-ray activity, 22 are purely afterglows (A), and 10 more carrythe signatures of an underlying activity (A(U)). We studied pair correlations of their gamma-ray andoptical parameters, e.g. total energetics, peak optical luminosities, and durations. The main outcomeof our study is the detection of source frame correlations between both optical peak luminosity and total energy and the redshift for classes A and A(U), and the absence of such a correlation for class Pevents. This result seems to provide evidence of the cosmological evolution of a medium around the burst defining class A and A(U) energetics, and the absence of cosmological evolution of the internal properties of GRB engines. We also discuss some other prominent correlations.

GW optical counterpart search in the Multi-Messenger Astronomy Era

We report on the deep optical follow-up surveys of the four gravitational-wave events accomplished by the GRAvitational Wave Inaf TeAm Collaboration (GRAWITA) using the VLT Survey Telescope (VST). We responded promptly to the gravitational-wave alerts sent by the LIGO and Virgo Collaborations, covering a region of

GRB 080319B: TORTORA light curve.

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GRB 100713A: optical upper limit.

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TORTORA observations of GRB 080319B .

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Gamma-ray bursts with known redshifts (Badjin+, 2009)

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GRB 090313: optical observations.

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GRB 080723A: optical upper limit.

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