Energia e innovazione tra flussi globali e circuiti locali

La tematica energetica \ue8 di fortissima attualit\ue0 e rilevanza sia per questioni antiche (sicurezza nazionale, sviluppo economico) sia per questioni pi\uf9 recenti come il cambiamento climatico. Gran parte delle emissioni che provocano il surriscaldamento del pianeta provengono dalla combustione di fonti fossili. La transizione verso un uso pi\uf9 sostenibile dell\u2019energia sta per\uf2 segnando il passo. Ai buoni risultati ottenuti dall\u2019industria si sommano crescenti consumi civili, in particolare nel settore dei trasporti. I fattori di rallentamento non sono tutti legati alla contingenza economica mondiale, ma riguardano anche fenomeni sociali e istituzionali. Il libro indaga a largo spettro questi fattori, includendo tavole dei flussi energetici per settore, la distribuzione dei consumi su scala urbana e regionale, i sistemi che mirano all\u2019autosufficienza (comunit\ue0 energetiche), i conflitti sulle centrali e le modalit\ue0 giuridiche per regolarli. Ne esce un quadro con luci e ombre. Nonostante l\u2019impegno di molte agenzie e la disponibilit\ue0 di nuovi pacchetti tecnologici, vi \ue8 tuttora una insufficiente consapevolezza del cambiamento climatico, dell\u2019importanza delle nuove fonti di energia, in primis quella solare, e degli effetti re-distributivi su ricchezza e consumi. Una transizione pi\uf9 rapida avverr\ue0 quando questione energetica e coesione sociale saranno contemperate in una prassi ecologica integrata

Constraining the optical emission from the double pulsar system J0737-3039

We present the first optical observations of the unique system J0737-3039 (composed of two pulsars, hereafter PSR-A and PSR-B). Ultra-deep optical observations, performed with the High Resolution Camera of the Advanced Camera for Surveys on board the Hubble Space Telescope could not detect any optical emission from the system down to m_F435W=27.0 and m_F606W=28.3. The estimated optical flux limits are used to constrain the three-component (two thermal and one non-thermal) model recently proposed to reproduce the XMM-Newton X-ray spectrum. They suggest the presence of a break at low energies in the non-thermal power law component of PSR-A and are compatible with the expected black-body emission from the PSR-B surface. The corresponding efficiency of the optical emission from PSR-A's magnetosphere would be comparable to that of other Myr-old pulsars, thus suggesting that this parameter may not dramatically evolve over a time-scale of a few Myr.Comment: 16 pages, 3 figures, ApJ accepte

Study of the performance of standard RPC chambers as a function of bakelite temperature

A systematic study of the performance of the Resistive Plate Chambers as a function of the bakelite temperature is presented. The current, the rate and the efficiency were measured in the temperature range 22-40degreesC. The values of the relative humidity during the data taking were in the range 40-60%. Measurements show a strong dependence of the efficiency on bakelite temperature. (C) 2003 Elsevier Science B.V. All rights reserved

Phase-resolved spectroscopy of Geminga shows rotating hot spot(s)

Isolated neutron stars are seen in x-rays through their nonthermal and/or surface thermal emissions. XMM-Newton observations of the Geminga pulsar show a 43 electron volt spectrum from the whole neutron star surface, as well as a power-law component above 2 kiloelectron volts. In addition, we have detected a hot (170 electron volts) thermal emission from an 60-meter-radius spot on the pulsar s surface. Such a thermal emission, only visible at selected phase intervals, may be coming from polar hot spot(s), long thought to exist as a result of heating from magnetospheric accelerated particles. It may provide the missing link between the x-ray and gamma-ray emission of the pulsar.Comment: Published in Science, 16 July 200

Discovery of 59ms Pulsations from 1RXS J141256.0+792204 (Calvera)

We report on a multi-wavelength study of the compact object candidate 1RXS J141256.0+792204 (Calvera). Calvera was observed in the X-rays with XMM/EPIC twice for a total exposure time of ~50 ks. The source spectrum is thermal and well reproduced by a two component model composed of either two hydrogen atmosphere models, or two blackbodies (kT_1~ 55/150 eV, kT_2~ 80/250 eV, respectively, as measured at infinity). Evidence was found for an absorption feature at ~0.65 keV; no power-law high-energy tail is statistically required. Using pn and MOS data we discovered pulsations in the X-ray emission at a period P=59.2 ms. The detection is highly significant (> 11 sigma), and unambiguously confirms the neutron star nature of Calvera. The pulse profile is nearly sinusoidal, with a pulsed fraction of ~18%. We looked for the timing signature of Calvera in the Fermi Large Area Telescope (LAT) database and found a significant (~5 sigma) pulsed signal at a period coincident with the X-ray value. The gamma-ray timing analysis yielded a tight upper limit on the period derivative, dP/dt < 5E-18 s/s (dE_rot/dt <1E33 erg/s, B<5E10 G for magneto- dipolar spin-down). Radio searches at 1.36 GHz with the 100-m Effelsberg radio telescope yielded negative results, with a deep upper limit on the pulsed flux of 0.05 mJy. Diffuse, soft (< 1 keV) X-ray emission about 13' west of the Calvera position is present both in our pointed observations and in archive ROSAT all-sky survey images, but is unlikely associated with the X-ray pulsar. Its spectrum is compatible with an old supernova remnant (SNR); no evidence for diffuse emission in the radio and optical bands was found. The most likely interpretations are that Calvera is either a central compact object escaped from a SNR or a mildly recycled pulsar; in both cases the source would be the first ever member of the class detected at gamma-ray energies.Comment: 20 pages, 15 figures and 4 tables. Accepted for publication in MNRA

X-ray follow-ups of XSSJ12270-4859: a low-mass X-ray binary with gamma ray FERMI-LAT association

XSSJ1227.0-4859 is a peculiar, hard X-ray source recently positionally associated to the Fermi-LAT source 1FGLJ1227.9-4852/2FGLJ1227.7-4853. Multi-wavelength observations have added information on this source, indicating a low-luminosity low-mass X-ray binary (LMXB), but its nature is still unclear. To progress in our understanding, we present new X-ray data from a monitoring campaign performed in 2011 with the XMM-Newton, RXTE, and Swift satellites and combine them with new gamma-ray data from the Fermi and AGILE satellites. We complement the study with simultaneous near-UV photometry from XMM-Newton and with previous UV/optical and near-IR data. The X-ray history of XSSJ1227.0-4859 over 7yr shows a persistent and rather stable low-luminosity (~6x10^33 d_{1\,kpc}^2 erg/s) source, with flares and dips being peculiar and permanent characteristics. The associated Fermi-LAT source 2FGLJ1227.7-4853 is also stable over an overlapping period of 4.7\,yr. Searches for X-ray fast pulsations down to msec give upper limits to pulse fractional amplitudes of 15-25% that do not rule out a fast spinning pulsar. The combined UV/optical/near-IR spectrum reveals a hot component at ~13\,kK and a cool one at ~4.6\,kK. The latter would suggest a late-type K2-K5 companion star, a distance range of1.4--3.6kpc and an orbital period of 7--9 h. A near-UV variability (>6\,h) also suggests a longer orbital period than previously estimated. The analysis shows that the X-ray and UV/optical/near-IR emissions are more compatible with an accretion-powered compact object than with a rotational powered pulsar. The X-ray to UV bolometric luminosity ratio could be consistent with a binary hosting a neutron star, but the uncertainties in the radio data may also allow an LMXB black hole with a compact jet. In this case it would be the first associated with a high-energy gamma-ray source.Comment: 17 pages, 14 figures, 1 table; Accepted for publication in Astronomy & Astrophysics Main Journa