A study of optical pulsars from gamma to radio frequency

This thesis reports a study of optical pulsars in different energy bands. The main focus is on the results obtained in the visible with two high speed photometers, Aqueye and Iqueye. A section is then dedicated to the search of new optical candidates, starting from the catalogs of known pulsars in other energy bandsQuesta tesi presenta uno studio delle pulsar ottiche in diverse bande di energia. L'approfondimento principale riguarda i risultati ottenuti nel visibile grazie all'uso di due fotometri, Aqueye e Iqueye, in grado di analizzare fenomeni astrofisici in rapida variazione. Una sezione della tesi è poi dedicata alla ricerca di nuove pulsar ottiche, selezionando possibili candidati a partire dai cataloghi di pulsar già note in altre lunghezze d'ond

Timing of optical pulsars with two high time resolution photometers at Asiago and NTT2011 XXXth URSI General Assembly and Scientific Symposium

We\ua0have\ua0built\ua0two\ua0single\ua0photon\ua0very\ua0high\ua0speed\ua0photometers\ua0(Aqueye\ua0for\ua0the\ua0Asiago\ua01.8m\ua0telescope\ua0and\ua0Iqueye\ua0for\ua0the\ua03.5m\ua0ESO\ua0NTT)\ua0as\ua0prototypes\ua0of\ua0a\ua0\u2018quantum\u2019\ua0photometer\ua0for\ua0the\ua0European\ua0Extremely\ua0Large\ua0Telescope\ua0(E\u2010ELT) \ua0 The\ua0two\ua0photometers\ua0are\ua0the\ua0most\ua0accurate\ua0'time\ua0machines'\ua0available\ua0to\ua0optical\ua0astronomy.\ua0Under\ua0the\ua0control\ua0of\ua0a\ua0GPS\ua0receiver\ua0and\ua0a\ua0Rubidium\ua0clock,\ua0the\ua0arrival\ua0time\ua0of\ua0each\ua0detected\ua0photon\ua0is\ua0referenced\ua0to\ua0UTC\ua0with\ua0a\ua0precision\ua0better\ua0than\ua0500\ua0picoseconds,\ua0continuously\ua0for\ua0hours\ua0of\ua0data\ua0acquisition.\ua0Light\ua0curves\ua0for\ua0three\ua0optical\ua0pulsars\ua0(Crab,\ua0B0540\u201069,\ua0Vela)\ua0will\ua0be\ua0reported.\ua0Results\ua0from\ua0simultaneous\ua0observations\ua0of\ua0the\ua0Crab\ua0pulsar\ua0with\ua0the\ua0Jodrell\ua0Bank\ua0RadioTelescope\ua0will\ua0also\ua0be\ua0reported. \ua

Quantum Astronomy with Iqueye

Iqueye is a high speed astronomical photon counting device, tested at the ESO 3.5 m New Technology Telescope in La Silla (Chile). The optics splits the telescope pupil into four portions each feeding a Single Photon Avalanche Diode. A time-to-digital converter board time tags the pulses from the 4 channels, and the times sent to a storage device. The instrument is capable of running continuously up to a rate of 8 MHz, with an absolute rms accuracy better that 0.5 ns. The time is obtained by means of a rubidium clock referenced to UTC through the GPS signal. The paper describes the analysis performed on data taken on bright stars in order to perform \u2018quantum-like\u2019 measurements in the photon stream, namely the calculation of the second-order correlation functions g(2)(x,0) and g(2)(0,t). To this end, an ad hoc software correlator has been developed. Taking advantage of the pupil-splitting concept, the calculation of g(2)(x,0) has been made between the sub-apertures of the telescope, as a first step to verify the zero-baseline correlation coefficient in an Hanbury-Brown Twiss intensity interferometer \u200e[1]. Our experiment demonstrates the value of an Iqueye-like instrument applied to larger telescopes, like the four 8 m VLTs or the two 10m Keck telescopes, and even more the sub-pupils of the future 42 m E-ELT for a novel exploitation of the photon stream from celestial objects

Aqueye and iqueye, very-high-time-resolution photon-counting photometers

We describe very high-time-resolution photometers capable of tagging the arrival time of each photon with a resolution and accuracy of few hundred picoseconds, for hours of continuous acquisition, and with a dynamic range of more than 6 orders of magnitude. The final goal is the conceptual definition of a "quantum" photometer for the E-ELT, capable of detecting and measuring second-order correlation effects in photon streams from celestial sources. Two prototype units have been built and operated, one for the Asiago 1.8-m telescope (AquEYE) and one for the 3.5-m NTT (IquEYE). Here we will present results obtained by IquEYE on the Crab Nebula pulsar in simultaneous radio observations with Jodrell Bank in December 2009

Aqueye and iqueye, very-high-time-resolution photon-counting photometers

We describe very high-time-resolution photometers capable of tagging the arrival time of each photon with a resolution and accuracy of few hundred picoseconds, for hours of continuous acquisition, and with a dynamic range of more than 6 orders of magnitude. The final goal is the conceptual definition of a "quantum" photometer for the E-ELT, capable of detecting and measuring second-order correlation effects in photon streams from celestial sources. Two prototype units have been built and operated, one for the Asiago 1.8-m telescope (AquEYE) and one for the 3.5-m NTT (IquEYE). Here we will present results obtained by IquEYE on the Crab Nebula pulsar in simultaneous radio observations with Jodrell Bank in December 2009

Crab pulsar: enhanced optical emission during giant radio pulses

Although optical pulsar studies have been limited to a few favoured objects, the observation of pulsars at optical wavelengths provides an opportunity to derive a number of important pulsar characteristics, including the energy spectrum of the emitting electrons and the geometry of the emission zone. These parameters will be vital for a comprehensive model of pulsar emission mechanisms. Observations of the Crab pulsar with the high-time-resolution photon-tagging photometer IquEYE show an optical-radio delay of similar to 178 mu s. Incorporating simultaneous Jodrell Bank radio observations suggested a correlation between giant radio pulses and enhanced optical pulses for this pulsar, thus offering possible evidence for the reprocessing of radio photons

Crab pulsar: Enhanced optical emission during giant radio pulses

Although optical pulsar studies have been limited to a few favoured objects, the observation of pulsars at optical wavelengths provides an opportunity to derive a number of important pulsar characteristics, including the energy spectrum of the emitting electrons and the geometry of the emission zone. These parameters will be vital for a comprehensive model of pulsar emission mechanisms. Observations of the Crab pulsar with the high-time-resolution photon-tagging photometer IquEYE show an optical-radio delay of similar to 178 mu s. Incorporating simultaneous Jodrell Bank radio observations suggested a correlation between giant radio pulses and enhanced optical pulses for this pulsar, thus offering possible evidence for the reprocessing of radio photons

Crab Pulsar: Enhanced Optical Emission During Giant Radio Pulses

none8Although optical pulsar studies have been limited to a few favoured objects, the observation of pulsars at optical wavelengths provides an opportunity to derive a number of important pulsar characteristics, including the energy spectrum of the emitting electrons and the geometry of the emission zone. These parameters will be vital for a comprehensive model of pulsar emission mechanisms. Observations of the Crab pulsar with the high-time-resolution photon-tagging photometer IquEYE show an optical-radio delay of ~178 μs. Incorporating simultaneous Jodrell Bank radio observations suggested a correlation between giant radio pulses and enhanced optical pulses for this pulsar, thus offering possible evidence for the reprocessing of radio photons.noneS. Collins; A. Shearer;B. Stappers; C. Barbieri; G. Naletto; L. Zampieri; E. Verroi; S. GradariS., Collins; A., Shearer; B., Stappers; Barbieri, Cesare; Naletto, Giampiero; L., Zampieri; Verroi, Enrico; Gradari, Seren

Upgrade of Iqueye, a novel photon-counting photometer for the ESO New Technology Telescope

Iqueye is a novel extremely high speed photon-counting photometer for the European Southern Observatory New Technology Telescope in La Silla (Chile). Iqueye collects the light from the telescope through a few arcsec aperture, and splits it along four independent channels, each feeding a single photon avalanche diode. The produced count pulses are collected by a time-to-digital converter board and suitably time-tagged. Thanks to a rubidium oscillator and a GPS receiver, an absolute rms timing accuracy better than 0.5 ns during one-hour observations can be achieved by postprocessing the data. The system can sustain a count rate of up to 8 MHz uninterruptedly for an entire night of observation. After the first run in January 2009, some improvements have been evidenced and realized: a more practical mechanical structure, a better optimization of the optical design, an additional filter wheel per each channel, a fifth photon counting detector for monitoring the sky, a more interactive interface software. The updated Iqueye has been tested in December 2009, and the obtained results showed still better performance. As an example, the light curves of visible pulsars down to the 25th visible magnitude have been obtained in a few hours of observation