925 research outputs found
What brakes the Crab pulsar?
Optical observations provide convincing evidence that the optical phase of
the Crab pulsar follows the radio one closely. Since optical data do not depend
on dispersion measure variations, they provide a robust and independent
confirmation of the radio timing solution. The aim of this paper is to find a
global mathematical description of Crab pulsar's phase as a function of time
for the complete set of published Jodrell Bank radio ephemerides (JBE) in the
period 1988-2014. We apply the mathematical techniques developed for analyzing
optical observations to the analysis of JBE. We break the whole period into a
series of episodes and express the phase of the pulsar in each episode as the
sum of two analytical functions. The first function is the best-fitting local
braking index law, and the second function represents small residuals from this
law with an amplitude of only a few turns, which rapidly relaxes to the local
braking index law. From our analysis, we demonstrate that the power law index
undergoes "instantaneous" changes at the time of observed jumps in rotational
frequency (glitches). We find that the phase evolution of the Crab pulsar is
dominated by a series of constant braking law episodes, with the braking index
changing abruptly after each episode in the range of values between 2.1 and
2.6. Deviations from such a regular phase description behave as oscillations
triggered by glitches and amount to fewer than 40 turns during the above
period, in which the pulsar has made more than 2.0e10 turns. Our analysis does
not favor the explanation that glitches are connected to phenomena occurring in
the interior of the pulsar. On the contrary, timing irregularities and changes
in slow down rate seem to point to electromagnetic interaction of the pulsar
with the surrounding environment.Comment: 11 pages, 8 figures, 3 tables; accepted for publication in Astronomy
& Astrophysic
Quantum Astronomy at the University and INAF Astronomical Observatory of Padova, Italy
Twenty years ago, we started to apply quantum optics to the astronomical research carried
out inside the Department of Physics and Astronomy and the INAF Astronomical Observatory
in Padova, Italy. The initial activities were stimulated by the project of the European Southern
Observatory (ESO) to build a 100 m diameter telescope, the Overwhelmingly Large (OWL) telescope.
The enormous photon flux expected from such an aperture suggested that quantum optics concepts
be utilized in order to obtain novel astrophysical results. Following initial successful attempts to
utilize the orbital angular momentum of the light beam to enhance the visibility of faint companions
to bright stars, the Padova team concentrated its efforts on very high time resolution, in order to
measure and store the arrival time of celestial photons to better than one nanosecond. To obtain
observational results, we built two photon counting photometers (AquEye and IquEye) to be used
with our telescopes of the Asiago Observatory and with 4 m class telescopes such as the ESO New
Technology Telescope (NTT) in Chile. This paper firstly describes these two instruments and then
expounds the results obtained on pulsar light curves, lunar occultations and the first photon counting
intensity interferometry measurements of the bright star Vega. Indeed, the correlation of photon
arrival times on two or more apertures can lead to extremely high angular resolutions, as shown
around 1970 by Hanbury Brown and Twiss. Prospects for quantum intensity interferometry with
arrays of Cherenkov light telescopes will also be described
Precise optical timing of PSR J1023+0038, the first millisecond pulsar detected with Aqueye+ in Asiago
We report the first detection of an optical millisecond pulsar with the fast
photon counter Aqueye+ in Asiago. This is an independent confirmation of the
detection of millisecond pulsations from PSR J1023+0038 obtained with SiFAP at
the Telescopio Nazionale Galileo. We observed the transitional millisecond
pulsar PSR J1023+0038 with Aqueye+ mounted at the Copernicus telescope in
January 2018. Highly significant pulsations were detected. The rotational
period is in agreement with the value extrapolated from the X-ray ephemeris,
while the time of passage at the ascending node is shifted by
s from the value predicted using the orbital period from the X-rays. An
independent optical timing solution is derived over a baseline of a few days,
that has an accuracy of in pulse phase ( s in time).
This level of precision is needed to derive an accurate coherent timing
solution for the pulsar and to search for possible phase shifts between the
optical and X-ray pulses using future simultaneous X-ray and optical
observations.Comment: 6 pages, 4 figures, accepted for publication in Monthly Notices of
the Royal Astronomical Society Letter
Optical phase coherent timing of the Crab nebula pulsar with Iqueye at the ESO New Technology Telescope
The Crab nebula pulsar was observed in 2009 January and December with a novel
very fast optical photon counter, Iqueye, mounted at the ESO 3.5 m New
Technology Telescope. Thanks to the exquisite quality of the Iqueye data, we
computed accurate phase coherent timing solutions for the two observing runs
and over the entire year 2009. Our statistical uncertainty on the determination
of the phase of the main pulse and the rotational period of the pulsar for
short (a few days) time intervals are s and ~0.5 ps,
respectively. Comparison with the Jodrell Bank radio ephemerides shows that the
optical pulse leads the radio one by ~240 s in January and ~160 s in
December, in agreement with a number of other measurements performed after
1996. A third-order polynomial fit adequately describes the spin-down for the
2009 January plus December optical observations. The phase noise is consistent
with being Gaussian distributed with a dispersion of s in most observations, in agreement with theoretical expectations for
photon noise-induced phase variability.Comment: 10 pages, 5 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
QuantEYE: The Quantum Optics Instrument for OWL
QuantEYE is designed to be the highest time-resolution instrument on ESO:s
planned Overwhelmingly Large Telescope, devised to explore astrophysical
variability on microsecond and nanosecond scales, down to the quantum-optical
limit. Expected phenomena include instabilities of photon-gas bubbles in
accretion flows, p-mode oscillations in neutron stars, and quantum-optical
photon bunching in time. Precise timescales are both variable and unknown, and
studies must be of photon-stream statistics, e.g., their power spectra or
autocorrelations. Such functions increase with the square of the intensity,
implying an enormously increased sensitivity at the largest telescopes.
QuantEYE covers the optical, and its design involves an array of
photon-counting avalanche-diode detectors, each viewing one segment of the OWL
entrance pupil. QuantEYE will work already with a partially filled OWL main
mirror, and also without [full] adaptive optics.Comment: 7 pages; Proceedings from meeting 'Instrumentation for Extremely
Large Telescopes', held at Ringberg Castle, July 2005 (T.Herbst, ed.
Aqueye+: a new ultrafast single photon counter for optical high time resolution astrophysics
Aqueye+ is a new ultrafast optical single photon counter, based on single
photon avalanche photodiodes (SPAD) and a 4-fold split-pupil concept. It is a
completely revisited version of its predecessor, Aqueye, successfully mounted
at the 182 cm Copernicus telescope in Asiago. Here we will present the new
technological features implemented on Aqueye+, namely a state of the art timing
system, a dedicated and optimized optical train, a high sensitivity and high
frame rate field camera and remote control, which will give Aqueye plus much
superior performances with respect to its predecessor, unparalleled by any
other existing fast photometer. The instrument will host also an optical
vorticity module to achieve high performance astronomical coronography and a
real time acquisition of atmospheric seeing unit. The present paper describes
the instrument and its first performances.Comment: Proceedings of the SPIE, Volume 9504, id. 95040C 14 pp. (2015
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