Guida: A graphical user interface for optical data analysis of isolated pulsars

Studying pulsars from ground-based telescopes needs data analysis to be performed according to specific requirements. Because of the periodic behavior of these objects such requirements are expressed in terms of timing. In fact, several factors must be taken into account to correctly extract the period (frequency) and then light curves of pulsars. Until now, analysis software packages have been mainly developed for satellite data and are not completely suitable for optical observations from the ground. A software package called GUIDA has been developed to analyze optical photometric data recorded by the SiFAP instrument, completely conceived and realized at the Physics Department of La Sapienza-Università di Roma. This software package is capable of analyzing data relative to ground observations, including timing corrections, and of deriving corrected pulsar light curves

Photon Counting for Studying Faint Astronomical Variable Signals in Optical Band

Although physics of neutron stars as pulsars together with their emission mechanisms leave discussions open, such objects represent the best targets to be deeply investigated by photon counting through the high-speed photometry technique. In this scenario, the capability of devices based on the silicon photomultiplier technology allows detecting single photons with remarkable time resolutions (few tens of nanoseconds). Whenever performing (optical) ground-based observations of variable sources, time of arrivals of incoming photons must be corrected because Earth’s reference frame system is not inertial. Time corrections provide time of arrivals to be moved to the Solar System Barycentre inertial reference frame. If the pulsar belongs to a binary system, further corrective terms, due to the orbital motion of the companion star, have to be taken into account. In this chapter, we report experimental results obtained from observations performed on two different variable sources, the isolated Crab pulsar and Hz Her/Her X-1 binary system, with a very fast custom astronomical photometer

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 $11.55 \pm 0.08$ 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 $\sim 0.007$ in pulse phase ($\sim 12$ $\mu$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

A New Fast Silicon Photomultiplier Photometer

The realization of low-cost instruments with high technical performance is a goal which deserves some efforts in an epoch of fast technological developments: indeed such instruments can be easily reproduced and therefore allow to open new research programs in several Observatories. We realized a fast optical photometer based on the SiPM technology, using commercially available modules. Using low-cost components we have developed a custom electronic chain to extract the signal produced by a commercial MPPC module produced by Hamamatsu, in order to obtain sub millisecond sampling of the light curve of astronomical sources, typically pulsars. In the early February 2011 we observed the Crab Pulsar at the Cassini telescope with our prototype photometer, deriving its period, power spectrum and shape of its light curve in very good agreement with the results obtained in the past with other instruments.Comment: Accepted for Publications of the Astronomical Society of Pacific (PASP), 8 pages, 8 figure

SiFAP: A New Fast Astronomical Photometer

A fast photometer based on SiPM technology was developed and tested at the University of Rome "La Sapienza" and at the Bologna Observatory. In this paper we present the improvements applied to our instrument, concerning new cooled sensors, a new version of the electronics and an upgraded control timing software

SiFAP: A New Fast Astronomical Photometer

A fast photometer based on SiPM technology was developed and tested at the University of Rome "La Sapienza" and at the Bologna Observatory. In this paper we present the improvements applied to our instrument, concerning new cooled sensors, a new version of the electronics and an upgraded control timing software

CHANTI: a Fast and Efficient Charged Particle Veto Detector for the NA62 Experiment at CERN

The design, construction and test of a charged particle detector made of scintillation counters read by Silicon Photomultipliers (SiPM) is described. The detector, which operates in vacuum and is used as a veto counter in the NA62 experiment at CERN, has a single channel time resolution of 1.14 ns, a spatial resolution of ~2.5 mm and an efficiency very close to 1 for penetrating charged particles

Spin-down rate of the transitional millisecond pulsar PSR J1023+0038 in the optical band with Aqueye+

We present a timing analysis of the transitional millisecond pulsar PSR J1023+0038 using observations taken between January 2018 and January 2020 with the high time resolution photon counter Aqueye+ mounted at the 1.82 m Copernicus telescope in Asiago. We report the first measurement of the timing solution and the frequency derivative of PSR J1023+0038 based entirely on optical data. The spin-down rate of the pulsar is $(-2.53 \pm 0.04) \times 10^{-15}$ Hz$^2$, which is $\sim$20% slower than that measured from the X-ray observations taken in 2013-2016 and $\sim$5% faster than that measured in the radio band during the rotation-powered state.Comment: 6 pages, 4 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Letter

Direct regulation of microRNA biogenesis and expression by estrogen receptor beta in hormone-responsive breast cancer.

Estrogen effects on mammary epithelial and breast cancer (BC) cells are mediated by the nuclear receptors ERα and ERβ, transcription factors that display functional antagonism with each other, with ERβ acting as oncosuppressor and interfering with the effects of ERα on cell proliferation, tumor promotion and progression. Indeed, hormone-responsive, ERα+ BC cells often lack ERβ, which when present associates with a less aggressive clinical phenotype of the disease. Recent evidences point to a significant role of microRNAs (miRNAs) in BC, where specific miRNA expression profiles associate with distinct clinical and biological phenotypes of the lesion. Considering the possibility that ERβ might influence BC cell behavior via miRNAs, we compared miRNome expression in ERβ+ vs ERβ- hormone-responsive BC cells and found a widespread effect of this ER subtype on the expression pattern of these non-coding RNAs. More importantly, the expression pattern of 67 miRNAs, including 10 regulated by ERβ in BC cells, clearly distinguishes ERβ+, node-negative, from ERβ-, metastatic, mammary tumors. Molecular dissection of miRNA biogenesis revealed multiple mechanisms for direct regulation of this process by ERβ+ in BC cell nuclei. In particular, ERβ downregulates miR-30a by binding to two specific sites proximal to the gene and thereby inhibiting pri-miR synthesis. On the other hand, the receptor promotes miR-23b, -27b and 24-1 accumulation in the cell by binding in close proximity of the corresponding gene cluster and preventing in situ the inhibitory effects of ERα on pri-miR maturation by the p68/DDX5-Drosha microprocessor complex. These results indicate that cell autonomous regulation of miRNA expression is part of the mechanism of action of ERβ in BC cells and could contribute to establishment or maintenance of a less aggressive tumor phenotype mediated by this nuclear receptor