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

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

Particle monitoring capability of the Solar Orbiter Metis coronagraph through the increasing phase of solar cycle 25

Context. Galactic cosmic rays (GCRs) and solar particles with energies greater than tens of MeV penetrate spacecraft and instruments hosted aboard space missions. The Solar Orbiter Metis coronagraph is aimed at observing the solar corona in both visible (VL) and ultraviolet (UV) light. Particle tracks are observed in the Metis images of the corona. An algorithm has been implemented in the Metis processing electronics to detect the VL image pixels crossed by cosmic rays. This algorithm was initially enabled for the VL instrument only, since the process of separating the particle tracks in the UV images has proven to be very challenging. Aims. We study the impact of the overall bulk of particles of galactic and solar origin on the Metis coronagraph images. We discuss the effects of the increasing solar activity after the Solar Orbiter mission launch on the secondary particle production in the spacecraft. Methods. We compared Monte Carlo simulations of GCRs crossing or interacting in the Metis VL CMOS sensor to observations gathered in 2020 and 2022. We also evaluated the impact of solar energetic particle events of different intensities on the Metis images. Results. The study of the role of abundant and rare cosmic rays in firing pixels in the Metis VL images of the corona allows us to estimate the efficiency of the algorithm applied for cosmic-ray track removal from the images and to demonstrate that the instrument performance had remained unchanged during the first two years of the Solar Orbiter operations. The outcome of this work can be used to estimate the Solar Orbiter instrument's deep charging and the order of magnitude for energetic particles crossing the images of Metis and other instruments such as STIX and EUI.Comment: 8 pages, 6 figure

Investigation of Gamma-ray Pulsars with the Cherenkov Telescope Array and the ASTRI Mini-array

This Thesis presents the prospects for investigating gamma-ray pulsars with future Cherenkov facilities, the Cherenkov Telescope Array (CTA) and ASTRI mini-array (possible precursor for CTA). Gamma-ray pulsars are compact astrophysical objects which emit photons with energies up to ~100 GeV. The nature of the gamma-ray emission from these sources is not fully understood. In addition, the recent detection of the Crab pulsar with Cherenkov telescopes such as MAGIC and VERITAS at very high energies (VHE, >100 GeV) challenged current theoretical models. CTA will be a next-generation ground-based VHE gamma-ray instrument, designed to achieve a sensitivity of the order of one magnitude better than that of currently operating Cherenkov installations. It will consist of two arrays, one in northern and one in southern hemisphere, each with a large number of different-sized telescopes. Early observations can be carried out with CTA precursors, such as the ASTRI mini-array. I simulated the VHE emission from the 12 most energetic Fermi pulsars. I analyzed the Fermi-LAT data of these pulsars above 10 GeV and extrapolated their gamma-ray spectra up to ~160 TeV, in order to estimate how many of them will be detectable with CTA. In addition, I performed a detailed investigation of the pulsed VHE emission from the Crab pulsar, simulating the light curve detectable with CTA. I calculated with which accuracy it will be possible to study the timing properties of this pulsar with CTA and the ASTRI mini-array. Finally, I investigated VHE gamma rays from the Vela X region. Assuming different spatial distributions for the emission from the Vela pulsar wind nebula, I calculated more realistic estimates of the significance of the Vela pulsar detection with CTA. Using different software packages (ctools and Asrtisim), I also studied the extended Vela X emission and tested the resolving capabilities of CTA and the ASTRI mini-array.Questa Tesi contiene i risultati di uno studio dell'emissione delle pulsar a raggi gamma osservate con futuri telescopi Cherenkov, il Cherenkov Telescope Array (CTA) ed il mini-array ASTRI (uno dei possibili precursori per CTA). Le pulsar a raggi gamma sono oggetti astrofisici compatti che emettono fotoni con energie fino a ~100 GeV. La natura dell'emissione di raggi gamma da queste sorgenti non è chiara. Inoltre, la recente rivelazione di emissione di altissima energia (VHE, >100 GeV) da parte della Crab pulsar con i telescopi Cherenkov MAGIC e VERITAS reppresenta una sfida per attuali modelli teorici. CTA sarà uno strumento nuova generazione, progettato per raggiungere una sensibilità un'ordine di grandezza migliore di quella dei telescopi Cherenkov attualmente in funzione. Esso comprenderà un array in ciascun emisfero con un gran numero di telescopi di dimensioni diverse. Le prime osservazioni verranno eseguite con precursori di CTA, come il mini-array ASTRI. Ho simulato l'emissione VHE dalle 12 Fermi pulsar più energiche. Ho analizzato i dati Fermi-LAT di queste pulsar ad energie superiori a 10 GeV ed estrapolato i loro spettri gamma fino a ~160 TeV, per stimare quante di loro saranno rivelabili con CTA. Inoltre, ho eseguito un esame più dettagliato dell'emissione VHE pulsata dalla Crab pulsar, simulando la curva di luce osservabile con CTA. Ho calcolato con quali accuratezza sarà possibile studiare le proprietà del timing di questa pulsar con CTA ed il mini-array ASTRI. Infine, ho studiato l'emissione di altissima energia (VHE) dalla sorgente Vela X. Assumendo diverse distribuzioni spaziali per l'emissione della wind nebula della Vela pulsar, ho calcolato stime più realistiche delle significatività della Vela pulsar con CTA. Utilizzando diversi pacchetti software (ctools e Asrtisim), ho anche studiato l'emissione estesa della Vela X e verificato la risoluzione angolare ottenibile con CTA ed il mini-array ASTRI

Investigation of Gamma-ray Pulsars with the Cherenkov Telescope Array and the ASTRI Mini-array

This Thesis presents the prospects for investigating gamma-ray pulsars with future Cherenkov facilities, the Cherenkov Telescope Array (CTA) and ASTRI mini-array (possible precursor for CTA). Gamma-ray pulsars are compact astrophysical objects which emit photons with energies up to ~100 GeV. The nature of the gamma-ray emission from these sources is not fully understood. In addition, the recent detection of the Crab pulsar with Cherenkov telescopes such as MAGIC and VERITAS at very high energies (VHE, >100 GeV) challenged current theoretical models. CTA will be a next-generation ground-based VHE gamma-ray instrument, designed to achieve a sensitivity of the order of one magnitude better than that of currently operating Cherenkov installations. It will consist of two arrays, one in northern and one in southern hemisphere, each with a large number of different-sized telescopes. Early observations can be carried out with CTA precursors, such as the ASTRI mini-array. I simulated the VHE emission from the 12 most energetic Fermi pulsars. I analyzed the Fermi-LAT data of these pulsars above 10 GeV and extrapolated their gamma-ray spectra up to ~160 TeV, in order to estimate how many of them will be detectable with CTA. In addition, I performed a detailed investigation of the pulsed VHE emission from the Crab pulsar, simulating the light curve detectable with CTA. I calculated with which accuracy it will be possible to study the timing properties of this pulsar with CTA and the ASTRI mini-array. Finally, I investigated VHE gamma rays from the Vela X region. Assuming different spatial distributions for the emission from the Vela pulsar wind nebula, I calculated more realistic estimates of the significance of the Vela pulsar detection with CTA. Using different software packages (ctools and Asrtisim), I also studied the extended Vela X emission and tested the resolving capabilities of CTA and the ASTRI mini-array.Questa Tesi contiene i risultati di uno studio dell'emissione delle pulsar a raggi gamma osservate con futuri telescopi Cherenkov, il Cherenkov Telescope Array (CTA) ed il mini-array ASTRI (uno dei possibili precursori per CTA). Le pulsar a raggi gamma sono oggetti astrofisici compatti che emettono fotoni con energie fino a ~100 GeV. La natura dell'emissione di raggi gamma da queste sorgenti non è chiara. Inoltre, la recente rivelazione di emissione di altissima energia (VHE, >100 GeV) da parte della Crab pulsar con i telescopi Cherenkov MAGIC e VERITAS reppresenta una sfida per attuali modelli teorici. CTA sarà uno strumento nuova generazione, progettato per raggiungere una sensibilità un'ordine di grandezza migliore di quella dei telescopi Cherenkov attualmente in funzione. Esso comprenderà un array in ciascun emisfero con un gran numero di telescopi di dimensioni diverse. Le prime osservazioni verranno eseguite con precursori di CTA, come il mini-array ASTRI. Ho simulato l'emissione VHE dalle 12 Fermi pulsar più energiche. Ho analizzato i dati Fermi-LAT di queste pulsar ad energie superiori a 10 GeV ed estrapolato i loro spettri gamma fino a ~160 TeV, per stimare quante di loro saranno rivelabili con CTA. Inoltre, ho eseguito un esame più dettagliato dell'emissione VHE pulsata dalla Crab pulsar, simulando la curva di luce osservabile con CTA. Ho calcolato con quali accuratezza sarà possibile studiare le proprietà del timing di questa pulsar con CTA ed il mini-array ASTRI. Infine, ho studiato l'emissione di altissima energia (VHE) dalla sorgente Vela X. Assumendo diverse distribuzioni spaziali per l'emissione della wind nebula della Vela pulsar, ho calcolato stime più realistiche delle significatività della Vela pulsar con CTA. Utilizzando diversi pacchetti software (ctools e Asrtisim), ho anche studiato l'emissione estesa della Vela X e verificato la risoluzione angolare ottenibile con CTA ed il mini-array ASTRI

Low-frequency optical QPO in MAXI J1820+070 detected with IFI+IQUEYE@Galileo

The Astronomer's Telegram, No. 1172

Optical timing observations of MAXI J1820+070 with IFI+IQUEYE and AQUEYE+ soon after state transition

The Astronomer's Telegram, No. 1193

Timing analysis and pulse profile of the Vela pulsar in the optical band from Iqueye observations

The Vela pulsar is among a number of pulsars which show detectable optical pulsations. We performed optical observations of this pulsar in 2009 January and December with the Iqueye instrument mounted at the ESO 3.5 m New Technology Telescope. Our aim was to perform phase fitting of the Iqueye data, and to measure the optical pulse profile of the Vela pulsar at high time resolution, its absolute phase, and rotational period. We calculated for the first time an independent optical timing solution and obtained the most detailed optical pulse profile available to date. Iqueye detected a distinct narrow component on the top of one of the two main optical peaks, which was not resolved in previous observations, and a third statistically significant optical peak not aligned with the radio one. The quality of the Iqueye data allowed us to determine the relative time of arrival of the radio-optical-gamma-ray peaks with an accuracy of a fraction of a millisecond.We compare the shape of the Iqueye pulse profile with that observed in other energy bands and discuss its complex multiwavelength structure

Other low-frequency optical QPO-like features in MAXI J1820+070 detected with IFI+IQUEYE@Galileo

The Astronomer's Telegram, #1182