OA@INAF - Istituto Nazionale di Astrofisica
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Faraday Tomography with CHIME: The “Tadpole” Feature G137+7
Get PDFA direct consequence of Faraday rotation is that the polarized radio sky does not resemble the total intensity sky at long wavelengths. We analyze G137+7, which is undetectable in total intensity but appears as a depolarization feature. We use the first polarization maps from the Canadian Hydrogen Intensity Mapping Experiment. Our 400–729 MHz bandwidth and angular resolution, – , allow us to use Faraday synthesis to analyze the polarization structure. In polarized intensity and polarization angle maps, we find a tail extending 10° from the head and designate the combined object, the tadpole. Similar polarization angles, distinct from the background, indicate that the head and tail are physically associated. The head appears as a depolarized ring in single channels, but wideband observations show that it is a Faraday rotation feature. Our investigations of H I and Hα find no connections to the tadpole. The tail suggests motion of either the gas or an ionizing star through the interstellar medium; the B2(e) star HD 20336 is a candidate. While the head features a coherent, ∼ ‑8 rad m‑2 Faraday depth, Faraday synthesis also identifies multiple components in both the head and tail. We verify the locations of the components in the spectra using QU fitting. Our results show that approximately octave-bandwidth Faraday rotation observations at ∼600 MHz are sensitive to low-density ionized or partially ionized gas, which is undetectable in other tracers
Stampante Raise 3D Pro 3 Plus
Get PDFPanoramica generale, setup ed esempi di stampa della stampante Raise 3D Pro3 Plu
Timing of Millisecond Pulsars in NGC 6752. III. On the Presence of Nonluminous Matter in the Cluster’s Core
Get PDFMillisecond pulsars are subject to accelerations in globular clusters (GCs) that manifest themselves in both the first and second spin period time derivatives, and can be used to explore the mass distribution of the potentials they inhabit. Here we report on over 20 yr of pulsar timing observations of five millisecond radio pulsars in the core of the core-collapse GC NGC 6752 with the Parkes (Murriyang) and MeerKAT radio telescopes, which have allowed us to measure the proper motions, positions, and first and second time derivatives of the pulsars. The pulsar timing parameters indicate that all the pulsars in the core experience accelerations and jerks that can be explained only if an amount of nonluminous mass of at least 2.56x10^3 M_SUN is present in the core of NGC 6752. On the other hand, our studies highly disfavor the presence of an intermediate-mass black hole at the center of the cluster, with a mass equal to or greater than ~3000M_SUN
The GAPS programme at TNG. LVII. TOI-5076b: A warm sub-Neptune planet orbiting a thin-to-thick-disk transition star in a wide binary system
Get PDFAims: We report the confirmation of a new transiting exoplanet orbiting the star TOI-5076. Methods: We present our vetting procedure and follow-up observations which led to the confirmation of the exoplanet TOI-5076b. In particular, we employed high-precision TESS photometry, high-angular-resolution imaging from several telescopes, and high-precision radial velocities from HARPS-N. Results: From the HARPS-N spectroscopy, we determined the spectroscopic parameters of the host star: Teff = (5070±143) K, log = (4.6±0.3), [Fe/H] = (+0.20±0.08), and [α/Fe] = 0.05±0.06. The transiting planet is a warm sub-Neptune with a mass mp = (16±2) M⊙, a radius rp =(3.2±0.l) R⊙ yielding a density ρp = (2.8±0.5) g cm−3. It revolves around its star approximately every 23.445 days. Conclusions: The host star is a metal-rich, K2V dwarf, located at about 82 pc from the Sun with a radius of R⋆ = (0.78±0.01) R⊙ and a mass of M⋆ = (0.80±0.07) M⊙. It forms a common proper motion pair with an M-dwarf companion star located at a projected separation of 2178 au. The chemical analysis of the host-star and the Galactic-space velocities indicate that TOI-5076 belongs to the old population of thin-to-thick-disk transition stars. The density of TOI-5076b suggests the presence of a large fraction by volume of volatiles overlying a massive core. We found that a circular orbit solution is marginally favored with respect to an eccentric orbit solution for TOI-5076b. Full Tables 2 and 3 are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/687/A226</A
Characterisation of the TOI-421 planetary system using CHEOPS, TESS, and archival radial velocity data
Get PDFContext. The TOI-421 planetary system contains two sub-Neptune-type planets (Pb ~ 5.2 days, Teqb ~ 900 K, and Pc ~ 16.1 days, Teq,c ~ 650 K) and is a prime target to study the formation and evolution of planets and their atmospheres. The inner planet is especially interesting as the existence of a hydrogen-dominated atmosphere at its orbital separation cannot be explained by current formation models without previous orbital migration. Aims. We aim to improve the system parameters to further use them to model the interior structure and simulate the atmospheric evolution of both planets, to finally gain insights into their formation and evolution. We also investigate the possibility of detecting transit timing variations (TTVs). Methods. We jointly analysed photometric data of three TESS sectors and six CHEOPS visits as well as 156 radial velocity data points to retrieve improved planetary parameters. We also searched for TTVs and modelled the interior structure of the planets. Finally, we simulated the evolution of the primordial H-He atmospheres of the planets using two different modelling frameworks. Results. We determine the planetary radii and masses of TOI-421 b and c to be Rb = 2.64 ± 0.08 R, Mb = 6.7 ± 0.6 M, Rc = 5.09 ± 0.07 R, and Mc = 14.1 ± 1.4 M. Using these results we retrieved average planetary densities of ρb = 0.37 ± 0.05ρ and ρc = 0.107 ± 0.012 ρ. We do not detect any statistically significant TTV signals. Assuming the presence of a hydrogen-dominated atmosphere, the interior structure modelling results in both planets having extensive envelopes. While the modelling of the atmospheric evolution predicts for TOI-421 b to have lost any primordial atmosphere that it could have accreted at its current orbital position, TOI-421 c could have started out with an initial atmospheric mass fraction somewhere between 10 and 35%. Conclusions. We conclude that the low observed mean density of TOI-421 b can only be explained by either a bias in the measured planetary parameters (e.g. driven by high-altitude clouds) and/or in the context of orbital migration. We also find that the results of atmospheric evolution models are strongly dependent on the employed planetary structure model
Planets observed with CHEOPS. Two super-Earths orbiting the red dwarf star TOI-776
Get PDFContext. M-dwarf stars are the most common of potential exoplanet host stars in the Galaxy. It is therefore very important to understand planetary systems orbiting such stars and to determine the physical parameters of such planets with high precision. Also with the launch of the James Webb Space Telescope (JWST) the observation of atmospheric parameters of planets orbiting these stars has begun. It is therefore required to determine properties of potential targets. Aims: Two planets around the red dwarf TOI-776 were detected by TESS. The objective of our study was to use transit observations obtained by the CHEOPS space mission to improve the current precision of the planetary radii, as well as additional radial velocity (RV) data in order to improve mass estimates of the two planets. Using these quantities, we wanted to derive the bulk densities of those planets, improving the precision in earlier results, and use this information to put them in context of other exoplanetary systems involving very low mass stars. Methods: Utilizing new transit data from the CHEOPS satellite and its photometric telescope, we obtained very high precision planetary transit measurements. Interpretation of these provides updated planetary radii, along with other system parameters. A concurrent ESO large observing program using the high precision spectrograph HARPS has doubled the available radial velocity data. Calculating the power spectrum of a number of stellar activity indices we update the previously estimated stellar rotation period to a lower value. Results: The CHEOPS data provide precise transit depths of 909 and 1177 ppm translating into radii of Rb = 1.798−0.077+0.078 R⊕ and Rc = 2.047−0.078+0.081 R⊕, respectively. Our interpretation of the radial velocities and activity indicator time series data estimates a stellar rotation period for this early M dwarf of ~21.1 days. A further multi-dimensional Gaussian process approach confirm this new estimate. By performing a Skew-Normal (SN) fit onto the Cross Correlation Functions we extracted the RV data and the activity indicators to estimate the planetary masses, obtaining Mb = 5.0−1.6+1.6 M⊕ and Mc = 6.9−2.5+2.6 M⊕. Conclusions: We improve the precision in planetary radius for TOI-776 b and c by a factor of more than two. Our data and modelling give us parameters of both bodies consistent with mini-Neptunes, albeit with a relatively high density. The stellar activity of TOI-776 is found to have increased by a factor larger than 2 since the last set of observations. Radial velocity data are available at the CDS to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/684/A12 This article uses data from CHEOPS programme CH_PR100031
ShowTel: a solar alarm system and real-time monitoring tool for the INAF radio telescopes
Get PDFThis technical note describes the open-source Python package ShowTel and guides the user/observer to use this tool properly. ShowTel – successfully tested – is aimed at the
real-time monitoring of the operations of a radio telescope during an observing session, such as (1) the status of the antenna control system, (2) general information about the
observing session, (3) the angular distance between the Sun (and the Moon) and the radio telescope pointing, (4) the sky position of the Sun, Moon and the astrophysical object under observation, and (5) the Radio Frequency Interference (RFI) of the sky region pointed by the radio telescope, at the running observing frequency. ShowTel appears as an interactive widget that compactly and smartly shows in real-time all this information to the observer, to (1) mitigate unpleasant inconveniences during observation campaigns, and (2) check the proper working of the radio telescope. These inconveniences are reported to the observer thanks to an efficient alarm system, whose sound is audible also when the observer is temporarily far away from the control room of the radio telescope. This Python package is designed for the observing operations of the Sardinia Radio Telescope (SRT), but it can be easily suitable – with a specific tuning – also for other radio telescopes of the INAF Network (such as the Medicina "Gavril Grueff" Radio Telescope and the Noto Radio Telescope) in the near future. ShowTel represents a crucial tool to complete – and not to replace – the Sun avoidance system soon available in the DISCOS control system of the INAF radio telescopes, to automatically prevent the direct pointing of the antenna in the Sun (or in its proximity) during no-solar observation sessions.
ShowTel will be enhanced through the upgrading of SRT with the new cryogenically cooled receivers, operating in the frequency range 33 – 116 GHz, in the context of the National Operative Programme (Programma Operativo Nazionale-PON); this project will provide in the near future an upgrading with the new receivers up to 116 GHz also for the Grueff and
Noto Radio Telescopes, to provide the scientific community with the instrumentation suited to the study of the Universe at high radio frequencies
Magnetic field properties inside the jet of Mrk 421. Multiwavelength polarimetry, including the Imaging X-ray Polarimetry Explorer
Get PDFAims: We aim to probe the magnetic field geometry and particle acceleration mechanism in the relativistic jets of supermassive black holes. Methods: We conducted a polarimetry campaign from radio to X-ray wavelengths of the high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging X-ray Polarimetry Explorer (IXPE) measurements from 2022 December 6-8. During the IXPE observation, we also monitored Mrk 421 using Swift-XRT and obtained a single observation with XMM-Newton to improve the X-ray spectral analysis. The time-averaged X-ray polarization was determined consistently using the event-by-event Stokes parameter analysis, spectropolarimetric fit, and maximum likelihood methods. We examined the polarization variability over both time and energy, the former via analysis of IXPE data obtained over a time span of 7 months. Results: We detected X-ray polarization of Mrk 421 with a degree of ΠX = 14 ± 1% and an electric-vector position angle ψX = 107 ± 3° in the 2-8 keV band. From the time variability analysis, we find a significant episodic variation in ψX. During the 7 months from the first IXPE pointing of Mrk 421 in 2022 May, ψX varied in the range 0° to 180°, while ΠX remained relatively constant within ∼10-15%. Furthermore, a swing in ψX in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that ΠX was generally ∼2-3 times greater than Π at longer wavelengths, while ψ fluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that the rotation of ψ occurred in the opposite direction with respect to the rotation of ψX and over longer timescales at similar epochs. Conclusions: The polarization behavior observed across multiple wavelengths is consistent with previous IXPE findings for HSP blazars. This result favors the energy-stratified shock model developed to explain variable emission in relativistic jets. We considered two versions of the model, one with linear and the other with radial stratification geometry, to explain the rotation of ψX. The accompanying spectral variation during the ψX rotation can be explained by a fluctuation in the physical conditions, for example in the energy distribution of relativistic electrons. The opposite rotation direction of ψ between the X-ray and longer wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths. Moreover, we identify a highly polarized knot of radio emission moving down the parsec-scale jet during the episode of ψX rotation, although it is unclear whether there is any connection between the two events
Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations
Get PDFVariability can be the pathway to understanding the physical processes in
astrophysical jets, however, the high-cadence observations required to test
particle acceleration models are still missing. Here we report on the first
attempt to produce continuous, >24 hour polarization light curves of blazars
using telescopes distributed across the globe and the rotation of the Earth to
avoid the rising Sun. Our campaign involved 16 telescopes in Asia, Europe, and
North America. We observed BL Lacertae and CGRaBS J0211+1051 for a combined 685
telescope hours. We find large variations in the polarization degree and angle
for both sources in sub-hour timescales as well as a ~180 degree rotation of
the polarization angle in CGRaBS J0211+1051 in less than two days. We compared
our high-cadence observations to Particle-In-Cell magnetic reconnection and
turbulent plasma simulations. We find that although the state of the art
simulation frameworks can produce a large fraction of the polarization
properties, they do not account for the entirety of the observed polarization
behavior in blazar jets