OA@INAF - Istituto Nazionale di Astrofisica
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2nd generation ITM M2
Get PDFThis report describes the study of an alternative optical design for the ITM (International Telescope Maffei) ex-IRAIT telescope installed at Concordia Base in Antarctica1234 . The goal is to reduce the focal number of the telescope
Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley
Get PDFContext. TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. Inferring a reliable demographics for this type of systems is key to understanding their formation and evolution mechanisms.
Aims: By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets.
Methods: We performed a global Markov chain Monte Carlo analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a support vector machine (SVM) procedure.
Results: TOI-732b is an ultrashort-period planet (P = 0.76837931-0.00000042+0.0000039 days) with a radius Rb = 1.325-0.058+0.057R⊕, a mass Mb = 2.46 ± 0.19 M⊕, and thus a mean density ρb = 5.8-0.8+1.0 g cm-3, while the outer planet at P = 12.252284 ± 0.000013 days has Rc = 2.39-0.11+0.10R⊕, Mc = 8.04-0.48+0.50M⊕, and thus ρc = 3.24-0.43+0.55 g cm-3. Even with respect to the most recently reported values, this work yields uncertainties on the transit depths and on the RV semi-amplitudes that are smaller up to a factor of ~1.6 and ~2.4 for TOI-732 b and c, respectively. Our calculations for the interior structure and the location of the planets in the mass-radius diagram lead us to classify TOI-732 b as a super-Earth and TOI-732 c as a mini-Neptune. Following the SVM approach, we quantified d log Rp,valley / d logP = -0.065-0.013+0.024, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as d log ρ^valley / d log P = -0.02-0.04+0.12.
Conclusions: Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms.
TESS and CHEOPS detrended light curves 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/682/A66
This article uses data from CHEOPS programme CH_PR100031
The PEPSI Exoplanet Transit Survey (PETS)
Get PDFContext. Hot giant planets such as MASCARA-1 b are expected to have thermally inverted atmospheres, which makes them perfect laboratories for atmospheric characterization through high-resolution spectroscopy. Nonetheless, previous attempts at detecting the atmosphere of MASCARA-1 b in transmission have led to negative results. Aims. We aim to detect the optical emission spectrum of MASCARA-1 b. Methods. We used the high-resolution spectrograph PEPSI to observe MASCARA-1 (spectral type A8) near the secondary eclipse of the planet. We cross-correlated the spectra with synthetic templates computed for several atomic and molecular species. Results. We detect Fe I, Cr I, and Ti I in the atmosphere of MASCARA-1 b with a S/N ≈ 7, 4, and 5, respectively, and confirm the expected systemic velocity of ≈ 13 km s-1 and the radial velocity semi-amplitude of MASCARA-1 b of ≈200 km s-1. The detection of Ti is of particular importance in the context of the recently proposed phenomenon of Ti cold-trapping below a certain planetary equilibrium temperature. Conclusions. We confirm the presence of an atmosphere around MASCARA-1 b through emission spectroscopy. We conclude that the atmospheric non-detection in transmission spectroscopy is due to the strong gravity of the planet and/or to the overlap between the planetary track and its Doppler shadow
Non-ideal magnetohydrodynamics of self-gravitating filaments
Get PDFFilaments have been studied in detail through observations and simulations. A
range of numerical works have separately investigated how chemistry and
diffusion effects, as well as magnetic fields and their structure impact the
gas dynamics of the filament. However, non-ideal effects have hardly been
explored thus far. We investigate how non-ideal magnetohydrodynamic (MHD)
effects, combined with a simplified chemical model affect the evolution and
accretion of a star-forming filament. We modeled an accreting self-gravitating
turbulent filament using lemongrab, a one-dimensional (1D) non-ideal MHD code
that includes chemistry. We explore the influence of non-ideal MHD, the
orientation and strength of the magnetic field, and the cosmic ray ionization
rate, on the evolution of the filament, with particular focus on the width and
accretion rate. We find that the filament width and the accretion rate are
determined by the magnetic field properties, including the initial strength,
the coupling with the gas controlled by the cosmic ray ionization rate, and the
orientation of the magnetic field with respect to the accretion flow direction.
Increasing the cosmic-ray ionization rate leads to a behavior closer to that of
ideal MHD, reducing the magnetic pressure support and, hence, damping the
accretion efficiency with a consequent broadening of the filament width. For
the same reason, we obtained a narrower width and a larger accretion rate when
we reduced the initial magnetic field strength. Overall, while these factors
affect the final results by approximately a factor of~2, removing the non-ideal
MHD effects results in a much greater variation (up to a factor of~7). The
inclusion of non-ideal MHD effects and the cosmic-ray ionization is crucial for
the study of self-gravitating filaments and in determining critical observable
quantities, such as the filament width and accretion rate
The Northern Cross Fast Radio Burst project: III. The FRB-magnetar connection in a sample of nearby galaxies
Get PDFContext. Fast radio bursts (FRBs) are millisecond radio transients observed at cosmological distances. The nature of their progenitors is still a matter of debate, although magnetars are invoked by most models. The proposed FRB-magnetar connection was strengthened by the discovery of an FRB-like event from the Galactic magnetar SGR J1935+2154. Aims. In this work we aim to investigate how prevalent magnetars such as SGR J1935+2154 are within FRB progenitors. Methods. To this end, we carried out an FRB search in a sample of seven nearby (a 1034 erg from magnetars such as SGR J1935+2154 appear more rarely compared to previous observations and further disfavour them as unique progenitors for the cosmological FRB population. This provides support to the idea that there is a greater contribution from a population of more exotic magnetars not born via core-collapsed supernovae
Simultaneous and panchromatic observations of the fast radio burst FRB 20180916B
Get PDFAims. Fast radio bursts are bright radio transients whose origins are not yet understood. The search for a multi-wavelength counterpart of those events can set a tight constraint on the emission mechanism and the progenitor source. Methods. We conducted a multi-wavelength observational campaign on FRB 20180916B between October 2020 and August 2021 over eight activity cycles of the source. Observations were carried out in the radio band by the SRT both at 336 and 1547 MHz and the uGMRT at 400 MHz. Simultaneous observations were conducted by the optical telescopes Asiago (Galileo and Copernico), CMO SAI MSU, CAHA 2.2 m, RTT-150 and TNG, and X/γ-ray detectorss on board the AGILE, Insight-HXMT, INTEGRAL, and Swift satellites. Results. We present the detection of 14 new radio bursts detected with the SRT at 336 MHz and seven new bursts with the uGMRT from this source. We provide the deepest prompt upper limits in the optical band for FRB 20180916B to date. In fact, the TNG/SiFAP2 observation simultaneous to a burst detection by uGMRT gives an upper limit Eoptical/Eradio 2. Another burst detected by the SRT at 336 MHz was also co-observed by Insight-HXMT. The non-detection in the X-rays yields an upper limit (1-30 keV band) of EX-ray/Eradio in the range of (0.9-1.3) × 107, depending on the model that is considered for the X-ray emission
WEAVE-StePS: A stellar population survey using WEAVE at WHT
Get PDFContext. The upcoming new generation of optical spectrographs on four-meter-class telescopes will provide valuable opportunities for forthcoming galaxy surveys through their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage. Aims: WEAVE is a new wide-field spectroscopic facility mounted on the 4.2 m William Herschel Telescope in La Palma. WEAVE-StePS is one of the five extragalactic surveys that will use WEAVE during its first five years of operations. It will observe galaxies using WEAVE MOS (∼950 fibres distributed across a field of view of ∼3 square degrees on the sky) in low-resolution mode (R ∼ 5000, spanning the wavelength range 3660 − 9590 Å). Methods: WEAVE-StePS will obtain high-quality spectra (S/N ∼ 10 Å−1 at R ∼ 5000) for a magnitude-limited (IAB = 20.5) sample of ∼25 000 galaxies, the majority selected at z ≥ 0.3. The survey goal is to provide precise spectral measurements in the crucial interval that bridges the gap between LEGA-C and SDSS data. The wide area coverage of ∼25 square degrees will enable us to observe galaxies in a variety of environments. The ancillary data available in each of the observed fields (including X-ray coverage, multi-narrow-band photometry and spectroscopic redshift information) will provide an environmental characterisation for each observed galaxy. Results: This paper presents the science case of WEAVE-StePS, the fields to be observed, the parent catalogues used to define the target sample, and the observing strategy that was chosen after a forecast of the expected performance of the instrument for our typical targets. Conclusions: WEAVE-StePS will go back further in cosmic time than SDSS, extending its reach to encompass more than ∼6 Gyr. This is nearly half of the age of the Universe. The spectral and redshift range covered by WEAVE-StePS will open a new observational window by continuously tracing the evolutionary path of galaxies in the largely unexplored intermediate-redshift range