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PENELLOPE. IV. A comparison between optical forbidden lines and H_2 UV lines in the Orion OB1b and σ-Ori associations
No full textContext. Observing the spatial distribution and excitation processes of atomic and molecular gas in the inner regions ( Aims: In the framework of the PENELLOPE and ULLYSES projects, we aim to characterize the atomic and molecular component of protoplanetary disks in a sample of 11 classical T Tauri stars of the Orion OB1 and σ-Orionis associations. Methods: We analyzed the flux-calibrated optical forbidden lines and the fluorescent ultraviolet H2 progressions using spectra acquired with ESPRESSO at VLT, UVES at VLT, and HST-COS. Line morphologies were characterized through Gaussian decomposition. We then focused on the properties of the narrow low-velocity (full width half maximum −1 and |υp| −1) component (NLVC) of the [O I] 630 nm line and compared them with those of the UV-H2 lines. Results: We found that the [O I]630 NLVC and the UV-H2 lines are strongly correlated in terms of peak velocities, full width at half maximum values, and luminosity. Assuming that the line width is dominated by Keplerian broadening, the [O I]630 NLVC originates from a disk region between 0.5 and 3.5 au, while that of UV-H2 originates in a region from 0.05 to 1 au. The luminosities of [O I]630 NLVC and UV-H2 correlate with an accretion luminosity with a similar slope, as well as with the luminosity of the C IV154.8, 155 nm doublet. We discuss such correlations in the framework of the currently suggested excitation processes for the [O I]630 NLVC. Conclusions: Our results can be interpreted in a scenario in which the [O I]630 NLVC and UV-H2 have a common disk origin with a partially overlapped radial extension. We also suggest that the excitation of the [O I] NLVC is mainly induced by stellar far-ultraviolet continuum photons, than being of mostly thermal origin. This study demonstrates the potential of contemporaneous wide-band highresolution spectroscopy in linking different tracers of protoplanetary disks
Probing z ≳ six massive black holes with gravitational waves
No full textWe investigate the coalescence of massive black hole () binaries (MBHBs) at 6 3σ) overdense regions (Mh ~ 1012 M⊙ dark matter haloes at z = 6) of the Universe. We first analyse the impact of different resolutions and AGN feedback prescriptions on the merger rate, assuming instantaneous mergers. Then, we compute the halo bias correction factor due to the overdense simulated region. Our simulations predict merger rates that range between 3 and 15 at z ~6, depending on the run considered, and after correcting for a bias factor of ~20-30. For our fiducial model, we further consider the effect of delay in the MBHB coalescence due to dynamical friction. We find that 83 per cent of MBHBs will merge within the Hubble time, and 21 per cent within 1 Gyr, namely the age of the Universe at z > 6. We finally compute the expected properties of the gravitational wave (GW) signals and find the fraction of LISA detectable events with high signal-to-noise ratio (SNR > 5) to range between 66 per cent and 69 per cent. However, identifying the electro-magnetic counterpart of these events remains challenging due to the poor LISA sky localization that, for the loudest signals ( at z = 6), is around 10
A polarimetrically oriented X-ray stare at the accreting pulsar EXO 2030+375
No full textAccreting X-ray pulsars (XRPs) are presumed to be ideal targets for polarization measurements, as their high magnetic field strength is expected to polarize the emission up to a polarization degree of ∼80%. However, such expectations are being challenged by recent observations of XRPs with the Imaging X-ray Polarimeter Explorer (IXPE). Here, we report on the results of yet another XRP, namely, EXO 2030+375, observed with IXPE and contemporarily monitored with Insight-HXMT and SRG/ART-XC. In line with recent results obtained with IXPE for similar sources, an analysis of the EXO 2030+375 data returns a low polarization degree of 0%-3% in the phase-averaged study and a variation in the range of 2%-7% in the phase-resolved study. Using the rotating vector model, we constrained the geometry of the system and obtained a value of ∼60° for the magnetic obliquity. When considering the estimated pulsar inclination of ∼130°, this also indicates that the magnetic axis swings close to the observer's line of sight. Our joint polarimetric, spectral, and timing analyses hint toward a complex accreting geometry, whereby magnetic multipoles with an asymmetric topology and gravitational light bending significantly affect the behavior of the observed source
Centro di calcolo oas plesso cnr struttura e servizi offerti
Get PDFQuesto documento fornisce una sintetica descrizione dei servizi
presenti nel Centro di Calcolo di OAS situato nel Plesso CNR.
Moto utile per comprendere l'evoluzione nel tempo del Centro di Calcolo
Magnetic field evolution in cosmic filaments with LOFAR data
Get PDFMeasuring the magnetic field in cosmic filaments reveals how the Universe is
magnetised and the process that magnetised it. Using the Rotation Measures (RM)
at 144-MHz from the LoTSS DR2 data, we analyse the rms of the RM extragalactic
component as a function of redshift to investigate the evolution with redshift
of the magnetic field in filaments. From previous results, we find that the
extragalactic term of the RM rms at 144-MHz is dominated by the contribution
from filaments (more than 90 percent). Including an error term to account for
the minor contribution local to the sources, we fit the data with a model of
the physical filament magnetic field, evolving as
and with a density drawn from cosmological simulations of five magnetogenesis
scenarios. We find that the best-fit slope is in the range with uncertainty of --0.5, which is consistent with
no evolution. The comoving field decreases with redshift with a slope of
. The mean field strength at is in
the range --84~nG. For a typical filament gas overdensity of
the filament field strength at is in the range
--26~nG. A primordial stochastic magnetic field model with
initial comoving field of --0.11~nG is favoured. The
primordial uniform field model is rejected
Improvement of the Marsis on-board SW, on the Mars Express mission. Preliminary scientific results on Phobos and Mars
Get PDFThe Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) is a powerful instrument for subsurface remote sensing of the Mars planet. Since the beginning of operations, about fifteen year ago, many successful observations have been carried out. At this point of this fruitful mission, having acquired a good knowledge of the Mars environment, it was decided to improve the instrument science performances, mitigating some technical limitations, that were required at the beginning of the mission, but which were proven to be excessive and, above all, limiting.
The new on-board Software is now operative on the instrument and almost fully commissioned. Recently, it allowed to see beneath the surfaces of Mars and its moon Phobos in more detail than ever before
First assessment of non-X-ray background in Line Emission Mapper (LEM) focal plane detector.
Get PDFThe LEM (Line Emission Mapper) mission proposal envisions a cryogenic microcalorimeter array optimized for the 0.2–2 keV energy band, based on the X-IFU heritage. The array will consist of 13,806 absorber pixels with a 290 µm pitch, in hexagonal arrangement, that for a 4 m focal length will cover a solid angle equal to 29.4 square degrees. The orbit for LEM is currently under study with the Sun-Earth Lagrange points L1 and L2 possible candidates.
For what concerns the non X-Ray background (NXB), the premises are very similar to the X-IFU case. The background estimates are performed using Monte Carlo simulations with the Geant4 software [RD1] and, as a consequence, minor modifications to the X-IFU simulations can give precious insights on the NXB level to be expected for the instrument.
Furthermore, it is possible to test the effect of changes to the instrument mass model (sensitivity analysis) and identify the configuration that optimizes the detector performances
Problem with MODS data in the blue channel
Get PDFDuring the 2013 June Italian run, a MODS blue proposal (MOS) has been observed (ID 31) and reduced. The PI is interested in measuring absorption features of high redshift objects. These feature are expected to be observed in the bluest region of the spectra
