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Revealing the burning and soft heart of the bright bare AGN ESO 141-G55: X-ray broadband and SED analysis
Full text link[Abridged] ESO 141-G55 is a nearby X-ray bright BLS1, which has been
classified as a bare AGN due to the lack of warm absorption along its
line-of-sight, providing an unhampered view into its disc-corona system. We aim
to probe its disc-corona system thanks to the first simultaneous XMM-Newton and
NuSTAR observation obtained on October 1-2, 2022. We carry out the X-ray
broadband spectral analysis to determine the dominant process(es) at work, as
well as the SED analysis to determine the disc-corona properties. The
simultaneous broadband X-ray spectrum of ESO 141-G55 is characterised by the
presence of a prominent smooth soft X-ray excess, a broad Fe K emission line
and a significant Compton hump. The RGS spectra confirmed the lack of intrinsic
warm-absorbing gas along our line of sight in the AGN rest frame, confirming
that it is still in a bare state. However, soft X-ray emission lines are
observed indicating substantial warm gas out of our line of sight. The
intermediate inclination of the disc-corona system, ~43{\deg}, may offer us a
favourable configuration to observe UFOs from the disc, but none is found in
this 2022 observation, contrary to a previous 2007 XMM-Newton one. Relativistic
reflection alone on a standard disc is ruled out from the X-ray broadband
analysis, while a combination of soft and hard Comptonisation by a warm and hot
corona (relagn), plus relativistic reflection (reflkerrd) reproduces its SED
quite well. The hot corona temperature is very hot, ~140 keV, much higher than
about 80% of the AGNs, whereas the warm corona temperature, ~0.3 keV, is
similar to the values found in other sub-Eddington AGNs. ESO 141-G55 is
accreting at a moderate Eddington accretion rate (~10--20%). Our analysis
points to a significant contribution of an optically-thick warm corona to both
the soft X-ray and UV emission in ESO 141-G55
UVC-Mirror for effective pathogens inactivation in air ducts
Full text linkImproving the air quality of indoor environments (IAQ) is of utmost importance to safeguard public health as people spend about 80-90% of their time indoor. Efficient Ultraviolet germicidal irradiation (UVGI) system represents a strategic and sustainable solution to protect from recurrent and new airborne pathogens. Here, we present a new approach to design highly efficient UVGI systems, which can be installed in existing Air Treatment Units (ATU) plants with minimal effort. The increased efficiency relies on the concept of an optical cavity, thanks to its shape and source position. The internal volume consists of a highly reflective cavity illuminated with UV-C lamps. Optical simulations permitted the variation of the parameters to maximize the internal irradiance and, thus, the performance. The sanitation efficacy of the system was assessed on a full-scale pilot system. Tests were carried out under normal operating conditions against various microorganisms showed an inactivation rate of > 99%. The benefits of such systems are triple and encompass economic, environmental, and societal aspects. Since the system requires little energy to operate, its application for air disinfection may yield significant energy savings and ensure a balance between energy sustainability and good IAQ
TRAPUM pulsar and transient search in the Sextans A and B galaxies and discovery of background FRB 20210924D
Full text linkThe Small and Large Magellanic Clouds are the only galaxies outside our own in which radio pulsars have been discovered to date. The sensitivity of the MeerKAT radio interferometer offers an opportunity to search for a population of more distant extragalactic pulsars. The TRAPUM (TRansients And PUlsars with MeerKAT) collaboration has performed a radio-domain search for pulsars and transients in the dwarf star-forming galaxies Sextans A and B, situated at the edge of the Local Group 1.4 Mpc away. We conducted three 2-h multibeam observations at L band (856–1712 MHz) with the full array of MeerKAT. No pulsars were found down to a radio pseudo-luminosity upper limit of 7.9±0.4 Jy kpc2 at 1400 MHz, which is 28 times more sensitive than the previous limit from the Murriyang telescope. This luminosity is 30 per cent greater than that of the brightest known radio pulsar and sets a cut-off on the luminosity distributions of the entire Sextans A and B galaxies for unobscured radio pulsars beamed in our direction. A fast radio burst was detected in one of the Sextans A observations at a dispersion measure (DM) of 737 pc cm−3. We believe this is a background event not associated with the dwarf galaxy due to its large DM and its signal-to-noise ratio being strongest in the wide-field incoherent beam of MeerKAT
The second data release from the European Pulsar Timing Array. IV. Implications for massive black holes, dark matter, and the early Universe
Full text linkThe European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) collaborations have measured a low-frequency common signal in the combination of their second and first data releases, respectively, with the correlation properties of a gravitational wave background (GWB). Such a signal may have its origin in a number of physical processes including a cosmic population of inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, cosmic strings, and tensor mode generation by the non-linear evolution of scalar perturbations in the early Universe; and oscillations of the Galactic potential in the presence of ultra-light dark matter (ULDM). At the current stage of emerging evidence, it is impossible to discriminate among the different origins. Therefore, for this paper, we consider each process separately, and investigated the implications of the signal under the hypothesis that it is generated by that specific process. We find that the signal is consistent with a cosmic population of inspiralling SMBHBs, and its relatively high amplitude can be used to place constraints on binary merger timescales and the SMBH-host galaxy scaling relations. If this origin is confirmed, this would be the first direct evidence that SMBHBs merge in nature, adding an important observational piece to the puzzle of structure formation and galaxy evolution. As for early Universe processes, the measurement would place tight constraints on the cosmic string tension and on the level of turbulence developed by first-order phase transitions. Other processes would require non-standard scenarios, such as a blue-tilted inflationary spectrum or an excess in the primordial spectrum of scalar perturbations at large wavenumbers. Finally, a ULDM origin of the detected signal is disfavoured, which leads to direct constraints on the abundance of ULDM in our Galaxy. The EPTA+InPTA DR2 data used to perform the analysis presented in this paper can be found at: https://zenodo.org/record/8091568 https://zenodo.org/record/8091568; https://gitlab.in2p3.fr/epta/epta-dr2..
Climatology and Diurnal Variation of Ozone Column Abundances for 2.5 Mars Years as Measured by the NOMAD-UVIS Spectrometer
Full text linkThe distribution of Mars ozone (O3) is well established; however, our knowledge on the dayside diurnal variation of O3 is limited. We present measurements of Mars O3 column abundances, spanning Mars Year (MY) 34 to the end of MY 36, by the Ultraviolet and VIsible Spectrometer (UVIS), part of the Nadir and Occultation for MArs Discovery (NOMAD) instrument, aboard the ExoMars Trace Gas Orbiter. UVIS provides the capability to measure dayside diurnal variations of O3 and for the first time, a characterization of the dayside diurnal variations of O3 is attempted. The observed O3 climatology for Mars Years (MY) 34–36 follows the established seasonal trends observed through previous O3 measurements. At aphelion, the equatorial O3 distribution is observed to be strongly correlated with the water ice distribution. We show that the early dust storm in MY 35 resulted in a near-global reduction in O3 during northern spring and the O3 abundances remained 14% lower in northern summer compared to MY36. Strong latitudinal and longitudinal variation was observed in the diurnal behavior of O3 around the northern summer solstice. In areas with a weak O3 upper layer, O3 column abundance peaks in the mid-morning, driven by changes in the near-surface O3 layer. In regions with greater O3 column abundances, O3 is observed to gradually increase throughout the day. This is consistent with the expected diurnal trend of O3 above the hygropause and suggests that in these areas an upper O3 layer persists throughout the Martian day
EWOCS-II: X-ray properties of the Wolf-Rayet stars in the young Galactic super star cluster Westerlund 1
Full text linkContext. Wolf-Rayet (WR) stars are massive evolved stars that exhibit particularly fast and dense stellar winds. Although they constitute a very short phase near the end of a massive star's life, they play a crucial role in the evolution of massive stars and have a substantial impact on their surrounding environment. Aims. We present the most comprehensive and deepest X-ray study to date of the properties of the richest Wolf-Rayet population observed in a single stellar cluster, Westerlund 1 (Wd1). By examining the X-ray signatures of WR stars, we aim to shed light on the hottest plasma in their stellar winds and gain insights into whether they exist as single stars or within binary systems. Methods. This work is based on 36 Chandra observations obtained from the "Extended Westerlund 1 and 2 Open Clusters Survey"(EWOCS) project, plus 8 archival Chandra observations. The overall exposure depth Ms) and baseline of the EWOCS observations extending over more than one year enable us to perform a detailed photometric, colour, and spectral analysis, as well as to search for short- and long-term periodicity. Results. In X-rays, we detect 20 out of the 24 known Wolf-Rayet stars in Wd1 down to an observed luminosity of ∼7 × 1029 erg s-1 (assuming a distance of 4.23 kpc to Wd1), with 8 WR stars being detected in X-rays for the first time. Nine stars show clear evidence of variability over the year-long baseline, with clear signs of periodicity. The X-ray colours and spectral analysis reveal that the vast majority of the WR stars are hard X-ray sources (kT≥2.0 keV). The Fe XXV emission line at ∼6.7 keV, which commonly originates from the wind-wind collision zone in binary systems, is detected for the first time in the spectra of 17 WR stars in Wd1. In addition the ∼6.4 keV fluorescent line is observed in the spectra of three stars, which are among the very few massive stars exhibiting this line, indicating that dense cold material coexists with the hot gas in these systems. Overall, our X-ray results alone suggest a very high binary fraction (≥80%) for the WR star population in Wd1. When combining our results with properties of the WR population from other wavelengths, we estimate a binary fraction of ≥92%, which could even reach unity. This suggests that either all the most massive stars are found in binary systems within Wd1, or that binarity is essential for the formation of such a rich population of WR stars
FAST: A software suite for automatic weather and optical turbulence forecast on ground-based telescope sites
Full text linkIn this contribution we present the FAST, which is a comprehensive software suite that aims to streamline and automatically manage the forecast of atmospheric and astroclimatic parameters (provided respectively by Meso-Nh and Astro-Meso-Nh models) on large ground-based telescope installations. The forecast of the aforementioned parameters is becoming crucial for the operation of the large telescope installations which possess atmospheric-sensitive equipment equipped with Adaptive Optics (AO) systems. FAST performs automatically all the steps of an atmosphere forecast process: initialisation and forcing data, atmospheric simulation, postprocessing and managing of the outputs.The role of such service is useful both in optimizing beforehand AO instruments to the next atmospheric conditions and in planning telescope observations (especially in “service mode”) in order to maximize the scientific output. FAST was applied first to the ALTA Center project (3), which provides forecasts for the LBT telescope. Then it was extended to the more recent project FATE that is a similar forecast system applied to the VLT. Since its first version FAST evolved and it has has been modified to fit with the different technical specifications of the different projects gaining in modularity. It is now able to provide forecasts on different timescales (from days to hours before) and to provide forecast during night and day time. After several years of continuous development we can say that FAST reached full maturity and it is now ready for applications to other projects/sites
The Survey of Surveys: machine learning for stellar parametrization
Full text linkWe present a machine learning method to assign stellar parameters (temperature, surface gravity, metallicity) to the photometric data of large photometric surveys such as SDSS and SKYMAPPER. The method makes use of our previous effort in homogenizing and recalibrating spectroscopic data from surveys like APOGEE, GALAH, or LAMOST into a single catalog, which is used to inform a neural network. We obtain spectroscopic-quality parameters for millions of stars that have only been observed photometrically. The typical uncertainties are of the order of 100K in temperature, 0.1 dex in surface gravity, and 0.1 dex in metallicity and the method performs well down to low metallicity, were obtaining reliable results is known to be difficult
LNA all’interno del carrier, studiato per funzionare a temperature criogeniche
Full text linkIl cuore del lavoro è l’attività di ‘packaging’ degli LNA all’interno del modulo (carrier), studiato per funzionare a temperature criogeniche.
Tale attività ha evidenziato potenziali criticità che si desidera, attraverso questa nota tecnica, approfondire
Signatures of X-Ray-dominated Chemistry in the Spectra of Exoplanetary Atmospheres
Full text linkHigh-energy radiation from stars impacts planetary atmospheres, deeply affecting their chemistry and providing departures from chemical equilibrium. While the upper atmospheric layers are dominated by ionizations induced by extreme-ultraviolet radiation, deeper into the atmosphere, molecular abundances are controlled by a characteristic X-ray-dominated chemistry, mainly driven by an energetic secondary electron cascade. In this work, we aim at identifying molecular photochemically induced fingerprints in the transmission spectra of a giant planet atmosphere. We have developed a numerical code capable of synthesizing transmission spectra with arbitrary spectral resolution, exploiting updated infrared photoabsorption cross sections. Chemical mixing ratios are computed using a photochemical model tailored to investigate high-energy ionization processes. We find that in the case of high levels of stellar activity, synthetic spectra in both low and high resolutions show significant, potentially observable out-of-equilibrium signatures arising mainly from CO, CH4, C2H2, and HCN