Hard synchrotron BL Lacs: the case of 1ES 1101-232

The bright X-ray selected BL Lac object 1ES1101--232 shows a flat X-ray spectrum, making it detectable with high statistics over the wide BeppoSAX energy range. We have observed it in two different epochs with BeppoSAX, and found a variation of the flux of about 30% that can be explained by a change in the spectral index above the synchrotron peak. We present here the data and infer limits on the strength of the magnetic field based on models of emission for High-frequency peaked BL Lacs.Comment: 4 pages, proceedings of `X-ray Astronomy '999 -- Stellar Endpoints, AGN and the Diffuse Background", held in Bologna - Italy, September 6-10, 1999, Astrophysical Letters and Communications. Needs bo99.st

An Energy Saving Road Sweeper Using Deep Vision for Garbage Detection

Road sweepers are ubiquitous machines that help preserve our cities cleanliness and health by collecting road garbage and sweeping out dirt from our streets and sidewalks. They are often very mechanical instruments, needing to operate in harsh conditions dealing with all sorts of abandoned trash and natural garbage. They are usually composed of rotating brushes, collector belts and bins, and sometimes water or air streams. All of these mechanical tools are usually high in power demand and strongly subject to wear and tear. Moreover, due to the simple working logic often implied by these cleaning machines, these tools work in an “always on”/“max power” state, and any further regulation is left to the pilot. Therefore, adding artificial intelligence able to correctly operate these tools in a semi-automatic way would be greatly beneficial. In this paper, we propose an automatic road garbage detection system, able to locate with great precision most types of road waste, and to correctly instruct a road sweeper in order to handle them. With this simple addition to an existing sweeper, we will be able to save more than 80% electrical power currently absorbed by the cleaning systems and reduce by the same amount brush weariness (prolonging their lifetime). This is done by choosing when to use the brushes and when not to, with how much strength, and where. The only hardware components needed by the system will be a camera and a PC board able to read the camera output (and communicate via CanBus). The software of the system will be mainly composed of a deep neural network for semantic segmentation of images, and a real-time software program to control the sweeper actuators with the appropriate timings. To prove the claimed results, we run extensive tests onboard of such a truck, as well as benchmark tests for accuracy, sensitivity, specificity and inference speed of the system

The environment and distribution of emitting electrons as a function of source activity in Markarian 421

For the high-frequency peaked BL Lac object Mrk 421 we study the variation of the spectral energy distribution (SED) as a function of source activity, from quiescent to active. We use a fully automatized chi-squared minimization procedure, instead of the "eyeball" procedure more commonly used in the literature, to model nine SED datasets with a one-zone Synchrotron-Self-Compton (SSC) model and examine how the model parameters vary with source activity. The latter issue can finally be addressed now, because simultaneous broad-band SEDs (spanning from optical to VHE photon energies) have finally become available. Our results suggest that in Mrk 421 the magnetic field decreases with source activity, whereas the electron spectrum's break energy and the Doppler factor increase -- the other SSC parameters turn out to be uncorrelated with source activity. In the SSC framework these results are interpreted in a picture where the synchrotron power and peak frequency remain constant with varying source activity, through a combination of decreasing magnetic field and increasing number density of electrons below the break energy: since this leads to an increased electron-photon scattering efficiency, the resulting Compton power increases, and so does the total (= synchrotron plus Compton) emission.Comment: Accepted for publication in Astrophysical Journal; 23 pages, 3 figures, 2 table

Emitting electrons and source activity in Markarian 501

We study the variation of the broad-band spectral energy distribution (SED) of the BL Lac object Mrk 501 as a function of source activity, from quiescent to flaring. Through chi-square-minimization we model eight simultaneous SED datasets with a one-zone Synchrotron-Self-Compton (SSC) model, and examine how model parameters vary with source activity. The emerging variability pattern of Mrk 501 is complex, with the Compton component arising from gamma-electron scatterings that sometimes are (mostly) Thomson and sometimes (mostly) extreme Klein-Nishina. This can be seen from the variation of the Compton to synchrotron peak distance according to source state. The underlying electron spectra are faint/soft in quiescent states and bright/hard in flaring states. A comparison with Mrk 421 suggests that the typical values of the SSC parameters are different in the two sources: however, in both jets the energy density is particle dominated in all states.Comment: 8 pages, 4 figures, 1 table; accepted for publication in Ap

Blazar candidates beyond redshift 4 observed by Swift

We have selected SDSS J222032.50+002537.5 and SDSS J142048.01+120545.9 as best blazar candidates out of a complete sample of extremely radio-loud quasars at z > 4, with highly massive black holes. We observed them and a third serendipitous candidate with similar features (PMN J2134-0419) in the X-rays with the Swift/XRT telescope, to confirm their blazar nature. We observed strong and hard X-ray fluxes (i.e. α_X ̃ ≪ap 0.6, where F(ν )∝ ν ^{-α_X} in the 0.3-10 keV observed energy range, ̃1-40 keV rest frame) in all three cases. This allowed us to classify our candidates as real blazars, being characterized by large Lorentz factors (̃13) and very small viewing angles (̃3°). All three sources have black hole masses exceeding 109 M☉ and their classification provides intriguing constraints on supermassive black hole formation and evolution models. We confirm our earlier suggestion that there are different formation epochs of extremely massive black holes hosted in jetted (z ̃ 4) and non-jetted systems (z ̃ 2.5)

The Jet-Disk Connection and Blazar Unification

We discuss the relation between the power carried by relativistic jets and the nuclear power provided by accretion, for a group of blazars including FSRQs and BL Lac objects. They are characterized by good quality broad band X-ray data provided by the Beppo SAX satellite. The jet powers are estimated using physical parameters determined from uniformly modelling their spectral energy distributions (SEDs). Our analysis indicates that for Flat Spectrum Radio Quasars the total jet power is of the same order as the accretion power. We suggest that blazar jets are likely powered by energy extraction from a rapidly spinning black hole through the magnetic field provided by the accretion disk. FSRQs must have large BH masses (10^8 - 10^9 solar masses) and high, near Eddington accretion rates. For BL Lac objects the jet luminosity is larger than the disk luminosity. This can be understood within the same scenario if BL Lac objects have masses similar to FSRQ but accrete at largely subcritical rates, whereby the accretion disk radiates inefficiently. Thus the ``unification'' of the two classes into a single blazar population, previously proposed on the basis of a spectral sequence governed by luminosity, finds a physical basis.Comment: 27 pages, 3 figures, ApJ in pres

Il riallestimento del Museo Astronomico di Brera

Grazie a uno stanziamento della Regione Lombardia ottenuto tramite il bando “Progetti di valorizzazione e promozione di Istituti, Luoghi della cultura, siti UNESCO, itinerari culturali e di catalogazione del patrimonio culturale - ambito museo 2019” tra il maggio e il dicembre 2020 è stato realizzato il nuovo allestimento della galleria del MusAB. Il MusAB ha in questa nuova esposizione l’ambizione di rispondere alla domanda “Cosa fa l’astronoma/o”? “Osservare, scoprire, misurare, rappresentare, sono queste le operazioni che compiono gli astronomi; noi cercheremo di illustrarle con l’aiuto degli antichi strumenti della Specola di Brera.” Così si legge nella rinnovata pannellistica del Museo mentre il telescopio Gualtieri, il Magnetometro, Boscovich e Napoleone ci guidano in prima persona alla scoperta di questa straordinaria disciplina. Van Gogh, Shakespeare, Tomasi di Lampedusa fanno da cornice alla visita e ci conducono fino a Marte dove il ricco patrimonio archivistico dell’INAF – Osservatorio Astronomico di Brera viene illustrato grazie alle riproduzioni digitali

Influence of the fabrication accuracy of hot-embossed PCL scaffolds on cell growths

Polycaprolactone (PCL) is a biocompatible and biodegradable polymer widely used for the realization of 3D scaffold for tissue engineering applications. The hot embossing technique (HE) allows the obtainment of PCL scaffolds with a regular array of micro pillars on their surface. The main drawback affecting this kind of micro fabrication process is that such structural superficial details can be damaged when detaching the replica from the mold. Therefore, the present study has focused on the optimization of the HE processes through the development of an analytical model for the prediction of the demolding force as a function of temperature. This model allowed calculating the minimum demolding force to obtain regular micropillars without defects. We demonstrated that the results obtained by the analytical model agree with the experimental data. To address the importance of controlling accurately the fabricated microstructures, we seeded on the PCL scaffolds human stromal cell line (HS-5) and monocytic leukemia cell line (THP-1) to evaluate how the presence of regular or deformed pillars affect cells viability. In vitro viability results, scanning electron and fluorescence microscope imaging analysis show that the HS-5 preferentially grows on regular microstructured surfaces, while the THP-1 on irregular microstructured ones

Simbol-X: a formation flight mission with an unprecedented imaging capability in the 0.5-80 keV energy band

The discovery of X-ray emission from cosmic sources in the 1960s has opened a new powerful observing window on the Universe. In fact, the exploration of the X-ray sky during the 70s-90s has established X-ray astronomy as a fundamental field of astrophysics. Today, the emission from astrophysical sources is by large best known at energies below 10 keV. The main reason for this situation is purely technical since grazing incidence reflection has so far been limited to the soft X-ray band. Above 10 keV all the observations have been obtained with collimated detectors or coded mask instruments. To make a leap step forward in Xray astronomy above 10 keV it is necessary to extend the principle of focusing X ray optics to higher energies, up to 80 keV and beyond. To this end, ASI and CNES are presently studying the implementation of a X-ray mission called Simbol-X. Taking advantage of emerging technology in mirror manufacturing and spacecraft formation flying, Simbol-X will push grazing incidence imaging up to 80 keV and beyond, providing a strong improvement both in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. This technological breakthrough will open a new highenergy window in astrophysics and cosmology. Here we will address the problematic of the development for such a distributed and deformable instrument. We will focus on the main performances of the telescope, like angular resolution, sensitivity and source localization. We will also describe the specificity of the calibration aspects of the payload distributed over two satellites and therefore in a not "frozen" configuration