ASI - Agenzia Spaziale Italiana - L´Agenzia ASI - Agenzia Spaziale Italiana - L´Agenzia

News

Le nostre ultime pubblicazioni e le novità editoriali

 

Journal articles

 

INRRI-EDM/2016: the first laser retroreflector on the surface of Mars
S. Dell’Agnello, G. Delle Monache, L. Porcelli [...], Enrico Flamini*, et al. ...
*Agenzia Spaziale Italiana - Headquarters (ASI-HQ), Via del Politecnico snc, 00133 Rome, Italy
Advances in Space Research, Volume 59, Issue 2, 15 January 2017, Pages 645–655
Abstract
During Summer 2015 the SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and cube/microsat Characterization Facilities Laboratory, www.lnf.infn.it/esperimenti/etrusco) Team of INFN-LNF, with support by ASI, carried out an intense activity of final design, manufacturing and testing in order to construct, space qualify and finally integrate INRRI-EDM/2016 on ESA’s ExoMars EDM spacecraft (also dubbed ‘Schiaparelli’), which was successfully launched on March 14, 2016. INRRI (INstrument for landing-Roving laser Retroreflector Investigation) for the EDM (Entry descent and landing Demonstration Module) 2016 mission is a compact, lightweight, passive, maintenance-free array of eight cube corner laser retroreflectors fixed to an aluminum alloy frame through the use of silicon rubber suitable for space applications. INRRI was installed on the top panel of the EDM Central Bay on October 14, 2015. It will enable the EDM to be laser-located from Mars orbiters, through laser ranging and altimetry, lidar atmospheric observations from orbit, laser flashes emitted by orbiters, and lasercom. One or all of the above means of observation can be supported by INRRI when there is an active, laser-equipped orbiter, especially after EDM end-of-life and for a long time. INRRI goals will cover science (Mars geodesy/geophysics, future Mars test of General Relativity, GR), technology and exploration. Concerning the latter two, INRRI will support mars-georeferencing of the EDM landing site, support potential precision lidar-based landing next to the EDM, support test & diagnostics of lasercom for data exchange among Mars orbit, Mars surface and Earth, and it will be a precursor for additional Mars surface retroreflectors, for example on exploration rovers. This paper describes in detail our innovative payload, hopefully the very first to be deployed safely with the lander Schiaparelli on the Mars surface, and its space qualification for the ExoMars EDM 2016 mission. Despite the fate of the Schiaparelli landing, which is still under the investigation of ESA and the industry, this paper remains a valuable reference for next INRRI-like laser retroreflectors arrays.

 

First limits on the very-high energy gamma-ray afterglow emission of a fast radio burstH.E.S.S. observations of FRB 150418
H. Abdalla, A. Abramowski, F. Aharonian; [...], Elisabetta Cavazzuti*, et al...
*Agenzia Spaziale Italiana - Headquarters (ASI-HQ), Via del Politecnico snc, 00133 Rome, Italy

Astronomy & Astrophysics. Volume 597, January 2017, Pages 1-5
Abstract
Context. Blazars are the dominant type of extragalactic sources at microwave and at γ-ray energies. In the most energetic part of the electromagnetic spectrum (E ≳ 100 GeV) a high fraction of high Galactic latitude sources are blazars of the high synchrotron peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. Building new large samples of HSP blazars is key to understand the properties of jets under extreme conditions, and to study the demographics and the peculiar cosmological evolution of these sources. Aims. High synchrotron peaked blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys, some of which include hundreds of millions of sources. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. Methods. The sample was defined starting from a primary list of infrared colour–colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray), we estimated synchrotron peak frequencies and fluxes of each object. Results. We assembled a sample including 992 sources, which is currently the largest existing list of confirmed and candidates HSP blazars. All objects are expected to radiate up to the highest γ-ray photon energies. In fact, 299 of these are confirmed emitters of GeV γ-ray photons (based on Fermi-LAT catalogues), and 36 have already been detected in the TeV band. The majority of sources in the sample are within reach of the upcoming Cherenkov Telescope Array (CTA), and many may be detectable even by the current generation of Cherenkov telescopes during flaring episodes. The sample includes 425 previously known blazars, 151 new identifications, and 416 HSP candidates (mostly faint sources) for which no optical spectra is available yet.

 

Gamma-Ray Blazars within the First 2 Billion Years

M. Ackermann, M. Ajello, L. Baldini; [...], Elisabetta Cavazzuti*, et al...

*Agenzia Spaziale Italiana - Headquarters (ASI-HQ), Via del Politecnico snc, 00133 Rome, Italy

The Astrophysical Journal Letters, Volume 837, Number 1, February, Pages 1-8

Abstract
The detection of high-redshift () blazars enables the study of the evolution of the most luminous relativistic jets over cosmic time. More importantly, high-redshift blazars tend to host massive black holes and can be used to constrain the space density of heavy black holes in the early universe. Here, we report the first detection with the Fermi-Large Area Telescope of five γ-ray-emitting blazars beyond z = 3.1, more distant than any blazars previously detected in γ-rays. Among these five objects, NVSS J151002+570243 is now the most distant known γ-ray-emitting blazar at z = 4.31. These objects have steeply falling γ-ray spectral energy distributions (SEDs), and  those that have been observed in X-rays have a very hard X-ray spectrum, both typical of powerful blazars. Their Compton dominance (ratio of the inverse Compton to synchrotron peak luminosities) is also very large (). All of these properties place these objects among the most extreme members of the blazar population. Their optical spectra and the modeling of their optical-UV SEDs confirm that these objects harbor massive black holes (). We find that, at , the space density of black holes hosted in radio-loud and radio-quiet active galactic nuclei are similar, implying that radio-loudness may play a key role in rapid black hole growth in the early universe.

 

Gamma-ray blazar spectra with H.E.S.S. II mono analysis: The case of PKS 2155−304 and PG 1553+113

H. Abdalla, A. Abramowski, F. Aharonian; [...], Sergio Colafrancesco*, et al...

*Agenzia Spaziale Italiana - Headquarters (ASI-HQ), Via del Politecnico snc, 00133 Rome, Italy

Astronomy & Astrophysics. Volume 600, April 2017, Pages 1-13

Abstract

Context. The addition of a 28 m Cherenkov telescope (CT5) to the H.E.S.S. array extended the experiment’s sensitivityto lower energies. The lowest energy threshold is obtained using monoscopic analysis of data taken with CT5, providing access to gamma-ray energies below 100 GeV for small zenith angle observations. Such an extension of the instrument’s energy range is particularly beneficial for studies of active galactic nuclei with soft spectra, as expected for those at a redshift ≥0.5. The high-frequency peaked BL Lac objects PKS 2155−304 (z = 0.116) and PG 1553+113 (0.43 < z < 0.58) are among the brightest objects in the gamma-ray sky, both showing clear signatures of gamma-ray absorption at E > 100 GeV interpreted as being due to interactions with the extragalactic background light (EBL).

Aims. The aims of this work are twofold: to demonstrate the monoscopic analysis of CT5 data with a low energy threshold, and to obtain accurate measurements of the spectral energy distributions (SED) of PKS 2155−304 and PG 1553+113 near their SED peaks at energies ≈100 GeV.

Methods. Multiple observational campaigns of PKS 2155−304 and PG 1553+113 were conducted during 2013 and 2014 using the full H.E.S.S. II instrument (CT1–5). A monoscopic analysis of the data taken with the new CT5 telescope was developed along with an investigation into the systematic uncertainties on the spectral parameters which are derived from this analysis.

Results. Using the data from CT5, the energy spectra of PKS 2155−304 and PG 1553+113 were reconstructed down to conservative threshold energies of 80 GeV for PKS 2155−304, which transits near zenith, and 110 GeV for the more northern PG 1553+113. The measured spectra, well fitted in both cases by a log-parabola spectral model (with a 5.0σ statistical preference for non-zero curvature for PKS 2155−304 and 4.5σ for PG 1553+113), were found consistent with spectra derived from contemporaneous Fermi-LAT data, indicating a sharp break in the observed spectra of both sources at E ≈ 100 GeV. When corrected for EBL absorption, the intrinsic H.E.S.S. II mono and Fermi-LAT spectrum of PKS 2155−304 was found to show significant curvature. For PG 1553+113, however, no significant detection of curvature in the intrinsic spectrum could be found within statistical and systematic uncertainties.

 

The Fermi Galactic Center GeV Excess and Implications for Dark Matter

H. Abdalla, M. Ackermann, M. Ajello, A. Albert; [...], Elisabetta Cavazzuti*, et al...

*Agenzia Spaziale Italiana - Headquarters (ASI-HQ), Via del Politecnico snc, 00133 Rome, Italy

The Astrophysical Journal, Volume 840, Number 1, May 2017, Pages 1-34

Abstract
The region around the Galactic Center (GC) is now well established to be brighter at energies of a few GeV than what is expected from conventional models of diffuse gamma-ray emission and catalogs of known gamma-ray sources. We study the GeV excess using 6.5 yr of data from the Fermi Large Area Telescope. We characterize the uncertainty of the GC excess spectrum and morphology due to uncertainties in cosmic-ray source distributions and propagation, uncertainties in the distribution of interstellar gas in the Milky Way, and uncertainties due to a potential contribution from the Fermi bubbles. We also evaluate uncertainties in the excess properties due to resolved point sources of gamma rays. The GC is of particular interest, as it would be expected to have the brightest signal from annihilation of weakly interacting massive dark matter (DM) particles. However, control regions along the Galactic plane, where a DM signal is not expected, show excesses of similar amplitude relative to the local background. Based on the magnitude of the systematic uncertainties, we conservatively report upper limits for the annihilation cross-section as a function of particle mass and annihilation channel.

 

ROXA J081009.9+384757.0: a erg s blazar with hard X-ray synchrotron peak or a new type of radio loud AGN?

Paolo Giommi*, E. Massaro, P. Padovani;[...], Elisabetta Cavazzuti*, et al...

*Agenzia Spaziale Italiana - Headquarters (ASI-HQ), Via del Politecnico snc, 00133 Rome, Italy

Astronomy & Astrophysics. Volume 468, Number 1, June II 2017, 97-101

Abstract
We report the discovery of ROXA J081009.9+384757.0 = SDSS J081009.9+384757.0, a z=3.95 blazar with a highly unusual Spectral Energy Distribution. This object was first noticed as a probable high , high-luminosity blazar within the error region of a 10-12 erg cm-2 s-1 ROSAT source which, however, also included a much brighter late-type star. We describe the results of a recent Swift observation that establishes beyond doubt that the correct counterpart of the X-ray source is the flat spectrum radio quasar. With a luminosity well in excess of 1047 erg s-1 ROXA J081009.9+384757.0 is therefore one of the most luminous blazars known. We consider various possibilities for the nature of the electromagnetic emission from this source. In particular, we show that the SED is consistent with that of a blazar with synchrotron power peaking in the hard X-ray band. If this is indeed the case, the combination of high-luminosity and synchrotron peak in the hard-X-ray band contradicts the claimed anti-correlation between luminosity and position of the synchrotron peak usually referred to as the "blazar sequence". An alternative possibility is that the X-rays are not due to synchrotron emission, in this case the very peculiar SED of ROXA J081009.9+384757.0 would make it the first example of a new class of radio loud AGN.

 

 

Libri

Carlo Buongiorno. Lo Spazio di una vita. Intervista al primo Direttore Generale dell'Agenzia Spaziale Italiana

 

di Enrico Ferrone ; prefazione di Jean-Jacques Dordain ed Enrico Saggese; postfazione di Luigi Pasquali e Francesco Depasquale

Vicchio; LoGisma, 2011

295 p., [8] carte di tav. : ill.; 24 cm.

ISBN 978-88-87621-93-8

«[…] Carlo Buongiorno era nato a Roma il 12 marzo 1930 ed era stato allievo di Luigi Broglio. Si era laureato in Ingegneria Elettronica e in Ingegneria Aeronautica presso l'Università di Roma "La Sapienza" dove successivamente avrebbe svolto la sua attività didattica. Nel 1954 si era trasferito negli Stati Uniti per occuparsi di volo ipersonico e supersonico in qualità di ricercatore presso il Politecnico di Brooklyn. A partire dal 1957, dopo il suo rientro in Italia, si era dedicato all'insegnamento presso l'Università "La Sapienza", dove teneva il corso di Propulsione Aerospaziale. Buongiorno ha affiancato alla docenza un'intensa attività in ambito spaziale, diventandouno dei principali protagonisti del settore spaziale italiano. Dopo aver svolto il ruolo di Segretario Tecnico della Commissione Ricerche Spaziali del CNR, dal1961 si era dedicato - accanto al suo maestro Luigi Broglio - al Progetto San Marco e successivamentefu attivo anche nel processo che portò nel 1975 all'istituzione dell'agenzia spaziale europea (ESA).Buongiorno ha, tra l'altro, ricoperto gli incarichi di Responsabile dell'Ufficio Spazio del Ministero dell'Università e della Ricerca e Capo della Delegazione Italiana presso l'ESA.Il suo lungo e fecondo percorso nel settore spaziale italiano lo ha poi condotto all'ASI, di cui è stato il primo Direttore Generale. In questa veste Buongiorno ha portato al successo numerosi progetti e missioni, tra cui si ricordano ITALSAT 1 e 2, IRIS LAGEOS e TSS.».