483 research outputs found
The M31 pixel lensing plan campaign : macho lensing and self-lensing signals
No full textA.G. was supported by NSF grant AST-1103471. M.D. is thankful to Qatar National Research Fund (QNRF), member of Qatar Foundation, for support by grant NPRP 09-476-1-078. P.J. acknowledges support by the Swiss National Science Foundation.We present the final analysis of the observational campaign carried out by the PLAN (Pixel Lensing Andromeda) collaboration to detect a dark matter signal in form of MACHOs through the microlensing effect. The campaign consists of about 1 month/year observations carried out over 4 years (2007-2010) at the 1.5 m Cassini telescope in Loiano (Astronomical Observatory of BOLOGNA, OAB) plus 10 days of data taken in 2010 at the 2 m Himalayan Chandra Telescope monitoring the central part of M31 (two fields of about 13′ × 12.′6). We establish a fully automated pipeline for the search and the characterization of microlensing flux variations. As a result, we detect three microlensing candidates. We evaluate the expected signal through a full Monte Carlo simulation of the experiment completed by an analysis of the detection efficiency of our pipeline. We consider both "self lensing" and "MACHO lensing" lens populations, given by M31 stars and dark matter halo MACHOs, in M31 and the Milky Way, respectively. The total number of events is consistent with the expected self-lensing rate. Specifically, we evaluate an expected signal of about two self-lensing events. As for MACHO lensing, for full 0.5(10-2) M☉ MACHO halos, our prediction is for about four (seven) events. The comparatively small number of expected MACHO versus self-lensing events, together with the small number statistics at our disposal, do not enable us to put strong constraints on that population. Rather, the hypothesis, suggested by a previous analysis, on the MACHO nature of OAB-07-N2, one of the microlensing candidates, translates into a sizeable lower limit for the halo mass fraction in form of the would-be MACHO population, f, of about 15% for 0.5 M☉ MACHOs.Peer reviewe
Gravitational lensing by the supermassive black hole in the center of M31
No full textWe examine the possibility of observing gravitational lensing in the weak deflection regime by the supermassive black hole in the center of the galaxy M31. This black hole is significantly more massive than the black hole in the center of our Galaxy, qualifying itself as a more effective lens. However, it is also more distant, and the candidate stellar sources appear consequently fainter. We separately consider as potential sources stars belonging to the bulge, to the disk, and to the triple nucleus formed by P1 + P2 and by the recently discovered inner cluster P3. We calculate the number of simultaneously lensed stars at a given time as a function of the threshold magnitude required for the secondary image. For observations in the K band we find 1.4 expected stars having secondary images brighter than K = 24 and 182 brighter than K = 30. For observations in the V band we expect 1.3 secondary images brighter than V = 27 and 271 brighter than V = 33. The bulge stars have the highest chance of being lensed by the supermassive black hole, whereas the disk and the composite nucleus stars contribute 10% each. The typical angular separation of the secondary images from the black hole range from 1 mas to 0.1''. For each population we also show the distribution of the lensed sources as a function of their distance and absolute magnitude, the expected angular positions and velocities of the generated secondary images, and the rate and the typical duration of the lensing events
La scienza è ormai divenuta internazionale. Il carteggio inedito Mussafia-Novati
No full textTra la seconda metà dell’Ottocento e il primo Novecento Adolfo Mussafia fu una fondamentale figura-ponte fra la nuova Wissenschaft tedesca e il mondo culturale e accademico italiano. Su queste basi il presente contributo per la prima volta pubblica e contestualizza sia le nove lettere e tre cartoline inviate dal romanista spalatino a Francesco Novati (Milano, Biblioteca nazionale Braidense, carteggio Novati; Milano, Biblioteca della Società Storica Lombarda, fondo Novati), sia le risposte (nove lettere e una cartolina) del cofondatore del «Giornale storico della letteratura italiana» (Firenze, Biblioteca Umanistica dell’Università degli Studi, fondo Mussafia). L’amicizia tra Mussafia, linguista-filologo, e Novati, filologo della “scuola storica”, alimenta la collaborazione scientifica. Ad esempio gli spogli di codici ambrosiani condotti da Novati servono a Mussafia per gli studi mariologici culminati nella monumentale serie di Marienlegenden, 1886-1898, I-V. A sua volta Novati pubblica una nuova versione in prosa del racconto faceto De lumaca et Lombardo su indicazione del suo corrispondente, che gli fornisce copia di due manoscritti viennesi. In definitiva, l’analisi del carteggio inedito permette da una parte di aggiungere ulteriori tasselli alla biografia e all’attività scientifica dei due studiosi, dall’altra di lumeggiare aspetti della vita intellettuale europea a cavallo dei due secoli
V. — Giornale storico della letteratura italiana, diretto e redatto da A. Graf, Fr. Novati, R. Renier. Roma, Torino, Firenze, E. Loescher. I, n° 1
No full textM. P. V. — Giornale storico della letteratura italiana, diretto e redatto da A. Graf, Fr. Novati, R. Renier. Roma, Torino, Firenze, E. Loescher. I, n° 1. In: Romania, tome 12 n°46-47, 1883. pp. 413-414
V. — Giornale Storico della Letteratura italiana, diretto e redattoda A. Graf, Fr. Novati, R. Renier. Roma, Torino, Firenze, E. Lœscher. N° 2 (t. I, 1883)
No full textM. P. V. — Giornale Storico della Letteratura italiana, diretto e redattoda A. Graf, Fr. Novati, R. Renier. Roma, Torino, Firenze, E. Lœscher. N° 2 (t. I, 1883). In: Romania, tome 13 n°50-51, 1884. pp. 467-471
Symmetric Galerkin BEM in 3D elasticity: computational aspects and applications to fracture mechanics
No full textL'ISOLA DI LESBO NEL ROMANZO DI LONGO SOFISTA
No full textThis doctoral thesis aims to provide the reader with a geographical analysis of Longus’ depiction of the island of Lesbos. In the first chapter, I sketch in broad outline the birth and growth of geographers’ concern about literary texts and literary descriptions of landscapes and places. However, note that such a concern seems, so far, to have overlooked Greek and Roman literature: geographers have investigated exclusively modern and contemporary literary texts. In the second chapter, after briefly introducing to ancient Greek novel, its authors, its audience and its features, I focus specifically on Longus and his Pastoralia. The third chapter examines some scholars’ hypotheses about the possible topographical realism in the novelist’s portrayal of Lesbos. Finally, the fourth chapter analyses the lesbian landscape of the novel in order to reach a conclusion concerning Longus’ Lesbos. I will try to answer a fundamental question: does Longus describe the real Lesbos in his novel or does he create a fictional island without any relationship with the real world
Gravitational lensing by the supermassive black hole in the center of M31
No full textWe examine the possibility of observing gravitational lensing in the weak deflection regime by the supermassive black hole in the center of the galaxy M31. This black hole is significantly more massive than the black hole in the center of our Galaxy, qualifying itself as a more effective lens. However, it is also more distant, and the candidate stellar sources appear consequently fainter. We separately consider as potential sources stars belonging to the bulge, to the disk, and to the triple nucleus formed by P1 + P2 and by the recently discovered inner cluster P3. We calculate the number of simultaneously lensed stars at a given time as a function of the threshold magnitude required for the secondary image. For observations in the K band we find 1.4 expected stars having secondary images brighter than K = 24 and 182 brighter than K = 30. For observations in the V band we expect 1.3 secondary images brighter than V = 27 and 271 brighter than V = 33. The bulge stars have the highest chance of being lensed by the supermassive black hole, whereas the disk and the composite nucleus stars contribute 10% each. The typical angular separation of the secondary images from the black hole range from 1 mas to 0.1 ''. For each population we also show the distribution of the lensed sources as a function of their distance and absolute magnitude, the expected angular positions and velocities of the generated secondary images, and the rate and the typical duration of the lensing events
Boundary element analysis of rotationally symmetric systems under general boundary conditions
No full textEngineering systems often exhibit cyclic symmetry (or rotational periodicity) of geometrical and physical properties. This paper deals with the use of this feature in the context of the direct boundary element method, and shows how to decompose an elastostatic and steady state b. v. problem with general (not cyclically symmetric) boundary conditions into a number of much smaller problems over a single segment. There is no need to discretize the interfaces between adjacent segments. The decomposition is achieved by rotational transformations of physical into cyclic components
BEM-FEM coupling for fracture mechanics applications
No full textAttention is here focused on the implementation
of a coupled BEM–FEM procedure employing the BE
method for the modelling of the near-crack region and
the FEM for the far-field, where no singularities in the
stress field are expected to arise. The symmetric variational
version of the BE method is utilized, allowing to
obtain a final linear system endowed with a symmetric
matrix. With respect to 3D linear elastic fracture
mechanics, the code developed is used to evaluate stress
intensity factors for some benchmarks and simulate
fracture propagation
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