Melis A.,National institute for astrophysics |
Concu R.,National institute for astrophysics |
Pari P.,IRA Bologna |
Maccone C.,Istituto di Astrofisica Spaziale e Fisica Cosmica |
And 16 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016
SETI, the Search for ExtraTerrestrial Intelligence, is the search for radio signals emitted by alien civilizations living in the Galaxy. Narrow-band FFT-based approaches have been preferred in SETI, since their computation time only grows like N∗lnN, where N is the number of time samples. On the contrary, a wide-band approach based on the Kahrunen-Lo'eve Transform (KLT) algorithm would be preferable, but it would scale like N∗N. In this paper, we describe a hardware-software infrastructure based on FPGA boards and GPU-based PCs that circumvents this computation-time problem allowing for a real-time KLT. © 2016 SPIE.
Hoare M.G.,University of Leeds |
Purcell C.R.,University of Leeds |
Purcell C.R.,University of Manchester |
Purcell C.R.,University of Sydney |
And 30 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2012
We describe the motivation, design, and implementation of the CORNISH survey, an arcsecondresolution radio continuum survey of the inner galactic plane at 5 GHz using the Very Large Array (VLA). It is a blind survey coordinated with the northern Spitzer GLIMPSE I region covering 10° < l < 65° and |b| < 1° at similar resolution. We discuss in detail the strategy that we employed to control the shape of the synthesised beam across this survey, which covers a wide range of fairly low declinations. Two snapshots separated by 4h kept the beam elongation to less that 1.5 over 75% of the survey area and less than 2 over 98% of the survey. The prime scientific motivation is to provide an unbiased survey for ultra-compact H II regions to study this key phase in massive star formation. A sensitivity around 2 mJy will allow the automatic distinction between radio-loud and radio-quiet mid- IR sources found in the Spitzer surveys. This survey has many legacy applications beyond star formation, including evolved stars, active stars and binaries, and extragalactic sources. The CORNISH survey for compact ionized sources complements other Galactic plane surveys that target diffuse and nonthermal sources, as well as atomic and molecular phases to build up a complete picture of the interstellar medium in the Galaxy. © 2012. The Astronomical Society of the Pacific.
Brown P.J.,Pennsylvania State University |
Brown P.J.,University of Utah |
Roming P.W.A.,Pennsylvania State University |
Roming P.W.A.,Southwest Research Institute |
And 25 more authors.
Astrophysical Journal | Year: 2010
We examine the absolute magnitudes and light-curve shapes of 14 nearby (redshift z = 0.004-0.027) Type Ia supernovae (SNe Ia) observed in the ultraviolet (UV) with the Swift Ultraviolet/Optical Telescope. Colors and absolutemagnitudes are calculated using both a standardMilkyWay extinction lawand one for the LargeMagellanic Cloud that has been modified by circumstellar scattering. We find very different behavior in the near-UV filters (uvw1rc covering ∼2600-3300 Å after removing optical light, and u ≈ 3000-4000 Å) compared to a mid-UV filter (uvm2 ≈ 2000-2400 Å). The uvw1rc - b colors show a scatter of ∼0.3 mag while uvm2-b scatters by nearly 0.9 mag. Similarly, while the scatter in colors between neighboring filters is small in the optical and somewhat larger in the near-UV, the large scatter in the uvm2 - uvw1 colors implies significantly larger spectral variability below 2600 Å. We find that in the near-UV the absolute magnitudes at peak brightness of normal SNe Ia in our sample are correlated with the optical decay rate with a scatter of 0.4 mag, comparable to that found for the optical in our sample. However, in the mid-UV the scatter is larger, ∼1 mag, possibly indicating differences in metallicity. We find no strong correlation between either the UV light-curve shapes or the UV colors and the UV absolute magnitudes. With larger samples, the UV luminosity might be useful as an additional constraint to help determine distance, extinction, and metallicity in order to improve the utility of SNe Ia as standardized candles. © 2010. The American Astronomical Society. All rights reserved.
Bhatta G.,Jagiellonian University |
Goyal A.,Jagiellonian University |
Ostrowski M.,Jagiellonian University |
Stawarz L.,Jagiellonian University |
And 45 more authors.
Astrophysical Journal Letters | Year: 2015
The occurrence of low-amplitude flux variations in blazars on hourly timescales, commonly known as microvariability, is still a widely debated subject in high-energy astrophysics. Several competing scenarios have been proposed to explain such occurrences, including various jet plasma instabilities leading to the formation of shocks, magnetic reconnection sites, and turbulence. In this Letter, we present the results of our detailed investigation of a prominent, five-hour-long optical microflare detected during the recent WEBT campaign on 2014 March 2-6 targeting the blazar 0716+714. After separating the flaring component from the underlying base emission continuum of the blazar, we find that the microflare is highly polarized, with the polarization degree ∼(40-60)% ± (2-10)% and the electric vector position angle ∼(10-20)° ± (1-8)° slightly misaligned with respect to the position angle of the radio jet. The microflare evolution in the (Q,U) Stokes parameter space exhibits a looping behavior with a counterclockwise rotation, meaning the polarization degree decreases with the flux (but is higher in the flux decaying phase), and an approximately stable polarization angle. The overall very high polarization degree of the flare, its symmetric flux rise and decay profiles, and also its structured evolution in the Q-U plane all imply that the observed flux variation corresponds to a single emission region characterized by a highly ordered magnetic field. As discussed in the paper, a small-scale but strong shock propagating within the outflow, and compressing a disordered magnetic field component, provides a natural, though not unique, interpretation of our findings. © 2015. The American Astronomical Society. All rights reserved.
Paladini R.,California Institute of Technology |
Ingallinera A.,Osservatorio Astrofisico di Catania |
Agliozzo C.,Osservatorio Astrofisico di Catania |
Agliozzo C.,Andrés Bello University |
And 5 more authors.
Astrophysical Journal | Year: 2015
The detection of an excess of emission at microwave frequencies with respect to the predicted free-free emission has been reported for several Galactic H ii regions. Here, we investigate the case of RCW 49, for which the Cosmic Background Imager tentatively (∼3σ) detected Anomalous Microwave Emission (AME) at 31 GHz on angular scales of 7′. Using the Australia Telescope Compact Array, we carried out a multi-frequency (5, 19, and 34 GHz) continuum study of the region, complemented by observations of the H109α radio recombination line. The analysis shows that: (1) the spatial correlation between the microwave and IR emission persists on angular scales from 3.′4 to 0.″4, although the degree of the correlation slightly decreases at higher frequencies and on smaller angular scales; (2) the spectral indices between 1.4 and 5 GHz are globally in agreement with optically thin free-free emission, however, ∼30% of these are positive and much greater than -0.1, consistent with a stellar wind scenario; and (3) no major evidence for inverted free-free radiation is found, indicating that this is likely not the cause of the Anomalous Emission in RCW 49. Although our results cannot rule out the spinning dust hypothesis to explain the tentative detection of AME in RCW 49, they emphasize the complexity of astronomical sources that are very well known and studied, such as H ii regions, and suggest that, at least in these objects, the reported excess of emission might be ascribed to alternative mechanisms such as stellar winds and shocks. © 2015. The American Astronomical Society. All rights reserved.
Benetti S.,National institute for astrophysics |
Turatto M.,Osservatorio Astrofisico di Catania |
Valenti S.,Queen's University of Belfast |
Pastorello A.,Queen's University of Belfast |
And 10 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011
Extensive optical and near-infrared observations of the Type Ib supernova (SNIb) 1999dn are presented, covering the first year after explosion. These new data turn this object, already considered a prototypical SNIb, into one of the best observed objects of its class. The light curve of SN 1999dn is mostly similar in shape to that of other SNeIb but with a moderately faint peak (MV=-17.2mag). From the bolometric light curve and ejecta expansion velocities, we estimate that about 0.11M⊙ of 56Ni were produced during the explosion and that the total ejecta mass was 4-6M⊙ with a kinetic energy of at least 5 × 1051erg. The spectra of SN 1999dn at various epochs are similar to those of other stripped envelope SNe showing clear presence of H at early epochs. The high explosion energy and ejected mass, along with the small flux ratio [Caii]/[Oi] measured in the nebular spectrum, together with the lack of signatures of dust formation and the moderate metallicity environment is not inconsistent with a single massive progenitor (MZAMS≥ 23-25M⊙) for SN 1999dn. © 2010 The Authors Monthly Notices of the Royal Astronomical Society © 2010 RAS.
Cakirli O.,Ege University |
Ibanoglu C.,Ege University |
Sipahi E.,Ege University |
Frasca A.,Osservatorio Astrofisico di Catania |
Catanzaro G.,Osservatorio Astrofisico di Catania
New Astronomy | Year: 2015
We present new spectroscopic observations of the early type, double-lined eclipsing binary V1441 Aql. The radial velocities and the available photometric data obtained by ASAS is analysed for deriving the parameters of the components. The components of V1441 Aql are shown to be a B3 IV primary with a mass M p=8.02±0.51M⊙ and radius Rp=7. 33±0.19R⊙ and a B9 III secondary with a mass M s=1.92±0.14M⊙ and radius Rs=4. 22±0.11R⊙. Our analyses show that V1441 Aql is a double-contact system with rapidly rotating components. Based on the position of the components plotted on the theoretical Hertzsprung-Russell diagram, we estimate that the ages of V1441 Aql is about 30 Myr, neglecting the effects of mass exchange between the components. Using the UBVJHK magnitudes and interstellar absorption we estimated the mean distance to the system V1441 Aql as 550 ± 25 pc. © 2014 Elsevier B.V. All rights reserved.