Search results for "LSA"
showing 10 items of 832 documents
Searching for pulsed emission from XTE J0929-314 at high radio frequencies
2009
The aim of this work is to search for radio signals in the quiescent phase of accreting millisecond X-ray pulsars, in this way giving an ultimate proof of the recycling model, thereby unambiguously establishing that accreting millisecond X-ray pulsars are the progenitors of radio millisecond pulsars. To overcome the possible free-free absorption caused by matter surrounding accreting millisecond X-ray pulsars in their quiescence phase, we performed the observations at high frequencies. Making use of particularly precise orbital and spin parameters obtained from X-ray observations, we carried out a deep search for radio-pulsed emission from the accreting millisecond X-ray pulsar XTE J0929-31…
On Low Mass X-ray Binaries and Millisecond Pulsar
2013
The detection, in 1998, of the first Accreting Millisecond Pulsar, started an exciting season of continuing discoveries in the fashinating field of compact binary systems harbouring a neutron star. Indeed, in these last three lustres, thanks to the extraordinary performances of astronomical detectors, on ground as well as on board of satellites, mainly in the Radio, Optical, X-ray, and Gamma-ray bands, astrophysicists had the opportunity to thoroughly investigate the so-called Recycling Scenario: the evolutionary path leading to the formation of a Millisecond Radio Pulsar. The most intriguing phase is certainly the spin-up stage during which, because of the accretion of matter and angular m…
The pulse profile and spin evolution of the accreting pulsar in Terzan 5, IGR J17480-2446, during its 2010 outburst
2012
(abridged) We analyse the spectral and pulse properties of the 11 Hz transient accreting pulsar, IGR J17480-2446, in the globular cluster Terzan 5, considering all the available RXTE, Swift and INTEGRAL observations performed between October and November, 2010. By measuring the pulse phase evolution we conclude that the NS spun up at an average rate of =1.48(2)E-12 Hz/s, compatible with the accretion of the Keplerian angular momentum of matter at the inner disc boundary. Similar to other accreting pulsars, the stability of the pulse phases determined by using the second harmonic component is higher than that of the phases based on the fundamental frequency. Under the assumption that the sec…
Timing Analysis of the 2022 Outburst of the Accreting Millisecond X-Ray Pulsar SAX J1808.4-3658: Hints of an Orbital Shrinking
2022
We present a pulse timing analysis of NICER observations of the accreting millisecond X-ray pulsar SAX J1808.4$-$3658 during the outburst that started on 2022 August 19. Similar to previous outbursts, after decaying from a peak luminosity of $\simeq 1\times10^{36} \, \mathrm{erg \, s^{-1}}$ in about a week, the pulsar entered in a $\sim 1$ month-long reflaring stage. Comparison of the average pulsar spin frequency during the outburst with those previously measured confirmed the long-term spin derivative of $\dot{\nu}_{\textrm{SD}}=-(1.15\pm0.06)\times 10^{-15} \, \mathrm{Hz\,s^{-1}}$, compatible with the spin-down torque of a $\approx 10^{26} \, \mathrm{G \, cm^3}$ rotating magnetic dipole.…
NuSTARandXMM–Newtonbroad-band spectrum of SAX J1808.4–3658 during its latest outburst in 2015
2018
The first discovered accreting millisecond pulsar, SAX J1808.4-3658, went into X-ray outburst in April 2015. We triggered a 100 ks XMM-Newton ToO, taken at the peak of the outburst, and a 55 ks NuSTAR ToO, performed four days apart. We report here the results of a detailed spectral analysis of both the XMM-Newton and NuSTAR spectra. While the XMM-Newton spectrum appears much softer than in previous observations, the NuSTAR spectrum confirms the results obtained with XMM-Newton during the 2008 outburst. We find clear evidence of a broad iron line that we interpret as produced by reflection from the inner accretion disk. For the first time, we use a self-consistent reflection model to fit the…
Astrophysical constraints on extended gravity models
2015
We investigate the propagation of gravitational waves in the context of fourth order gravity nonminimally coupled to a massive scalar field. Using the damping of the orbital period of coalescing stellar binary systems, we impose constraints on the free parameters of extended gravity models. In particular, we find that the variation of the orbital period is a function of three mass scales which depend on the free parameters of the model under consideration; we can constrain these mass scales from current observational data.
Highlights from the ARGO-YBJ Experiment
2012
""The ARGO-YBJ experiment at YangBaJing in Tibet (4300m a.s.l.) has been taking data with its full layout since October 2007. Here we present a few significant results obtained in gamma-ray astronomy and cosmic-ray physics. Emphasis is placed on the analysis of gamma-ray emission from point-like sources (Crab Nebula, MRK 421), on the preliminary limit on the antiproton\\\/proton flux ratio, on the large-scale cosmic-ray anisotropy and on the proton-air cross-section. The performance of the detector is also discussed, and the perspectives of the experiment are outlined.""
New insights into the composition of historical remedies and pharmaceutical formulations: the identification of natural resins and balsams by gas chr…
2020
AbstractThe present paper reports one of the first studies on the identification of natural resins and balsams in modern era drug formulations. Gas chromatography coupled with mass spectrometry (GC-MS) was applied to investigate the composition of ancient remedies and pharmaceutical formulations coming from the Spezieria di Santa Maria della Scala in Rome, founded at the end of the seventeenth century by the Discalced Carmelites. The obtained results highlight the presence of complex mixtures containing resinaceous and lipidic-based compounds. Thanks to the detection of characteristic markers, it was possible to identify several natural resins, such as guaiacum resin, ladano resin and scamm…
Una Comunità di Chatbot per i Beni Culturali
2005
L'intuizione occupa un ruolo fondamentale nella capacità di ragionamento degli esseri umani. L'obiettivo del lavoro è la progettazione di un'infrastruttura in grado di fornire informazioni che oltre ad appoggiarsi ad un insieme di conoscenze basato su regole sia dotata anche di capacità intuitive. A tal fine è presentato un sistema preliminare che rappresenta il primo passo verso la realizzazione di tale infrastruttura. Il sistema permette ad un utente di interagire con una comunità di chat-bot aventi competenze specifiche in modo da navigare in uno spazio concettuale generato automaticamente con il paradigma di analisi della semantica latente (LSA). La base di conoscenza di ciascun chat-bo…
Wechselwirkungen zwischen Acetylsalicylsäure und Lysin in Lösung
1985
Der pH-abhangige Einflus von Lysin auf die Hydrolyse von Acetylsalicylsaure zu Salicylsaure und auf die Bildung von Lysinderivaten der Acetylsalicylsaure wurde durch HPLC-Untersuchungen geklart. Die Bildung von e-N-Acetyl-lysin, α-N-Acetyl-lysin und wenig Diacetyl-lysin erfolgt rasch bei pH-Werten der Losung von 6 und hoher, sehr langsam jedoch bei dem fur gebrauchliche Injektionslosungen eingestellten pH-Wert 5. Das Auftreten des postulierten Salicyloyllysins in Acetylsalicylsaure-Lysin-Losungen wurde durch Vergleich mit der unabhangig synthetisierten Verbindung ausgeschlossen. Interactions of Acetylsalicyclic Acid and Lysine in Solution The influence of lysine on the hydrolysis, and on th…