Is the Bursting Radio-source GCRT J1745-3009 a Double Neutron Star Binary ?

GCRT J1745-3009 is a peculiar transient radio-source in the direction of the Galactic Center. It was observed to emit a series of ~ 1 Jy bursts at 0.33 GHz, with typical duration ~ 10 min and at apparently regular intervals of ~ 77 min. If the source is indeed at the distance of the Galactic Center as it seems likely, we show that its observational properties are compatible with those expected from a double neutron star binary, similar to the double pulsar system J0737-3039. In the picture we propose the (coherent) radio emission comes from the shock originating in the interaction of the wind of the more energetic pulsar with the magnetosphere of the companion. The observed modulation of the radio signal is the consequence of an eccentric orbit, along which the separation between the two stars varies. This cyclically drives the shock inside the light cylinder radius of the less energetic pulsar.Comment: 5 pages, 3 figures, accepted for publication in The Astrophysical Journal Letters, comment on geodetic precession adde

The optical companion to the intermediate mass millisecond pulsar J1439-5501 in the Galactic field

We present the identification of the companion star to the intermediate mass binary pulsar J1439-5501 obtained by means of ground-based deep images in the B, V and I bands, acquired with FORS2 mounted at the ESO-VLT. The companion is a massive white dwarf (WD) with B=23.57+-0.02, V=23.21+-0.01 and I=22.96+-0.01, located at only ~0.05" from the pulsar radio position. Comparing the WD location in the (B, B-V) and (V, V-I) Color-Magnitude diagrams with theoretical cooling sequences we derived a range of plausible combinations of companion masses (1<~Mcom<~1.3 Msun), distances (d<~1200 pc), radii (<~7.8 10^3 Rsun) and temperatures (T=31350^{+21500}_{-7400}). From the PSR mass function and the estimated mass range we also constrained the inclination angle i >~ 55 degrees and the pulsar mass (Mpsr <~2.2 Msun). The comparison between the WD cooling age and the spin down age suggests that the latter is overestimated by a factor of about ten.Comment: Accepted for publication by ApJ; 19 pages, 5 figures, 1 tabl

INORGANIC PRODUCTS USED IN THE CONSERVATION OF CULTURAL HERITAGE: INTERACTION WITH CARBONATIC SUBSTRATES AND NEWLY-FORMED CRYSTALLINE PHASES

Diammonium hydrogenphosphate (DAP) water solutions are promising inorganic-mineral treatments for the consolidation of ornamental carbonatic stones and, in the last few years, DAP-based treatments are gaining increasing interest by the open literature. The core idea of the treatment is to transform part of the original stone material in insoluble newly-formed phosphate phases, through the reaction of the phosphate ions of the reagent with calcium ions of the substrate. At present, there is a growing quest for a deeper insight on their interaction with carbonatic stone matrixes, as well as the development of analytical protocol to characterize their diffusion and penetration profile within the matrix. The research project of this PhD thesis aims to define the crystal-chemistry and distribution of reaction products within carbonatic substrates, exploring the effects induced by the crystallization to the stone matrix. Different multi-analytical approaches were used. Case by case, the combination of conventional and innovative analytical techniques allowed exploring the feasibility and potentiality of high resolution ATR-FTIR microspectroscopy, synchrotron radiation (SR) X-ray diffraction in transmittance and grazing geometry, and of SR micro-computed tomography to study inorganic-mineral treatments and their interactions with stone substrates. Starting from the DAP reaction with calcite of two representative lithotypes, a compact metamorphic stone (Carrara marble) and a porous sedimentary one (Noto limestone), we investigated the crystallization of newly-formed phosphates, describing the variables that affect the reaction mechanism and the nucleation of the reaction products. The nucleation of different phosphate phases resulted influenced by the availability of free calcium ions, which, in turn, is influenced by several factors mutually interfering. The DAP molarity, the pH and the pH variation during the reaction, the lithotype and the application methods were found crucial factors in the formation of specific crystallites, determining their composition, crystallinity and localization. The effects induced by the nucleation of phosphates to the stone substrate were evaluated in terms of micro-structural variations, modification of the porosity (pore size distribution, total open porosity, average of pore radius, specific surface area) and penetration depth. The composition and distribution of specific phases in the matrix, as well as the arrangement of the new phases into the voids, were investigated by combining different techniques, including qualitative and quantitative-morphometric imaging analysis. On the basis of the experimental data collected on laboratory stone specimens, an applicative study was carried out on a decayed carved artefact (Angera stone), in order explore the effects of DAP consolidation when complex weathered stone matrixes are involved. We expect that the experimental findings of this research activity will be transferred to the conservation practice, providing guidelines to restorers in order to perform treatments with improved performances, considering the peculiarity of specific case studies and the conservative history of stone artworks

Variability of sulfate signal in ice core records based on five replicate cores

International audienceCurrent volcanic reconstructions based on ice core analysis have significantly improved over the past few decades by incorporating multiple-core analyses with a high temporal resolution from different parts of the polar regions into a composite common volcanic eruption record. Regional patterns of volcanic deposition are based on composite records, built from cores taken at both poles. However, in many cases only a single record at a given site is used for these reconstructions. This assumes that transport and regional meteorological patterns are the only source of the dispersion of the volcanic products. Here we evaluate the local-scale variability of a sulfate profile in a low-accumulation site (Dome C, Antarctica), in order to assess the representativeness of one core for such a reconstruction. We evaluate the variability with depth, statistical occurrence, and sulfate flux deposition variability of volcanic eruptions detected in five ice cores, drilled 1 m apart from each other. Local-scale variability, essentially attributed to snow drift and surface roughness at Dome C, can lead to a non-exhaustive record of volcanic events when a single core is used as the site reference , with a bulk probability of 30 % of missing volcanic events and close to 65 % uncertainty on one volcanic flux measurement (based on the standard deviation obtained from a five-core comparison). Averaging n records reduces the uncertainty of the deposited flux mean significantly (by a factor 1/ √ n); in the case of five cores, the uncertainty of the mean flux can therefore be reduced to 29 %

Spin-down evolution and radio disappearance of the magnetar PSR J1622−-4950

We report on 2.4 yr of radio timing measurements of the magnetar PSR J1622$-$4950 using the Parkes telescope, between 2011 November and 2014 March. During this period the torque on the neutron star (inferred from the rotational frequency derivative) varied greatly, though much less erratically than in the 2 yr following its discovery in 2009. During the last year of our measurements the frequency derivative decreased in magnitude monotonically by 20\%, to a value of $-1.3\times10^{-13}$ s$^{-2}$, a factor of 8 smaller than when discovered. The flux density continued to vary greatly during our monitoring through 2014 March, reaching a relatively steady low level after late 2012. The pulse profile varied secularly on a similar timescale as the flux density and torque. A relatively rapid transition in all three properties is evident in early 2013. After PSR J1622$-$4950 was detected in all of our 87 observations up to 2014 March, we did not detect the magnetar in our resumed monitoring starting in 2015 January and have not detected it in any of the 30 observations done through 2016 September.Comment: 8 pages, 5 figures, submitted to Ap

Pulsar Wind Nebulae in the SKA era

Neutron stars lose the bulk of their rotational energy in the form of a pulsar wind: an ultra-relativistic outflow of predominantly electrons and positrons. This pulsar wind significantly impacts the environment and possible binary companion of the neutron star, and studying the resultant pulsar wind nebulae is critical for understanding the formation of neutron stars and millisecond pulsars, the physics of the neutron star magnetosphere, the acceleration of leptons up to PeV energies, and how these particles impact the interstellar medium. With the SKA1 and the SKA2, it could be possible to study literally hundreds of PWNe in detail, critical for understanding the many open questions in the topics listed above.Comment: Comments: 10 pages, 3 figures, to be published in: "Advancing Astrophysics with the Square Kilometre Array", Proceedings of Science, PoS(AASKA14

Long Term Study of the Double Pulsar J0737-3039 with XMM-Newton: pulsar timing

The relativistic double neutron star binary PSR J0737-3039 shows clear evidence of orbital phase-dependent wind-companion interaction, both in radio and X-rays. In this paper we present the results of timing analysis of PSR J0737-3039 performed during 2006 and 2011 XMM-Newton Large Programs that collected ~20,000 X-ray counts from the system. We detected pulsations from PSR J0737-3039A (PSR A) through the most accurate timing measurement obtained by XMM-Newton so far, the spin period error being of 2x10^-13 s. PSR A's pulse profile in X-rays is very stable despite significant relativistic spin precession that occurred within the time span of observations. This yields a constraint on the misalignment between the spin axis and the orbital momentum axis Delta_A ~6.6^{+1.3}_{-5.4} deg, consistent with estimates based on radio data. We confirmed pulsed emission from PSR J0737-3039B (PSR B) in X-rays even after its disappearance in radio. The unusual phenomenology of PSR B's X-ray emission includes orbital pulsed flux and profile variations as well as a loss of pulsar phase coherence on time scales of years. We hypothesize that this is due to the interaction of PSR A's wind with PSR B's magnetosphere and orbital-dependent penetration of the wind plasma onto PSR B closed field lines. Finally, the analysis of the full XMM-Newton dataset provided evidences of orbital flux variability (~7%) for the first time, involving a bow-shock scenario between PSR A's wind and PSR B's magnetosphere.Comment: Comments: 16 Pages, 6 Figures. Accepted for publication in Astrophysical Journal (Draft Version

Antiulcerogenic activity of peptide concentrates obtained from hydrolysis of whey proteins by proteases from Cynara cardunculus

Peptide concentrates generated by hydrolysis of whey with aqueous extracts of flowers of Cynara cardunculus were studied for possible protection of the stomach mucosa against ulcerative lesions caused by oral administration of absolute ethanol. Both the whole peptide fraction obtained via hydrolysis of whey protein concentrate (peptide concentrate, PepC) and its fraction below 3 kDa (PepCF) were able to reduce gastric injuries to significant levels (p < 0.05). Single-dose experiments, using 100 mg kg(-1) body weight (bw) of either PepCF or PepC, led to 68.5% and 37.4% protection, respectively - which compare well with 93.4% protection by 200 mg kg (1) bw carbenoxolone (a positive control). No dose-response correlation could be demonstrated. Gastric cytoprotection by PepCF appears to depend on sulphydryl-containing moieties, whereas PepC likely protects the gastric mucosa via the prostaglandin cycle and production of nitric oxide.info:eu-repo/semantics/acceptedVersio

Synchrotron radiation &#956; X-ray diffraction in transmission geometry for investigating the penetration depth of conservation treatments on cultural heritage stone materials

The assessment of the penetration depth of conservation treatments applied to cultural heritage stone materials is a burning issue in conservation science. Several analytical approaches have been proposed but, at present, many of them are not fully exhaustive to define in a direct way the composition and location of the conservation products formed after inorganic mineral treatments. Here, we explored, for the first time, the analytical capability of synchrotron radiation m X-ray diffraction in transmission geometry (SR-mTXRD) for the study of the crystal chemistry and penetration depth of the consolidating phases formed after the application of diammonium hydrogen phosphate (DAP) treatments on a porous carbonatic stone (Noto limestone). The SR-mTXRD approach provided unambiguous information on the nature of the newly formed calcium phosphates (hydroxyapatite, HAP, and octacalcium phosphate, OCP) with depth, supplying important indications of the diffusion mechanism and the reactivity of the substrate. Qualitative and semi-quantitative data were obtained at the microscale with a non-destructive protocol and an outstanding signal-to-noise ratio. The SR-mTXRD approach opens a new analytical scenario for the investigation of a wide range of cultural heritage materials, including natural and artificial stone materials, painted stratigraphies, metals, glasses and their decay products. Furthermore, it can potentially be used to characterize the penetration depth of a phase \u201cA\u201d (or more crystalline phases) in a matrix \u201cB\u201d also beyond the cultural heritage field, demonstrating the potential wide impact of the study