103 research outputs found
DW Cancri in x-rays
We report on the -Newton observation of DW Cnc, a candidate intermediate
polar candidate whose historical optical light curve shows the existence of
periods at , and minutes which were
interpreted as the white dwarf spin, the orbital and the spin-orbit beat
periodicities. By studying the keV light curves, we confirm the
existence of a period at minutes and find in the OM light curve a
signature for a period at minutes which is consistent with both the
orbital and spin-orbit beat. { These findings allow us to unveil without any
doubt, the nature of DW Cnc as an accreting intermediate polar. The EPIC and
RGS source spectra were analyzed and a best fit model, consisting of a
multi-temperature plasma, was found. The maximum temperature found when fitting
the data is keV which can be interpreted as an upper limit
to the temperature of the shock.Comment: 2019. Accepted for publication on MNRAS. 5 figures, 1 table. Updated
as, by mistake, an author affiliation was missing from the lis
HP Cet and Swift J0820.6-2805: two candidate intermediate polars observed by XMM-Newton
We report on the XMM-Newton observation of HP Cet and Swift J0820.6-2805, two
X-ray photon sources that are candidates to be members of the intermediate
polar class of cataclysmic variables. If the historical optical light curve of
HP Cet shows a periodic feature at minutes, a clear identification
of such a signature in the high energy band (apart for a variability on a time
scale of minutes as detected by the ROSAT satellite) is lacking. By
using XMM-Newton archive data, we clearly identify a feature (at
minutes) which is marginally consistent with one of the binary system orbital
periods reported in the literature. We also found a signature of a periodic
features on the time scale of minutes. In the case of Swift
J0820.6-2805, the intermediate polar nature was previously unclear and the
orbital and the white dwarf spin periods were unknown. Here, the 0.3-10 keV
data undoubtedly reveal an orbital period and a white dwarf spin of minutes and minutes, respectively. The spectral analysis
showed that both HP Cet and Swift J0820.6-280 are members of the under-luminous
IP subclass since their luminosity in the keV band is estimated to be
erg s and erg
s, respectively.Comment: Accepted for publication on MNRAS, main journal, 2020. 9 Pages. 9
Figure
Optical, near-IR and -ray observations of SN 2015J and its host galaxy
SN 2015J was discovered on April 27th 2015 and is classified as a type IIn
supernova. At first, it appeared to be an orphan SN candidate, i.e. without any
clear identification of its host galaxy. Here, we present the analysis of the
observations carried out {by the VLT 8-m class telescope with the FORS2 camera
in the R band and the Magellan telescope (6.5 m) equipped with the IMACS
Short-Camera (V and I filters) and the FourStar camera (Ks filter)}. We show
that SN 2015J resides in what appears to be a very compact galaxy establishing
a relation between the SN event and its natural host. We also present and
discuss archival and new -ray data centred on SN 2015J. At the time of the
supernova explosion, Swift/XRT observations were made and a weak X-ray source
was detected at the location of SN 2015J. Almost one year later, the same
source was unambiguously identified during serendipitous observations by
Swift/XRT and -Newton, clearly showing an enhancement of the 0.3-10 keV
band flux by a factor with respect to the initial state. Swift/XRT
observations show that the source is still active in the -rays at a level of
counts s. The unabsorbed X-ray luminosity derived from the
{\it XMM}-Newton slew and SWIFT observations, erg
s, places SN 2015J among the brightest young supernovae in X-rays.Comment: The Astrophysical Journal, Volume 850, Number
Discovery of a bright microlensing event with planetary features towards the Taurus region: a super Earth planet
The transient event labeled as TCP J05074264+2447555 recently discovered
towards the Taurus region was quickly recognized to be an ongoing microlensing
event on a source located at distance of only pc from Earth. Here, we
show that observations with high sampling rate close to the time of maximum
magnification revealed features that imply the presence of a binary lens system
with very low mass ratio components. We present a complete description of the
binary lens system which hosts an Earth-like planet with most likely mass of
M. Furthermore, the source estimated location and
detailed Monte Carlo simulations allowed us to classify the event as due to the
closest lens system, being at a distance of pc and mass M.Comment: Accepted for publication on MNRAS, 2018. 6 Pages, 5 Figures.
References update
Bimacrocyclic Effect in Anion Recognition by a Copper(II) Bicyclam Complex
The dicopper(II) complex of the bimacrocyclic ligand α,α′-bis(5,7-dimethyl-1,4,8,11-tetraazacyclotetradecan-6-yl)-o-xylene, 2, interacts with selected anions in dimethyl sulfoxide solution according to two different modes: (i) halides (Cl-, Br-, and I-) and N3- coordinate the two metal centers at the same time between the two macrocyclic subunits that face each other and (ii) anionic species that do not fit the bridging coordination mode (e.g., NCO-, SCN-, CH3COO-, NO3-, and H2PO4-) interact with copper(II) ions only at the "external" positions or their interaction is too weak to be detected. Occurrence of the bridging interaction is demonstrated by X-ray crystallographic studies performed on the adduct formed by [Cu2(2)]4+ with azide and by electron paramagnetic resonance investigation, as the anion coordination between the two copper(II) centers induces spin-spin coupling. Isothermal titration calorimetry experiments performed on [Cu2(2)]4+ and, for comparison, on [(5,7-dimethyl-6-benzyl-1,4,8,11-tetraazacyclotetradecane)copper(II)], representing the mononuclear analogue, allowed determination of thermodynamic parameters (log K, ΔH, and TΔS) associated with the considered complex/anion equilibria. Thermodynamic data showed that adducts formed by [Cu2(2)]4+ with halides and azide benefit from an extra stability that can be explained on the basis of the anion advantage of simultaneously binding the two metal centers, i.e., in terms of the bimacrocyclic effect
Surface and interface treatments on wooden artefacts: Potentialities and limits of a non-invasive multi-technique study
Wooden artefacts embrace wide-ranging types of objects, like paintings on panel, sculptures, musical instruments, and furniture. Generally, in the manufacturing process of an artwork, wood is firstly treated with organic and inorganic materials to make it nonporous and morphologically homogeneous, and, at last, the surface treatment consists of varnishes or coatings applied with the aims of conferring aesthetic properties and protecting wood from biological growth and external degradation agents, as well as mechanical damage. In this work, different wooden mock-ups were prepared by varying some parameters: concentration of filler and pigment, respectively, in the ground and paint layers, thickness of the protective varnish coat, and sequence of the layers. The mock-ups were subsequently exposed to time-varying artificial aging processes. The multi-analytical non-invasive approach involved spectroscopic (reflection FT-IR, Raman, and X-ray fluorescence), tomographic (optical coherence tomography) and colorimetric techniques. Data were interpreted using both univariate and multivariate methods. The aim was to evaluate potential and limits of each non-invasive technique into the study of different stratigraphies of wooden artworks. This approach was supported by microscopic observations of cross-sections obtained from selected mock-ups. The methodological approach proposed here would add valuable technical know-how and information about the non-invasive techniques applied to the study of wooden artworks
X-rays investigations for the characterization of two 17th century brass instruments from Nuremberg
A recent finding at the Castello Sforzesco in Milan of two brass natural horns from the end of the 17th century and assigned to the Haas family from Nuremberg brought to light new information about this class of objects. The instruments were heavily damaged, but their historical value was great. In this study, a multidisciplinary approach mainly based on non-invasive analytical techniques and including X-rays investigations (X-ray radiography, X-ray fluorescence and X-ray diffraction) was used. The present study was aimed at: i) pointing out the executive techniques for archaeometric purposes; ii) characterizing the morphological and the chemical features of materials; and iii) identifying and mapping the damages of the structure and the alterations of the surface
Surface and interface treatments on wooden artefacts: Potentialities and limits of a non-invasive multi-technique study
Wooden artefacts embrace wide-ranging types of objects, like paintings on panel, sculptures, musical instruments, and furniture. Generally, in the manufacturing process of an artwork, wood is firstly treated with organic and inorganic materials to make it nonporous and morphologically homogeneous, and, at last, the surface treatment consists of varnishes or coatings applied with the aims of conferring aesthetic properties and protecting wood from biological growth and external degradation agents, as well as mechanical damage. In this work, different wooden mock-ups were prepared by varying some parameters: concentration of filler and pigment, respectively, in the ground and paint layers, thickness of the protective varnish coat, and sequence of the layers. The mock-ups were subsequently exposed to time-varying artificial aging processes. The multi-analytical non-invasive approach involved spectroscopic (reflection FT-IR, Raman, and X-ray fluorescence), tomographic (optical coherence tomography) and colorimetric techniques. Data were interpreted using both univariate and multivariate methods. The aim was to evaluate potential and limits of each non-invasive technique into the study of different stratigraphies of wooden artworks. This approach was supported by microscopic observations of cross-sections obtained from selected mock-ups. The methodological approach proposed here would add valuable technical know-how and information about the non-invasive techniques applied to the study of wooden artworks
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