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Intermediate polars are a class of cataclysmic variables in which a white dwarf accretes material from a companion star. The intermediate polar nature confirmation usually derives from the detection of two periods in both X -ray and optical photometry. In this respect, the high-energy signal is often characterized by modulations on the white dwarf spin and the orbital period. However, noting that the periodograms may be characterized by strong features also at the synodic period and/or other sidebands, the timing analysis of the X -ray signal may offer the unique possibility to firmly discover an intermediate polar candidate. Here, we concentrate on a sample of five cataclysmic variable binary candidates: i.e. SAXJ1748.2-2808, 1RXS J211336.1 + 542226, CXOGC J174622.7-285218, CXOGC J174517.4-290650, and V381 Vel, listed in the IPHome catalogue. Our main aim is to confirm if they belong to the intermediate polar class or not. The results of our analysis show that we can safely assess the intermediate polar nature of all the considered sources, apart for the case of V381 Vel which instead behaves like a cataclysmic variable of the polar subclass. Moreover, the source SAXJ1748.2-2808, previously classified as an HMXB, appears to be, most likely, an intermediate polar variable. [ABSTRACT FROM AUTHOR]

Intermediate polars are members of the cataclysmic variable binary stars. They are characterized by a moderately magnetized white dwarf accreting matter from a cool main-sequence companion star. In many cases, this accretion gives rise to a detectable X-ray emission. VZ Sex is an interesting X-ray source whose nature needs a robust confirmation. Here, we used archived XMM-Newton observations to assign the source to the intermediate polar class. We applied the Lomb–Scargle periodogram method to detect any relevant periodic feature in the 0.1–10 keV light curve and performed a spectral fitting of the X-ray spectrum in order to get information on the on-going accretion mechanism. By inspecting the periodogram, we detected a clear periodic feature at ≃20.3 minutes that we interpret as the spin period of the white dwarf. We additionally found the typical side bands expected as the consequence of the beat between the spin and the orbital period of ≃3.581 hr. The source is characterized by an unabsorbed flux of ≃2.98 × 10−12 erg cm−2 s−1 corresponding to an intrinsic luminosity of ≃7 × 1031 erg s−1 for a distance of ≃433 pc. The existence of such features allows us to classify VZ Sex as a clear member of the intermediate polar class. Furthermore, with the estimated WD spin, the ratio Pspin/Porb is ≃0.09, i.e., consistent with that expected for a typical IP system above the period gap. In addition, the estimated intrinsic luminosity opens the possibility that a bridge linking the normally bright IPs to the faint population of sources does exist. [ABSTRACT FROM AUTHOR]

We show that the optical flare event discovered by Graham et al. towards the active galactic nucleus J1249+3449 is fully consistent with being a quasar microlensing event due to a ≃0.1 M⊙ star, although other explanations, such as that, mainly supported by Graham et al. of being the electromagnetic counterpart associated with a binary black hole merger, cannot be completely excluded at present. [ABSTRACT FROM AUTHOR]

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 ≃96 min, a clear identification of such a signature in the high energy band (apart for a variability on a time-scale of ≃8 min as detected by the ROSAT satellite) is lacking. By using XMM – Newton archive data, we clearly identify a feature (at ≃88 min) 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 ≃5.6 min. 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 ≃87.5 and ≃27.9 min, respectively. The spectral analysis showed that both HP Cet and Swift J0820.6–280 are members of the underluminous IP subclass since their luminosity in the 0.3–10 keV band is estimated to be ≃5 × 1030 and ≃3.8 × 1029 erg s−1, respectively. [ABSTRACT FROM AUTHOR]

We report on the XMM – Newton observation of DW Cnc, a candidate intermediate polar candidate whose historical optical light curve shows the existence of periods at ≃38, ≃86, and ≃69 min, which were interpreted as the white dwarf spin, the orbital and the spin–orbit beat periodicities. By studying the 0.3–10 keV light curves, we confirm the existence of a period at ≃ 38 min and find in the OM light curve a signature for a period at 75 ± 21 min, 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 analysed and a best-fitting model, consisting of a multitemperature plasma, was found. The maximum temperature found when fitting the data is kT max ≃ 31 keV, which can be interpreted as an upper limit to the temperature of the shock. [ABSTRACT FROM AUTHOR]

The transient event labelled 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 700–800 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 host an Earth-like planet with most likely mass of 9.2 ± 6.6 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 ≃380 pc and mass ≃0.25 M⊙. [ABSTRACT FROM AUTHOR]

The evidence of the water erosion on Mars is particularly interesting since present climatic conditions are such that liquid water cannot exist at the surface. But, if water was present on the planet in the past, there may have been life, too. Since the discovery of carbonates on Mars also may have very important implications on the possibility that life developed there, we are studying minerals that can have biotic or abiotic origin: calcite (CaCO(3)) and aragonite, a metastable state of calcite.We have analysed biomineral aragonite, in the form of recent sea shells, as well as crystals of mineral aragonite. Infrared spectroscopy in the 2-25 mum wavelength range reveals that, after thermal processing, the biotic samples have a different spectral behaviour from the abiotic ones. As a result, it is possible to distinguish abiotic mineral aragonite from aragonite of recent biological origin.Obviously, if life existed in the past on the Red Planet, we could expect to find "ancient" biotic carbonates, which should therefore be investigated, in order to search for a way of discriminating them from abiotic minerals. For this reason, at the beginning we have considered samples of crushed fossil shells of aragonite composition. Afterwards, in order to take into account that fossilization processes almost always produce a transformation of metastable form (aragonite) into more stable form (calcite), we also studied samples of mineral calcite and different types of fossils completely transformed into calcite. All these biotic fossil samples show the same spectral behaviour as the fresh biotic material after thermal annealing at 485 degrees C. Instead, the calcite behaves like abiotic aragonite.Furthermore, it is known that seashells and other biominerals are formed through an intimate association of inorganic materials with organic macromolecules. The macromolecules control the nucleation, structure, morphology, crystal orientation and spatial confinement of the inorganic phase: this differentiates biominerals from minerals. Analysing the aragonite or calcite fossils with a Scanning Electron Microscope, we found that the fossilization process did not modify the structure of the biominerals which maintain their microscopic characteristics. Looking at the morphology of fossil biominerals, it is evident that the crystals are arranged in complex architectures compared with the compact structure of the mineral crystals. In conclusion, the properties and structure of the biominerals are different from those of the minerals. The rapid increase of the crystalline structure developed under biotic conditions makes these minerals less resistant to thermal treatments, compared with samples of abiotic origin. This result holds both for recent shells as well as all fossil samples. The spectroscopic behaviour of all analysed calcium carbonates of biotic origin is different from that of the abiotic one. Therefore, the infrared spectroscopy is a valid technique to discern the origin of the samples and a powerful tool for analysing in-situ and "sample-return" Mars missions specimens. Also Optical and Scanning Electron Microscopy can be useful to support this type of studies.