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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 $\simeq 38$, $\simeq 86$ and $\simeq 69$ minutes 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 $\simeq 38$ minutes and find in the OM light curve a signature for a period at $75\pm 21$ 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 $kT_{max}\simeq 31$ 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 list

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 archive $XMM$-Newton observation 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 $\simeq 20.3$ 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 $\simeq 3.581$ hours. The source is characterized by a unabsorbed flux of $\simeq 2.98\times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$ corresponding to an intrinsic luminosity {of $\simeq 7 \times 10^{31}$ erg s$^{-1}$ } {for a distance of $\simeq 433$ pc}. The existence of such features allow us to classify VZ Sex as a clear member of the intermediate polar class. Furthermore, with the estimated WD spin, the ratio $P_{spin}/P_{orb}$ is $\simeq 0.09$, 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., Comment: Accepted for publication on The Astrophysical Journal. 10 pages, 5 figures

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 $\simeq 96$ minutes, a clear identification of such a signature in the high energy band (apart for a variability on a time scale of $\simeq 8$ minutes as detected by the ROSAT satellite) is lacking. By using XMM-Newton archive data, we clearly identify a feature (at $\simeq 88$ 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 $\simeq 5.6$ 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 $\simeq 87.5$ minutes and $\simeq 27.9$ 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 $0.3-10$ keV band is estimated to be $\simeq 5\times 10^{30}$ erg s$^{-1}$ and $\simeq 3.8\times 10^{29}$ erg s$^{-1}$, respectively., Accepted for publication on MNRAS, main journal, 2020. 9 Pages. 9 Figures

We show that the optical flare event discovered by Graham et al. (2020) towards the active galactic nucleus J1249+3449 is fully consistent with being a quasar microlensing event due to a $\simeq 0.1 M_{\odot}$ star, although other explanations, such as that, mainly supported by Graham et al. (2020), of being the electromagnetic counterpart associated to a binary black hole merger, cannot be completely excluded at present., Accepted for publication on the Monthly Notices of the Royal Astronomical Society Letters - (MNRAS Letter) -, 2020, 5 pages, 2 figures

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 $700-800$ 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 hosts an Earth-like planet with most likely mass of $9.2\pm 6.6$ M$_{\oplus}$. 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 $\simeq 380$ pc and mass $\simeq 0.25$ M$_{\odot}$., Accepted for publication on MNRAS, 2018. 6 Pages, 5 Figures. References updated

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 $X$-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 $XMM$-Newton, clearly showing an enhancement of the 0.3-10 keV band flux by a factor $\simeq 30$ with respect to the initial state. Swift/XRT observations show that the source is still active in the $X$-rays at a level of $\simeq 0.05$ counts s$^{-1}$. The unabsorbed X-ray luminosity derived from the {\it XMM}-Newton slew and SWIFT observations, $L_{x}\simeq 5\times10^{41}$ erg s$^{-1}$, places SN 2015J among the brightest young supernovae in X-rays., The Astrophysical Journal, Volume 850, Number 2