TYC 2675-663-1: A newly discovered W UMa system in an active state

The recently discovered eclipsing binary system TYC 2675-663-1 is a X-ray source, and shows properties in the optical that are similar to the W UMa systems, but are somewhat unusual compared to what is seen in other contact binary systems. The goal of this work is to characterize its properties and investigate its nature by means of detailed photometric and spectroscopic observations. We have performed extensive V-band photometric measurements with the INTEGRAL satellite along with ground-based multi-band photometric observations, as well as high-resolution spectroscopic monitoring from which we have measured the radial velocities of the components. These data have been analysed to determine the stellar properties, including the absolute masses and radii. Additional low-resolution spectroscopy was obtained to investigate spectral features. From the measured eclipse timings we determine an orbital period for the binary of P=0.4223576+-0.0000009 days. The light-curve and spectroscopic analyses reveal the observations to be well represented by a model of an overcontact system composed of main-sequence F5 and G7 stars (temperature difference of nearly 1000 K), with the possible presence of a third star. Low-resolution optical spectroscopy reveals a complex H alpha emission, and other features that are not yet understood. The unusually large mass ratio of q=0.81+-0.05 places it in the rare "H" (high mass ratio) subclass of the W UMa systems, which are presumably on their way to coalescence.Comment: 12 pages in double column format. Accepted for publication in Astronomy and Astrophysic

Computational thinking and robotics in education

After the computational thinking sessions in the previous 2016-2018 editions of TEEM Conference, the fourth edition of this track has been organized in the current 2019 edition. Computational thinking is still a very significant topic, especially, but not only, in pre-university education. In this edition, the robotic has a special role in the track, with a strength relationship with the STEM and STEAM education of children at the pre-university levels, seeding the future of our society

Cu2ZnSnS4 thin film solar cells grown by fast thermal evaporation and thermal treatment

Cu2ZnSnS4 thin films have been produced via rapid thermal evaporation of off-stoichiometric kesterite powder followed by annealing in an Ar atmosphere. Different heating rates were applied during the thermal treatments. The chemical composition and structural properties of the deposited layers as well as the distribution of the elements through the kesterite thin film have been investigated. The initial growth of a SnS secondary phase during evaporation led to the formation of this secondary phase next to the Mo back contact. Solar cell power conversion efficiencies were limited to values about 3 % due to this secondary phase. Furthermore, an increased open circuit voltage was demonstrated by using a Zn(O,S) buffer layerThis work was supported by DAAD project (INTERKEST, Ref: 57050358), Marie Curie-ITN (KESTCELLS, GA: 316488) and MINECO project (SUNBEAM, ENE2013-49136-C4-3-R). RC and ES acknowledge financial support from Spanish MINECO within the Ramón y Cajal program (RYC-2011-08521) and (RYC-2011-09212) respectively. SG also thanks the Government of Spain for the FPI fellowship (BES-2014-068533)

XMM-Newton observations of the hot spot galaxy NGC 2903

We report on the first deeper X-ray broad-band observation of the hot spot galaxy NGC 2903 obtained with XMM-Newton. X-ray imaging and spectra of the spiral barred galaxy were obtained from XMM-Newton archival data to study its X-ray population and the conditions of the hot gas in its central region. We investigate the spectral properties of the discrete point-source population and give estimates of their X-ray spectral parameters. By analysing the RGS spectra, we derive temperature and abundances for the hot gas located in its central region. A total of six X-ray point sources (four of them ULX candidates) were detected in the energy range of 0.3-10.0 keV located within the galaxy D25 optical disk. Three of these sources are detected for the first time, and one of them with a luminosity of higher than 10^39 erg/s. After fitting three different models, we were able to estimate their luminosities, which are compatible with those of binaries with a compact object in the form of black holes (BHs) rather than neutron stars (NSs). We extracted the combined first-order RGS1 and RGS2 spectra of its central region, which display several emission lines. Both O\,{\sc vii} $f$ and $r$ lines seem to be of similar strength, which is consistent with the presence of the collisionally ionized gas that is typical of starburst galaxies. We fitted the spectrum to a model for a plasma in collisional ionization equilibrium (CIE) and the continuum was modelled with a power law, resulting in a plasma temperature of T = 0.31 \pm 0.01 keV and an emission measure EM \equiv n_Hn_eV =6.4_{-0.4}^{+0.5}\times 10^{61}$~cm$^{-3}. We also estimated abundances that are consistent with solar values.Comment: 5 pages, 2 figures, accepted for publication in A&A, resubmission corrects typographical errors and improves exposition according to the referee's suggestion

The 1989 and 2015 outbursts of V404 Cygni: a global study of wind-related optical features

The black hole transient V404 Cygni exhibited a bright outburst in June 2015 that was intensively followed over a wide range of wavelengths. Our team obtained high time resolution optical spectroscopy (~90 s), which included a detailed coverage of the most active phase of the event. We present a database consisting of 651 optical spectra obtained during this event, that we combine with 58 spectra gathered during the fainter December 2015 sequel outburst, as well as with 57 spectra from the 1989 event. We previously reported the discovery of wind-related features (P-Cygni and broad-wing line profiles) during both 2015 outbursts. Here, we build diagnostic diagrams that enable us to study the evolution of typical emission line parameters, such as line fluxes and equivalent widths, and develop a technique to systematically detect outflow signatures. We find that these are present throughout the outburst, even at very low optical fluxes, and that both types of outflow features are observed simultaneously in some spectra, confirming the idea of a common origin. We also show that the nebular phases depict loop patterns in many diagnostic diagrams, while P-Cygni profiles are highly variable on time-scales of minutes. The comparison between the three outbursts reveals that the spectra obtained during June and December 2015 share many similarities, while those from 1989 exhibit narrower emission lines and lower wind terminal velocities. The diagnostic diagrams presented in this work have been produced using standard measurement techniques and thus may be applied to other active low-mass X-ray binaries.Comment: Accepted for publication in MNRAS. 23 pages paper, plus a 9 pages appendix with extra tables and figures. 18 figures are included in the paper and 8 in the appendi

Cognitive stimulation as alternative treatment to improve psychological disorders in patients with mild cognitive impairment

(1) Background: Mild cognitive impairment is becoming one of the most common clinical manifestations affecting older people. For this reason, developing non-pharmacological strategies to help improve or maintain the physical condition of patients with mild dementia has become a priority. Therefore, the objective of this study is to provide evidence about the effects of a cognitive stimulation program on cognitive performance, anxiety, depression, and quality of life in people with mild cognitive impairment (MCI) and aged > 70. (2) Methods: This study is a randomized clinical trial. A total of 72 elderly people with MCI participated: 35 in the control group who did not receive any intervention and 36 in the experimental group who received a cognitive stimulation program for 12 weeks. Cognitive performance, depression, anxiety and health-related quality of life (HRQoL) were measured using the Mini-Mental State Examination (MMSE), the Yesavage Geriatric Depression Scale, the Hamilton Rating Scale, and the SF-12, respectively. (3) Results: In the experimental group, significant results were obtained on cognitive performance, depression, anxiety and general health, emotional role, social functioning, vitality, mental health and mental component summary domains of the SF-12. (4) Conclusions: a cognitive stimulation program of 12 weeks improves cognitive performance, anxiety, depression, and HRQoL in people with MCI aged > 70