A search for hidden white dwarfs in the ROSAT EUV survey II: Discovery of a distant DA+F6/7V binary system in a direction of low density neutral hydrogen

We report the results of our final search for hot white dwarfs in unresolved, Sirius-type, binary systems with IUE. One new system, RE J0500-364 (DA+F6/7V), has been identified. This star appears to lie at a distance of between 500-1000pc, making it one of the most distant white dwarfs, if not the most distant, to be detected in the EUV surveys. The very low line-of-sight neutral hydrogen volume density to this object could place a lower limit on the length of the Beta CMa interstellar tunnel of diffuse gas, which stretches away from the Local Bubble in a similar direction to RE J0500-364.Comment: 1 LaTex file plus 15 figures; accepted for publication in Monthly Notices of the Royal Astronomical Societ

Hubble Space Telescope Imaging and Spectroscopy of the Sirius-Like Triple Star System HD 217411

We present Hubble Space Telescope imaging and spectroscopy of HD 217411, a G3 V star associated with the extreme ultraviolet excess source (EUV 2RE J2300-07.0). This star is revealed to be a triple system with a G 3V primary (HD 217411 A) separated by ~1.1" from a secondary that is in turn composed of an unresolved K0 V star (HD 217411 Ba) and a hot DA white dwarf (HD 217411 Bb). The hot white dwarf dominates the UV flux of the system. However; it is in turn dominated by the K0 V component beyond 3000 {\AA}. A revised distance of 143 pc is estimated for the system. A low level photometric modulation having a period of 0.61 days has also been observed in this system along with a rotational velocity on the order of 60 km s-1 in the K0 V star. Together both observations point to a possible wind induced spin up of the K0 V star during the AGB phase of the white dwarf. The nature of all three components is discussed as are constraints on the orbits, system age and evolution.Comment: 11 pages, 6 figure

Considering Educators’ Perceptions of Ethics and Safety in Virtual Learning Environments (VLEs)

With the proliferation of students’ abilities to use technology, in particular virtual reality (VR) applications, teachers are experimenting with VR in virtual learning environments (VLE) to engage students; but clear ethics and safety guidelines are not available. Within the field of education additional research is needed to determine how VR is employed in VLEs. Additionally, what are the decision-making processes of educators for the VR programs chosen for classroom use based on ethics and student safety? Through qualitative inquiry, educators from K–12 and higher education shared their perceptions of ethics and safety concerns in VR applications for use in the classroom. We collected data from a sample of K–12 and higher education professionals from the Association for Educational Communications and Technology (AECT) membership, an educational organization emphasizing technology integration and learning. Data analysis from the individual interviews with open-ended questions revealed five primary themes and twelve sub-themes. Participants agreed that they need ethical and safety guidelines as they embark on new horizons that influence student well-being. The findings from this study may provide an in-depth understanding of the importance of developing ethics and safety guidelines for educational VR programs when used by students

Component masses of young, wide, non-magnetic white dwarf binaries in the SDSS DR7

We present a spectroscopic component analysis of 18 candidate young, wide, non-magnetic, double-degenerate binaries identified from a search of the Sloan Digital Sky Survey Data Release 7 (DR7). All but two pairings are likely to be physical systems. We show SDSS J084952.47+471247.7 + SDSS J084952.87+471249.4 to be a wide DA+DB binary, only the second identified to date. Combining our measurements for the components of 16 new binaries with results for three similar, previously known systems within the DR7, we have constructed a mass distribution for the largest sample to date (38) of white dwarfs in young, wide, non-magnetic, double-degenerate pairings. This is broadly similar in form to that of the isolated field population with a substantial peak around M~0.6 Msun. We identify an excess of ultra-massive white dwarfs and attribute this to the primordial separation distribution of their progenitor systems peaking at relatively larger values and the greater expansion of their binary orbits during the final stages of stellar evolution. We exploit this mass distribution to probe the origins of unusual types of degenerates, confirming a mild preference for the progenitor systems of high-field-magnetic white dwarfs, at least within these binaries, to be associated with early-type stars. Additionally, we consider the 19 systems in the context of the stellar initial mass-final mass relation. None appear to be strongly discordant with current understanding of this relationship.Comment: 20 pages, 5 Tables, 7 figures. accepted for publication in MNRA