Follow-up observations of pulsating subdwarf B stars: Multisite campaigns on PG 1618+563B and PG 0048+091

We present follow-up observations of pulsating subdwarf B (sdB) stars as part of our efforts to resolve the pulsation spectra for use in asteroseismological analyses. This paper reports on multisite campaigns of the pulsating sdB stars PG 1618+563B and PG 0048+091. Data were obtained from observatories placed around the globe for coverage from all longitudes. For PG 1618+563B, our five-site campaign uncovered a dichotomy of pulsation states: Early during the campaign the amplitudes and phases (and perhaps frequencies) were quite variable while data obtained late in the campaign were able to fully resolve five stable pulsation frequencies. For PG 0048+091, our five-site campaign uncovered a plethora of frequencies with short pulsation lifetimes. We find them to have observed properties consistent with stochastically excited oscillations, an unexpected result for subdwarf B stars. We discuss our findings and their impact on subdwarf B asteroseismology.Comment: 50 pages including 17 figures and 10 tables. Accepted for publication in the Astrophysical Journa

Towards ensemble asteroseismology of the young open clusters Chi Persei and NGC 6910

As a result of the variability survey in Chi Persei and NGC6910, the number of Beta Cep stars that are members of these two open clusters is increased to twenty stars, nine in NGC6910 and eleven in Chi Persei. We compare pulsational properties, in particular the frequency spectra, of Beta Cep stars in both clusters and explain the differences in terms of the global parameters of the clusters. We also indicate that the more complicated pattern of the variability among B type stars in Chi Persei is very likely caused by higher rotational velocities of stars in this cluster. We conclude that the sample of pulsating stars in the two open clusters constitutes a very good starting point for the ensemble asteroseismology of Beta Cep-type stars and maybe also for other B-type pulsators.Comment: 4 pages, Astronomische Nachrichten, HELAS IV Conference, Arecife, Lanzarote, Feb 2010, submitte

Photometric multi-site campaign on the open cluster NGC 884 I. Detection of the variable stars

CONTEXT: Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. AIMS: To improve our comprehension of the beta Cep stars, we studied the young open cluster NGC 884 to discover new B-type pulsators, besides the two known beta Cep stars, and other variable stars. METHODS: An extensive multi-site campaign was set up to gather accurate CCD photometry time series in four filters (U, B, V, I) of a field of NGC884. Fifteen different instruments collected almost 77500 CCD images in 1286 hours. The images were calibrated and reduced to transform the CCD frames into interpretable differential light curves. Various variability indicators and frequency analyses were applied to detect variable stars in the field. Absolute photometry was taken to deduce some general cluster and stellar properties. RESULTS: We achieved an accuracy for the brightest stars of 5.7 mmag in V, 6.9 mmag in B, 5.0 mmag in I and 5.3 mmag in U. The noise level in the amplitude spectra is 50 micromag in the V band. Our campaign confirms the previously known pulsators, and we report more than one hundred new multi- and mono-periodic B-, A- and F-type stars. Their interpretation in terms of classical instability domains is not straightforward, pointing to imperfections in theoretical instability computations. In addition, we have discovered six new eclipsing binaries and four candidates as well as other irregular variable stars in the observed field.Comment: Accepted for publication in Astronomy and Astrophysics, 21 pages, 14 figures, 4 tables. The full appendix is available at http://www.ster.kuleuven.be/~sophies/Appendix.pdf (74 MB, 169 pages, 343 figures, 1 table

Death anxiety resilience; a mixed methods investigation

Research was conducted examining how death anxiety influenced PTSD and mental health among people who have experienced a life-threatening event. This study was conducted using undergraduate university students in Lithuania. The study used a mixed-method design and in phase 1, participants (N = 97) completed self-report questionnaires that gathered information on demographics, death anxiety, trauma and well-being. Data indicated a significant correlation between death anxiety and PTSD, but not psychiatric co-morbidity. Phase 2 attempted to further explore the phenomenological experience of participants with full PTSD, and 6 semi-structured interviews were conducted. IPA analysis found three major themes in response to the life-threatening event; self-efficacy, religious coping and existential attitude. Overall these coping mechanisms allowed participants to develop resilience against the effects of death anxiety and minimize its negative impact on mental health

Information Warfare : A Philosophical Perspective

This paper focuses on Information Warfare – the warfare characterised by the use of information and communication technologies. This is a fast growing phenomenon, which poses a number of issues ranging from the military use of such technologies to its political and ethical implications. The paper presents a conceptual analysis of this phenomenon with the goal of investigating its nature. Such an analysis is deemed to be necessary in order to lay the groundwork for future investigations into this topic, addressing the ethical problems engendered by this kind of warfare. The conceptual analysis is developed in three parts. First, it delineates the relation between Informational Warfare and the Information revolution. It then focuses attention on the effects that the diffusion of this phenomenon has on the concepts of state and war. On the basis of this analysis, a definition of Information Warfare is provided as a phenomenon not necessarily sanguinary and violent, and rather transversal concerning the environment in which it is waged, the way it is waged and the ontological and social status of its agents. The paper concludes by taking into consideration Just War Theory and the problems arising from its application to the case of Informational Warfare.Peer reviewe