The Recurrent Eclipse of an Unusual Pre--Main-Sequence Star in IC 348

The recurrence of a previously documented eclipse of a solar-like pre--main-sequence star in the young cluster IC 348 has been observed. The recurrence interval is 4.7 $\pm 0.1$ yr and portions of 4 cycles have now been seen. The duration of each eclipse is at least 3.5 years, or $\sim 75$% of a cycle, verifying that this is not an eclipse by a stellar companion. The light curve is generally symmetric and approximately flat-bottomed. Brightness at maximum and minimum have been rather stable over the years but the light curve is not perfectly repetitive or smooth and small variations exist at all phases. We confirm that the star is redder when fainter. Models are discussed and it is proposed that this could be a system similar to KH 15D in NGC 2264. Specifically, it may be an eccentric binary in which a portion of the orbit of one member is currently occulted during some binary phases by a circumbinary disk. The star deserves sustained observational attention for what it may reveal about the circumstellar environment of low-mass stars of planet-forming age.Comment: Accepted for publication in ApJ (Letters

The Variability and Rotation of Pre-main Sequence Stars in IC 348: Does Intracluster Environment Influence Stellar Rotation?

A variability study of the young cluster IC 348 at Van Vleck Observatory has been extended to a total of seven years. Twelve new periodic stars have been found in the last two years, bringing the total discovered by this program to 40. In addition, we confirm 16 of the periods reported by others and resolve some discrepancies. The total number of known rotation periods in the cluster, from all studies has now reached 70. This is sufficient to demonstrate that the parent population of K5-M2 stars is rotationally indistinguishable from that in the Orion Nebula Cluster even though their radii are 20% smaller and they would be expected to spin about twice as fast if angular momentum were conserved. The median radius and, therefore, inferred age of the IC 348 stars actually closely matches that of NGC 2264, but the stars spin significantly more slowly. This suggests that another factor besides mass and age plays a role in establishing the rotation properties within a cluster and we suggest that it is environment. If disk locking were to persist for longer times in less harsh environments, because the disks themselves persist for longer times, it could explain the generally slower rotation rates observed for stars in this cluster, whose earliest type star is of class B5. We have also obtained radial velocities, the first for PMS stars in IC348, and v sin i measurements for 30 cluster stars to assist in the study of rotation and as an independent check on stellar radii. Several unusual variable stars are discussed; in some or all cases their behavior may be linked to occultations by circumstellar material. A strong correlation exists between the range of photometric variability and the slope of the spectral energy distribution in the infrared. Nineteen of the 21 stars with I ranges exceeding 0.4 mag show infrared evidence for circumstellar disks.Comment: Accepted for publication in A

Modulation of Circumstellar Extinction in a Young Binary System with a Low-Mass Companion in a Noncoplanar Orbit

The cyclic activity model of a young star with the low-mass secondary component (q = M2/M1 <= 0.1) accreting a matter from circumbinary disk is considered. It is assumed that the orbit is circular and the disk and orbital planes are non-coplanar. Sets of hydrodynamics models of such a system have been calculated by the SPH method and then the variations of the circumstellar extinction and phase light curves were determined. The calculations showed that depending on the model parameters and orientation of the system in regards to an observer the different in shape and amplitude light curves can be observed. An important property of the considered models is also the dependence of the mass accretion rate onto the components on the phase of the orbital period. The results of the calculation can be used for analysis of the cyclic activity of UX Ori stars and young stars with the long-lasting eclipses.Comment: 14 pages, 7 figure

Bullying behaviour in schools, socioeconomic position and psychiatric morbidity: a cross-sectional study in late adolescents in Greece

<p>Abstract</p> <p>Background</p> <p>Bullying is quite prevalent in the school setting and has been associated with the socioeconomic position and psychiatric morbidity of the pupils. The aim of the study was to investigate the association between bullying and socioeconomic status in a sample of Greek adolescents and to examine whether this is confounded by the presence of psychiatric morbidity, including sub-threshold forms of illness.</p> <p>Methods</p> <p>5,614 adolescents aged 16-18 years old and attending 25 senior high schools were screened and a stratified random sample of 2,427 were selected for a detailed interview. Psychiatric morbidity was assessed with a fully structured psychiatric interview, the revised Clinical Interview Schedule (CIS-R), while bullying was assessed with the revised Olweus bully/victim questionnaire. The following socio-economic variables were assessed: parental educational level and employment status, financial difficulties of the family and adolescents' school performance. The associations were investigated using multinomial logit models.</p> <p>Results</p> <p>26.4% of the pupils were involved in bullying-related behaviours at least once monthly either as victims, perpetrators or both, while more frequent involvement (at least once weekly) was reported by 4.1%. Psychiatric morbidity was associated with all types of bullying-related behaviours. No socioeconomic associations were reported for victimization. A lower school performance and unemployment of the father were significantly more likely among perpetrators, while economic inactivity of the mother was more likely in pupils who were both victims and perpetrators. These results were largely confirmed when we focused on high frequency behaviours only. In addition, being overweight increased the risk of frequent victimization.</p> <p>Conclusions</p> <p>The prevalence of bullying among Greek pupils is substantial. Perpetration was associated with some dimensions of adolescents' socioeconomic status, while victimization showed no socioeconomic associations. Our findings may add to the understanding of possible risk factors for bullying behaviours in adolescence.</p

Overvåking i Grønavassdraget i Trysil i 1999

Rapporten gir en beskrivelse av påvirkningen av et større utslipp av sigevann/avløpsvann fra Heggvin avfallsplass til en mindre bekk "Hattemakerbekken". Utslippet som varte i 68 døgn skjedde fra en pumpekum som ligger i Hattemakerbekkens øvre del. Øvre deler av Hattemakerbekken ble sterkt påvirket av fersk fekal forurensning. Videre medførte utslipp av næringssalter og lettnedbrytbart organisk stoff til oksygensvikt, hydrogensulfidproduksjon og stor forekomst av heterotrofe begroingsorganismer. Mesteparten av Hattemakerbekken ble biologisk sett totalskadet. Utslippet medførte også til at bekken ble tilført potensielle miljøgifter. Utslippet av miljøgifter var likevel lite og vil høgst sannsynligvis ikke medføre fremtidige problem. fremtidige problem. Hattemakerbekken ble berørt av utslippet f.o.m. den 26. juni i 1998 t.o.m. høsten 1999, dvs i litt over et år. F.o.m. november i 1999 kan ingen effekter fra utslippet spores bortsett fra at det fortsatt ligger igjen en del næringsrikt slam i bekkens kildeområde. Hattemakerbekken er likevel fortsatt klart forurenset fra lokale forurensningskilder som boligkloakk og/eller sigevann fra gjødselkjellere