92 research outputs found
Orbital parameters and evolutionary status of the highly-peculiar binary system HD 66051
The spectroscopic binary system HD 66051 (V414 Pup) consists of a highlypeculiar CP3 (HgMn) star and an A-type component. It also shows out-of-eclipsevariability that is due to chemical spots. This combination allows thederivation of tight constraints for the testing of time-dependent diffusionmodels. We analysed radial velocity and photometric data using two differentmethods to determine astrophysical parameters and the orbit of the system.Appropriate isochrones were used to derive the age of the system. The orbitalsolution and the estimates from the isochrones are in excellent agreement withthe estimates from a prior spectroscopic study. The system is very close to thezero-age main sequence and younger than 120 Myr. HD 66051 is a most importantspectroscopic binary system that can be used to test the predictions of thediffusion theory explaining the peculiar surface abundances of CP3 stars.Fil: Paunzen, E.. Masaryk University; RepĂșblica ChecaFil: Fedurco, M.. Masaryk University; RepĂșblica ChecaFil: Helminiak, K.G.. Masaryk University; RepĂșblica ChecaFil: Pintado, Olga Ines. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - TucumĂĄn. Instituto Superior de CorrelaciĂłn GeolĂłgica. Universidad Nacional de TucumĂĄn. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de GeologĂa. CĂĄtedra GeologĂa Estructural. Instituto Superior de CorrelaciĂłn GeolĂłgica; Argentin
Engaging MSW Students in Faculty Research: Studentsâ Perspectives of Involvement in a Program Evaluation
Engaging social work students in research is challenging, in part, because of the way research is taught in the classroom and the need for learners to effectively develop connections between the âabstract worldâ of research concepts with the âreal worldâ of professional experiences. This article describes the experiences of graduate social work students involved in a process and outcome evaluation of a community-based program. Analysis of student learning outcomes and the team-based model used to engage students in the evaluation are provided to put forth a paradigm of teaching social work research through direct, supervised, and collaborative engagement
Absolute properties of the main-sequence eclipsing binary FM Leo
First spectroscopic and new photometric observations of the eclipsing binary
FM Leo are presented. The main aims were to determine orbital and stellar
parameters of two components and their evolutionary stage. First spectroscopic
observations of the system were obtained with DDO and PST spectrographs. The
results of the orbital solution from radial velocity curves are combined with
those derived from the light-curve analysis (ASAS-3 photometry and
supplementary observations of eclipses with 1 m and 0.35 m telescopes) to
derive orbital and stellar parameters. JKTEBOP, Wilson-Devinney binary
modelling codes and a two-dimensional cross-correlation (TODCOR) method were
applied for the analysis. We find the masses to be M_1 = 1.318 0.007 and
M_2 = 1.287 0.007 M_sun, the radii to be R_1 = 1.648 0.043 and R_2
= 1.511 0.049 R_sun for primary and secondary stars, respectively. The
evolutionary stage of the system is briefly discussed by comparing physical
parameters with current stellar evolution models. We find the components are
located at the main sequence, with an age of about 3 Gyr.Comment: 5 pages, 4 figures, to appear in MNRA
The teachable moment: engaging students in social justice movements
Social justice has long been at the forefront of the core values of the social work profession. Social workers are charged to confront social injustices and advocate for social change. In 2014, there was a societal response across the United States to the deaths of two African-American men, Mike Brown and Eric Garner, and the decision to not indict the police officers who killed them. The collective reaction was reflective of a country unsettled by the criminal justice systemâs ongoing acceptance of structural discrimination. This article will focus on one universityâs social work facultyâs collective response to the brutal killings of African-American men by police officers. With a main campus located in the suburbs and a satellite campus situated in a major city, the faculty felt compelled to guide students from both campuses through an understanding of what was happening locally and nationally by facilitating forums and programs to engage in dialog, not only in the classroom, but throughout the campus community. The concept of the living classroom is introduced and applied as a way to combat discrimination and advocate for social justice and human rights
Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - IX. Spotted pairs with red giants
We present spectroscopic and photometric solutions for three spotted systems with red giant components. Absolute physical and orbital parameters for these double-lined detached eclipsing binary stars are presented for the first time. These were derived from the V-, and I-band ASAS and WASP photometry, and new radial velocities calculated from high quality optical spectra we obtained with a wide range of spectrographs and using the two-dimensional cross-correlation technique (TODCOR). All of the investigated systems (ASAS J184949-1518.7, BQ Aqr, and V1207 Cen) show the differential evolutionary phase of their components consisting of a main-sequence star or a subgiant and a red giant, and thus constitute very informative objects in terms of testing stellar evolution models. Additionally, the systems show significant chromospheric activity of both components. They can be also classified as classical RS CVn-type stars. Besides the standard analysis of radial velocities and photometry, we applied spectral disentangling to obtain separate spectra for both components of each analysed system which allowed for a more detailed spectroscopic study. We also compared the properties of red giant stars in binaries that show spots, with those that do not, and found that the activity phenomenon is substantially suppressed for stars with Rossby number higher than âŒ1 and radii larger than âŒ20 Râ
High Precision Astrometry with MICADO at the European Extremely Large Telescope
In this article we identify and discuss various statistical and systematic
effects influencing the astrometric accuracy achievable with MICADO, the
near-infrared imaging camera proposed for the 42-metre European Extremely Large
Telescope (E-ELT). These effects are instrumental (e.g. geometric distortion),
atmospheric (e.g. chromatic differential refraction), and astronomical
(reference source selection). We find that there are several phenomena having
impact on ~100 micro-arcsec scales, meaning they can be substantially larger
than the theoretical statistical astrometric accuracy of an optical/NIR
42m-telescope. Depending on type, these effects need to be controlled via
dedicated instrumental design properties or via dedicated calibration
procedures. We conclude that if this is done properly, astrometric accuracies
of 40 micro-arcsec or better - with 40 micro-arcsec/year in proper motions
corresponding to ~20 km/s at 100 kpc distance - can be achieved in one epoch of
actual observationsComment: 15 pages, 9 figures, 3 tables. Accepted by MNRA
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