High resolution observations of Cen A: Yellow and red supergiants in a region of jet-induced star formation?

We present the analysis of near infrared (NIR), adaptive optics (AO) Subaru and archived HST imaging data of a region near the northern middle lobe (NML) of the Centaurus A (Cen A) jet, at a distance of $\sim15$ kpc north-east (NE) from the center of NGC5128. Low-pass filtering of the NIR images reveals strong -- $>3\sigma$ above the background mean -- signal at the expected position of the brightest star in the equivalent HST field. Statistical analysis of the NIR background noise suggests that the probability to observe $>3\sigma$ signal at the same position, in three independent measurements due to stochastic background fluctuations alone is negligible ($\leq10^{-7}\%$) and, therefore, that this signal should reflect the detection of the NIR counterparts of the brightest HST star. An extensive photometric analysis of this star yields $V-I$, visual-NIR, and NIR colors expected from a yellow supergiant (YSG) with an estimated age $\sim10^{+4}_{-3}$ Myr. Furthermore, the second and third brighter HST stars are, likely, also supergiants in Cen A, with estimated ages $\sim16^{+6}_{-3}$ Myr and $\sim25^{+15}_{-9}$ Myr, respectively. The ages of these three supergiants are in good agreement with the ages of the young massive stars that were previously found in the vicinity and are thought to have formed during the later phases of the jet-HI cloud interaction that appears to drive the star formation (SF) in the region for the past $\sim100$ Myr.Comment: 11 pages, 6 figures, 2 tables, accepted for publication in Ap

Social network analysis workshop for water and resource management

April 2014.Includes bibliographical references.Social network analysis (SNA) is a system for studying relationships and transactions between people, organizations, countries, and other entities. The purpose of this CWI project was to research and apply SNA techniques, then develop materials to provide a Fall 2013 half-day introductory workshop in Social Network Analysis for Water and Natural Resources Management at Colorado State University (CSU). The SNA workshop introduced interested students and professionals in engineering, natural resources, agriculture, and other scientific disciplines to complimentary analysis for human dimensions of their work and research through SNA principles and techniques. Complex social-ecological systems cannot be well-studied by only relying on technical analysis of the natural systems. SNA can help analyze how humans interact with resources and their environment and how their ties affect management choices. Social network structure can then be improved to enhance cooperation and innovation. CSU TILT instructional designers were involved in periodic workshop materials review with focus on implementing Research-Based Instructional (RBI) design. The workshop was marketed intensively for three weeks prior to delivery. The most effective means of participant recruitment were word of mouth and group emails, rather than posted flyers or campus-wide online calendars and newsletters. Instead of a traditional classroom, the SNA workshop was held in a conference room that permitted all attendees to sit facing one another around a large oval table, which enhanced participation and shared learning. Expert speakers with real world experience and warnings helped attendees better understand SNA application context and nuance. Providing two smaller sessions, rather than one larger offering, also allowed all attendees to participate more fully, and post-workshop evaluations from the first session were used to improve the second session by most evaluation measures. Follow-up included posting an SNA software demo online using CSU Echo 360 software and expanding other resources and discussion at the SNA Workshop Collaborative website to serve as an ongoing source for learning and sharing. Although not in the scope of the original project, in the Spring of 2014, a half-hour panel brief, a shortened seminar for undergraduates, and SNA software training for graduate students were also tested for SNA technical education merit. The SNA workshop will continue to be refined and tailored to specific CSU departments and programs, and it may be offered to more academic institutions and for other groups and agencies statewide and nationwide. Since attendees felt more time was needed to cover the many related topics and better learn SNA software tools for different applications, the SNA workshop will also be developed into a semester-long course and related textbook

Metropolitan water intelligence systems completion report, phase III

Submitted to: U.S. Department of the Interior, Office of Water Resources Research.Series numbering taken from cover.June 1974.Grant no. 14-31-0001-9028

Comment une collectivité et les services de lutte s'organisent-ils face à une augmentation des risques incendies ? L'exemple du département du Var -

Face à la perspective d'une augmentation des risques incendies, nous avons demandé à Jean Labadie et Stéphane Farcy, respectivement forestier au Conseil général du Var et lieutenant colonel au Service d'incendie et de secours du même département, de nous décrire comment leurs institutions anticipent la question : réflexions, nouvelles politiques, stratégies d'interventions, premières mesures..

Extreme mass ratios and fast rotation in three massive binaries

The origin of rapid rotation in massive stars remains debated, although binary interactions are now often advocated as a cause. However, the broad and shallow lines in the spectra of fast rotators make direct detection of binarity difficult. In this paper, we report on the discovery and analysis of multiplicity for three fast-rotating massive stars: HD25631 (B3V), HD191495 (B0V), and HD46485 (O7V). They display strikingly similar TESS light curves, with two narrow eclipses superimposed on a sinusoidal variation due to reflection effects. We complement these photometric data by spectroscopy from various instruments (X-Shooter, Espadons, FUSE...), to further constrain the nature of these systems. The detailed analyses of these data demonstrates that the companions of the massive OB stars have low masses (~1Msol) with rather large radii (2-4 Rsol) and low temperatures (<15 kK). These companions display no UV signature, which would exclude a hot subdwarf nature, but disentangling of the large set of X-Shooter spectra of HD25631 revealed the typical signature of chromospheric activity in the companion's spectrum. In addition, despite the short orbital periods (P=3-7d), the fast-rotating OB-stars still display non-synchronized rotation and all systems appear young (<20Myr). This suggests that, as in a few other cases, these massive stars are paired in those systems with non-degenerate, low-mass PMS companions, implying that fast rotation would not be a consequence of a past binary interactions in their case.Comment: accepted for publication by MNRA

Photometric variability of the LAMOST sample of magnetic chemically peculiar stars as seen by TESS

High-quality light curves from space missions have opened up a new window on the rotational and pulsational properties of magnetic chemically peculiar (mCP) stars and have fuelled asteroseismic studies. They allow the internal effects of surface magnetic fields to be probed and numerous astrophysical parameters to be derived with great precision. We present an investigation of the photometric variability of a sample of 1002 mCP stars discovered in the LAMOST archival spectra with the aims of measuring their rotational periods and identifying interesting objects for follow-up studies. TESS photometry was available for 782 mCP stars and was analysed using a Fourier two-term frequency fit to determine the stars' rotational periods. The rotational signal was then subtracted from the light curve to identify non-rotational variability. A pixel-level blending analysis was performed to check whether the variability originates in the target star or a nearby blended neighbour. We investigated correlations between the rotational periods, fractional age on the main sequence, mass, and several other observables. We present rotational periods and period estimates for 720 mCP stars. In addition, we identified four eclipsing binary systems that likely host an mCP star, as well as 25 stars with additional signals consistent with pulsation (12 stars with frequencies above 10 d$^{-1}$ and 13 stars with frequencies below 10 $^{-1}$). We find that more evolved stars have longer rotation periods, in agreement with the assumption of the conservation of angular momentum during main-sequence evolution. With our work, we increase the sample size of mCP stars with known rotation periods and identify prime candidates for detailed follow-up studies. This enables two paths towards future investigations: population studies of even larger samples of mCP stars and the detailed characterisation of high-value targets.Comment: 30 pages, 9 figures, 1 table. Accepted for publication in the Journal of Astronomy and Astrophysics (A&A

Lucky Imaging Adaptive Optics of the brown dwarf binary GJ569Bab

The potential of combining Adaptive Optics (AO) and Lucky Imaging (LI) to achieve high precision astrometry and differential photometry in the optical is investigated by conducting observations of the close 0\farcs1 brown dwarf binary GJ569Bab. We took 50000 $I$-band images with our LI instrument FastCam attached to NAOMI, the 4.2-m William Herschel Telescope (WHT) AO facility. In order to extract the most of the astrometry and photometry of the GJ569Bab system we have resorted to a PSF fitting technique using the primary star GJ569A as a suitable PSF reference which exhibits an $I$-band magnitude of $7.78\pm0.03$. The AO+LI observations at WHT were able to resolve the binary system GJ569Bab located at 4\farcs 92 \pm 0\farcs05 from GJ569A. We measure a separation of $98.4 \pm 1.1$ mas and $I$-band magnitudes of $13.86 \pm 0.03$ and $14.48 \pm 0.03$ and $I-J$ colors of 2.72$\pm$0.08 and 2.83$\pm$0.08 for the Ba and Bb components, respectively. Our study rules out the presence of any other companion to GJ569A down to magnitude I$\sim$ 17 at distances larger than 1\arcsec. The $I-J$ colors measured are consistent with M8.5-M9 spectral types for the Ba and Bb components. The available dynamical, photometric and spectroscopic data are consistent with a binary system with Ba being slightly (10-20%) more massive than Bb. We obtain new orbital parameters which are in good agreement with those in the literature.Comment: 13 pages, 9 figures, 7 tables, in press in MNRA