Time-resolved, multi-color photometry and spectroscopy of Virgo 4 (OU Vir): a high orbital inclination, short orbital period dwarf nova

We present multi-color photometry and time resolved spectroscopy of OU Vir. The analysis of the quiescent light curve shows that OU Vir is characterized by i) strong cycle-to-cycle brightness variations, and ii) hot spot modulated light curve with grazing eclipse of the impact region. Colors are derived both in- and out- of eclipse. The time-resolved spectroscopy allows us to produce the radial velocity curve from the H$\alpha$ accretion disk emission line which possibly reveals only weak evidence for hot spot line emission. The hot spot is believed to be a turbulent optically thick region, producing mostly continuum emission.Comment: 8 pages (including figures), 7 figures. To Be published in A&

Thirty Meter Telescope Site Testing I: Overview

As part of the conceptual and preliminary design processes of the Thirty Meter Telescope (TMT), the TMT site testing team has spent the last five years measuring the atmospheric properties of five candidate mountains in North and South America with an unprecedented array of instrumentation. The site testing period was preceded by several years of analyses selecting the five candidates, Cerros Tolar, Armazones and Tolonchar in northern Chile; San Pedro Martir in Baja California, Mexico and the 13 North (13N) site on Mauna Kea, Hawaii. Site testing was concluded by the selection of two remaining sites for further consideration, Armazones and Mauna Kea 13N. It showed that all five candidates are excellent sites for an extremely large astronomical observatory and that none of the sites stands out as the obvious and only logical choice based on its combined properties. This is the first article in a series discussing the TMT site testing project.Comment: Accepted for publication in PASP, April 2009 issu

Bioarchaeological and Climatological Evidence for the Fate of Norse Farmers in Medieval Greenland

Greenland, far north land of the Atlantic, has often been beyond the limit of European farming settlement. One of its Norse settlements, colonized just before AD 1000, is — astonishingly — not even at the southern tip, but a way up the west coast, the \u27Western Settlement\u27. Environmental studies show why its occupation came to an end within five centuries, leaving Greenland once more a place of Arctic-adapted hunters

Hubble Space Telescope Observations of UV Oscillations in WZ Sagittae During the Decline from Outburst

We present a time series analysis of Hubble Space Telescope observations of WZ Sge obtained in 2001 September, October, November and December as WZ Sge declined from its 2001 July superoutburst. Previous analysis of these data showed the temperature of the white dwarf decreased from ~29,000 K to ~18,000 K. In this study we binned the spectra over wavelength to yield ultraviolet light curves at each epoch that were then analyzed for the presence of the well-known 27.87 s and 28.96 s oscillations. We detect the 29 s periodicity at all four epochs, but the 28 s periodicity is absent. The origin of these oscillations has been debated since their discovery in the 1970s and competing hypotheses are based on either white dwarf non-radial g-mode pulsations or magnetically-channelled accretion onto a rotating white dwarf. By analogy with the ZZ Ceti stars, we argue that the non-radial g-mode pulsation model demands a strong dependence of pulse period on the white dwarf's temperature. However, these observations show the 29 s oscillation is independent of the white dwarf's temperature. Thus we reject the white dwarf non-radial g-mode pulsation hypothesis as the sole origin of the oscillations. It remains unclear if magnetically-funnelled accretion onto a rapidly rotating white dwarf (or belt on the white dwarf) is responsible for producing the oscillations. We also report the detection of a QPO with period ~18 s in the September light curve. The amplitudes of the 29 s oscillation and the QPO vary erratically on short timescales and are not correlated with the mean system brightness nor with each other.Comment: 20 pages, 3 figures, 1 table; accepted for publication in Ap

Witnessing and re-enacting in Cambodia: reflection on shifting testimonies

Thirty years after the collapse of the Khmer Rouge regime (1975-1979) how do Cambodians cope with the traumatic legacy of Pol Pot's reign of terror? What forms does witnessing take on in post-socialist and transitional Cambodia as senior Khmer Rouge leaders await prosecution at the Cambodian Tribunal? The paper examines aspects of witnessing in today's Cambodia, expressing each in its own way the idea of the 'shifting' of witnessing: the transformation of testimonies due to time passing and contrasted systems of justice through a comparison of testimonies in the trial of the 'Pol Pot/Ieng Sary clique' (1979) and the current Cambodian Tribunal; the complex forms of witnessing emerging from participatory projects developed with Western authors in 'We want (u) to know' (documentary movie made by an international film crew with the inhabitants of the village of Thnol Lok in 2009) and 'Breaking the silence' (theatre play realised by the Dutch dramaturge Annemarie Prins that premiered in Phnom Penh in 2009 and toured Cambodia in the following years); the relationship between documentary and legal forms of witnessing through the example of Vann Nath, a survivor of S-21/Tuol Sleng, the prison where the Khmer Rouge tortured and killed thousands of their fellow countrymen. The paper analyses the difficulty Western organisers of participatory projects experienced in applying the hybrid model of transitional justice to sociocultural contexts of witnessing. Nevertheless it points out their contribution to processes of 'recognition beyond recognition' in which cultural differences in coming to terms with historical trauma are expressed and recorded

Multi Aperture Scintillation Sensor (MASS) used in the site selection of the Thirty Meter Telescope (TMT)

One of the main tools used in the TMT site testing campaign is the turbulence profiler MASS. We describe empirical investigations and a side by side comparison of two MASS systems which were performed in order to identify the accuracy of MASS turbulence data and its dependence on the instrument calibration. The accuracy of the total seeing delivered by the TMT MASS systems is found to be better than 0"05. The combination of MASS and DIMM allows to observe the seeing within the first few hundred meters of the atmosphere and can be used to investigate possible correlations with meteorological parameters measured close to the ground. We also compare the detection of clouds and cirrus by means of MASS data (LOSSAM method) with measurements of the thermal emission of clouds using a net radiation sensor. These methods are compared with the visual cloud detection using all sky cameras

Cyberinfrastructure Deployments on Public Research Clouds Enable Accessible Environmental Data Science Education

Modern science depends on computers, but not all scientists have access to the scale of computation they need. A digital divide separates scientists who accelerate their science using large cyberinfrastructure from those who do not, or who do not have access to the compute resources or learning opportunities to develop the skills needed. The exclusionary nature of the digital divide threatens equity and the future of innovation by leaving people out of the scientific process while over-amplifying the voices of a small group who have resources. However, there are potential solutions: recent advancements in public research cyberinfrastructure and resources developed during the open science revolution are providing tools that can help bridge this divide. These tools can enable access to fast and powerful computation with modest internet connections and personal computers. Here we contribute another resource for narrowing the digital divide: scalable virtual machines running on public cloud infrastructure. We describe the tools, infrastructure, and methods that enabled successful deployment of a reproducible and scalable cyberinfrastructure architecture for a collaborative data synthesis working group in February 2023. This platform enabled 45 scientists with varying data and compute skills to leverage 40,000 hours of compute time over a 4-day workshop. Our approach provides an open framework that can be replicated for educational and collaborative data synthesis experiences in any data- and compute-intensive discipline

Monitoring of the environmental conditions inside the dome of the 4m Blanco Telescope at CTIO

Between February and April 2009 a number of ultrasonic anemometers, temperature probes and dust sensors were operated inside the CTIO Blanco telescope dome. These sensors were distributed in a way that temperature and 3 dimensional wind speeds were monitored along the line of sight of the telescope. During telescope operations, occasional seeing measurements were obtained using the Mosaic CCD imager and the CTIO site monitoring MASS-DIMM system. In addition, also a Lunar Scintillometer (LuSci) was operated over the course of a few nights inside the dome. We describe the instrumental setup and first preliminary results on the linkage of the atmospheric conditions inside the dome to the overall image quality