Photometric Variability in the CSTAR Field: Results From the 2008 Data Set

The Chinese Small Telescope ARray (CSTAR) is the first telescope facility built at Dome A, Antarctica. During the 2008 observing season, the installation provided long-baseline and high-cadence photometric observations in the i-band for 18,145 targets within 20 deg2 CSTAR field around the South Celestial Pole for the purpose of monitoring the astronomical observing quality of Dome A and detecting various types of photometric variability. Using sensitive and robust detection methods, we discover 274 potential variables from this data set, 83 of which are new discoveries. We characterize most of them, providing the periods, amplitudes and classes of variability. The catalog of all these variables is presented along with the discussion of their statistical properties.Comment: 38 pages, 11 figures, 4 tables; Accepted for publication in ApJ

Photometry of Variable Stars from Dome A, Antarctica

Dome A on the Antarctic plateau is likely one of the best observing sites on Earth thanks to the excellent atmospheric conditions present at the site during the long polar winter night. We present high-cadence time-series aperture photometry of 10,000 stars with i<14.5 mag located in a 23 square-degree region centered on the south celestial pole. The photometry was obtained with one of the CSTAR telescopes during 128 days of the 2008 Antarctic winter. We used this photometric data set to derive site statistics for Dome A and to search for variable stars. Thanks to the nearly-uninterrupted synoptic coverage, we find 6 times as many variables as previous surveys with similar magnitude limits. We detected 157 variable stars, of which 55% are unclassified, 27% are likely binaries and 17% are likely pulsating stars. The latter category includes delta Scuti, gamma Doradus and RR Lyrae variables. One variable may be a transiting exoplanet.Comment: Accepted for publication in the Astronomical Journal. PDF version with high-resolution figures available at http://faculty.physics.tamu.edu/lmacri/papers/wang11.pd

Eclipsing Binaries From the CSTAR Project at Dome A, Antarctica

The Chinese Small Telescope ARray (CSTAR) has observed an area around the Celestial South Pole at Dome A since 2008. About $20,000$ light curves in the i band were obtained lasting from March to July, 2008. The photometric precision achieves about 4 mmag at i = 7.5 and 20 mmag at i = 12 within a 30 s exposure time. These light curves are analyzed using Lomb--Scargle, Phase Dispersion Minimization, and Box Least Squares methods to search for periodic signals. False positives may appear as a variable signature caused by contaminating stars and the observation mode of CSTAR. Therefore the period and position of each variable candidate are checked to eliminate false positives. Eclipsing binaries are removed by visual inspection, frequency spectrum analysis and locally linear embedding technique. We identify 53 eclipsing binaries in the field of view of CSTAR, containing 24 detached binaries, 8 semi-detached binaries, 18 contact binaries, and 3 ellipsoidal variables. To derive the parameters of these binaries, we use the Eclipsing Binaries via Artificial Intelligence (EBAI) method. The primary and the secondary eclipse timing variations (ETVs) for semi-detached and contact systems are analyzed. Correlated primary and secondary ETVs confirmed by false alarm tests may indicate an unseen perturbing companion. Through ETV analysis, we identify two triple systems (CSTAR J084612.64-883342.9 and CSTAR J220502.55-895206.7). The orbital parameters of the third body in CSTAR J220502.55-895206.7 are derived using a simple dynamical model.Comment: 41 pages, 12 figures; published online in ApJ

The sky brightness and transparency in i-band at Dome A, Antarctica

The i-band observing conditions at Dome A on the Antarctic plateau have been investigated using data acquired during 2008 with the Chinese Small Telescope ARray. The sky brightness, variations in atmospheric transparency, cloud cover, and the presence of aurorae are obtained from these images. The median sky brightness of moonless clear nights is 20.5 mag arcsec^{-2} in the SDSS $i$ band at the South Celestial Pole (which includes a contribution of about 0.06 mag from diffuse Galactic light). The median over all Moon phases in the Antarctic winter is about 19.8 mag arcsec^{-2}. There were no thick clouds in 2008. We model contributions of the Sun and the Moon to the sky background to obtain the relationship between the sky brightness and transparency. Aurorae are identified by comparing the observed sky brightness to the sky brightness expected from this model. About 2% of the images are affected by relatively strong aurorae.Comment: There are 1 Latex file and 14 figures accepted by A

Monitoring international migration flows in Europe. Towards a statistical data base combining data from different sources

The paper reviews techniques developed in demography, geography and statistics that are useful for bridging the gap between available data on international migration flows and the information required for policy making and research. The basic idea of the paper is as follows: to establish a coherent and consistent data base that contains sufficiently detailed, up-to-date and accurate information, data from several sources should be combined. That raises issues of definition and measurement, and of how to combine data from different origins properly. The issues may be tackled more easily if the statistics that are being compiled are viewed as different outcomes or manifestations of underlying stochastic processes governing migration. The link between the processes and their outcomes is described by models, the parameters of which must be estimated from the available data. That may be done within the context of socio-demographic accounting. The paper discusses the experience of the U.S. Bureau of the Census in combining migration data from several sources. It also summarizes the many efforts in Europe to establish a coherent and consistent data base on international migration. The paper was written at IIASA. It is part of the Migration Estimation Study, which is a collaborative IIASA-University of Groningen project, funded by the Netherlands Organization for Scientific Research (NWO). The project aims at developing techniques to obtain improved estimates of international migration flows by country of origin and country of destination

The First Release of the CSTAR Point Source Catalog from Dome A, Antarctica

In 2008 January the 24th Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to DomeA, the highest point on the Antarctic plateau. CSTAR consists of four 14.5cm optical telescopes, each with a different filter (g, r, i and open) and has a 4.5degree x 4.5degree field of view (FOV). It operates robotically as part of the Plateau Observatory, PLATO, with each telescope taking an image every 30 seconds throughout the year whenever it is dark. During 2008, CSTAR #1 performed almost flawlessly, acquiring more than 0.3 million i-band images for a total integration time of 1728 hours during 158 days of observations. For each image taken under good sky conditions, more than 10,000 sources down to 16 mag could be detected. We performed aperture photometry on all the sources in the field to create the catalog described herein. Since CSTAR has a fixed pointing centered on the South Celestial Pole (Dec =-90 degree), all the sources within the FOV of CSTAR were monitored continuously for several months. The photometric catalog can be used for studying any variability in these sources, and for the discovery of transient sources such as supernovae, gamma-ray bursts and minor planets.Comment: 1 latex file and 9 figures The paper is accepted by PAS

Airglow and Aurorae at Dome A, Antarctica

Despite the absence of artificial light pollution at Antarctic plateau sites such as Dome A, other factors such as airglow, aurorae, and extended periods of twilight have the potential to adversely affect optical observations. We present a statistical analysis of the airglow and aurorae at Dome A using spectroscopic data from Nigel, an optical/near-IR spectrometer operating in the 300–850 nm range. These data complement photometric images from Gattini, a wide-field (90°) CCD camera with B, V, and R filters, allowing the background sky brightness to be disentangled from the various airglow and auroral emission lines. The median auroral contribution to the B, V, and R photometric bands is found to be 22.9, 23.4, and 23.0 mag arcsec^(-2), respectively. Auroral emissions most frequently occur between 10–23 hr local time, when up to 50% of observations are above airglow-level intensities. While infrequent, the strongest emissions detected occurred in the hours just prior to magnetic midnight. We are also able to quantify the amount of annual dark time available as a function of wavelength, as well as in the standard BVR photometric bands. On average, twilight ends when the Sun reaches a zenith distance of 102.6°

Modifications in host cell cytoskeleton structure and function mediated by intracellular HIV-1 Tat protein are greatly dependent on the second coding exon

Supplementary Data are available at NAR OnlineThe human immunodeficiency virus type 1 (HIV-1) regulator Tat is essential for viral replication because it achieves complete elongation of viral transcripts. Tat can be released to the extracellular space and taken up by adjacent cells, exerting profound cytoskeleton rearrangements that lead to apoptosis. In contrast, intracellular Tat has been described as protector from apoptosis. Tat gene is composed by two coding exons that yield a protein of 101 amino acids (aa). First exon (1–72aa) is sufficient for viral transcript elongation and second exon (73–101 aa) appears to contribute to non-transcriptional functions. We observed that Jurkat cells stably expressing intracellular Tat101 showed gene expression deregulation 4-fold higher than cells expressing Tat72. Functional experiments were performed to evaluate the effect of this deregulation. First, NF-iB-, NF-AT- and Sp1-dependent transcriptional activities were greatly enhanced in Jurkat-Tat101, whereas Tat72 induced milder but efficient activation. Second, cytoskeleton-related functions as cell morphology, proliferation, chemotaxis, polarization and actin polymerization were deeply altered in Jurkat- Tat101, but not in Jurkat-Tat72. Finally, expression of several cell surface receptors was dramatically impaired by intracellular Tat101 but not by Tat72. Consequently, these modifications were greatly dependent on Tat second exon and they could be related to the anergy observed in HIV-1-infected T cells.Plan Nacional del SIDA (MVI 1434/05–5), FIPSE 36584/ 06 and 36633/07, VIRHORST Network from Comunidad de Madrid (Spain), FIS PI040614 and PI0808752, ISCIII-RETIC RD06/0006, EUROPRISE Network of Excellence of the EU (Grant no. LSHP CT-2006- 037611), and BIO2008-04384 from the Ministerio de Ciencia e Innovacio´ n, Espan˜ a. Funding for open access charge: Instituto de Salud Carlos III, Ministry of Science and Technology, Spain.Peer reviewe

Revisiting and modelling the woodland farming system of the early Neolithic Linear Pottery Culture (LBK), 5600–4900 B.C

International audienceThis article presents the conception and the conceptual results of a modelling representation of the farming systems of the Linearbandkeramik Culture (LBK). Assuming that there were permanent fields (PF) then, we suggest four ways that support the sustainability of such a farming system over time: a generalized pollarding and coppicing of trees to increase the productivity of woodland areas for foddering more livestock, which itself can then provide more manure for the fields, a generalized use of pulses grown together with cereals during the same cropping season, thereby reducing the needs for manure. Along with assumptions limiting bias on village and family organizations, the conceptual model which we propose for human environment in the LBK aims to be sustainable for long periods and can thereby overcome doubts about the PFs hypothesis for the LBK farming system. Thanks to a reconstruction of the climate of western Europe and the consequent vegetation pattern and productivity arising from it, we propose a protocol of experiments and validation procedures for both testing the PFs hypothesis and defining its eco-geographical area