2,191 research outputs found

    Time Domain Explorations With Digital Sky Surveys

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    One of the new frontiers of astronomical research is the exploration of time variability on the sky at different wavelengths and flux levels. We have carried out a pilot project using DPOSS data to study strong variables and transients, and are now extending it to the new Palomar-QUEST synoptic sky survey. We report on our early findings and outline the methodology to be implemented in preparation for a real-time transient detection pipeline. In addition to large numbers of known types of highly variable sources (e.g., SNe, CVs, OVV QSOs, etc.), we expect to find numerous transients whose nature may be established by a rapid follow-up. Whereas we will make all detected variables publicly available through the web, we anticipate that email alerts would be issued in the real time for a subset of events deemed to be the most interesting. This real-time process entails many challenges, in an effort to maintain a high completeness while keeping the contamination low. We will utilize distributed Grid services developed by the GRIST project, and implement a variety of advanced statistical and machine learning techniques.Comment: 5 pages, 2 postscript figures, uses adassconf.sty. To be published in: "ADASS XIV (2004)", Eds. Patrick Shopbell, Matthew Britton and Rick Ebert, ASP Conference Serie

    Primary accumulation in the Soviet transition

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    The Soviet background to the idea of primary socialist accumulation is presented. The mobilisation of labour power and of products into public sector investment from outside are shown to have been the two original forms of the concept. In Soviet primary accumulation the mobilisation of labour power was apparently more decisive than the mobilisation of products. The primary accumulation process had both intended and unintended results. Intended results included bringing most of the economy into the public sector, and industrialisation of the economy as a whole. Unintended results included substantial economic losses, and the proliferation of coercive institutions damaging to attainment of the ultimate goal - the building of a communist society

    Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction

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    We present photospheric-phase observations of LSQ12gdj, a slowly-declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude MB=19.8M_B = -19.8, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600-23800 \AA) light curve out to 45 days past BB-band maximum light. We estimate that LSQ12gdj produced 0.96±0.070.96 \pm 0.07 MM_\odot of 56^{56}Ni, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27% of the flux at the earliest observed phases, and 17% at maximum light, is emitted bluewards of 3300 \AA. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 \AA, and the absence of narrow line emission and strong Na I D absorption all argue against a significant contribution from ongoing shock interaction. However, up to 10% of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius <1013< 10^{13} cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios.Comment: 18 pages, 10 figures, accepted to MNRAS; v2 accepted version. Spectra available on WISEReP (http://www.weizmann.ac.il/astrophysics/wiserep/). Natural-system photometry and bolometric light curve available as online tables in MNRAS versio

    Massive stars exploding in a He-rich circumstellar medium. VI. Observations of two distant Type Ibn supernova candidates discovered by La Silla-QUEST

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    We present optical observations of the peculiar stripped-envelope supernovae (SNe) LSQ12btw and LSQ13ccw discovered by the La Silla-QUEST survey. LSQ12btw reaches an absolute peak magnitude of M(g) = -19.3 +- 0.2, and shows an asymmetric light curve. Stringent prediscovery limits constrain its rise time to maximum light to less than 4 days, with a slower post-peak luminosity decline, similar to that experienced by the prototypical SN~Ibn 2006jc. LSQ13ccw is somewhat different: while it also exhibits a very fast rise to maximum, it reaches a fainter absolute peak magnitude (M(g) = -18.4 +- 0.2), and experiences an extremely rapid post-peak decline similar to that observed in the peculiar SN~Ib 2002bj. A stringent prediscovery limit and an early marginal detection of LSQ13ccw allow us to determine the explosion time with an uncertainty of 1 day. The spectra of LSQ12btw show the typical narrow He~I emission lines characterising Type Ibn SNe, suggesting that the SN ejecta are interacting with He-rich circumstellar material. The He I lines in the spectra of LSQ13ccw exhibit weak narrow emissions superposed on broad components. An unresolved Halpha line is also detected, suggesting a tentative Type Ibn/IIn classification. As for other SNe~Ibn, we argue that LSQ12btw and LSQ13ccw likely result from the explosions of Wolf-Rayet stars that experienced instability phases prior to core collapse. We inspect the host galaxies of SNe Ibn, and we show that all of them but one are hosted in spiral galaxies, likely in environments spanning a wide metallicity range.Comment: 15 pages, 9 figures, 4 tables. Accepted by MNRA

    Identification of Non-unitary triplet pairing in a heavy Fermion superconductor UPt_3

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    A NMR experiment recently done by Tou et al. on a heavy Fermion superconductor UPt3_3 is interpreted in terms of a non-unitary spin-triplet pairing state which we have been advocating. The proposed state successfully explains various aspects of the seemingly complicated Knight shift behaviors probed for major orientations, including a remarkable d-vector rotation under weak fields. This entitles UPt3_3 as the first example that a charged many body system forms a spin-triplet odd-par ity pairing at low temperatures and demonstrates unambiguously that the putative spin-orbit coupling in UPt3_3 is weak.Comment: 4 pages, 2 eps figures, to be published in J. Phys. Soc. Jpn. 67 (1998) No.

    The QUEST large area CCD camera

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    We have designed, constructed, and put into operation a very large area CCD camera that covers the field of view of the 1.2 m Samuel Oschin Schmidt Telescope at the Palomar Observatory. The camera consists of 112 CCDs arranged in a mosaic of four rows with 28 CCDs each. The CCDs are 600 x 2400 pixel Sarnoff thinned, back-illuminated devices with 13 µm x 13 µm pixels. The camera covers an area of 4.6° x 3.6° on the sky with an active area of 9.6 deg_2. This camera has been installed at the prime focus of the telescope and commissioned, and scientific-quality observations on the Palomar-QUEST Variability Sky Survey were started in 2003 September. The design considerations, construction features, and performance parameters of this camera are described in this paper

    Pretraživanje tradicionalnih europskih ljekovitih biljaka na inhibiciju acetilkolinesteraze i butirilkolinesteraze

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    Acetylcholinesterase (AChE) inhibitors are widely used for the symptomatic treatment of Alzheimer’s disease (AD) to enhance central cholinergic transmission. On the other hand, butyrylcholinesterase (BuChE) inhibitors were reported to produce significant increases in brain extracellular AChE without triggering severe peripheral or central side-effects. In the present study, we selected twelve plants used in traditional European medicine to treat different central nervous system (CNS) disorders or to improve memory. Methanolic and hexane extracts of these plants were tested for the AChE and BuChE inhibitory activity using Ellman’s colorimetric method. The most potent AChE and BuChE inhibition was observed in the hexane extracts of the flowers of Arnica chamissonis Less. susb. foliosa and Ruta graveolens L. herb at a concentration of 400 μg mL1. However, methanolic extracts of the flowers of Arnica chamissonis Less. susb. foliosa and the Hypericum perforatum L. herb demonstrated at the same concentration, selective inhibition only against AChE but not against BuChE. The other extracts did not show any significant AChE or BuChE inhibitory activity. Our results show that further investigations of the extracts of arnica, rue and St. John’s Wort are needed to identify the compounds responsible for the AChE and BuChE inhibitory activityInhibitori acetilkolinesteraze (AChE) povećavaju kolinergičku transmisiju u mozgu, pa se koriste za simptomatsko liječenje Alzheimerove bolesti (AD). S druge strane, inhibitori butirilkolinesteraze (BuChE) značajno povećavaju ekstracelularnu količinu AChE u mozgu, a da pri tome ne uzrokuju snažne nuspojave ni u središnjem ni i perifernom živčanom sustavu. Galantamin, jedan od odobrenih AChE inhibitora, alkaloid iz lukovica narcisa, pokazuje da su biljke značajni izvor novih potencijalnih AChE- i BuChE- inhibitora. U ovom radu, ispitivali smo učinak dvanaest biljaka koje se koriste u tradicionalnoj europskoj medicini na različite poremećaje središnjeg živčanog sustava i na poboljšanje pamćenja. Pomoću Ellmanove kolorimetrijske metode praćen je inhibitorni učinak metanolnih i heksanskih ekstrakata tih biljaka na AChE i BuChE. Najjači inhibitorni učinak pokazali su heksanski ekstrakti cvjetova Arnica chamissonis Less. susb. foliosa i nadzemnih dijelova Ruta graveolens L. u koncentraciji od 400 μg mL1. Međutim, metanolni ekstrakti cvjetova Arnica chamissonis Less. susb. foliosa i nadzemnih dijelova Hypericum perforatum L. u istim koncentracijama pokazuju selektivnu inhibiciju samo na AChE. Ostali ekstrakti bili su nedjelotvorni. Rezultati ukazuju na potrebu daljnjih ispitivanja ekstrakata arnike, rute i gospine trave da se utvrdi koji su sastojci ekstrakata odgovorni za inhibiciju AChE i BuChE
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