62 research outputs found

    BCL-6 and other genomic alterations in non-Hodgkin's lymphoma (NHL).

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    This study reports on the frequency and disease association pattern of a number of gene rearrangements in a large panel of lymphoid tumours (n = 94). We detected the t(11;14) translocation, involving rearrangement of the BCL-1 locus, in 60% of mantle cell lymphomas. The BCL-2 gene, located at band 18q21, was rearranged in 42% of follicle centre lymphomas (FCL) and in 15% of diffuse large B-cell (DLBC) lymphomas. In this study, 80% of the c-MYC rearrangements were detected in aggressive diffuse lymphoma subsets but, interestingly, 9% of FCL showed involvement of t(8q24) translocation. In our study, rearrangements of the BCL-6 gene at band 3q27 were found in 31% of DLBC lymphomas. Interestingly, 50% of the BCL-6 rearrangement positive lymphoma cases had coexisting gene rearrangements involving all of the aforementioned gene loci. The molecular dissection of these genes will improve our understanding of the genesis of the diverse clinicopathological subtypes

    The Asiago-ESO/RASS QSO Survey II. The Southern Sample

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    This is the second paper of a series describing the Asiago-ESO/RASS QSO survey, a project aimed at the construction of an all-sky statistically well-defined sample of very bright QSOs (B_J < 15). Such a survey is required to remove the present uncertainties about the properties of the local QSO population and constitutes an homogeneous database for detailed evolutionary studies of AGN. We present here the complete Southern Sample, which comprises 243 bright (12.60 < B_J < 15.13) QSO candidates at high galactic latitudes (|b_{gal}| > 30^{\circ}). The area covered by the survey is 5660 sq. deg. Spectroscopy for the 137 still unidentified objects has been obtained. The total number of AGN turns out to be 111, 63 of which are new identifications. The properties of the selection are discussed. The completeness and the success rate for this survey at the final stage are 63% and 46%, respectively.Comment: 36 pages Latex, with 15 PostScript figures. Accepted for publication in Astronomical Journa

    Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I

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    We have embarked on a project, under the aegis of the Nearby Stars (NStars)/ Space Interferometry Mission Preparatory Science Program to obtain spectra, spectral types, and, where feasible, basic physical parameters for the 3600 dwarf and giant stars earlier than M0 within 40 parsecs of the sun. In this paper we report on the results of this project for the first 664 stars in the northern hemisphere. These results include precise, homogeneous spectral types, basic physical parameters (including the effective temperature, surface gravity and the overall metallicity, [M/H]) and measures of the chromospheric activity of our program stars. Observed and derived data presented in this paper are also available on the project's website at http://stellar.phys.appstate.edu/

    The Young Solar Analogs Project. I. Spectroscopic and Photometric Methods and Multi-year Timescale Spectroscopic Results

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    This is the first in a series of papers presenting methods and results from the Young Solar Analogs Project, which began in 2007. This project monitors both spectroscopically and photometrically a set of 31 young (300–1500 Myr) solar-type stars with the goal of gaining insight into the space environment of the Earth during the period when life first appeared. From our spectroscopic observations we derive the Mount Wilson S chromospheric activity index (SMW), and describe the method we use to transform our instrumental indices to SMW without the need for a color term. We introduce three photospheric indices based on strong absorption features in the blue-violet spectrum—the G-band, the Ca i resonance line, and the Hydrogen-γ line—with the expectation that these indices might prove to be useful in detecting variations in the surface temperatures of active solar-type stars. We also describe our photometric program, and in particular our Superstar technique for differential photometry which, instead of relying on a handful of comparison stars, uses the photon flux in the entire star field in the CCD image to derive the program star magnitude. This enables photometric errors on the order of 0.005–0.007 magnitude. We present time series plots of our spectroscopic data for all four indices, and carry out extensive statistical tests on those time series demonstrating the reality of variations on timescales of years in all four indices. We also statistically test for and discover correlations and anti-correlations between the four indices. We discuss the physical basis of those correlations. As it turns out, the photospheric indices appear to be most strongly affected by emission in the Paschen continuum. We thus anticipate that these indices may prove to be useful proxies for monitoring emission in the ultraviolet Balmer continuum. Future papers in this series will discuss variability of the program stars on medium (days–months) and short (minutes to hours) timescales

    The Distance to SN 1999em from the Expanding Photosphere Method

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    We present optical and IR spectroscopy of the first two months of evolution of the Type II SN 1999em. We combine these data with high-quality optical/IR photometry beginning only three days after shock breakout, in order to study the performance of the ``Expanding Photosphere Method'' (EPM) in the determination of distances. With this purpose we develop a technique to measure accurate photospheric velocities by cross-correlating observed and model spectra. The application of this technique to SN 1999em shows that we can reach an average uncertainty of 11% in velocity from an individual spectrum. Our analysis shows that EPM is quite robust to the effects of dust. In particular, the distances derived from the VI filters change by only 7% when the adopted visual extinction in the host galaxy is varied by 0.45 mag. The superb time sampling of the BVIZJHK light-curves of SN 1999em permits us to study the internal consistency of EPM and test the dilution factors computed from atmosphere models for Type II plateau supernovae. We find that, in the first week since explosion, the EPM distances are up to 50% lower than the average, possibly due the presence of circumstellar material. Over the following 65 days, on the other hand, our tests lend strong credence to the atmosphere models, and confirm previous claims that EPM can produce consistent distances without having to craft specific models to each supernova. This is particularly true for the VI filters which yield distances with an internal consistency of 4%. From the whole set of BVIZJHK photometry, we obtain an average distance of 7.5+/-0.5 Mpc, where the quoted uncertainty (7%) is a conservative estimate of the internal precision of the method obtained from the analysis of the first 70 days of the supernova evolution.Comment: 68 pages, 15 tables, 22 figures, to appear in Ap

    Debris disks in main sequence binary systems

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    We observed 69 A3-F8 main sequence binary star systems using the Multiband Imaging Photometer for Spitzer onboard the Spitzer Space Telescope. We find emission significantly in excess of predicted photospheric flux levels for 9(+4/-3)% and 40(+7/-6)% of these systems at 24 and 70 microns, respectively. Twenty two systems total have excess emission, including four systems that show excess emission at both wavelengths. A very large fraction (nearly 60%) of observed binary systems with small (<3 AU) separations have excess thermal mission. We interpret the observed infrared excesses as thermal emission from dust produced by collisions in planetesimal belts. The incidence of debris disks around main sequence A3-F8 binaries is marginally higher than that for single old AFGK stars. Whatever combination of nature (birth conditions of binary systems) and nurture (interactions between the two stars) drives the evolution of debris disks in binary systems, it is clear that planetesimal formation is not inhibited to any great degree. We model these dust disks through fitting the spectral energy distributions and derive typical dust temperatures in the range 100--200 K and typical fractional luminosities around 10^-5, with both parameters similar to other Spitzer-discovered debris disks. Our calculated dust temperatures suggest that about half the excesses we observe are derived from circumbinary planetesimal belts and around one third of the excesses clearly suggest circumstellar material. Three systems with excesses have dust in dynamically unstable regions, and we discuss possible scenarios for the origin of this short-lived dust.Comment: ApJ, in press. 57 pages, including 7 figures (one of which is in color

    Lamost observations in the kepler field. I. Database of low-resolution spectra*

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    The nearly continuous light curves with micromagnitude precision provided by the space mission Kepler are revolutionizing our view of pulsating stars. They have revealed a vast sea of low-amplitude pulsation modes that were undetectable from Earth. The long time base of Kepler light curves allows for the accurate determination of the frequencies and amplitudes of pulsation modes needed for in-depth asteroseismic modeling. However, for an asteroseismic study to be successful, the first estimates of stellar parameters need to be known and they cannot be derived from the Kepler photometry itself. The Kepler Input Catalog provides values for the effective temperature, surface gravity, and metallicity, but not always with sufficient accuracy. Moreover, information on the chemical composition and rotation rate is lacking. We are collecting low-resolution spectra for objects in the Kepler field of view with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, Xinglong observatory, China). All of the requested fields have now been observed at least once. In this paper, we describe those observations and provide a useful database for the whole astronomical communit

    Color-color Relations for Red Giants in Star Clusters

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    New Johnson-Cousins UBVRI photometry of giants in globular clusters is combined with JHK photometry on the CIT system to produce color sequences for giants from the globular clusters M3, M5, M13, and M92. UBVRI data are also presented for giants in the metal-rich open cluster NGC 6791. These data fill a gap in the literature, especially for the R & I bands. We provide the empirical relations between broad band colors for various [Fe/H] values for metal-poor giants. The color sequences for U-B and B-V show clear separations for different [Fe/H] values. We also find weak, though unexpected, metallicity dependences of V-R, V-I, and J-K colors. H-K is metal-insensitive. The above colors are plotted as a function of V-K, and a literature (V-K) - T_{eff} relation is given.Comment: 21 pages, 7 figures; AASTeX 4.0; to appear in the July 1998 edition of PASP. Revised version; includes discussion on possible effects of reddening error

    LAMOST Observations in 15 \textit{K}2 Campaigns: I. Low resolution spectra from LAMOST DR6

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    The LAMOST-\textit{K}2 (L\textit{K}2) project, initiated in 2015, aims to collect low-resolution spectra of targets in the \textit{K}2 campaigns, similar to LAMOST-\textit{Kepler} project. By the end of 2018, a total of 126 L\textit{K}2 plates had been observed by LAMOST. After cross-matching the catalog of the LAMOST data release 6 (DR6) with that of the \textit{K}2 approved targets, we found 160,619 usable spectra of 84,012 objects, most of which had been observed more than once. The effective temperature, surface gravity, metallicity, and radial velocity from 129,974 spectra for 70,895 objects are derived through the LAMOST Stellar Parameter Pipeline (LASP). The internal uncertainties were estimated to be 81 K, 0.15 dex, 0.09 dex and 5 kms1^{-1}, respectively, when derived from a spectrum with a signal-to-noise ratio in the gg band (SNRg_g) of 10. These estimates are based on results for targets with multiple visits. The external accuracies were assessed by comparing the parameters of targets in common with the APOGEE and GAIA surveys, for which we generally found linear relationships. A final calibration is provided, combining external and internal uncertainties for giants and dwarfs, separately. We foresee that these spectroscopic data will be used widely in different research fields, especially in combination with \textit{K}2 photometry.Comment: 31 pages, 9 figures, 6 tables, accepted by ApJ

    "Give me some space" : exploring youth to parent aggression and violence

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    A small scale qualitative project, undertaken by an interdisciplinary domestic violence research group involving academic researchers and research assistants, with colleagues from Independent Domestic Abuse Services (IDAS), investigated youth aggression and violence against parents. Following the literature review, data was generated through several research conversations with young people (n = 2), through semi-structured interviews with mothers (n = 3) and practitioners (n = 5), and through a practitioner focus group (n = 8). Thematic analysis and triangulation of the data from parents, practitioners and young people, elicited interconnected and complex overarching themes. Young people could be both victim and perpetrator. The witnessing or experiencing of domestic aggression and violence raised the concept of ‘bystander children’. The impact of young people experiencing familial violence was underestimated by parents. For practitioners, the effects of working with domestic violence was shown to be significant - both positively and negatively
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