323 research outputs found
Non-blackbody disks can help explain inferred AGN accretion disk sizes
If the atmospheric density ρatm in the accretion disk of an active galactic nucleus (AGN) is sufficiently low, scattering in the atmosphere can produce a non-blackbody emergent spectrum. For a given bolometric luminosity, at ultraviolet and optical wavelengths such disks have lower fluxes and apparently larger sizes as compared to disks that emit as blackbodies. We show that models in which ρatm is a sufficiently low fixed fraction of the interior density ρ can match the AGN STORM observations of NGC 5548 but produce disk spectral energy distributions that peak at shorter wavelengths than observed in luminous AGN in general. Thus, scattering atmospheres can contribute to the explanation for large inferred AGN accretion disk sizes but are unlikely to be the only contributor. In the appendix section, we present unified equations for the interior ρ and T in gas pressure-dominated regions of a thin accretion disk.PostprintPeer reviewe
High Speed photometry of faint Cataclysmic Variables: I. V359 Cen, XZ Eri, HY Lup, V351 Pup, V630 Sgr, YY Tel, CQ Vel, CE-315
The first results of a photometric survey of faint Cataclysmic Variables are
presented. V359 Cen is an SU UMa star with a period of 112 min. Even though
observed at quiescence, the mass transfer rate in this old nova may be
sufficiently high that in such a short period system (with its implied small
mass ratio) the disc may be excited into an elliptical shape with the result
that the observed brightness modulation gives a superhump period rather than an
orbital period. XZ Eri is an eclipsing dwarf nova with an orbital period
(P(orb)) of 88.1 min. HY Lup has only slight variability. V351 Pup, the remnant
of Nova Puppis 1991, has P(orb) = 2.837 h and a light curve that strongly
resembles that of the magnetic Nova Cyg 1975. V630 Sgr is the first nova
remnant that has both positive superhumps (P(sh) = 2.980 h) and eclipses
(P(orb) = 2.831 h). The YY Tel identification is somewhat uncertain. The
correct identification for CQ Vel is provided from discovery of its flickering
activity. The light curve of CE-315, a recently discovered AM CVn star, shows
similarities to that of GP Com, with no apparent orbital modulation.Comment: 8 pages, 12 figures, accepted for publication in MNRA
The Plant PTM Viewer, a central resource for exploring plant protein modifications
Posttranslational modifications (PTMs) of proteins are central in any kind of cellular signaling. Modern mass spectrometry technologies enable comprehensive identification and quantification of various PTMs. Given the increased numbers and types of mapped protein modifications, a database is necessary that simultaneously integrates and compares site‐specific information for different PTMs, especially in plants for which the available PTM data are poorly catalogued. Here, we present the Plant PTM Viewer (http://www.psb.ugent.be/PlantPTMViewer), an integrative PTM resource that comprises approximately 370,000 PTM sites for 19 types of protein modifications in plant proteins from five different species. The Plant PTM Viewer provides the user with a protein sequence overview in which the experimentally evidenced PTMs are highlighted together with an estimate of the confidence by which the modified peptides and, if possible, the actual modification sites were identified and with functional protein domains or active site residues. The PTM sequence search tool can query PTM combinations in specific protein sequences, whereas the PTM BLAST tool searches for modified protein sequences to detect conserved PTMs in homologous sequences. Taken together, these tools help to assume the role and potential interplay of PTMs in specific proteins or within a broader systems biology context. The Plant PTM Viewer is an open repository that allows the submission of mass spectrometry‐based PTM data to remain at pace with future PTM plant studies
The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines
We explore the variability of quasars in the MgII and Hbeta broad emission
lines and UV/optical continuum emission using the Sloan Digital Sky Survey
Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic
study of quasar variability to date: our study includes 29 spectroscopic epochs
from SDSS-RM over months, containing 357 quasars with MgII and 41 quasars
with Hbeta . On longer timescales, the study is also supplemented with
two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional
quasars with MgII and 572 quasars with Hbeta. The MgII emission line is
significantly variable ( 10% on 100-day timescales), a necessary
prerequisite for its use for reverberation mapping studies. The data also
confirm that continuum variability increases with timescale and decreases with
luminosity, and the continuum light curves are consistent with a damped
random-walk model on rest-frame timescales of days. We compare the
emission-line and continuum variability to investigate the structure of the
broad-line region. Broad-line variability shows a shallower increase with
timescale compared to the continuum emission, demonstrating that the broad-line
transfer function is not a -function. Hbeta is more variable than MgII
(roughly by a factor of ), suggesting different excitation mechanisms,
optical depths and/or geometrical configuration for each emission line. The
ensemble spectroscopic variability measurements enabled by the SDSS-RM project
have important consequences for future studies of reverberation mapping and
black hole mass estimation of quasars.Comment: 20 pages, 25 figures. ApJ accepted: minor revisions following referee
repor
Machine learning techniques for intermediate mass gap lepton partner searches at the large hadron collider
We consider machine learning techniques associated with the application of a boosted decision tree (BDT) to searches at the Large Hadron Collider (LHC) for pair-produced lepton partners which decay to leptons and invisible particles. This scenario can arise in the minimal supersymmetric Standard Model (MSSM), but can be realized in many other extensions of the Standard Model (SM). We focus on the case of intermediate mass splitting (∼30 GeV) between the dark matter (DM) and the scalar. For these mass splittings, the LHC has made little improvement over LEP due to large electroweak backgrounds. We find that the use of machine learning techniques can push the LHC well past discovery sensitivity for a benchmark model with a lepton partner mass of ∼110 GeV, for an integrated luminosity of 300 fb-1, with a signal-to-background ratio of ∼0.3. The LHC could exclude models with a lepton partner mass as large as ∼160 GeV with the same luminosity. The use of machine learning techniques in searches for scalar lepton partners at the LHC could thus definitively probe the parameter space of the MSSM in which scalar muon mediated interactions between SM muons and Majorana singlet DM can both deplete the relic density through dark matter annihilation and satisfy the recently measured anomalous magnetic moment of the muon. We identify several machine learning techniques which can be useful in other LHC searches involving large and complex backgrounds
57 second oscillations in Nova Centauri 1986 (V842 Cen)
High speed photometry in 2008 shows that the light curve of V842 Cen
possesses a coherent modulation at 56.825 s, with sidebands at 56.598 s and
57.054 s. These have appeared since this nova remnant was observed in 2000 and
2002. We deduce that the dominant signal is the rotation period of the white
dwarf primary and the sidebands are caused by reprocessing from a surface
moving with an orbital period of 3.94 h. Thus V842 Cen is an intermediate polar
(IP) of the DQ Herculis subclass, is the fastest rotating white dwarf among the
IPs and is the third fastest known in a cataclysmic variable. As in other IPs
we see no dwarf nova oscillations, but there are often quasi-periodic
oscillations in the range 350 - 1500 s. There is a strong brightness modulation
with a period of 3.78 h, which we attribute to negative superhumps, and there
is an even stronger signal at 2.886 h which is of unknown origin but is
probably a further example of that seen in GW Lib and some other systems. We
used the Swift satellite to observe V842 Cen in the ultra-violet and in X-rays,
although no periodic modulation was detected in the short observations. The
X-ray luminosity of this object appears to be much lower than that of other IPs
in which the accretion region is directly visible.Comment: 6 pages, 10 figures, accepted for publication in MNRA
The Sloan Digital Sky Survey Reverberation Mapping Project: No Evidence for Evolution in the M-sigma Relation to z~1
We present host stellar velocity dispersion measurements for a sample of 88
broad-line quasars at 0.10.6) from the Sloan Digital Sky Survey
Reverberation Mapping (SDSS-RM) project. High signal-to-noise ratio coadded
spectra (average S/N~30 per 69 km/s pixel) from SDSS-RM allowed decomposition
of the host and quasar spectra, and measurement of the host stellar velocity
dispersions and black hole (BH) masses using the single-epoch (SE) virial
method. The large sample size and dynamic range in luminosity
(L5100=10^(43.2-44.7) erg/s) lead to the first clear detection of a correlation
between SE virial BH mass and host stellar velocity dispersion far beyond the
local universe. However, the observed correlation is significantly flatter than
the local relation, suggesting that there are selection biases in high-z
luminosity-threshold quasar samples for such studies. Our uniform sample and
analysis enable an investigation of the redshift evolution of the M-sigma
relation free of caveats by comparing different samples/analyses at disjoint
redshifts. We do not observe evolution of the M-sigma relation in our sample,
up to z~1, but there is an indication that the relation flattens towards higher
redshifts. Coupled with the increasing threshold luminosity with redshift in
our sample, this again suggests certain selection biases are at work, and
simple simulations demonstrate that a constant M-sigma relation is favored to
z~1. Our results highlight the scientific potential of deep coadded
spectroscopy from quasar monitoring programs, and offer a new path to probe the
co-evolution of BHs and galaxies at earlier times.Comment: replaced with the accepted version (minor changes and updated
references); ApJ in press; changed title to highlight the main resul
Association of past Chlamydia trachomatis infection with miscarriage: Chlamydia trachomatis infection and miscarriage
From Naples 1963 to Rome 2013 - A brief review of how the international research group on Ostracoda (IRGO) developed as a social communication system
The 1st International Symposiumon Ostracoda (ISO) was held in Naples (1963). The philosophy behind this symposiumand the logical outcome of what is nowknown as the International Research Group on Ostracoda (IRGO) are here reviewed, namely ostracodology over the last 50 years is sociologically analysed. Three different and important historic moments for the scientific achievements of this domain are recognised. The first one, between about 1963 and 1983, is related to applied research for the oil industry aswell as to the great interest in the better description of the marine environment by both zoologists and palaeontologists. Another important aspect during this period was thework by researchers dealing with Palaeozoic ostracods,who had their own discussion group, IRGPO. Gradually, the merger of this latter group with those dealing with post-Palaeozoic ostracods at various meetings improved the communication between the two groups of specialists. A second period was approximately delineated between 1983 and 2003. During this time-slice, more emphasis was addressed to environmental research with topics such as the study of global events and long-term climate change. Ostracodologists profited also from the research "politics" within national and international programmes. Large international research teams emerged using new research methods. During the third period (2003-2013), communication and collaborative research reached a global dimension. Amongst the topics of research we cite the reconstruction of palaeoclimate using transfer functions, the building of large datasets of ostracod distributions for regional and intercontinental studies, and the implementation of actions that should lead to taxonomic harmonisation. Projects within which molecular biological techniques are routinely used, combined with sophisticated morphological information, expanded now in their importance. The documentation of the ostracod description improved through new techniques to visualise morphological details, which stimulated also communication between ostracodologists. Efforts of making available ostracod information through newsletters and electronic media are evoked
The Sloan Digital Sky Survey Reverberation Mapping Project: Technical Overview
The Sloan Digital Sky Survey Reverberation Mapping project (SDSS-RM) is a
dedicated multi-object RM experiment that has spectroscopically monitored a
sample of 849 broad-line quasars in a single 7 deg field with the SDSS-III
BOSS spectrograph. The RM quasar sample is flux-limited to i_psf=21.7 mag, and
covers a redshift range of 0.1<z<4.5. Optical spectroscopy was performed during
2014 Jan-Jul dark/grey time, with an average cadence of ~4 days, totaling more
than 30 epochs. Supporting photometric monitoring in the g and i bands was
conducted at multiple facilities including the CFHT and the Steward Observatory
Bok telescopes in 2014, with a cadence of ~2 days and covering all lunar
phases. The RM field (RA, DEC=14:14:49.00, +53:05:00.0) lies within the CFHT-LS
W3 field, and coincides with the Pan-STARRS 1 (PS1) Medium Deep Field MD07,
with three prior years of multi-band PS1 light curves. The SDSS-RM 6-month
baseline program aims to detect time lags between the quasar continuum and
broad line region (BLR) variability on timescales of up to several months (in
the observed frame) for ~10% of the sample, and to anchor the time baseline for
continued monitoring in the future to detect lags on longer timescales and at
higher redshift. SDSS-RM is the first major program to systematically explore
the potential of RM for broad-line quasars at z>0.3, and will investigate the
prospects of RM with all major broad lines covered in optical spectroscopy.
SDSS-RM will provide guidance on future multi-object RM campaigns on larger
scales, and is aiming to deliver more than tens of BLR lag detections for a
homogeneous sample of quasars. We describe the motivation, design and
implementation of this program, and outline the science impact expected from
the resulting data for RM and general quasar science.Comment: 25 pages, submitted to ApJS; project website at http://www.sdssrm.or
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