As the second largest cause of biodiversity loss worldwide, there is an urgent need to study the dynamics of biological invasions and identify factors limiting the distribution of invasive alien ...species. In the present study we analyze national-scale hunting bag data from Germany to predict the dispersal of raccoons in the largest non-native population of the species. Our focus is (1) to document changes in the distribution and abundance of raccoons, (2) to identify the species–environment relationship and predict which areas will be suitable for future colonization and (3) to apply a dispersal model to predict how fast the raccoon will spread to these areas. The increase from about 9000 harvested raccoons in 2000/01 to about 71,000 in 2011/12 reflects the extensive amount of suitable habitat for this omnivorous species in Central Europe. The best model for explaining range expansion in Germany identified coverage of agriculture and fragmentation and coverage of forests as the most important explanatory variables. The range of raccoons (area with harvest index >0.1 per 100 ha) increased from 26,515 km² in 2001 to 111,630 km² in 2011, and is predicted to expand to 252,940 km² by 2061, 71 % of the area of Germany. This vast area encompasses strategically important areas for conservation biology, such as wetlands with endangered native terrapins. The combination of merging of separated introduced populations and accelerating population growth highlights the potential for future impacts of raccoons on native communities, ecosystems and economic life in Germany and Central Europe.
The direct single-ionization cross section for Ar by positron impact has been measured in the region above the first ionization threshold. These measurements are compared to semiclassical ...calculations which give rise to a power law variation of the cross section in the threshold region. The experimental results appear to be in disagreement with extensions to the Wannier theory applied to positron impact ionization, with a smaller exponent than that calculated by most previous works. In fact, in this work, we see no difference in threshold behavior between the positron and electron cases. Possible reasons for this discrepancy are discussed.
We present ultraviolet (UV) observations of six nearby Type Ia supernovae (SNe Ia) obtained with the Hubble Space Telescope, three of which were also observed in the near-IR (NIR) with Wide-Field ...Camera 3. UV observations with the Swift satellite, as well as ground-based optical and NIR data provide complementary information. The combined data set covers the wavelength range 0.2–2 μm. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to E(B − V) = 1.4 mag. We study the wavelength-dependent extinction of each individual SN and find a diversity of reddening laws when characterized by the total-to-selective extinction R
V
. In particular, we note that for the two SNe with E(B − V) ≳ 1 mag, for which the colour excess is dominated by dust extinction, we find R
V
= 1.4 ± 0.1 and R
V
= 2.8 ± 0.1. Adding UV photometry reduces the uncertainty of fitted R
V
by ∼50 per cent allowing us to also measure R
V
of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe Ia are used for studying the expansion history of the Universe.
The identification and quantification of micro and nanoplastics (MPs and NPs respectively) requires the development of standardised analytical methods. Thermal analysis methods are generally not ...considered a method of choice for MPs analysis, especially in aqueous samples due to limited sample size introduction to the instrument, decreasing the detection levels. In this article, pyrolysis - Gas chromatography time of flight mass spectrometry (Py-GCToF) is used as a method of choice for detection of MPs and NPs due to its unprecedented detection capabilities, in combination with PTFE membranes as sample support, allow for smaller particle sizes (>0.1 μm) in water samples to be identified. The utilisation of these widely used membranes and the identification of several and specific (marker) ions for the three plastics in study (polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC)), allows for the extraction of individual plastics from complex signals at trace levels. The method was validated against a number of standards, containing known quantities of MPs. Detection levels were then determined for PVC and PS and were found to be below <50 μg/L, with repeatable data showing good precision (%RSD <20%). Further verification of this new method was achieved by the analysis of a complex sample, sourced from a river. The results were positive for the presence of PS with a semi-quantifiable result of 241.8 μg/L. Therefore PY-GCToF seems to be a fit for purpose method for the identification of MPs and NPs from complex mixtures and matrices which have been deposited on PTFE membranes.
•Py-GCToF presented as a standard methodology for identification and semi-quantification of micro and nanoplastics.•Fast sample preparation and obtainment of repeatable results even in real environmental aqueous samples.•Use of PTFE membranes as a sample support; an affordable, common and broadly applied material in the industry.
We report the detection of an extrasolar planet of mass ratio image in microlensing event MOA-2007-BLG-192. The best-fit microlensing model shows both the microlensing parallax and finite source ...effects, and these can be combined to obtain the lens masses of image for the primary and image for the planet. However, the observational coverage of the planetary deviation is sparse and incomplete, and the radius of the source was estimated without the benefit of a source star color measurement. As a result, the 2 capital sigma limits on the mass ratio and finite source measurements are weak. Nevertheless, the microlensing parallax signal clearly favors a substellar mass planetary host, and the measurement of finite source effects in the light curve supports this conclusion. Adaptive optics images taken with the Very Large Telescope (VLT) NACO instrument are consistent with a lens star that is either a brown dwarf or a star at the bottom of the main sequence. Follow-up VLT and/or Hubble Space Telescope (HST) observations will either confirm that the primary is a brown dwarf or detect the low-mass lens star and enable a precise determination of its mass. In either case, the lens star, MOA-2007-BLG-192L, is the lowest mass primary known to have a companion with a planetary mass ratio, and the planet, MOA-2007-BLG-192Lb, is probably the lowest mass exoplanet found to date, aside from the lowest mass pulsar planet.
We present the discovery of a substellar companion to the primary host lens in the microlensing event MOA-2012-BLG-006. The companion-to-host mass ratio is 0.016, corresponding to a companion mass of ...≈8 MJup(M∗/ 0.5 M⊙). Thus, the companion is either a high-mass giant planet or a low-mass brown dwarf, depending on the mass of the primary M∗. The companion signal was separated from the peak of the primary event by a time that was as much as four times longer than the event timescale. We therefore infer a relatively large projected separation of the companion from its host of ≈10 au(M∗/ 0.5 M⊙)1 / 2 for a wide range (3–7 kpc) of host star distances from the Earth. We also challenge a previous claim of a planetary companion to the lens star in microlensing event OGLE-2002-BLG-045.
The rise-time of Type II supernovae González-Gaitán, S; Tominaga, N; Molina, J ...
Monthly Notices of the Royal Astronomical Society,
08/2015, Letnik:
451, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We investigate the early-time light curves of a large sample of 223 Type II supernovae (SNe II) from the Sloan Digital Sky Survey and the Supernova Legacy Survey. Having a cadence of a few days and ...sufficient non-detections prior to explosion, we constrain rise-times, i.e. the durations from estimated first to maximum light, as a function of effective wavelength. At rest-frame g
′ band (λeff = 4722 Å), we find a distribution of fast rise-times with median of (7.5 ± 0.3) d. Comparing these durations with analytical shock models of Rabinak & Waxman and Nakar & Sari, and hydrodynamical models of Tominaga et al., which are mostly sensitive to progenitor radius at these epochs, we find a median characteristic radius of less than 400 solar radii. The inferred radii are on average much smaller than the radii obtained for observed red supergiants (RSG). Investigating the post-maximum slopes as a function of effective wavelength in the light of theoretical models, we find that massive hydrogen envelopes are still needed to explain the plateaus of SNe II. We therefore argue that the SN II rise-times we observe are either (a) the shock cooling resulting from the core collapse of RSG with small and dense envelopes, or (b) the delayed and prolonged shock breakout of the collapse of an RSG with an extended atmosphere or embedded within pre-SN circumstellar material.
Abstract
We present a study of the optical and near-infrared (NIR) spectra of SN 2013ai along with its light curves. These data range from discovery until 380 days after explosion. SN 2013ai is a ...fast declining Type II supernova (SN II) with an unusually long rise time, 18.9 ± 2.7 days in the
V
-band, and a bright
V
-band peak absolute magnitude of −18.7 ± 0.06 mag. The spectra are dominated by hydrogen features in the optical and NIR. The spectral features of SN 2013ai are unique in their expansion velocities, which, when compared to large samples of SNe II, are more than 1,000 km s
−1
faster at 50 days past explosion. In addition, the long rise time of the light curve more closely resembles SNe IIb rather than SNe II. If SN 2013ai is coeval with a nearby compact cluster, we infer a progenitor zero-age main-sequence mass of ∼17
M
⊙
. After performing light-curve modeling, we find that SN 2013ai could be the result of the explosion of a star with little hydrogen mass, a large amount of synthesized
56
Ni, 0.3–0.4
M
⊙
, and an explosion energy of 2.5–3.0 × 10
51
erg. The density structure and expansion velocities of SN 2013ai are similar to those of the prototypical SN IIb, SN 1993J. However, SN 2013ai shows no strong helium features in the optical, likely due to the presence of a dense core that prevents the majority of
γ
-rays from escaping to excite helium. Our analysis suggests that SN 2013ai could be a link between SNe II and stripped-envelope SNe.
PDF
