23 research outputs found
Optical and Near-Infrared Observations of the Highly Reddened, Rapidly Expanding Type Ia Supernova 2006X in M100
We present extensive optical (UBVRI), near-infrared (JK) light curves and
optical spectroscopy of the Type Ia supernova (SN) 2006X in the nearby galaxy
NGC 4321 (M100). Our observations suggest that either SN 2006X has an
intrinsically peculiar color evolution, or it is highly reddened [E(B -
V)_{host} = 1.42+/-0.04 mag] with R_V = 1.48+/-0.06, much lower than the
canonical value of 3.1 for the average Galactic dust. SN 2006X also has one of
the highest expansion velocities ever published for a SN Ia. Compared with the
other SNe Ia we analyzed, SN 2006X has a broader light curve in the U band, a
more prominent bump/shoulder feature in the V and R bands, a more pronounced
secondary maximum in the I and near-infrared bands, and a remarkably smaller
late-time decline rate in the B band. The B - V color evolution shows an
obvious deviation from the Lira-Phillips relation at 1 to 3 months after
maximum brightness. At early times, optical spectra of SN 2006X displayed
strong, high-velocity features of both intermediate-mass elements (Si, Ca, and
S) and iron-peak elements, while at late times they showed a relatively blue
continuum, consistent with the blue U-B and B-V colors at similar epochs. A
light echo and/or the interaction of the SN ejecta and its circumstellar
material may provide a plausible explanation for its late-time photometric and
spectroscopic behavior. Using the Cepheid distance of M100, we derive a Hubble
constant of 72.7+/-8.2 km s^{-1} Mpc^{-1}(statistical) from the normalized
dereddened luminosity of SN 2006X. We briefly discuss whether abnormal dust is
a universal signature for all SNe Ia, and whether the most rapidly expanding
objects form a subclass with distinct photometric and spectroscopic properties.Comment: 48 pages, 20 figures and 11 tables. Accepted Version (ApJ, 2008,
March issue
The GALAH survey: New diffuse interstellar bands found in residuals of 872,000 stellar spectra
We use more than 872,000 mid-to-high resolution (R 20,000) spectra of
stars from the GALAH survey to discern the spectra of diffuse interstellar
bands (DIBs). We use four windows with the wavelength range from 4718 to 4903,
5649 to 5873, 6481 to 6739, and 7590 to 7890 \AA, giving a total coverage of
967 \AA. We produce 400,000 spectra of interstellar medium (ISM)
absorption features and correct them for radial velocities of the DIB clouds.
Ultimately, we combine the 33,115 best ISM spectra into six reddening bins with
a range of . A total
of 183 absorption features in these spectra qualify as DIBs, their fitted model
parameters are summarized in a detailed catalogue. From these, 64 are not
reported in the literature, among these 17 are certain, 14 are probable and 33
are possible. We find that the broad DIBs can be fitted with a multitude of
narrower DIBs. Finally, we create a synthetic DIB spectrum at unit reddening
which should allow us to narrow down the possible carriers of DIBs and explore
the composition of the ISM and ultimately better model dust and star formation
as well as to correct Galactic and extragalactic observations. The majority of
certain DIBs show a significant excess of equivalent width when compared to
reddening. We explain this with observed lines of sight penetrating more
uniform DIB clouds compared to clumpy dust clouds.Comment: 28 pages, 15 figures, 11 tables, accepted for publication in MNRA
The Distance to NGC 1316 (Fornax A) From Observations of Four Type Ia Supernovae
The giant elliptical galaxy NGC 1316 (Fornax A) is a well-studied member of
the Fornax Cluster and a prolific producer of Type Ia supernovae, having hosted
four observed events since 1980. Here we present detailed optical and
near-infrared light curves of the spectroscopically normal SN 2006dd. These
data are used, along with previously published photometry of the normal SN
1980N and SN 1981D, and the fast-declining, low-luminosity SN 2006mr, to
compute independent estimates of the host reddening for each supernova, and the
distance to NGC 1316. From the three normal supernovae, we find a distance of
17.8 +/- 0.3 (random) +/- 0.3 (systematic) Mpc for Ho = 72. Distance moduli
derived from the "EBV" and Tripp methods give values that are mutually
consistent to 4 -- 8%. Moreover, the weighted means of the distance moduli for
these three SNe for three methods agree to within 3%. This consistency is
encouraging and supports the premise that Type Ia supernovae are reliable
distance indicators at the 5% precision level or better. On the other hand, the
two methods used to estimate the distance of the fast-declining SN 2006mr both
yield a distance to NGC 1316 which is 25-30% larger. This disparity casts doubt
on the suitability of fast-declining events for estimating extragalactic
distances. Modest-to-negligible host galaxy reddening values are derived for
all four supernovae. Nevertheless, two of them (SN 2006dd and SN 2006mr) show
strong NaID interstellar lines in the host galaxy system. The strength of this
absorption is completely inconsistent with the small reddening values derived
from the supernova light curves if the gas in NGC 1316 is typical of that found
in the interstellar medium of the Milky Way. In addition, the equivalent width
of the NaID lines in SN 2006dd appear to have weakened significantly some
100-150 days after explosion.Comment: 50 pages, 13 figures, 10 tables; constructive comments welcome.
Accepted for publication in A
Microplastics in marine sediments near Rothera Research Station, Antarctica
publisher: Elsevier articletitle: Microplastics in marine sediments near Rothera Research Station, Antarctica journaltitle: Marine Pollution Bulletin articlelink: https://doi.org/10.1016/j.marpolbul.2018.05.068 content_type: article copyright: © 2018 Elsevier Ltd. All rights reserved
Galaxy And Mass Assembly (GAMA): The effect of galaxy group environment on active galactic nuclei
In galaxy clusters, efficiently accreting active galactic nuclei (AGN) are preferentially located in the infall regions of the cluster projected phase-space, and are rarely found in the cluster core. This has been attributed to both an increase in triggering opportunities for infalling galaxies, and a reduction of those mechanisms in the hot, virialised, cluster core. Exploiting the depth and completeness (98 per cent at r9.9 in 695 groups with 11.53≤log 10 (M 200 /M ⊙ )≤14.56 at z13.5 , AGN are preferentially found in the infalling galaxy population with 3.6σ confidence. At lower halo masses we observe no difference in AGN fraction between core and infalling galaxies. These observations support a model where a reduced number of low-speed interactions, ram pressure stripping and intra-group/cluster medium temperature, the dominance of which increase with halo mass, work to inhibit AGN in the cores of groups and clusters with log 10 (M 200 /M ⊙ )>13.5 , but do not significantly affect nuclear activity in cores of less massive structures
The Most Slowly Declining Type Ia Supernova 2001ay
We present optical and near-infrared photometry, as well as ground-based
optical spectra and Hubble Space Telescope ultraviolet spectra, of the Type Ia
supernova (SN) 2001ay. At maximum light the Si II and Mg II lines indicated
expansion velocities of 14,000 km/sec, while Si III and S II showed velocities
of 9,000 km/sec There is also evidence for some unburned carbon at 12,000
km/sec. SN 2001ay exhibited a decline-rate parameter Delta m_15(B) = 0.68 \pm
0.05 mag; this and the B-band photometry at t > +25 d past maximum make it the
most slowly declining Type Ia SN yet discovered. Three of four
super-Chandrasekhar-mass candidates have decline rates almost as slow as this.
After correction for Galactic and host-galaxy extinction, SN 2001ay had M_B =
-19.19 and M_V = -19.17 mag at maximum light; thus, it was not overluminous in
optical bands. In near-infrared bands it was overluminous only at the 2-sigma
level at most. For a rise time of 18 d (explosion to bolometric maximum) the
implied Ni-56 yield was (0.58 \pm 0.15)/alpha M_Sun, with alpha = L_max/E_Ni
probably in the range 1.0 to 1.2. The Ni-56 yield is comparable to that of many
Type Ia supernovae. The "normal" Ni-56 yield and the typical peak optical
brightness suggest that the very broad optical light curve is explained by the
trapping of the gamma rays in the inner regions.Comment: 57 pages, 22 figures. To be published in the Astronomical Journal
(September 2011
Connecting photometric and spectroscopic granulation signals with CHEOPS and ESPRESSO
Context. Stellar granulation generates fluctuations in photometric and spectroscopic data whose properties depend on the stellar type, composition, and evolutionary state. Characterizing granulation is key for understanding stellar atmospheres and detecting planets. Aims. We aim to detect the signatures of stellar granulation, link spectroscopic and photometric signatures of convection for main-sequence stars, and test predictions from 3D hydrodynamic models. Methods. For the first time, we observed two bright stars (Teff = 5833 and 6205 K) with high-precision observations taken simultaneously with CHEOPS and ESPRESSO. We analyzed the properties of the stellar granulation signal in each individual dataset. We compared them to Kepler observations and 3D hydrodynamic models. While isolating the granulation-induced changes by attenuating and filtering the p-mode oscillation signals, we studied the relationship between photometric and spectroscopic observables. Results. The signature of stellar granulation is detected and precisely characterized for the hotter F star in the CHEOPS and ESPRESSO observations. For the cooler G star, we obtain a clear detection in the CHEOPS dataset only. The TESS observations are blind to this stellar signal. Based on CHEOPS observations, we show that the inferred properties of stellar granulation are in agreement with both Kepler observations and hydrodynamic models. Comparing their periodograms, we observe a strong link between spectroscopic and photometric observables. Correlations of this stellar signal in the time domain (flux versus radial velocities, RV) and with specific spectroscopic observables (shape of the cross-correlation functions) are however difficult to isolate due to S/N dependent variations. Conclusions. In the context of the upcoming PLATO mission and the extreme precision RV surveys, a thorough understanding of the properties of the stellar granulation signal is needed. The CHEOPS and ESPRESSO observations pave the way for detailed analyses of this stellar process
The CHEOPS mission
The CHaracterising ExOPlanet Satellite (CHEOPS) was selected in 2012, as the
first small mission in the ESA Science Programme and successfully launched in
December 2019. CHEOPS is a partnership between ESA and Switzerland with
important contributions by ten additional ESA Member States. CHEOPS is the
first mission dedicated to search for transits of exoplanets using ultrahigh
precision photometry on bright stars already known to host planets. As a
follow-up mission, CHEOPS is mainly dedicated to improving, whenever possible,
existing radii measurements or provide first accurate measurements for a subset
of those planets for which the mass has already been estimated from
ground-based spectroscopic surveys and to following phase curves. CHEOPS will
provide prime targets for future spectroscopic atmospheric characterisation.
Requirements on the photometric precision and stability have been derived for
stars with magnitudes ranging from 6 to 12 in the V band. In particular, CHEOPS
shall be able to detect Earth-size planets transiting G5 dwarf stars in the
magnitude range between 6 and 9 by achieving a photometric precision of 20 ppm
in 6 hours of integration. For K stars in the magnitude range between 9 and 12,
CHEOPS shall be able to detect transiting Neptune-size planets achieving a
photometric precision of 85 ppm in 3 hours of integration. This is achieved by
using a single, frame-transfer, back-illuminated CCD detector at the focal
plane assembly of a 33.5 cm diameter telescope. The 280 kg spacecraft has a
pointing accuracy of about 1 arcsec rms and orbits on a sun-synchronous
dusk-dawn orbit at 700 km altitude.
The nominal mission lifetime is 3.5 years. During this period, 20% of the
observing time is available to the community through a yearly call and a
discretionary time programme managed by ESA.Comment: Submitted to Experimental Astronom
Fauna Europaea: Diptera -Brachycera
Link to publication Citation for published version (APA): Pape, T., Beuk, P., Pont, A. C., Shatalkin, A. I., Ozerov, A. L., Woźnica, A. J., ... de Jong, Y. (2015). Fauna Europaea: 3, [e4187]. https://doi.org/10.3897/BDJ.3.e4187 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract Fauna Europaea provides a public web-service with an index of scientific names (including important synonyms) of all extant multicellular European terrestrial and freshwater animals and their geographical distribution at the level of countries and major islands (east of the Urals and excluding the Caucasus region). The Fauna Europaea project comprises about 230,000 taxonomic names, including 130,000 accepted species and 14,000 accepted subspecies, which is much more than the originally projected number of 100,000 species. Fauna Europaea represents a huge effort by more than 400 contributing taxonomic specialists throughout Europe and is a unique (standard) reference suitable for many user communities in science, government, industry, nature conservation and education. The Diptera-Brachycera is one of the 58 Fauna Europaea major taxonomic groups, and data have been compiled by a network of 55 specialists. Within the two-winged insects (Diptera), the Brachycera constitute a monophyletic group, which is generally given rank of suborder. The Brachycera may be classified into the probably paraphyletic 'lower brachyceran grade' and the monophyletic Eremoneura. The latter contains the Empidoidea, the Apystomyioidea with a single Nearctic species, and the Cyclorrhapha, which in turn is divided into the paraphyletic 'aschizan grade' and the monophyletic Schizophora. The latter is traditionally divided into the paraphyletic 'acalyptrate grade' and the monophyletic Calyptratae. Our knowledge of the European fauna of Diptera-Brachycera varies tremendously among families, from the reasonably well known hoverflies (Syrphidae) to the extremely poorly known scuttle flies (Phoridae). There has been a steady growth in our knowledge of European Diptera for the last two centuries, with no apparent slow down, but there is a shift towards a larger fraction of the new species being found among the families of the nematoceran grade (lower Diptera), which due to a larger number of small-sized species may be considered as taxonomically more challenging. Most of Europe is highly industrialised and has a high human population density, and the more fertile habitats are extensively cultivated. This has undoubtedly increased the extinction risk for numerous species of brachyceran flies, yet with the recent re-discovery of Thyreophora cynophila (Panzer), there are no known cases of extinction at a European level. However, few national Red Lists have extensive information on Diptera. For the Diptera-Brachycera, data from 96 families containing 11,751 species are included in this paper