bluuebunny/crossref_metadata_2025_split huggingface dataset:
Archival HST Search for Extragalactic Novae
Authors: Alis Sinan , Saygac A. Talat 
Published: January 2013

AbstractAn archival search for extragalactic novae was carried out using the data obtained with the Hubble Space Telescope (HST). Twenty-seven galaxies were examined where most of the targets are beyond the Local Group. Nova rates were calculated for the target galaxies and combined with other known nova rates to show dependence on galaxy types. Here we present the nova detections for six galaxies from our object list.
Optical and Near-Infrared Observations of Classical Nova V1723 Aql
Authors: Nagashima M. , Arai A. , Isogai M. , Arasaki T. , Kitao E. , Taguchi G. , Ikeda Y. , Kawakita H. , Yamanaka M. , Itoh R. , Sasada M. , Okushima T. , Uemura M. , Kawabata K. S. , Worters H. L. , Smits D. P. 
Published: January 2013

AbstractOptical and near-infrared observations of novae give us useful information for understanding the diversity of nova eruptions. Classical nova V1723 Aql was discovered by F. Kabashima and K. Nishiyama on 2010 September 11. We have conducted photometric and spectroscopic observations of V1723 Aql in both optical and near-infrared (NIR) wavelength regions since its discovery. The V-band decline time by 2 mag after the maximum, t2, was ~12 d. The apparent Fe II emission lines were also seen in the optical spectra. The Rc- and Ic-band light curves exhibited rapid declines (0.16 mag d−1 in Rc) 20 days after the visual maximum, while the NIR (J, H, and Ks) showed slow decline rates (~0.07 mag d−1). This rapid reddening suggests that dust particles formed during the very early phase of the expansion in V1723 Aql.
Obscuring Supersoft X-ray Sources in Stellar Winds
Authors: Nielsen Mikkel T. B. , Dominik Carsten , Nelemans Gijs 
Published: January 2013

AbstractWe investigate the possibility of obscuring supersoft X-ray sources in the winds of companion stars. We derive limits on the amount of circumstellar material needed to fully obscure a ‘canonical’ supersoft X-ray source in the Large Magellanic Cloud, as observed with the Chandra X-ray Observatory.
Why are Supersoft X-ray Fluxes So Weak in Early-type Galaxies? – A Clue to Type Ia SNe Progenitors –
Authors: Kato Mariko 
Published: January 2013

AbstractSupersoft X-ray fluxes in early-type galaxies provide an excellent test for Type Ia supernovae (SNe Ia) progenitors: the double degenerate (DD) scenario is believed to produce no supersoft sources (SSSs) except just before the SN Ia explosion, while the single degenerate (SD) scenario produces SSSs in some phases of the symbiotic channel. Recent observations of the supersoft X-ray flux of early-type galaxies show a remarkable agreement with theoretical predictions of the SD scenario, which thus turns out to be a strong support for the SD scenario, despite the original observations aimed at the opposite conclusion. Here I explain why X-ray fluxes are so weak in early-type galaxies. (1) Candidate binaries in the SD scenario become SSSs only during a short time on their way to SNe Ia explosions, because they spend a large part of their lifetime in a wind phase. (2) During the SSS phase, symbiotic stars emit very weak supersoft X-ray fluxes even if the WD is very massive. It should be emphasized that supersoft X-ray symbiotic stars are very rare and we need more observations to understand their nature.
Recurrent Novae: What Do We Know about Them?
Authors: Anupama G. C. 
Published: January 2013

AbstractRecurrent novae (RNe) belong to the group of cataclysmic variables that exhibit nova outbursts at intervals on the order of decades. They are rare, with 10 Galactic RNe known to date. Two are known in the LMC, while there are a few suspected RNe in M31. Nova outburst models require a high accretion rate on a massive white dwarf to explain the recurring nova outbursts, making this class of objects one of the most likely progenitor binary systems of Type Ia supernovae. The observational properties of the known Galactic recurrent novae are presented here, together with some discussion on the recent outbursts of RS Ophiuchi (2006), U Scorpii (2010), and T Pyxidis (2011).
Novae and Accreting White Dwarfs as Progenitors of Type Ia Supernovae
Authors: Kato Mariko 
Published: January 2013

AbstractI review various phenomena associated with mass-accreting white dwarfs (WDs) in relation to progenitors of Type Ia supernovae (SNe Ia). The WD mass can be estimated from light curve analysis in multiwavelength bands based on the theory of optically thick winds. In the single degenerate scenario of SNe Ia, two main channels are known, i.e., WD + main sequence (MS) channel and WD + red giant (RG) channel. In each channel, a typical binary undergoes three evolutionary stages before explosion, i.e., the wind phase, supersoft X-ray source (SSS) phase, and recurrent nova phase, in this order because the accretion rate decreases with time as the companion mass decreases. For some accreting WDs we can identify the corresponding stage of evolution. Intermittent supersoft X-ray sources like RX J0513.9−6951 and V Sge correspond to wind phase objects. For the SSS phase, CAL 87-type objects correspond to the WD+MS channel. For the WD + RG channel, soft X-ray observations of early type galaxies give statistical evidence of SSS phase binaries. Recurrent novae of U Sco-type and RS Oph-type correspond to the WD + MS channel and WD + RG channel, respectively. The majority of recurrent novae host a very massive WD (≳ 1.35 M⊙) and often show a plateau phase in their optical light curves corresponding to the long-lasting supersoft X-ray phase. These properties are indications of increasing WD masses.
Double White Dwarf Merger Rates
Authors: Toonen Silvia , Nelemans Gijs , Zwart Simon Portegies 
Published: January 2013

AbstractType Ia supernovae (SNe Ia) are very successfully used as standard candles on cosmological distance scales, but so far the nature of the progenitor(s) is unclear. A possible scenario for SNe Ia are merging carbon/oxygen white dwarfs with a combined mass exceeding the Chandrasekhar mass. We determine the theoretical rates and delay time distribution of these mergers for two different common envelope prescriptions and metallicities. The shape of the delay time distributions is rather insensitive to the assumptions. The normalization is a factor ~3–13 too low compared to observations.
Two Distributions Shedding Light on Type Ia Supernovae Progenitors: Delay Times and G-Dwarf Metallicities
Authors: Mennekens Nicki , Vanbeveren Dany , De Greve Jean-Pierre , De Donder Erwin 
Published: January 2013

AbstractUsing a population number synthesis code with detailed binary evolution, we calculate the distribution of the number of Type Ia supernovae as a function of time after starburst. This is done for both main progenitor scenarios (single degenerate and double degenerate), but also with various evolutionary assumptions (such as mass transfer efficiency, angular momentum loss, and common envelope description). The comparison of these theoretically predicted delay time distributions with observations in elliptical galaxies then allows us to constrain the evolutionary scenarios and parameters. From the morphological shape of the distributions, we conclude that all supernovae Ia cannot be produced through the single degenerate scenario alone, with the best match being obtained when both scenarios contribute. Within the double degenerate scenario, most systems go through a phase of quasi-conservative, stable Roche lobe overflow. We propose stellar rotation as a possible solution for the underestimation of the absolute numbers of events predicted by many theoretical population synthesis studies. A brief comparison with these other studies is made, showing good correspondence under the nontrivial condition of equivalent assumptions. We also investigate the influence of different supernova Ia progenitors and evolutionary parameters on the theoretical distribution of the iron abundance of G-type dwarfs in the Galactic disk. These stars are good indicators of the entire chemical history of the Galaxy, and their predicted metallicity distribution can also be compared to the observed ones. This again limits the number of acceptable combinations of assumptions. Supporting previous results, the best correspondence is found in the case where both the single and double degenerate scenario contribute.
Type Ia Supernovae and the Uncertainties in their Progenitor Evolution
Authors: Claeys J. S. W. , Pols O. R. , Izzard R. G. 
Published: January 2013

AbstractWe use binary population synthesis to study the main proposed channels leading to Type Ia supernovae, the single degenerate channel (SD) and double degenerate channel (DD). For this purpose, we discuss the progenitor evolution and the influence of the common envelope efficiency, αce, on the rate of the different channels. Our study demonstrates the large αce-dependence of both channels, especially for the SD channel.
Thermonuclear Supernova Explosions from White Dwarfs in Different Progenitor Systems
Authors: Röpke F. K. , Sim S. A. , Fink M. , Pakmor R. , Kromer M. , Seitenzahl I. R. , Ruiter A. J. , Hillebrandt W. 
Published: January 2013

AbstractSeveral progenitor scenarios have been suggested for Type Ia supernovae. Here we discuss the consequences for the explosion mechanism and for observables of some of them, which are explored by means of multi-dimensional hydrodynamic and radiation transfer simulations. While the observables predicted from delayed detonations of Chandrasekhar-mass white dwarfs agree reasonably well with the data, the corresponding progenitor systems may be too rare to account for the observed rate of Type Ia supernovae. Several alternatives are investigated of which violent mergers of two white dwarfs and, perhaps, double detonations of sub-Chandrasekhar mass white dwarfs hold promise for reproducing the observables of normal Type Ia supernovae.
Type Ia Supernovae from Sub-Chandrasekhar Mass White Dwarfs
Authors: Sim Stuart A. , Röpke Friedrich K. , Kromer Markus , Fink Michael , Ruiter Ashley J. , Seitenzahl Ivo R. , Pakmor Rüdiger , Hillebrandt Wolfgang 
Published: January 2013

AbstractWe argue that detonations of sub-Chandrasekhar mass white dwarfs can lead to bright explosions with light curves and spectra similar to those of observed Type Ia supernovae. Given that binary systems containing accreting sub-Chandrasekhar mass white dwarfs should be common, this suggests that a non-negligible fraction of the observed Type Ia supernova rate may arise from sub-Chandrasekhar mass explosions, if they can be ignited. We discuss aspects of how such explosions might be realized in nature and both merits and challenges associated with invoking sub-Chandrasekhar mass explosion models to account for observed Type Ia supernovae.
Hydrostatic 12C Burning in CO WDs: the Simmering Phase of SNe Ia Progenitors
Authors: Förster Francisco , Lesaffre Pierre , Podsiadlowski Philipp 
Published: January 2013

AbstractAmong the possible progenitor scenarios considered for Type Ia supernovae, those that involve a carbon–oxygen white dwarf (CO WD) accreting stably towards the Chandrasekhar mass should undergo a phase of hydrostatic carbon burning under high densities and strong convection: the simmering or carbon–flash phase, which can extend for a few hundred years before explosion. During this phase the progenitor CO WD can burn a small fraction of its carbon hydrostatically, releasing energy and ashes that make the star convective and able to capture electrons from the degenerate plasma. In this work we present simplified pre–supernova evolution models of CO WDs growing towards the Chandrasekhar mass accreting matter stably and evolving through the simmering phase towards ignition in order to explore the effects of different initial masses and cooling times in the final chemical composition of the WD before explosion. Preliminary results show that, as expected, denser systems at the start of the simmering phase undergo stronger neutronization. The amount of neutronization is less than what is found in the one–zone models of Chamulak et al. (2008), about a third, and can vary by about a factor of two depending on the exact path to explosion.
Optical Studies of the Low Velocity Gradient Type Ia Supernovae 2009an and 2009ig
Authors: Sahu D. K. , Anupama G. C. , Anto P. , Gurugubelli U. K. 
Published: January 2013

AbstractUBVRI photometry and medium resolution spectroscopy of two Type Ia supernovae, SN 2009an and SN 2009ig, are presented. Their Δm15(B) indicate these two SNe marginally deviate from “normal” Type Ia events. Spectroscopically, both SNe belong to the low velocity gradient group. The estimated mass of 56Ni ejected is almost a factor of two different for these two objects, with the estimates being ~0.4M⊙ for SN 2009an and ~0.8 M⊙ for SN 2009ig.
Late-Phase Observations of a Super-Chandrasekhar SN Ia
Authors: Yamanaka M. , Kawabata K. S. , Maeda K. , Tanaka M. , Yoshida M. , Hattori T. , Nomoto K. , Komatsu T. , Okushima T. 
Published: January 2013

AbstractA super-Chandrasekhar (SC) supernova (SN) has an extremely high luminosity and a slow decline rate of the light curve in the early-phase. We present late-phase observations of the SC SN 2009dc. We find that the optical luminosity a year after maximum is much fainter than that expected from its early luminosity. We attempt to fit the analytic light curve model to the observations using Arnett's rule. The model successfully explains the light curves until 120 days. This suggests that the extremely high luminosity originates from the 56Ni decay. We suggest that the late-phase decline would be caused by dust formation. The existence of strong carbon features in early-phase spectra would support this scenario. We also find a blend of [Ca ii] and [Ni ii] in its late-phase spectrum. This indicates that the calcium is distributed in the inner layer along with nickel and iron. We conclude that the mixing may occur in the inner parts of the ejecta.
Type Ia Progenitor Hunt in Ancient Remnants
Authors: Kerzendorf Wolfgang E. 
Published: January 2013

AbstractThere is broad agreement that the stars which explode as Type Ia supernovae are white dwarfs. They have accreted material in a binary system until they are near the Chandrasekhar mass and detonate/deflagrate. The two main scenarios for this accretion process are merging with a companion white dwarf (double degenerate scenario), or accretion from a main-sequence to red giant donor (single degenerate scenario). The donor star survives post-explosion and would provide substantial evidence for the single degenerate scenario, if found. Our team is analyzing stars in close proximity to Galactic Type Ia remnants to find surviving donor stars. In my talk I will introduce the different progenitor systems and the expected state for a donor star today. I will outline our search using high resolution spectroscopy and will present updated results.
On the Progenitor of SNR 0509-67.5
Authors: Pagnotta Ashley , Schaefer Bradley E. 
Published: January 2013

AbstractWe have used three independent methods to determine an accurate and precise geometric center of SNR 0509-67.5, at RA=05:09:31.208, DEC=−67:31:17.48 (J2000). This supernova, which occurred approximately 400 years ago in the Large Magellanic Cloud, was confirmed to be a Type Ia by Rest et al. (2005), Rest et al. (2008) based on spectra of a light echo from the eruption. If this supernova had a single-degenerate progenitor system, we would see the “leftover” companion star within a certain distance of the remnant's center. Accounting for an offset due to enhanced ISM in the west-southwest quadrant of the remnant, we find the eruption position to be at RA=05:09:30.976, DEC=−67:31:17.90; the error circle which should contain any possible ex-companion star has a radius of 1.60″ for 99.73% (3-sigma) containment. This accounts for the proper motion of the stars, the possibility of kicks from the supernova, and asymmetries in the explosion and remnant expansion. We find no possible ex-companion stars within this ellipse, to a limiting magnitude of V=26.9: there are no red giants, which precludes symbiotic progenitors, no subgiants, which when combined with the lack of red giants precludes recurrent nova progenitors, and no main sequence stars with mass greater than 1.16 solar masses (V brighter than 22.7 mag), which precludes persistent supersoft X-ray source progenitors. Indeed, all published SD models are eliminated, so we conclude that this particular Type Ia supernova had a double-degenerate progenitor.
Binary Paths to Type Ia Supernovae Explosions: the Highlights
Authors: Ferrario Lilia 
Published: January 2013

AbstractThis symposium was focused on the hunt for the progenitors of Type Ia supernovae (SNe Ia). Is there a main channel for the production of SNe Ia? If so, are these elusive progenitors single degenerate or double degenerate systems? Although most participants seemed to favor the single degenerate channel, there was no general agreement on the type of binary system at play. An observational puzzle that was highlighted was the apparent paucity of supersoft sources in our Galaxy and also in external galaxies. The single degenerate channel (and as it was pointed out, quite possibly also the double degenerate channel) requires the binary system to pass through a phase of steady nuclear burning. However, the observed number of supersoft sources falls short by a factor of up to 100 in explaining the estimated birth rates of SNe Ia. Thus, are these supersoft sources somehow hidden away and radiating at different wavelengths, or are we missing some important pieces of this puzzle that may lead to the elimination of a certain class of progenitor? Another unanswered question concerns the dependence of SNe Ia luminosities on the age of their host galaxy. Several hypotheses were put forward, but none was singled out as the most likely explanation.It is fair to say that at the end of the symposium the definitive answer to the vexed progenitor question remained well and truly wide open.
CRAVAT: cancer-related analysis of variants toolkit
Authors: Douville Christopher , Carter Hannah , Kim Rick , Niknafs Noushin , Diekhans Mark , Stenson Peter D. , Cooper David N. , Ryan Michael , Karchin Rachel 
Published: January 2013

Abstract
Summary: Advances in sequencing technology have greatly reduced the costs incurred in collecting raw sequencing data. Academic laboratories and researchers therefore now have access to very large datasets of genomic alterations but limited time and computational resources to analyse their potential biological importance. Here, we provide a web-based application, Cancer-Related Analysis of Variants Toolkit, designed with an easy-to-use interface to facilitate the high-throughput assessment and prioritization of genes and missense alterations important for cancer tumorigenesis. Cancer-Related Analysis of Variants Toolkit provides predictive scores for germline variants, somatic mutations and relative gene importance, as well as annotations from published literature and databases. Results are emailed to users as MS Excel spreadsheets and/or tab-separated text files.
Availability: http://www.cravat.us/
Contact: karchin@jhu.edu
Supplementary information: Supplementary data are available at Bioinformatics online.
DSK: k-mer counting with very low memory usage
Authors: Rizk Guillaume , Lavenier Dominique , Chikhi Rayan 
Published: January 2013

Abstract
Summary: Counting all the k-mers (substrings of length k) in DNA/RNA sequencing reads is the preliminary step of many bioinformatics applications. However, state of the art k-mer counting methods require that a large data structure resides in memory. Such structure typically grows with the number of distinct k-mers to count. We present a new streaming algorithm for k-mer counting, called DSK (disk streaming of k-mers), which only requires a fixed user-defined amount of memory and disk space. This approach realizes a memory, time and disk trade-off. The multi-set of all k-mers present in the reads is partitioned, and partitions are saved to disk. Then, each partition is separately loaded in memory in a temporary hash table. The k-mer counts are returned by traversing each hash table. Low-abundance k-mers are optionally filtered. DSK is the first approach that is able to count all the 27-mers of a human genome dataset using only 4.0 GB of memory and moderate disk space (160 GB), in 17.9 h. DSK can replace a popular k-mer counting software (Jellyfish) on small-memory servers.
Availability: http://minia.genouest.org/dsk
Contact: rayan.chikhi@ens-cachan.org
The impact of corporate social responsibility in food industry in product‐harm crises
Authors: Assiouras Ioannis , Ozgen Ozge , Skourtis George 
Published: January 2013

PurposeThe first purpose of this study is to analyse the impact of prior CSR information on the perceived degree of danger, attribution of blame, brand evaluation and buying intentions after a product‐harm crisis in the food industry. The second purpose is to examine the moderation effect of CSR importance ascribed by the consumers on the above mentioned relations.Design/methodology/approachAn experimental design consisting of three between‐subjects conditions was applied and three CSR initiative conditions were selected (positive, negative CSR and no CSR information as a control condition). In this framework, three different scenarios were designed and tested under the condition of a product‐harm crisis related to margarine.FindingsThis study highlights that CSR has an impact on attribution of blame, brand evaluation and buying intention but not on the perceived degree of danger. CSR importance has a moderation effect on the relationship between CSR and blame attribution, brand evaluation and buying intention.Practical implicationsCompanies in the food industry should generate CSR strategies and should develop favourable CSR history not only because CSR has an impact on brand evaluation and buying intention in routine situations but because it is a part of crisis management and response strategy as well.Originality/valueThere is lack of research directly emphasizing the role of CSR in product‐harm crises, in the food industry. Besides, the assessment of CSR as an antecedent assurance factor in crisis situations has significant meaning due to the high vulnerability of food industry.