2,972 research outputs found
E-BOSS: An Extensive stellar BOw Shock Survey. II. Catalogue second release
Context. Stellar bow shocks have been studied not only observationally, but
also theoretically since the late 1980s. Only a few catalogues of them exist.
The bow shocks show emission along all the electromagnetic spectrum, but they
are detected more easily in infrared wavelengths. The release of new and
high-quality infrared data eases the discovery and subsequent study of new
objects. Aims. We search stellar bow-shock candidates associated with nearby
runaway stars, and gather them together with those found elsewhere, to enlarge
the list of the E-BOSS first release. We aim to characterize the bow-shock
candidates and provide a database suitable for statistical studies. We
investigate the low-frequency radio emission at the position of the bow-shock
features, that can contribute to further studies of high-energy emission from
these objects. Methods. We considered samples from different literature sources
and searched for bow-shaped structures associated with stars in the Wide-field
Infrared Survey Explorer (WISE) images. We looked for each bow-shock candidate
on centimeter radio surveys. Results. We reunited 45 bow-shock candidates and
generated composed WISE images to show the emission in different infrared
bands. Among them there are new sources, previously studied objects, and bow
shocks found serendipitously. Five bow shocks show evidence of radio emission.
Conclusions. Stellar bow shocks constitute an active field with open questions
and enormous amounts of data to be analyzed. Future research at all wavelengths
databases, and use of instruments like Gaia, will provide a more complete
picture of these objects. For instance, infrared spectral energy distributions
can give information about physical parameters of the bow shock matter. In
addition, dedicated high-sensitivity radio observations can help to understand
the radio- connection.Comment: 20 pages, 11 figures, and 8 tables. Accepted for publication in A&
Non-thermal radiation from a runaway massive star
We present a study of the radio emission from a massive runaway star. The
star forms a bow shock that is clearly observed in the infrared. We have
performed VLA observations under the assumption that the reverse shock in the
stellar wind might accelerate charged particles up to relativistic energies.
Non-thermal radio emission of synchrotron origin has been detected, confirming
the hypothesis. We have then modeled the system and we predict a spectral
energy distribution that extends up to gamma-rays. Under some simplifying
assumptions, we find that the intensity at high energies is too low to be
detected by current instruments, but the future Cherenkov Telescope Array might
detect the source.Comment: Accepted for publication in the proceedings of the conference "The
multi-wavelength view of Hot, Massive Stars", held in Liege, July 12-16 201
Egg parasitoid exploitation of plant volatiles induced by single or concurrent attack of a zoophytophagous predator and an invasive phytophagous pest
Zoophytophagous insect predators can induce physiological responses in plants by activating defence signalling pathways, but whether plants can respond to facultative phytophagy by recruiting natural enemies remains to be investigated. In Y-tube olfactometer bioassays, using a system including a Vicia faba plant, the zoophytophagous predator Podisus maculiventris and the egg parasitoid Telenomus podisi, we first demonstrated that T. podisi females are attracted by broad bean plants damaged by feeding activity of P. maculiventris and on which host egg masses had been laid, while they are not attracted by undamaged plants or plants damaged by feeding activity alone. In a second experiment, we evaluated the impact of the invasive phytophagous pest Halyomorpha halys on this plant volatile-mediated tritrophic communication. Results showed that the invasive herbivorous adults do not induce plants to recruit the native egg parasitoid, but they can disrupt the local infochemical network. In fact, T. podisi females are not attracted by volatiles emitted by plants damaged by H. halys feeding alone or combined with oviposition activity, nor are they attracted by plants concurrently infested by P. maculiventris and H. halys, indicating the specificity in the parasitoid response and the ability of the invasive herbivore in interrupting the semiochemical communication between plants and native egg parasitoids. To the best of our knowledge, this is the first study showing that zoophytophagous predator attacks induce indirect plant defences similarly to those defence strategies adopted by plants as a consequence of single or concurrent infestations of herbivorous insects
Chemical Ecology of Floral Resources in Conservation Biological Control
Conservation biological control aims to enhance populations of natural enemies of insect pests in crop habitats, typically by intentional provision of flowering plants as food resources. Ideally, these flowering plants should be inherently attractive to natural enemies to ensure that they are frequently visited. We review the chemical ecology of floral resources in a conservation biological control context, with a focus on insect parasitoids. We highlight the role of floral volatiles as semiochemicals that attract parasitoids to the food resources. The discovery that nectar-inhabiting microbes can be hidden players in mediating parasitoid responses to flowering plants has highlighted the complexity of the interactions between plants and parasitoids. Furthermore, because food webs in agroecosystems do not generally stop at the third trophic level, we also consider responses of hyperparasitoids to floral resources. We thus provide an overview of floral compounds as semiochemicals from a multitrophic perspective, and we focus on the remaining questions that need to be addressed to move the field forward
A mobile application for assessment of air pollution exposure
In this paper the architecture of a mobile air quality monitoring system is introduced. A mobile application will act as a personal assistant, monitoring and giving advices about gas pollutants daily exposure. Currently in development stage as part of a larger air quality monitoring system project, the application will enable users to monitor their daily exposure to gas pollutants by combining user location data and urban air quality information provided by the network of fixed monitoring stations of the city of Palermo
Use of biorational insecticides for the control of Tuta absoluta (Meyrick) infestations on open field tomato
Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), the tomato leaf miner, is
one of the most devastating pests affecting tomato crops in Italy. Management
of T. absoluta was assessed in open-field tests using three biorational insecticides,
Azadirachtin, Bacillus thuringiensis var. kurstaki, and Beauveria
bassiana, and a combination of three synthetic insecticides, Emamectin, Indoxacarb
and Metaflumizone, as a control treatment. Our results showed that
only the combination of Azadirachtin \u2013 B. thuringiensis was able to reduce the
impact of tomato leaf miner on the fruit\u2019s marketable production similarly to
the control treatment. This finding suggests that biorational insecticides are a
good alternative to synthetic ones. Possible use of biorational insecticides in
the management of tomato leaf miner in organic farming system is discussed
Detection of nonthermal emission from the bow shock of a massive runaway star
The environs of massive, early-type stars have been inspected in recent years
in the search for sites where particles can be accelerated up to relativistic
energies. Wind regions of massive binaries that collide have already been
established as sources of high-energy emission; however, there is a different
scenario for massive stars where strong shocks can also be produced: the
bow-shaped region of matter piled up by the action of the stellar strong wind
of a runaway star interacting with the interstellar medium. We study the
bow-shock region produced by a very massive runaway star, BD+43 3654, to look
for nonthermal radio emission as evidence of a relativistic particle
population. We observed the field of BD+43 3654 at two frequencies, 1.42 and
4.86 GHz, with the Very Large Array (VLA), and obtained a spectral index map of
the radio emission. We have detected, for the first time, nonthermal radio
emission from the bow shock of a massive runaway star. After analyzing the
radiative mechanisms that can be at work, we conclude that the region under
study could produce enough relativistic particles whose radiation might be
detectable by forthcoming gamma-ray instruments, like CTA North.Comment: Accepted in Astronomy and Astrophysics Letter
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