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1

Nunes, Rafael. „Search for Sub-Solar Mass Binaries with Einstein Telescope and Cosmic Explorer“. Entropy 24, Nr. 2 (11.02.2022): 262. http://dx.doi.org/10.3390/e24020262.

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A possible detection of sub-solar mass ultra-compact objects would lead to new perspectives on the existence of black holes that are not of astrophysical origin and/or pertain to formation scenarios of exotic ultra-compact objects. Both possibilities open new perspectives for better understanding of our universe. In this work, we investigate the significance of detection of sub-solar mass binaries with components mass in the range: 10−2M⊙ up to 1M⊙, within the expected sensitivity of the ground-based gravitational waves detectors of third generation, viz., the Einstein Telescope (ET) and the Cosmic Explorer (CE). Assuming a minimum of amplitude signal-to-noise ratio for detection, viz., ρ=8, we find that the maximum horizon distances for an ultra-compact binary system with components mass 10−2M⊙ and 1M⊙ are 40 Mpc and 1.89 Gpc, respectively, for ET, and 125 Mpc and 5.8 Gpc, respectively, for CE. Other cases are also presented in the text. We derive the merger rate and discuss consequences on the abundances of primordial black hole (PBH), fPBH. Considering the entire mass range [10−2–1]M⊙, we find fPBH<0.70 (<0.06) for ET (CE), respectively.
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2

Gouliermis, Dimitrios, Alessandro Berton, Wolfgang Brandner, Thomas Henning und Markus Feldt. „The search for the sub-solar initial mass function in the Local Group“. Proceedings of the International Astronomical Union 1, S232 (November 2005): 261–64. http://dx.doi.org/10.1017/s1743921306000676.

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3

Garrett, M. A., S. Nair, R. W. Porcas und A. R. Patnaik. „A Search for Dark Matter in the Halos of Lensing Galaxies using VLBI“. Symposium - International Astronomical Union 173 (1996): 189–90. http://dx.doi.org/10.1017/s0074180900231264.

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Baryonic Dark Matter (BDM) candidates are segregated into two main mass ranges: (i) sub-solar mass dwarf stars (MACHOS) and (ii) ∼ 104–106M⊙ Very Massive Objects (VMOs). The lower mass range has been the target of the various micro-lensing programs but the first, tentative conclusions (see Stubbs et al. these proceedings) seem to suggest that MACHOs are unlikely to provide the bulk of the dark matter in the galactic halo. Meanwhile the upper mass range (104–106M⊙) remains largely unexplored. However, Wambsganss & Paczynski 1992 (hereafter WP92), have shown that this mass range is perfectly tuned to a straightforward and direct test: gravitational milli-lensing of macro-lensed images (Fig 1).
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4

Lovis, C., M. Mayor, F. Bouchy, F. Pepe, D. Queloz, S. Udry, W. Benz und C. Mordasini. „Towards the characterization of the hot Neptune/super-Earth population around nearby bright stars“. Proceedings of the International Astronomical Union 4, S253 (Mai 2008): 502–5. http://dx.doi.org/10.1017/s1743921308027051.

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AbstractThe HARPS search for low-mass extrasolar planets has been ongoing for more than 4 years, targeting originally about 400 bright FGK dwarfs in the solar neighbourhood. The published low-mass planetary systems coming from this survey are fully confirmed by subsequent observations, which demonstrate the sub-m/s long-term stability reached by HARPS. The complex RV curves of these systems have led us to focus on a smaller sample of stars, accumulating more data points per star. We perform a global search in our data to assess the existence of the large population of ice giants and super-Earths predicted by numerical simulations of planet formation. We indeed detect about 45 candidates having minimum masses below 30 M⊕ and orbital periods below 50 days. These numbers are preliminary since the existence of these objects has to be confirmed by subsequent observations. However, they indicate that about 30% of solar-type stars may have such close-in, low-mass planets. Some emerging properties of this low-mass population are presented. We finally discuss the prospects for finding transiting objects among these candidates, which may possibly yield the first nearby, transiting super-Earth.
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5

Hobson, M. J., X. Delfosse, N. Astudillo-Defru, I. Boisse, R. F. Díaz, F. Bouchy, X. Bonfils et al. „The SOPHIE search for northern extrasolar planets“. Astronomy & Astrophysics 625 (Mai 2019): A18. http://dx.doi.org/10.1051/0004-6361/201834890.

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We present the detection of a warm Neptune orbiting the M dwarf Gl 378, using radial velocity measurements obtained with the SOPHIE spectrograph at the Observatoire de Haute-Provence. The star was observed in the context of the SOPHIE exoplanet consortium’s sub-programme dedicated to finding planets around M dwarfs. Gl 378 is an M1 star, of solar metallicity, at a distance of 14.96 pc. The single planet detected, Gl 378 b, has a minimum mass of 13.02 MEarth and an orbital period of 3.82 days, which place it at the lower boundary of the hot Neptune desert. As one of only a few such planets around M dwarfs, Gl 378 b provides important clues to the evolutionary history of these close-in planets. In particular, the eccentricity of 0.1 may point to a high-eccentricity migration. The planet may also have lost part of its envelope due to irradiation.
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6

Unger, N., D. Ségransan, D. Queloz, S. Udry, C. Lovis, C. Mordasini, E. Ahrer et al. „The HARPS search for southern extra-solar planets“. Astronomy & Astrophysics 654 (Oktober 2021): A104. http://dx.doi.org/10.1051/0004-6361/202141351.

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Context. We present precise radial-velocity measurements of five solar-type stars observed with the HARPS Echelle spectrograph mounted on the 3.6-m telescope in La Silla (ESO, Chile). With a time span of more than 10 yr and a fairly dense sampling, the survey is sensitive to low mass planets down to super-Earths on orbital periods up to 100 days. Aims. Our goal was to search for planetary companions around the stars HD 39194, HD 93385, HD 96700, HD 154088, and HD 189567 and use Bayesian model comparison to make an informed choice on the number of planets present in the systems based on the radial velocity observations. These findings will contribute to the pool of known exoplanets and better constrain their orbital parameters. Methods. A first analysis was performed using the Data & Analysis Center for Exoplanets online tools to assess the activity level of the star and the potential planetary content of each system. We then used Bayesian model comparison on all targets to get a robust estimate on the number of planets per star. We did this using the nested sampling algorithm POLYCHORD. For some targets, we also compared different noise models to disentangle planetary signatures from stellar activity. Lastly, we ran an efficient Markov chain Monte Carlo algorithm for each target to get reliable estimates for the planets’ orbital parameters. Results. We identify 12 planets within several multiplanet systems. These planets are all in the super-Earth and sub-Neptune mass regime with minimum masses ranging between 4 and 13 M⊕ and orbital periods between 5 and 103 days. Three of these planets are new, namely HD 93385 b, HD 96700 c, and HD 189567 c.
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7

Klapdor-Kleingrothaus, H. V. „Perspectives of double beta and dark matter search as windows to new physics“. HNPS Proceedings 9 (11.02.2020): 130. http://dx.doi.org/10.12681/hnps.2779.

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Nuclear double beta decay provides an extraordinarily broad potential to search for beyond Standard Model physics, probing already now the TeV scale, on which new physics should manifest itself. These possibilities are reviewed here. First, the results of present generation experiments are presented. The most sensitive one of them - the Heidelberg-Moscow experiment in the Gran Sasso - probes the electron mass now in the sub eV region and has reached recently a limit of ~ 0.1 eV. This limit has striking influence on presently discussed neutrino mass scenarios. Basing to a large extent on the theoretical work of the Heidelberg Double Beta Group in the last two years, results are obtained also for SUSY models (R-parity breaking, sneutrino mass), leptoquarks (leptoquark-Higgs coupling), compositeness, right-handed W boson mass, test of special relativity and equivalence principle in the neutrino sector and others. These results are comfortably competitive to corresponding results from high-energy accelerators like TEVATRON, HERA, etc. One of the enriched 7Ge detectors also yields the most stringent limits for cold dark matter (WIMPs) to date by using raw data. Second, future perspectives of ßß research are discussed. A new Heidelberg experimental proposal (GENIUS) will allow to increase the sensitivity for Majorana neutrino masses from the present level of at best 0.1 eV down to 0.01 or even 0.001 eV. Its physical potential would be a breakthrough into the multi-TeV range for many beyond standard models. Its sensitivity for neutrino oscillation parameters would be larger than of all present terrestrial neutrino oscillation experiments and of those planned for the future. It could probe directly the large angle, and for almost degenerate neutrino mass scenarios even the small angle solution of the solar neutrino problem. It would further, already in a first step using only 100 kg of natural Ge detectors, cover almost the full MSSM parameter space for prediction of neutralinos as cold dark matter, making the experiment competitive to LHC in the search for supersymmetry. Finally GENIUS could be used as the first real time detector of solar pp neutrinos.
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8

Parise, Bérengère, Per Bergman und Karl Menten. „Characterizing the chemical pathways for water formation – a deep search for hydrogen peroxide“. Faraday Discuss. 168 (2014): 349–67. http://dx.doi.org/10.1039/c3fd00115f.

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In 2011, hydrogen peroxide (HOOH) was observed for the first time outside the solar system (Bergman et al., Astron. Astrophys., 2011, 531, L8). This detection appeared a posteriori to be quite natural, as HOOH is an intermediate product in the formation of water on the surface of dust grains. Following up on this detection, we present a search for HOOH in a diverse sample of sources in different environments, including low-mass protostars and regions with very high column densities, such as Infrared Dark Clouds (IRDCs). We do not detect the molecule in any other source than Oph A, and derive 3σ upper limits for the abundance of HOOH relative to H2 lower than that in Oph A for most sources. This result sheds a different light on our understanding of the detection of HOOH in Oph A, and shifts the question of why this source seems to be special. Therefore we rediscuss the detection of HOOH in Oph A, as well as the implications of the low abundance of HOOH, and its similarity with the case of O2. Our chemical models show that the production of HOOH is extremely sensitive to temperature, and is favored only in the range 20–30 K. The relatively high abundance of HOOH observed in Oph A suggests that the bulk of the material lies at a temperature in the range 20–30 K.
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9

Udry, S., M. Mayor und D. Queloz. „CORALIE–ELODIE new planets and planetary systems. Looking for fossil traces of formation and evolution“. Symposium - International Astronomical Union 202 (2004): 12–19. http://dx.doi.org/10.1017/s0074180900217403.

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6 new extra-solar planet candidates (HD 6434 b, HD 19994 b, HD 83443c, HD 92788b, HD 121504b, HD 190228b) are announced as part of our planet-search programmes in the northern and southern hemispheres. HD 83443 c is member of a 2-planet system with Saturnian and sub-Saturnian masses. Another system including a planet + a very low-mass brown dwarf orbiting HD 168443 is also presented. These 2 new systems and the new planetary detections rise to 25 the number of ELODIE and CORALIE candidates with minimum masses ≤20MJup. The orbital element distributions of giant-planet candidates, like the secondary mass function, the eccentricity and period distributions, compared to the equivalent distributions for spectroscopic binaries, strongly suggest different formation mechanisms for the two populations.
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10

Manchester, R. N. „The Ellery Lecture 1993: Pulsars—Setting the Standard“. Publications of the Astronomical Society of Australia 11, Nr. 1 (April 1994): 1–6. http://dx.doi.org/10.1017/s1323358000019561.

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AbstractOver 600 pulsars are now known, almost all of which lie in our Galaxy. Most pulsars have periods between 0 · 1 and a few seconds, but a very important sub-class, the ‘millisecond’ pulsars, have much shorter periods. Millisecond pulsars are often in a binary orbit with another star, suggesting that their short periods are a result of accreting mass from the companion star. They are also extraordinarily good clocks, with a stability comparable to that of the best atomic clocks. This combination of extreme period stability and binary motion has led to some very important results, including the first observational evidence for gravitational radiation and the first evidence for extra-solar planetary systems. It is probable that pulsars will be used to define the long-term standard of terrestrial time. A search of the southern sky using the Parkes radio telescope has found several millisecond pulsars which will make an important contribution to these precision-timing programs.
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11

Pathak, P., D. J. M. Petit dit de la Roche, M. Kasper, M. Sterzik, O. Absil, A. Boehle, F. Feng et al. „High-contrast imaging at ten microns: A search for exoplanets around Eps Indi A, Eps Eri, Tau Ceti, Sirius A, and Sirius B“. Astronomy & Astrophysics 652 (August 2021): A121. http://dx.doi.org/10.1051/0004-6361/202140529.

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Context. The direct imaging of rocky exoplanets is one of the major science goals of upcoming large telescopes. The contrast requirement for imaging such planets is challenging. However, the mid-IR (infrared) regime provides the optimum contrast to directly detect the thermal signatures of exoplanets in our solar neighbourhood. Aims. We aim to exploit novel fast-chopping techniques newly developed for astronomy with the aid of adaptive optics to look for thermal signatures of exoplanets around bright stars in the solar neighbourhood. Methods. We used the upgraded Very Large Telescope Imager and Spectrometer for the mid-InfraRed (VISIR) instrument with high-contrast imaging capability optimised for observations at 10 μm to look for exoplanets around five nearby (d < 4 pc) stars. The instrument provides an improved signal-to-noise ratio (S/N) by a factor of ~4 in the N-band compared to standard VISIR for a given S/N and time. Results. In this work, we achieve a detection sensitivity of sub-mJy, which is sufficient to detect a few Jupiter mass planets in nearby systems. Although no detections are made, we achieve most sensitive limits within <2″ for all the observed targets compared to previous campaigns. For ϵ Indi A and ϵ Eri, we achieve detection limits very close to the giant planets discovered by RV, with the limits on ϵ Indi A being the most sensitive to date. Our non-detection therefore supports an older age for ϵ Indi A. The results presented here are promising for high-contrast imaging and exoplanet detections in the mid-IR regime.
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12

KLAPDOR-KLEINGROTHAUS, H. V. „STATUS AND PERSPECTIVES OF DOUBLE BETA DECAY — WINDOW TO NEW PHYSICS BEYOND THE STANDARD MODEL OF PARTICLE PHYSICS“. International Journal of Modern Physics A 13, Nr. 23 (20.09.1998): 3953–92. http://dx.doi.org/10.1142/s0217751x98001852.

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Nuclear double beta decay provides an extraordinarily broad potential to search for beyond Standard Model physics, probing already now the TeV scale, on which new physics should manifest itself. These possibilities are reviewed here. First, the results of present generation experiments are presented. The most sensitive one of them — the Heidelberg–Moscow experiment in the Gran Sasso — probes the electron mass now in the sub eV region and will reach a limit of ~ 0.1 eV in a few years. Basing to a large extent on the theoretical work of the Heidelberg Double Beta Group in the last two years, results are obtained also for SUSY models (R-parity breaking, sneutrino mass), leptoquarks (leptoquark–Higgs coupling), compositeness, right-handed W boson mass and others. These results are comfortably competitive to corresponding results from high-energy accelerators like TEVATRON, HERA, etc. Second, future perspectives of ββ research are discussed. A new Heidelberg experimental proposal (GENIUS) is presented which would allow one to increase the sensitivity for Majorana neutrino masses from the present level of at best 0.1 eV down to 0.01 or even 0.001 eV. Its physical potential would be a breakthrough into the multi-TeV range for many beyond standard models. Its sensitivity for neutrino oscillation parameters would be higher than that for all present terrestrial neutrino oscillation experiments and of those planned for the future. It could probe directly the atmospheric neutrino problem and even the large angle solution of the solar neutrino problem. It would further, already in a first step, using only 100 kg of natural Ge detectors, cover almost the full MSSM parameter space for prediction of neutralinos as cold dark matter, making the experiment competitive to LHC in the search for supersymmetry.
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13

Lumbreras-Calle, A., C. Muñoz-Tuñón, J. Méndez-Abreu, J. M. Mas-Hesse, P. G. Pérez-González, B. Alcalde Pampliega, P. Arrabal Haro et al. „Star-forming galaxies at low-redshift in the SHARDS survey“. Astronomy & Astrophysics 621 (Januar 2019): A52. http://dx.doi.org/10.1051/0004-6361/201731670.

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Context. The physical processes driving the evolution of star formation (SF) in galaxies over cosmic time still present many open questions. Recent galaxy surveys allow now to study these processes in great detail at intermediate redshift (0 ≤ z ≤ 0.5). Aims. We build a complete sample of star-forming galaxies and analyze their properties, reaching systems with low stellar masses and low star formation rates (SFRs) at intermediate-to-low redshift. Methods. We use data from the SHARDS multiband survey in the GOODS-North field. Its depth (up to magnitude ⟨m3σ⟩~ 26.5) and its spectro-photometric resolution (R ~ 50) provides us with an ideal dataset to search for emission line galaxies (ELGs). We develop a new algorithm to identify low-redshift (z < 0.36) ELGs by detecting the [OIII]5007 and Hα emission lines simultaneously. We fit the spectral energy distribution (SED) of the selected sample, using a model with two single stellar populations. Results. We find 160 star-forming galaxies for which we derive equivalent widths (EWs) and absolute fluxes of both emission lines. We detect EWs as low as 12 Å, with median values for the sample of ~35 Å in [OIII]5007 and ~56 Å in Hα, respectively. Results from the SED fitting show a young stellar population with low median metallicity (36% of the solar value) and extinction (AV ~ 0.37), with median galaxy stellar mass ~108.5 M⊙. Gas-phase metallicities measured from available spectra are also low. ELGs in our sample present bluer colours in the UVJ plane than the median colour-selected star-forming galaxy in SHARDS. We suggest a new V-J colour criterion to separate ELGs from non-ELGs in blue galaxy samples. In addition, several galaxies present high densities of O-type stars, possibly producing galactic superwinds, which makes them interesting targets for follow-up spectroscopy. Conclusions. We have demonstrated the efficiency of SHARDS in detecting low-mass ELGs (~2 magnitudes deeper than previous spectroscopic surveys in the same field). The selected sample accounts for 20% of the global galaxy population at this redshift and luminosity, and is characterized by young SF bursts with sub-solar metallicities and low extinction. However, robust fits to the full SEDs can only be obtained including an old stellar population, suggesting the young component is built up by a recent burst of SF in an otherwise old galaxy.
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14

Rainot, A., M. Reggiani, H. Sana, J. Bodensteiner und O. Absil. „Carina High-contrast Imaging Project for massive Stars (CHIPS)“. Astronomy & Astrophysics 658 (Februar 2022): A198. http://dx.doi.org/10.1051/0004-6361/202141562.

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Context. Most massive stars belong to multiple systems, yet the formation process leading to such high multiplicity remains insufficiently understood. To help constrain the different formation scenarios that exist, insights into the low-mass end of the companion mass function of such stars is crucial. However, this is a challenging endeavour as (sub-)solar mass companions at angular separations (ρ) below 1″ (corresponding to 1000–3000 au in nearby young open clusters and OB associations) are difficult to detect due to the large brightness contrast with the central star. Aims. With the Carina High-contrast Imaging Project of massive Stars (CHIPS), we aim to obtain statistically significant constraints on the presence and properties of low-mass companions around massive stars in a previously unreachable observing window (Δmag ≳ 10 at ρ ≲ 1″). In the second paper of the series, we focus on the Trumpler 14 cluster, which harbours some of the youngest and most massive O-type stars in the Milky Way. Methods. We obtained VLT-SPHERE observations of seven O-type objects in Trumpler 14 using IRDIFS_EXT mode. These provide us with a 12″ × 12″ field of view (approximately ((3 × 3)×104 au) centred on each O star and allow us to search for companions at separations larger than 0″​​.15 (approx. 360 au) and down to magnitude contrast > 10 mag in the near-infrared. We used angular and spectral differential imaging along with Point Spread Function (PSF) fitting to detect sources and measure their flux relative to that of the central object. We then used grids of ATLAS9 and PHOENIX Local Thermodynamic Equilibrium (LTE) atmosphere models combined with (pre-)main-sequence evolutionary tracks to estimate the mass of the detected candidate companions. Results. We detected 211 sources with near-infrared magnitude contrast in the range of 2–12. Given the large surface number density of stars in Trumpler 14, one cannot reliably distinguish between cluster members and genuine companions for most of the detected sources. The closest companion, at only 0″​​.26, is characterised as a 1.4 M⊙ star with an age of 0.6 Myr, in excellent agreement with previous age estimates for Tr 14. The mass function peaks at about 0.4 M⊙ and presents a dearth of stars in the 0.5–0.8 M⊙ mass range compared to previous estimates of the initial mass function in Tr 14. While statistically significant, part of these differences may result from contamination of the K-band fluxes by circumstellar material. Conclusions. SPHERE is clearly suitable to probe the low-mass end of the mass function in the vicinity of massive stars. Follow-up SPHERE observations to obtain the full Y to K spectral energy distribution would allow for better constraints on the masses of the detected sources, and to confirm (or invalidate) the curious mass function that we derived for low-mass stars in the vicinity of the O-type objects in Trumpler 14.
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15

Nelson, C. J., S. Krishna Prasad und M. Mathioudakis. „Evolution of downflows in the transition region above a sunspot over short time-scales“. Astronomy & Astrophysics 640 (August 2020): A120. http://dx.doi.org/10.1051/0004-6361/202038155.

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Context. Downflows with potentially super-sonic velocities have been reported to occur in the transition region above many sunspots; however, how these signatures evolve over short time-scales in both spatial and spectral terms is still unknown and requires further research. Aims. In this article, we investigate the evolution of downflows detected within spectral lines sampling the transition region on time-scales of the order of minutes and we search for clues as to the formation mechanisms of these features in co-temporal imaging data. Methods. For the purposes of this article, we used high-resolution spectral and imaging data sampled by the Interface Region Imaging Spectrograph on the 20 and 21 May 2015 to identify and analyse downflows. Additionally, photospheric and coronal imaging data from the Hinode and Solar Dynamics Observatory satellites were studied to provide context about the wider solar atmosphere. Results. Four downflows were identified and analysed through time. The potential super-sonic components of these downflows had widths of around 2″ and were observed to evolve over time-scales of the order of minutes. The measured apparent downflow velocities were structured both in time and space, with the highest apparent velocities occurring above a bright region detected in Si IV 1400 Å images. Downflows with apparent velocities below the super-sonic threshold that was assumed here were observed to extend a few arcseconds away from the foot-points, suggesting that the potential super-sonic components are linked to larger-scale flows. The electron density and mass flux for these events were found to be within the ranges of 109.6–1010.2 cm−3 and 10−6.81–10−7.48 g cm−2 s−1, respectively. Finally, each downflow formed at the foot-point of thin “fingers”, extending out around 3–5″ in Si IV 1400 Å data with smaller widths (< 1″) than the super-sonic downflow components. Conclusions. Downflows can appear, disappear, and recur within time-scales of less than one hour in sunspots. As the potential super-sonic downflow signatures were detected at the foot-points of both extended fingers in Si IV 1400 SJI data and sub-sonic downflows in Si IV 1394 Å spectra, it is likely that these events are linked to larger-scale flows within structures such as coronal loops.
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16

Bohn, A. J., J. Southworth, C. Ginski, M. A. Kenworthy, P. F. L. Maxted und D. F. Evans. „A multiplicity study of transiting exoplanet host stars“. Astronomy & Astrophysics 635 (März 2020): A73. http://dx.doi.org/10.1051/0004-6361/201937127.

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Context. Many main-sequence stars are part of multiple systems. The effect of stellar multiplicity on planet formation and migration, however, is poorly understood. Aims. We study the multiplicity of stars hosting known transiting extra-solar planets to test competing theories on the formation mechanisms of hot Jupiters. Methods. We observed 45 exoplanet host stars using the infrared dual imaging spectrograph of the Spectro-Polarimetric High-Contrast Exoplanet Research (SPHERE) instrument at the Very Large Telescope to search for potential companions. For each identified candidate companion we determined the probability that it is gravitationally bound to its host by performing common proper motion checks and modelling of synthetic stellar populations around the host. In addition, we derived contrast limits as a function of angular separation to set upper limits on further companions in these systems. We converted the derived contrast into mass thresholds using AMES-Cond, AMES-Dusty, and BT-Settl models. Results. We detected new candidate companions around K2-38, WASP-72, WASP-80, WASP-87, WASP-88, WASP-108, WASP-118, WASP-120, WASP-122, WASP123, WASP-130, WASP-131, and WASP-137. The closest candidates were detected at separations of 0.′′124±0.′′007 and 0.′′189±0.′′003 around WASP-108 and WASP-131; the measured K-band contrasts indicate that these are stellar companions of 0.35 ± 0.02 M⊙ and 0.62−0.04+0.05 M⊙, respectively. Including the re-detection and confirmation of previously known companions in 13 other systems, we derived a multiplicity fraction of 55.4−9.4+5.9%. For the representative sub-sample of 40 hot Jupiter host stars among our targets, the derived multiplicity rate is 54.8−9.9+6.3%. Our data do not confirm any trend that systems with eccentric planetary companions are preferably part of multiple systems. On average, we reached a magnitude contrast of 8.5 ± 0.9 mag at an angular separation of 0.′′5. This allows us to exclude additional stellar companions with masses higher than 0.08M⊙ for almost all observed systems; around the closest and youngest systems, this sensitivity is achieved at physical separations as small as 10 au. Conclusions. Our study shows that SPHERE is an ideal instrument for detecting and characterising close companions to exoplanetary host stars. Although the second data release of the Gaia mission also provides useful constraints for some of the systems, the achieved sensitivity provided by the current data release of this mission is not good enough to measure parallaxes and proper motions for all detected candidates. For 14 identified companion candidates further astrometric epochs are required to confirm their common proper motion at 5σ significance.
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Drozdovskaya, Maria N., Laurent H. Coudert, Laurent Margulès, Audrey Coutens, Jes K. Jørgensen und Sébastien Manigand. „Successive deuteration in low-mass star-forming regions: The case of D2-methanol (CHD2OH) in IRAS 16293-2422“. Astronomy & Astrophysics 659 (März 2022): A69. http://dx.doi.org/10.1051/0004-6361/202142863.

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Context. Di-deuterated molecules are observed in the earliest stages of star formation at abundances of a few percent relative to their nondeuterated isotopologs, which is unexpected considering the scarcity of deuterium in the interstellar medium. With sensitive observations leading to the detection of a steadily increasing number of di-deuterated species, it is becoming possible to explore successive deuteration chains. Aims. The accurate quantification of the column density of di-deuterated methanol is a key piece of the puzzle that is missing in the otherwise thoroughly constrained family of D-bearing methanol in the deeply embedded low-mass protostellar system and astrochemical template source IRAS 16293-2422. A spectroscopic dataset for astrophysical purposes was built for CHD2OH and made publicly available to facilitate the accurate characterization of this species in astrochemical surveys. Methods. The newly computed line list and partition function were used to search for CHD2OH toward IRAS 16293-2422 A and B in data from the Atacama Large Millimeter/submillimeter Array (ALMA) Protostellar Interferometric Line Survey (PILS). Only nonblended, optically thin lines of CHD2OH were used for the synthetic spectral fitting. Results. The constructed spectroscopic database contains line frequencies and strengths for 7417 transitions in the 0–500 GHz frequency range. ALMA-PILS observations in the 329–363 GHz range were used to identify 105 unique, nonblended, optically thin line frequencies of CHD2OH for synthetic spectral fitting. The derived excitation temperatures and column densities yield high D/H ratios of CHD2OH in IRAS 16293-2422 A and B of 7.5 ± 1.1% and 7.7 ± 1.2%, respectively. Conclusions. Deuteration in IRAS 16293-2422 is not higher than in other low-mass star-forming regions (L483, SVS13-A, NGC 1333-IRAS2A, -IRAS4A, and -IRAS4B). Di-deuterated molecules consistently have higher D/H ratios than their mono-deuterated counterparts in all low-mass protostars, which may be a natural consequence of H–D substitution reactions as seen in laboratory experiments. The Solar System’s natal cloud, as traced by comet 67P/Churyumov–Gerasimenko, may have had a lower initial abundance of D, been warmer than the cloud of IRAS 16293-2422, or been partially reprocessed. In combination with accurate spectroscopy, a careful spectral analysis, and the consideration of the underlying assumptions, successive deuteration is a robust window on the physicochemical provenance of star-forming systems.
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Gibbs, Aidan, und Michael P. Fitzgerald. „Limits on the Auroral Generation of H3 + in Brown Dwarf and Extrasolar Giant Planet Atmospheres with the Keck Near Infrared Echelle Spectrograph“. Astronomical Journal 164, Nr. 2 (20.07.2022): 63. http://dx.doi.org/10.3847/1538-3881/ac7718.

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Abstract The molecular ion H3 + is a potentially powerful tracer of the ionospheres and thermal structures of Jovian planets but has never been detected in a planetary mass object outside of the solar system. Models predict that H3 + emission driven by EUV flux and solar wind on hot Jupiters, or by powerful aurorae on brown dwarfs, will be between 102 and 105 × more intense than that of Jupiter. If optimal conditions for the production of emission do exist, the emission may be detectable by current ground-based instruments or in the near future. We present the first search for H3 + line emission in brown dwarfs with Keck Near Infrared Echelle Spectrograph L′ high-resolution spectroscopy. Additionally, we survey stars hosting giant planets at semimajor axes near 0.1–0.2 au, which models suggest may be the best planetary targets. No candidate H3 + emission is found. The limits we place on the emission of H3 + from brown dwarfs indicate that auroral generation of H3 + in these environments likely does not linearly scale from the processes found on Jupiter, plausibly due to deeper atmospheric penetration by precipitating auroral electrons. Detection of H3 + emission in brown dwarfs may be possible with the James Webb Space Telescope, or future 33 m class telescopes.
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Saraiva, Samuel Vitor, Ricardo Ferreira Amorim, Frede Oliveira Carvalho und Leonardo Domingues. „Prognóstico de Radiação Solar Através Modelos que Combinam as Técnicas Wavelet e Redes Neurais (Forecast of Solar Radiation Through Models that Combine the Wavelet and Neural Networks Techniques)“. Revista Brasileira de Geografia Física 7, Nr. 5 (20.01.2015): 808. http://dx.doi.org/10.26848/rbgf.v7.5.p808-817.

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O prognostico de variáveis meteorológicas, como radiação solar, sempre foi de grande importância para a tomada de decisão em ocasião de ocorrências de eventos incomuns. Nesse contexto é justificável a busca por modelos matemáticos e estatísticos que produzam melhores prognósticos para tais variáveis. Desta forma investiga-se a estratégia de conjunção que se compõe de duas técnicas muito utilizadas no tratamento de série temporal; a transformada Wavelet que mostra analiticamente o sinal no domínio do tempo e da frequência; e as RNA’s a quais são modelos de inteligência artificial. A combinação dessas duas técnicas, o que se denomina modelo híbrido, tem se mostrado eficaz no prognóstico de variáveis meteorológicas. Os dados diários de radiação solar são do Instituto Agronômico do Paraná/PR coletados no período de 1990 até 1995. Neste trabalho são estudadas conjunções de modelos híbridos com Redes Neurais e técnicas Wavelets, apresentando o resumo de alguns dos modelos sintetizados na literatura, para o prognóstico de radiação solar. Tais modelos híbridos estudados se mostraram satisfatórios no prognóstico dessa variável, pois apresentaram um melhor desempenho em relação aos modelos que não são híbridos, sendo o modelo que se mostrou mais eficiente no prognóstico foi o que utiliza as sub-séries da decomposição como entrada da Rede Neural, pois apresenta regressão com valores significativos (R próximo a 1). A B S T R A C T The prognosis of meteorological variables such as solar radiation has always been of great importance for decision making in time of occurrence of unusual events. In this context it is justifiable to search for mathematical and statistical models that produce better prognosis for these variables. Thus investigates the combination strategy which uses two techniques widely used in the treatment time series; Wavelet transform analytically shows that the signal in the time domain and frequency; and the RNA's which models of artificial intelligence. The combination of these two techniques, which is called the hybrid models, has proven effective in predicting meteorological variables. Daily data of solar radiation are the Agronomic Institute of Parana / PR collected from 1990 to 1995. In this work conjunctions of hybrid models with neural networks and wavelets techniques are studied, presenting a summary of some of the synthesized models in the literature for the prediction of solar radiation. Such hybrid models studied were satisfactory prognosis with this variable because it showed better performance compared to models that are not hybrids in the model that is more efficient prognosis was that uses the sub-series decomposition as input the Network neural, it presents significant regression values (R close to 1). Keywords: Wavelet, Neural Network, Forecast.
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Arik, M., S. Aune, K. Barth, A. Belov, S. Borghi, H. Bräuninger, G. Cantatore et al. „Search for Sub-eV Mass Solar Axions by the CERN Axion Solar Telescope withHe3Buffer Gas“. Physical Review Letters 107, Nr. 26 (23.12.2011). http://dx.doi.org/10.1103/physrevlett.107.261302.

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Álvarez Melcón, A., S. Arguedas Cuendis, J. Baier, K. Barth, H. Bräuninger, S. Calatroni, G. Cantatore et al. „First results of the CAST-RADES haloscope search for axions at 34.67 μeV“. Journal of High Energy Physics 2021, Nr. 10 (Oktober 2021). http://dx.doi.org/10.1007/jhep10(2021)075.

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Abstract We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67 μeV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of gaγ ≳ 4 × 10−13 GeV−1 over a mass range of 34.6738 μeV < ma< 34.6771 μeV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25 μeV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavities.
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May Tzuc, Oscar, Jorge J. Chan-González, Iván E. Castañeda-Robles, Francisco Lezama-Zárraga, Moises Moheno-Barrueta, Mario Jiménez Torres und Roberto Best. „Multivariate inverse artificial neural network to analyze and improve the mass transfer of ammonia in a Plate Heat Exchanger-Type Absorber with NH3/H2O for solar cooling applications“. Energy Exploration & Exploitation, 11.02.2022, 014459872110731. http://dx.doi.org/10.1177/01445987211073175.

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This work presents a numerical approach to compute optimal operating conditions that maximize the absorption flux into a heat exchanger designed for absorption refrigeration systems. Experimental data were obtained from a test circuit that operates in bubble absorption mode with an inner vapor distributor into a Plate Heat Exchanger-type (PHE-type) and interacts with ammonia vapor, NH3-H2O refrigerant, and cooling water. An artificial neural network (ANN) was trained to correlate the thermal properties of the solution and absorption flux in function of easily measurable parameters (concentrations, mass flows, and pressures of saturated and diluted solutions, flow and temperature of the ammonium vapor, environment temperature, and solution temperature). According to results, ANN is adequate to correlate the operational parameters and the transport phenomena inside the heat exchanger with a precision > 99%. ANN also quantitatively identified the ammonium vapor flow (43.1%), dilute solution flow (18.1%), and dilute solution concentration (13.1%) as the variables most importantly in influencing absorption flux optimization. Subsequently, a multivariable inverse artificial neural network was applied to improve the mass transfer into the PHE-type.It was identified that simultaneous optimization of the ammonia and dilute concentration flow rates improves the absorption flow performance by up to 96.3% under a worst-case scenario (ammonia flow rate<1.4 kg/min) and even 7.04% when even when operating near the amino vapor flow limit (ammonia flow rate>2.0 kg/min). Finally, it was confirmed that incorporating the diluted solution concentration into the optimization contributes to improving the performance of the absorption process 1%. Results obtained are relevant in the search to produce more competitive absorption cooling systems, demonstrating the feasibility of improving the performance of heat exchangers without structural modifications. The proposed methodology represents an interesting option to be implemented to improve performance in solar cooling systems.
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Hamedani Golshan, Roya, Peter Schilke, Marta Sewilo, Thomas Moller, V. S. Veena und Gary A. Fuller. „High-mass star formation across the Large Magellanic Cloud. I. Chemical properties and hot molecular cores observed with ALMA at 1.2 mm“. Astronomy & Astrophysics, 07.05.2024. http://dx.doi.org/10.1051/0004-6361/202349077.

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The formation of massive stars passes through a so-called hot molecular core phase, where the temperature of molecular gas and dust rises to above 100 K within a size scale of approximately 0.1 pc. The hot molecular cores are rich in chemical compounds found in the gas phase, which are a great probe of ongoing star formation. To study the impact of the initial effects of metallicity (i.e., the abundance of elements heavier than helium) on star formation and the formation of different molecular species, we searched for hot molecular cores in the sub-solar metallicity environment of the Large Magellanic Cloud (LMC). We conducted Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations of 20 fields centered on young stellar objects (YSOs) distributed over the LMC in order to search for hot molecular cores in this galaxy. We detected a total of 65 compact 1.2 mm continuum cores in the 20 ALMA fields and analyzed their spectra with XCLASS software. The main temperature tracers are CH3OH and SO2 with more than two transitions detected in the observed frequency ranges. Other molecular lines with high detection rates in our sample are CS SO H^ CO^+ H^ CN HC^ N and SiO . More complex molecules, such as HNCO HDCO HC3N CH3CN and NH2CHO and multiple transitions of SO and SO2 isotopologues showed tentative or definite detection toward a small subset of the cores. According to the chemical richness of the cores and high temperatures from the XCLASS fitting, we report the detection of four hot cores and one hot core candidate. With one new hot core detection in this study, the number of detected hot cores in the LMC increases to seven. Six out of seven hot cores detected in the LMC to date are located in the stellar bar region of this galaxy. These six hot cores show emission from complex organic molecules (COMs), such as CH3OH CH3CN CH3OCHO and CH3OCH3 . The only known hot core in the LMC with no detection of COMs is located outside the bar region. The metallicity in the LMC presents a shallow gradient increasing from outer regions toward the bar. Various studies emphasize the interaction between the LMC and the Small Magellanic Cloud, which resulted in the mixing and inhomogeneity of the interstellar medium of the two galaxies. These interactions triggered a new generation of star formation in the LMC. We suggest that the formation of hot molecular cores containing COMs ensues from the new generation of stars forming in the more metal-rich environment of the LMC bar.
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Gulliver, Robyn. „Iconic 21st Century Activist "T-Shirt and Tote-Bag" Combination Is Hard to Miss These Days!“ M/C Journal 25, Nr. 4 (05.10.2022). http://dx.doi.org/10.5204/mcj.2922.

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Introduction Fashion has long been associated with resistance movements across Asia and Australia, from the hand-spun cotton Khadi of Mahatma Gandhi’s freedom struggle to the traditional ankle length robe worn by Tibetans in the ‘White Wednesday Movement’ (Singh et al.; Yangzom). There are many reasons why fashion and activism have been interlinked. Fashion can serve as a form of nonverbal communication (Crane), which can convey activists’ grievances and concerns while symbolising solidarity (Doerr). It can provide an avenue to enact individual agency against repressive, authoritarian regimes (Yangzom; Doerr et al.). Fashion can codify a degree of uniformity within groups and thereby signal social identity (Craik), while also providing a means of building community (Barry and Drak). Fashion, therefore, offers activists the opportunity to develop the three characteristics which unite a social or environmental movement: a shared concern about an issue, a sense of social identity, and connections between individuals and groups. But while these fashion functions map onto movement characteristics, it remains unclear whether activists across the world deliberately include fashion into their protest action repertoires. This uncertainty exists partly because of a research and media focus on large scale, mass protests (Lester and Hutchins), where fashion characteristics are immediately visible and amenable to retrospective interpretation. This focus helps explain the rich volume of research examining the manifestation of fashion in past protests, such as the black, red, and yellow colours worn during the 1988 Aboriginal Long March of Freedom, Justice, and Hope (Maynard Dress; Coghlan), and the pink anti-Trump ‘pussyhats’ (Thompson). However, the protest events used to identify these fashion characteristics are a relatively small proportion of actions used by environmental activists (Dalton et al.; Gulliver et al.), which include not only rallies and marches, but also information evenings, letter writing sessions, and eco-activities such as tree plantings. This article aims to respond to Barnard’s (Looking) call for more empirical work on what contemporary cultural groups visually do with what they wear (see also Gerbaudo and Treré) via a content analysis of 36,676 events promoted on Facebook by 728 Australian environmental groups between 2010 and 2019. The article firstly reports findings from an analysis of this dataset to identify how fashion manifests in environmental activism, building on research demonstrating the role of protest-related nonverbal communications, such as protest signage (Bloomfield and Doolin), images (Kim), and icons, slogans, and logos (Goodnow). The article then considers what activists may seek to achieve through incorporating fashion into their action repertoire, and whether this suggests solidarity with activists seeking to effect environmental change across the wider Asian region. Fashion Activism Fashion is created through a particular assemblage of clothes, accessories, and hairstyles (Barry and Drak), which in turn forms a prevailing custom or style of dress (Craik). It is a cultural practice, providing ‘real estate’ (Benda 7) for an individual to express their social roles (Craik) and political identity (Behnke). Some scholars argue that fashion became overtly political during the 1960s and 70s, as social movements politicised appearance (Edwards). This has only increased in relevance with the rise of far right, populist, and authoritarian regimes, whose sub-cultures enact politicised identities through their distinct fashion characteristics (Gaugele and Titton; Gaugele). Fashion can therefore play an important role in protest movements, as “political subjectivities, political authority, political power and discipline are rendered visible, and thereby real, by the way fashion co-establishes them” (Behnke 3). Across the literature scholars have identified two primary avenues by which fashion and activism are connected. The first of these relates to activism targeting the fashion industry. This type of activism is found in both Asia and Australia, and promotes sustainable consumption choices such as buying used goods and transforming existing items (Chung and Yim), as well as highlighting garment worker exploitation within the fashion industry (Khan and Richards). The second avenue is called ‘fashion activism’: the use of fashion to intentionally signal a message seeking to evoke social and/or political change (Thompson). In this conceptualisation, clothing is used to signify a particular message (Crane). An example of this type of fashion activism is the ‘SlutWalk’, a protest where participants deliberately wore outfits described as slutty or revealing as a response to victim-blaming of women who had experienced sexual assault (Thompson). A key element of fashion activism thus appears to be its message intentionality. Clothes are specifically utilised to convey a message, such as a grievance about victim-blaming, which can then be incorporated into design features displayed on t-shirts, pins, and signs both on the runway and in protest events (Titton). However, while this ‘sender/receiver’ model of fashion communication (Barnard, Fashion as) can be compelling for activists, it is complex in practice. A message receiver can never have full knowledge of what message the sender seeks to signify through a particular clothing item, nor can the message sender predict how a receiver will interpret that message. Particular arrangements of clothing only hold communicative power when they are easily interpreted and related to the movement and its message, usually only intelligible to a specific culture or subculture (Goodnow). Even within that subculture it remains problematic to infer a message from a particular style of dress, as demonstrated in examples where dress is used to imply sexual consent; for example, in rape and assault cases (Lennon et al.). Given the challenges of interpreting fashion, do activists appear to use the ‘real estate’ (Benda 7) afforded by it as a protest tool? To investigate this question a pre-existing dataset of 36,676 events was analysed to ascertain if, and how, environmental activism engages with fashion (a detailed methodology is available on the OSF). Across this dataset, event categories, titles, and descriptions were reviewed to collate events connecting environmental activism to fashion. Three categories of events were found and are discussed in the next section: street theatre, sustainable fashion practices, and disruptive protest. Street Theatre Street theatre is a form of entertainment which uses public performance to raise awareness of injustices and build support for collective action (Houston and Pulido). It uses costumes as a vehicle for conveying messages about political issues and for making demands visible, and has been utilised by protesters across Australia and Asia (Roces). Many examples of street theatre were found in the dataset. For example, Extinction Rebellion (XR) consistently promoted street theatre events via sub-groups such as the ‘Red Rebels’ – a dedicated team of volunteers specialising in costumed street theatre – as well as by inviting supporters to participate in open street theatre events, such as in the ‘Halloween Dead Things Disco’. Dressed as spooky skeletons (doot, doot) and ghosts, we'll slide and shimmy down Sydney's streets in a supernatural style, as we bring attention to all the species claimed by the Sixth Mass Extinction. These street theatre events appeared to prioritise spectacle rather than disruption as a means to attract attention to their message. The Cairns and Far North Environment Centre ‘Climate Action Float’, for example, requested that attendees: Wear blue and gold or dress as your favourite reef animal, solar panel, maybe even the sun itself!? Reef & Solar // Blue & Gold is the guiding theme but we want your creativity take it from there. Most groups used street theatre as one of a range of different actions organised across a period of time. However, Climacts, a performance collective which uses ‘spectacle and satire to communicate the urgency of the climate and biodiversity crisis’ (Climacts), utilised this tactic exclusively. Their Climate Guardians collective used distinctive angel costumes to perform at the Climate Conference of Parties 26, and in various places around Australia (see images on their Website). Fig. 1: Costumed protest against Downer EDI's proposed work on the Adani coalmine; Image by John Englart (CC BY-SA 2.0). Sustainable Fashion Practices The second most common type of event which connected fashion with activism were those promoting sustainable fashion practices. While much research has highlighted the role of activism in raising awareness of problems related to the fashion industry (e.g. Hirscher), groups in the dataset were primarily focussed on organising activities where supporters communally created their own fashion items. The most common of these was the ‘crafternoon’, with over 260 separate crafternoon events identified in the dataset. These events brought activists together to create protest-related kit such as banners, signs, and costumes from recycled or repurposed materials, as demonstrated by Hume Climate Action Now’s ‘Crafternoon for Climate’ event: Come along on Sunday arvo for a relaxed arvo making posters and banners for upcoming Hume Climate Action Now events… Bring: Paints, textas, cardboard, fabric – whatever you’ve got lying around. Don’t have anything? That’s cool, just bring yourself. Events highlighting fashion industry problems were less frequent and tended to prioritise sharing of information about the fashion industry rather than promoting protests. For example, Transition Town Vincent held a ‘Slowing Down Fast Fashion – Transition Town Vincent Movie Night’ while the Green Embassy promoted the ‘Eco Fashion Week’. This event, held in 2017, was described as Australia’s only eco-fashion week, and included runway shows, music, and public talks. Other events also focussed on public talks, such as a Conservation Council of ACT event called ‘Green Drinks Canberra October 2017: Summer Edwards on the fashion industry’ and a panel discussion organised by a group called SEE-Change entitled ‘The Sustainable Wardrobe’. Disruptive Protest and T-Shirts Few events in the dataset mentioned elements of fashion outside of street theatre or sustainable fashion practices, with only one organisation explicitly connecting fashion with activism in its event details. This group – Australian Youth Climate Coalition – organised an event called ‘Activism in Fashion: Tote Bags, T-shirts and Poster Painting!’, which asked: How can we consistently be involved in campaigning while life can be so busy? Can we still be loud and get a message across without saying a word? The iconic 21st century activist "t-shirt and tote-bag" combination is hard to miss these days! Unlike street theatre and sustainable fashion practices, fashion appeared to be a consideration for only a small number of disruptive protests promoted by environmental groups in Australia. XR Brisbane sought to organise a fashion parade during the 2019 Rebellion Week, while XR protesters in Melbourne stripped down to underwear for a march through Melbourne city arcades (see also Turbet). Few common fashion elements appeared consistently on individual activists participating in events, and these were limited to accessories, such as ‘Stop Adani’ earrings, or t-shirts sold for fundraising and promotional purposes. Indeed, t-shirts appeared to be the most promoted clothing item in the dataset, continuing a long tradition of their use in protests (e.g. Maynard, Blankets). Easy to create, suitable for displaying both text and imagery, t-shirts sharing anti-coal messages featured predominantly in the Stop Adani campaign, while yellow t-shirts were a common item in Knitting Nanna’s anti-coal seam gas mining protests. Fig. 2: Stop Adani earrings and t-shirts; Image by John Englart (CC BY-SA 2.0). The Role of Fashion in Environmental Activism As these findings demonstrate, fashion appears to be deliberately utilised in environmental activism primarily through street theatre and the promotion of sustainable fashion practices. While fewer examples of fashion in disruptive protest were found and no consistent fashion assemblage was identified, accessories and t-shirts were utilised by many groups. What may activists be seeking to achieve through incorporating fashion via street theatre and sustainable fashion practices? Some scholars have argued that incorporating fashion into protest allows activists to signal political dissent against authoritarian control. For example, Yanzoom noted that by utilising fashion as a means of communication, Tibetan activists were able to embody their political goals despite repression of speech and movement by political powerholders. However, a consistent fashion repertoire across protests in this Australian dataset was not found. The opportunities afforded by protected protest rights in Australia and absence of violent police repression of disruptive protests may be one explanation why distinctive dress such as the masks and black attire of Hong Kong pro-democracy protesters did not manifest in the dataset. Other scholars have observed that fashion sub-cultures also developed partly to express anti-establishment politics, such as the punk movement in the 1970s. Radical clothing accessorised by symbols, bright hair colours, body piercings, and heavy-duty books signalled opposition to the dominant political ideology (Craik). However, none of these purposes appeared to play a role in Australian environmental activism either. Instead, it appears that Maynard’s contention that Australian protest fashion barely deviates from everyday dress remains true today. Fashion within the events promoted in this large empirical dataset retained the ‘prevalence of everyday clothing’ (Maynard, Dress 111). The lack of a clearly discernible single protest fashion style within the dataset may be related to the shortcomings of the sender/receiver model of fashion communication. As Barnard (Fashion Statements) argued, fashion is not always used as a vehicle for conveying messages, but also as a platform for constructing and reproducing identity. Indeed, a multiplicity of researchers have noted how fashion acts as a signal of what social groups individuals belong to (see Roach-Higgins and Eicher). Activist groups have a variety of goals, which not only include promoting environmental change but also mobilising more people to join their cause (Gulliver et al., Understanding). Stereotyping can hinder achievement of these goals. It has been demonstrated, for example, that individuals who hold negative stereotypes of ‘typical’ activists are less likely to want to associate with them, and less likely to adopt their behaviours (Bashir et al.). Accordingly, some activist groups have been shown to actively promote dress associated with other identity groups, specifically to challenge cultural constructions of environmental activist stereotypes (see also Roces). For example, Bloomfield and Doolins’s study of the NZ anti-GE group MAdGE (Mothers against Genetic Engineering in Food and the Environment) demonstrated how visual protest artifacts conveyed the protesters’ social identity as mothers and customers rather than environmental activists, claiming an alternative cultural mandate for challenging the authority of science (see also Einwohner et al.). The data suggest that Australian activists are seeking to avoid this stereotype as well. The absence of a consistent fashion promoted within the dataset may reflect awareness of problematic stereotypes that activists may be then deliberately seeking to avoid. Maynard (Dress), for example, has noted how the everyday dress of Australian protesters serves to deflect stereotypical labelling of participants. This strategy is also mirrored by the changing nature of groups within the Australian environmental movement. The event database demonstrates that an increasing number of environmental groups are emerging with names highlighting non-stereotypical environmental identities: groups such as ‘Engineers Declare’ and ‘Bushfire Survivors for Climate Action’. Beyond these identity processes, the frequent use of costumed street theatre protest suggests that activists recognise the value of using fashion as a vehicle for communicating messages, despite the challenges of interpretation described above. Much of the language used to promote street theatre in the Facebook event listings suggests that these costumes were deliberately designed to signify a particular meaning, with individuals encouraged to dress up to be ‘a vehicle for myth and symbol’ (Lavender 11). It may be that costumes are also utilised in protest due to their suitability as an image event, convenient for dissemination by mass media seeking colourful and engaging imagery (Delicath and Deluca; Doerr). Furthermore, costumes, as with text or colours presented on t-shirts, may offer activists an avenue to clearly convey a visual message which is more resistant to stereotyping. This is especially relevant given that fashion can be re-interpreted and misinterpreted by audiences, as well as reframed and reinterpreted by the media (Maynard, Dress). While the prevalence of costumed performance and infrequent mentions of fashion in the dataset may be explained by stereotype avoidance and messaging clarity, sustainable fashion practices were more straightforward in intent. Groups used multiple approaches to educate audiences about sustainable fashion, whether through fostering sustainable fashion practices or raising awareness of fashion industry problems. In this regard, fashion in protest in Australia closely resembles Asian sustainable fashion activism (see e.g. Chon et al. regarding the Singaporean context). In particular, the large number of ‘crafternoons’ suggests their importance as sites of activism and community building. Craftivism – acts such as quilting banners, yarn bombing, and cross stitching feminist slogans – are used by many groups to draw attention to social, political and environmental issues (McGovern and Barnes). This type of ‘creative activism’ (Filippello) has been used to challenge aesthetic and political norms across a variety of contested socio-political landscapes. These activities not only develop activism skills, but also foster community (Barry and Drak). For environmental groups, these community building events can play a critical role in sustaining and supporting ongoing environmental activism (Gulliver et al., Understanding) as well as demonstrating solidarity with workers across Asia experiencing labour injustices linked to the fashion industry (Chung and Yim). Conclusion Studies examining protest fashion demonstrate that clothing provides a canvas for sharing protest messages and identities in both Asia and Australia (Benda; Yangzom; Craik). However, despite the fashion’s utility as communication tool for social and environmental movements, empirical studies of how fashion is used by activists in these contexts remain rare. This analysis demonstrates that Australian environmental activists use fashion in their action repertoire primarily through costumed street theatre performances and promoting sustainable fashion practices. By doing so they may be seeking to use fashion as a means of conveying messages, while avoiding stereotypes that can demobilise supporters and reduce support for their cause. Furthermore, sustainable fashion activism offers opportunities for activists to achieve multiple goals: to subvert the fast fashion industry, to provide participation avenues for new activists, to help build activist communities, and to express solidarity with those experiencing fast fashion-related labour injustices. These findings suggest that the use of fashion in protest actions can move beyond identity messaging to also enact sustainable practices while co-opting and resisting hegemonic ideas of consumerism. By integrating fashion into the vibrant and diverse actions promoted by environmental movements across Australia and Asia, activists can construct and perform identities while fostering the community bonds and networks from which movements demanding environmental change derive their strength. Ethics Approval Statement This study was approved by the Research Ethics Committee of the University of Queensland (2018000963). 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