Light with a self-torque: extreme-ultraviolet beams with time-varying orbital angular momentum

Twisted light fields carrying orbital angular momentum (OAM) provide powerful capabilities for applications in optical communications, microscopy, quantum optics and microparticle rotation. Here we introduce and experimentally validate a new class of light beams, whose unique property is associated with a temporal OAM variation along a pulse: the self-torque of light. Self-torque is a phenomenon that can arise from matter-field interactions in electrodynamics and general relativity, but to date, there has been no optical analog. In particular, the self-torque of light is an inherent property, which is distinguished from the mechanical torque exerted by OAM beams when interacting with physical systems. We demonstrate that self-torqued beams in the extreme-ultraviolet (EUV) naturally arise as a necessary consequence of angular momentum conservation in non-perturbative high-order harmonic generation when driven by time-delayed pulses with different OAM. In addition, the time-dependent OAM naturally induces an azimuthal frequency chirp, which provides a signature for monitoring the self-torque of high-harmonic EUV beams. Such self-torqued EUV beams can serve as unique tools for imaging magnetic and topological excitations, for launching selective excitation of quantum matter, and for manipulating molecules and nanostructures on unprecedented time and length scales.Comment: 24 pages, 4 figure

Physical properties of fullerene-containing Galactic planetary nebulae

We searched the Spitzer Space Telescope data archive for Galactic planetary nebulae (PNe), which show the characteristic 17.4 and 18.9 µm features due to C60, also known as buckminsterfullerene. Out of 338 objects with Spitzer/Infrared Spectrograph data, we found eleven C60-containing PNe, six of which (Hen2-68, IC2501, K3-62, M1-6, M1-9 and SaSt2-3) are new detections, not known to contain C60 prior to this work. The strongest 17.4 and 18.9 µm C60 features are seen in Tc1 and SaSt2-3, and these two sources also prominently show the C60 resonances at 7.0 and 8.5 µm. In the other nine sources, the 7.0 and 8.5 µm features due to C60 are much weaker. We analysed the spectra, along with ancillary data, using the photoionization code CLOUDY to establish the atomic line fluxes, and determine the properties of the radiation field, as set by the effective temperature of the central star. In addition, we measured the infrared spectral features due to dust grains. We find that the polycyclic aromatic hydrocarbon (PAH) profile over 6–9 µm in these C60-bearing carbon-rich PNe is of the more chemically processed class A. The intensity ratio of 3.3 to 11.3 µm PAH indicates that the number of C-atoms per PAH in C60-containing PNe is small compared to that in non-C60 PNe. The Spitzer spectra also show broad dust features around 11 and 30 µm. Analysis of the 30 µm feature shows that it is strongly correlated with the continuum, and we propose that a single carbon-based carrier is responsible for both the continuum and the feature. The strength of the 11 µm feature is correlated to the temperature of the dust, suggesting that it is at least partially due to a solid-state carrier. The chemical abundances of C60-containing PNe can be explained by asymptotic giant branch nucleosynthesis models for initially 1.5–2.5 M⊙ stars with Z = 0.004. We plotted the locations of C60-containing PNe on a face-on map of the Milky Way and we found that most of these PNe are outside the solar circle, consistent with low metallicity values. Their metallicity suggests that the progenitors are an older population

A Detailed Look at Chemical Abundances in Magellanic Cloud Planetary Nebulae. I. The Small Magellanic Cloud

We present an analysis of elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe), and focus initially on 14 PNe in the Small Magellanic Cloud (SMC). We derived the abundances from a combination of deep, high dispersion optical spectra, as well as mid-infrared (IR) spectra from the Spitzer Space Telescope. A detailed comparison with prior SMC PN studies shows that significant variations among authors of relative emission line flux determinations lead to systematic discrepancies in derived elemental abundances between studies that are >~0.15 dex, in spite of similar analysis methods. We used ionic abundances derived from IR emission lines, including those from ionization stages not observable in the optical, to examine the accuracy of some commonly used recipes for ionization correction factors (ICFs). These ICFs, which were developed for ions observed in the optical and ultraviolet, relate ionic abundances to total elemental abundances. We find that most of these ICFs work very well even in the limit of substantially sub-Solar metallicities, except for PNe with very high ionization. Our abundance analysis shows enhancements of He and N that are predicted from prior dredge-up processes of the progenitors on the AGB, as well as the well known correlations among O, Ne, S, and Ar that are little affected by nucleosynthesis in this mass range. We identified MG_8 as an interesting limiting case of a PN central star with a ~3.5 M_sun progenitor in which hot-bottom burning did not occur in its prior AGB evolution. We find no evidence for O depletion in the progenitor AGB stars via the O-N cycle, which is consistent with predictions for lower-mass stars. We also find low S/O ratios relative to SMC H_II regions, with a deficit comparable to what has been found for Galactic PNe.Comment: 9 figures, 6 tables; to be published in Ap

HST PanCET program: A Cloudy Atmosphere for the promising JWST target WASP-101b

We present results from the first observations of the Hubble Space Telescope (HST) Panchromatic Comparative Exoplanet Treasury (PanCET) program for WASP-101b, a highly inflated hot Jupiter and one of the community targets proposed for the James Webb Space Telescope (JWST) Early Release Science (ERS) program. From a single HST Wide Field Camera 3 (WFC3) observation, we find that the near-infrared transmission spectrum of WASP-101b contains no significant H$_2$O absorption features and we rule out a clear atmosphere at 13{\sigma}. Therefore, WASP-101b is not an optimum target for a JWST ERS program aimed at observing strong molecular transmission features. We compare WASP-101b to the well studied and nearly identical hot Jupiter WASP-31b. These twin planets show similar temperature-pressure profiles and atmospheric features in the near-infrared. We suggest exoplanets in the same parameter space as WASP-101b and WASP-31b will also exhibit cloudy transmission spectral features. For future HST exoplanet studies, our analysis also suggests that a lower count limit needs to be exceeded per pixel on the detector in order to avoid unwanted instrumental systematics.Comment: 7 pages, 4 figures, 1 table, Accepted to ApJ

New observations of the extended hydrogen exosphere of the extrasolar planet HD209458b

Atomic hydrogen escaping from the planet HD209458b provides the largest observational signature ever detected for an extrasolar planet atmosphere. However, the Space Telescope Imaging Spectrograph (STIS) used in previous observational studies is no longer available, whereas additional observations are still needed to better constrain the mechanisms subtending the evaporation process, and determine the evaporation state of other `hot Jupiters'. Here, we aim to detect the extended hydrogen exosphere of HD209458b with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST) and to find evidence for a hydrogen comet-like tail trailing the planet, which size would depend on the escape rate and the amount of ionizing radiation emitted by the star. These observations also provide a benchmark for other transiting planets, in the frame of a comparative study of the evaporation state of close-in giant planets. Eight HST orbits are used to observe two transits of HD209458b. Transit light curves are obtained by performing photometry of the unresolved stellar Lyman-alpha emission line during both transits. Absorption signatures of exospheric hydrogen during the transit are compared to light curve models predicting a hydrogen tail. Transit depths of (9.6 +/- 7.0)% and (5.3 +/- 10.0)% are measured on the whole Lyman-alpha line in visits 1 and 2, respectively. Averaging data from both visits, we find an absorption depth of (8.0 +/- 5.7)%, in good agreement with previous studies. The extended size of the exosphere confirms that the planet is likely loosing hydrogen to space. Yet, the photometric precision achieved does not allow us to better constrain the hydrogen mass loss rate.Comment: Accepted for publication in Astronomy & Astrophysics. 5 pages, 3 figure

Low Mass Stars and Brown Dwarfs in Praesepe

Presented are the results of a large and deep optical-near-infrared multi-epoch survey of the Praesepe open star cluster using data from the UKIDSS Galactic Clusters Survey. Multiple colour magnitude diagrams were used to select potential members and proper motions were used to assign levels of membership probability. From our sample, 145 objects were designated as high probability members (p >= 0.6) with most of these having been found by previous surveys although 14 new cluster members are also identified. Our membership assignment is restricted to the bright sample of objects (Z < 18). From the fainter sample, 39 candidates were found from an examination of multiple colour magnitude plots. Of these, 2 have small but significant membership probabilities. Finally, using theoretical models, cluster luminosity and mass functions were plotted with the later being fitted with a power law of alpha = 1.11 +/- 0.37 for the mass range 0.6 to 0.125 Msun and an assumed cluster age of 500 Myrs in the UKIDSS Z photometric band. Likewise taking an assumed cluster age of 1 Gyr we find alpha = 1.10 +/- 0.37. Similar values were also found for the J and K bands. These results compare favourably with the result of Kraus & Hillenbrand (2007) (alpha = 1.4 +/- 0.2) but are significantly lower than that of the more recent study conducted by Boudreault et al. (2009) (alpha = 1.8 +/- 0.1).Comment: 21 pages, 11 figures, 3 tables and 4 appendices. Accepted for publication in MNRAS, corrected a missing referenc

Incidence and management of inguinodynia after inguinal plasty

Background: Hernia is defined as a defect of fascial and muscle-aponeurotic structures, allowing the protrusion of elements. The most frequent is inguinal region, prevailing in men 3:1 vs female. The most frequent complications are persistent chronic pain.Methods: A descriptive, prospective and cross-sectional study was performed in postoperative inguinal plasty patients, using a laparoscopic approach and open approach, the presence or absence of inguinodynia was studied using the visual analogue pain scale (VAS) and the Semmes-Weinstein monofilament, in addition to a systematic investigation in the following PubMed, Medline, Clinical Key and Index Medicus databases, with articles from July 2019 to April 2020.Results: Inguinodynia was present in laparoscopic surgery and open approach, 58 patients had inguinodynia at two weeks associated with the inflammatory response of the tissues and the presence of a foreign body (mesh), 77% of the patients with persistence of pain at 3 months reported mild pain (VAS 1-4), 21% moderate pain that did not limit their daily activities (VAS 5-8) and 2% of the patients reported severe pain which limited physical activity and effort   (VAS 9-10).Conclusions: Inguinodynia has an impact on hospital costs and quality life, we consider it is essential to domain the anatomical variants of the region. We propose an extensive follow-up of this group of patients, to make a comparison of diagnostic methods, as well as conservative management vs. modern techniques for pain control

Singularities and Topology of Meromorphic Functions

We present several aspects of the "topology of meromorphic functions", which we conceive as a general theory which includes the topology of holomorphic functions, the topology of pencils on quasi-projective spaces and the topology of polynomial functions.Comment: 21 pages, 1 figur

An Improved Brane Anti-Brane Action from Boundary Superstring Field Theory and Multi-Vortex Solutions

We present an improved effective action for the D-brane-anti-D-brane system obtained from boundary superstring field theory. Although the action looks highly non-trivial, it has simple explicit multi-vortex (i.e. codimension-2 multi-BPS D-brane) multi-anti-vortex solutions. The solutions have a curious degeneracy corresponding to different ``magnetic'' fluxes at the core of each vortex. We also generalize the brane anti-brane effective action that is suitable for the study of the inflationary scenario and the production of defects in the early universe. We show that when a brane and anti-brane are distantly separated, although the system is classically stable it can decay via quantum tunneling through the barrier.Comment: 24 pages, 1 figure, JHEP3.cls; v2: references added, tunneling rate discussion expande

Integral field spectroscopy of nitrogen overabundant blue compact dwarf galaxies

We study the spatial distribution of the physical properties and of oxygen and nitrogen abundances in three Blue Compact Dwarf Galaxiess (HS 0128+2832, HS 0837+4717 and Mrk 930) with a reported excess of N/O in order to investigate the nature of this excess and, particularly, if it is associated with Wolf-Rayet (WR) stars We have observed these BCDs by using PMAS integral field spectroscopy in the optical spectral range (3700 - 6900 {\AA}), mapping their physical-chemical properties, using both the direct method and appropriate strong-line methods. We make a statistical analysis of the resulting distributions and we compare them with the integrated properties of the galaxies. Our results indicate that outer parts of the three galaxies are placed on the "AGN-zone" of the [NII]/H{\alpha} vs. [OIII]/H{\beta} diagnostic diagram most likely due to a high N/O combined with the excitation structure in these regions. From the statistical analysis, it is assumed that a certain property can be considered as spatially homogeneous (or uniform) if a normal gaussian function fits its distribution in several regions of the galaxy. Moreover, a disagreement between the integrated properties and the mean values of the distribution usually appears when a gaussian does not fit the corresponding distribution. We find that for Mrk 930, the uniformity is found for all parameters, except for electron density and reddening. The rotation curve together with the H{\alpha} map and UV images, reveal a perturbed morphology and possible interacting processes. The N/O is found to be constant in the three studied objects at spatial scales of the order of several kpc so we conclude that the number of WR stars estimated from spectroscopy is not sufficient to pollute the ISM and to produce the observed N/O excess in these objectsComment: 17 pages, 14 figures, accepted for publication in Astronomy & Astrophysic