ABSTRACT
Ultraviolet (UV) transmission spectroscopy probes atmospheric escape, which has a significant impact on planetary atmospheric evolution. If unaccounted for, interstellar medium absorption ...(ISM) at the position of specific UV lines might bias transit depth measurements, and thus potentially affect the (non-)detection of features in transmission spectra. Ultimately, this is connected to the so called ‘resolution-linked bias’ effect. We present a parametric study quantifying the impact of unresolved or unconsidered ISM absorption in transit depth measurements at the position of the Mg ii h&k resonance lines (i.e. 2802.705 Å and 2795.528 Å, respectively) in the near-ultraviolet spectral range. We consider main-sequence stars of different spectral types and vary the shape and amount of chromospheric emission, ISM absorption, and planetary absorption, as well as their relative velocities. We also evaluate the role played by integration bin and spectral resolution. We present an open-source tool enabling one to quantify the impact of unresolved or unconsidered Mg ii ISM absorption in transit depth measurements. We further apply this tool to a few already or soon to be observed systems. On average, we find that ignoring ISM absorption leads to biases in the Mg ii transit depth measurements comparable to the uncertainties obtained from the observations published to date. However, considering the bias induced by ISM absorption might become necessary when analysing observations obtained with the next generation space telescopes with UV coverage (e.g. LUVOIR, HABEX), which will provide transmission spectra with significantly smaller uncertainties compared to what obtained with current facilities (e.g. HST).
Atmospheric escape is an important factor shaping the exoplanet population and hence drives our understanding of planet formation. Atmospheric escape from giant planets is driven primarily by the ...stellar X-ray and extreme ultraviolet (EUV) radiation. Furthermore, EUV and longer wavelength UV radiation power disequilibrium chemistry in the middle and upper atmospheres. Our understanding of atmospheric escape and chemistry, therefore, depends on our knowledge of the stellar UV fluxes. While the far-ultraviolet (FUV) fluxes can be observed for some stars, most of the EUV range is unobservable due to the lack of a space telescope with EUV capabilities and, for the more distant stars, due to interstellar medium absorption. Therefore, it becomes essential to have an indirect means for inferring EUV fluxes from features observable at other wavelengths. We present here analytic functions for predicting the EUV emission of F-, G-, K-, and M-type stars from the log
R
′
HK
activity parameter that is commonly obtained from ground-based optical observations of the Ca
II
H&K lines. The scaling relations are based on a collection of about 100 nearby stars with published log
R
′
HK
and EUV flux values, the latter of which are either direct measurements or inferences from high-quality FUV spectra. The scaling relations presented here return EUV flux values with an accuracy of about a factor of three, which is slightly lower than that of other similar methods based on FUV or X-ray measurements.
Summary
Ultrahigh performance concrete (UHPC) is one of the recent advancements in construction building materials and popularly used as a precast applications or strengthening material. The current ...paper attempts to improve understanding about fracture and failure mechanisms of UHPC application as a strengthening material using acoustic emission (AE) technique. The paper proposes an integrated and nonintegrated approach to relate the mechanical energy with AE energy for (i) undamaged reinforced concrete (RC) beams and (ii) damaged RC beams strengthened with UHPC. The integrated approach evaluates the damage mechanisms by evaluating sentry function (logarithmic ratio of mechanical and acoustic energy), while nonintegrated approach considers superimposition of flexure and AE response, load versus AE energy behavior and damage index. To validate the proposed approach, experiments are conducted on (i) control RC beams and (ii) RC beams strengthened with UHPC layers of t, 1.5t, and 2t thickness (where t = 10 mm). From the study, it is found that analysis of structures using both the approaches can overcome corresponding limitations. Hence, to completely characterize the damage, both methods are recommended.
Abstract
Ultraviolet observations of ultrahot Jupiters, exoplanets with temperatures over 2000 K, provide us with an opportunity to investigate if and how atmospheric escape shapes their upper ...atmosphere. Near-ultraviolet transit spectroscopy offers a unique tool to study this process owing to the presence of strong metal lines and a bright photospheric continuum as the light source against which the absorbing gas is observed. WASP-189b is one of the hottest planets discovered to date, with a dayside temperature of about 3400 K orbiting a bright A-type star. We present the first near-ultraviolet observations of WASP-189b, acquired with the Colorado Ultraviolet Transit Experiment (CUTE). CUTE is a 6U NASA-funded ultraviolet spectroscopy mission, dedicated to monitoring short-period transiting planets. WASP-189b was one of the CUTE early science targets and was observed during three consecutive transits in 2022 March. We present an analysis of the CUTE observations and results demonstrating near-ultraviolet (2500–3300 Å) broadband transit depth (
1.08
−
0.08
+
0.08
%
) of about twice the visual transit depth indicating that the planet has an extended, hot upper atmosphere with a temperature of about 15,000 K and a moderate mass-loss rate of about 4 × 10
8
kg s
−1
. We observe absorption by Mg
ii
lines (
R
p
/
R
s
of
0.212
−
0.061
+
0.038
) beyond the Roche lobe at >4
σ
significance in the transmission spectrum at a resolution of 10 Å, while at lower resolution (100 Å), we observe a quasi-continuous absorption signal consistent with a “forest” of low-ionization metal absorption dominated by Fe
ii
. The results suggest an upper atmospheric temperature (∼15,000 K), higher than that predicted by current state-of-the-art hydrodynamic models.
There are several significant advantages to 3D concrete printing (3DCP) over conventional concreting techniques. Structures are built by printing them one layer at a time. This study aimed to improve ...the usability and accessibility of this technology to solve on‐site issues, such as those caused by chemical admixture. In order to construct concrete that can be printed in three dimensions, researchers added many chemical admixtures in controlled quantities. This experiment's main goals were to prepare 3D printable concrete (3DPC) without chemical admixture and to evaluate fresh and hardened properties. Slump, flow, extrudability, buildability, open time, and penetrometer tests were carried out for fresh properties. Compressive, flexural, splitting tensile strength, and modulus of elasticity were evaluated for hardened properties. The printed specimens in the longitudinal direction exhibited higher compressive strength than in the downward and lateral directions. Similarly, higher flexural and splitting tensile strength in the longitudinal direction of printed specimens than in the downward and lateral direction. The results of developing 3DPC without chemical admixtures demonstrated good performance in fresh and hardened properties.
We present here the signal-to-noise (S/N) calculator developed for the Colorado Ultraviolet Transit Experiment (CUTE) mission. CUTE is a 6U CubeSat operating in the near-ultraviolet (NUV) observing ...exoplanetary transits to study their upper atmospheres. CUTE was launched into a low-Earth orbit in September 2021 and it is currently gathering scientific data. As part of the S/N calculator, we also present the error propagation for computing transit depth uncertainties starting from the S/N of the original spectroscopic observations. The CUTE S/N calculator is currently extensively used for target selection and scheduling. The modular construction of the CUTE S/N calculator enables its adaptation and can be used also for other missions and instruments.
To explore the quasi-periodic secular variations in sunspot activity, we have defined M cycles as a modified variant of Gleissberg cycles. We have shown evidence of the influence of the M cycles on ...monsoon rainfall variability and the incidence of catastrophic droughts in India using direct and proxy observations dating back more than 1200 years. From 1901 to 2018 AD, the solar cycle averages of all Indian summer monsoon rainfall (AISMR) and the probability of observing below or above normal AISMR showed correlations with changes in sunspot cycle amplitude. During 650–2015 AD, major droughts in India tended to occur during the M cycle’s minima and declining phases. Neither global warming trends nor volcanic eruptions were found to obscure the solar influence on Indian monsoon rainfall during the present M cycle era (1901–2018 AD).
Introduction: Glaucoma is characterised by structural damage to optic nerve head with corresponding visual field defects and often associated with increased Intraocular Pressure (IOP). It may be ...broadly classified as Primary Angle Closure Glaucoma (PACG) and Primary Open Angle Glaucoma (POAG). It is one of the leading causes of global blindness, and a major proportion occurs in Indian population. Aim: To study the correlation between pretreatment IOP and extent of visual field loss in PACG and POAG. Materials and Methods: A cross-sectional observational study was carried out in Regional Institute of Ophthalmology, Trivandrum, Kerala, India from April 2016 to May 2017. Newly diagnosed cases of PACG (25 patients-13 males, 12 females, mean age 58.72±10.07 years) and POAG (85 patients- 45 males, 40 females, mean age 60.28±10.42 years) underwent a detailed glaucoma evaluation which included IOP measurement with Goldmann applanation tonometer and visual field testing using Humphrey Field Analysis (HFA) 24-2 pattern. Mean Deviation (MD), Pattern Standard Deviation (PSD) and Advanced Glaucoma Intervention Score (AGIS) score was calculated from reliable visual field test result. All data were coded and entered in to statistical software, Statistical Package for Social Sciences (SPSS) version 16.0 for analysis. The correlation between pretreatment IOP and visual field loss in patients with PACG and POAG was determined by Pearson Correlation of Coefficient. Results: Amongst the total 110 patients of this study, 25 patients were of PACG while POAG were in 85 patients. A significant correlation between pre treatment IOP and the extent of visual field loss in PACG was noted. There was no significant correlation in POAG. Linear regression analysis demonstrated a significant positive correlation between IOP and AGIS score in PACG (Pearson correlation coefficient(r)=0.805, p<0.001), not in POAG (r=0.026, p=0.816). Correlation between IOP and MD is statistically significant in PACG (r=0.812, p<0.001) but not in POAG (r=0.058, p=0.597). The correlation between IOP and PSD is not statistically significant in both groups (p-value >0.450). Conclusion: A significant correlation between IOP and visual field loss in PACG indicates that extent of visual field damage can be controlled by controlling IOP alone in PACG. The correlation between the pretreatment IOP and visual field loss in POAG is not statistically significant which agrees with the current proposed pathophysiology of optic neuropathy in which multiple factors influence in addition to IOP.
Observing the ultraviolet (UV) sky for time-varyiable phenomena is one of the many exciting science goals that can be achieved by a relatively small aperture telescope in space. The Near Ultraviolet ...Transient Surveyor (NUTS) is a wide-field (3
∘
) imager with a photon-counting detector in the near-UV (NUV, 200 – 300 nm), to be flown on an upcoming small satellite mission. It has a Ritchey–Chrétien (RC) telescope design with correction optics to enable wide-field observations while minimizing optical aberrations. We have used an intensified CMOS detector with a solar blind photocathode, to be operated in photon-counting mode. The main science goal of the instrument is the observation of transient sources in the UV, including flare stars, supernovae, and active galactic nuclei. NUTS’s aperture size and effective area enable observation of relatively unexplored, brighter parts of the UV sky which are usually not accessible to larger missions. We have designed, fabricated, and assembled the instrument, and the final calibrations and environmental tests are being carried out. In this paper, we provide the scientific motivation and technical overview of the instrument and describe the assembly and calibration steps.
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