| 1. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 2. |
- Bhattacharya, S., et al.
(författare)
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Evolution of collectivity and evidence of octupole correlations in Br 73
- 2019
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Ingår i: Physical Review C. - 2469-9985. ; 100:1
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in the Br73 nucleus have been populated via the Cr50(Si28,αp)Br73 fusion evaporation reaction with a beam energy of 90 MeV. The deexciting gamma rays were detected using the Indian National Gamma Array (INGA). Using the γ-γ coincidence technique, two new bands and eight new interconnecting transitions have been added. The strong interconnecting E1 transitions, between positive and negative parity bands, ensure the existence of octupole correlations at low spin. Line shapes have been observed for 17 transitions, which were analyzed by the Doppler-shift attenuation method to determine the lifetime of excited states of the yrast negative parity band and its signature partner band along with the positive parity band. The deduced transitional quadrupole moments Qt for the ground state band decrease with increasing spin, with their values ranging from 2.88 to 1.00 eb. A similar trend in the quadrupole moment has also been observed for the signature partner as well as for the positive parity band. This decrease in Qt with increasing spin for these bands is interpreted in terms of the cranked Nilsson-Strutinsky model and total Routhian surface calculations, which indicate possible band termination at higher spin.
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| 3. |
- Kumar, S., et al.
(författare)
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Band structures in Rh-99
- 2014
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Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 41:10
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Tidskriftsartikel (refereegranskat)abstract
- Excited states in the Rh-99 nucleus were populated using the fusion-evaporation reaction As-75(Si-28,2p2n) at E-lab = 120 MeV and the de-excitations were investigated through in-beam gamma-ray spectroscopic techniques using the INGA spectrometer consisting of 18 clover detectors. The observed band structures are discussed in the framework of tilted axis cranking shell-model calculations. Level structures at low energies are identified as resulting from the rotational bands based on the pi p(1/2) and pi g(9/2) configurations. The Delta I = 1 coupled bands are observed at higher excitation energies and have been interpreted as based on the pi g(9/2) circle times nu g(7/2) circle times nu d(5/2), pi p(1/2) circle times nu h(11/2) circle times nu d(5/2) and pi g(9/2) circle times nu h(11/2) circle times nu g(7/2) configurations. Calculations based on cranked Nilsson- Strutinsky (CNS) formalism have been performed to interpret the favoured states with I-pi = (41/2(-), 43/2(-)) and (51/2(-), 53/2(-)) as maximal spin aligned states built on the valence space nu(d(5/2)g(7/2))(15/2)(3), (17/2)(h(11/2))(11/2)(1) configuration combined with the fully-aligned pi(g(9/2))(25/2)(5) configuration and the pi(g(9/2))(15/2)(5) configuration with one anti-aligned g(9/2) proton, respectively.
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| 4. |
- Langlois, M., et al.
(författare)
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The SPHERE infrared survey for exoplanets (SHINE) : II. Observations, data reduction and analysis, detection performances, and initial results
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 651
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Tidskriftsartikel (refereegranskat)abstract
- Context. In recent decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) around their host stars. In striving to understand their formation and evolution mechanisms, in 2015 we initiated the SPHERE infrared survey for exoplanets (SHINE), a systematic direct imaging survey of young, nearby stars that is targeted at exploring their demographics.Aims. We aim to detect and characterize the population of giant planets and brown dwarfs beyond the snow line around young, nearby stars. Combined with the survey completeness, our observations offer the opportunity to constrain the statistical properties (occurrence, mass and orbital distributions, dependency on the stellar mass) of these young giant planets.Methods. In this study, we present the observing and data analysis strategy, the ranking process of the detected candidates, and the survey performances for a subsample of 150 stars that are representative of the full SHINE sample. Observations were conducted in a homogeneous way between February 2015 and February 2017 with the dedicated ground-based VLT/SPHERE instrument equipped with the IFS integral field spectrograph and the IRDIS dual-band imager, covering a spectral range between 0.9 and 2.3 μm. We used coronographic, angular, and spectral differential imaging techniques to achieve the best detection performances for this study, down to the planetary mass regime.Results. We processed, in a uniform manner, more than 300 SHINE observations and datasets to assess the survey typical sensitivity as a function of the host star and of the observing conditions. The median detection performance reached 5σ-contrasts of 13 mag at 200 mas and 14.2 mag at 800 mas with the IFS (YJ and YJH bands), and of 11.8 mag at 200 mas, 13.1 mag at 800 mas, and 15.8 mag at 3 as with IRDIS in H band, delivering one of the deepest sensitivity surveys thus far for young, nearby stars. A total of sixteen substellar companions were imaged in this first part of SHINE: seven brown dwarf companions and ten planetary-mass companions.These include two new discoveries, HIP 65426 b and HIP 64892 B, but not the planets around PDS70 that had not been originally selected for the SHINE core sample. A total of 1483 candidates were detected, mainly in the large field of view that characterizes IRDIS. The color-magnitude diagrams, low-resolution spectrum (when available with IFS), and follow-up observations enabled us to identify the nature (background contaminant or comoving companion) of about 86% of our subsample. The remaining cases are often connected to crowded-field follow-up observations that were missing. Finally, even though SHINE was not initially designed for disk searches, we imaged twelve circumstellar disks, including three new detections around the HIP 73145, HIP 86598, and HD 106906 systems.Conclusions. Nowadays, direct imaging provides a unique opportunity to probe the outer part of exoplanetary systems beyond 10 au to explore planetary architectures, as highlighted by the discoveries of: one new exoplanet, one new brown dwarf companion, and three new debris disks during this early phase of SHINE. It also offers the opportunity to explore and revisit the physical and orbital properties of these young, giant planets and brown dwarf companions (relative position, photometry, and low-resolution spectrum in near-infrared, predicted masses, and contrast in order to search for additional companions). Finally, these results highlight the importance of finalizing the SHINE systematic observation of about 500 young, nearby stars for a full exploration of their outer part to explore the demographics of young giant planets beyond 10 au and to identify the most interesting systems for the next generation of high-contrast imagers on very large and extremely large telescopes.
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| 5. |
- Kumar, R., et al.
(författare)
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ENHANCED 0(g.s.)(+) -> 2(1)(+) E2 TRANSITION STRENGTH IN Sn-112,Sn-114
- 2011
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Ingår i: Acta Physica Polonica B. - 0587-4254. ; 42:3-4, s. 813-816
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Konferensbidrag (refereegranskat)abstract
- The poorly known B(E2; 0(+) -> 2(+)) values of Sn-112 and Sn-114 have been measured to high precision. Two Coulomb excitation experiments were performed to determine the reduced transition probabilities relative to Sn-116 in order to minimize the systematic errors. The obtained B(E2 up arrow) values of 0.242(8) e(2)b(2) for Sn-112 and 0.232(8) e(2)b(2) for Sn-114 confirm the tendency of large B(E2 up arrow) values for the lighter tin isotopes below the midshell Sn-116 that has been observed recently in various radioactive ion beam experiments.
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| 6. |
- Zurlo, A., et al.
(författare)
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Orbital and dynamical analysis of the system around HR 8799 New astrometric epochs from VLT/SPHERE and LBT/LUCI
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
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Tidskriftsartikel (refereegranskat)abstract
- Context. HR 8799 is a young planetary system composed of four planets and a double debris belt. Being the first multi-planetary system discovered with the direct imaging technique, it has been observed extensively since 1998. This wide baseline of astrometric measurements, counting over 50 observations in 20 years, permits a detailed orbital and dynamical analysis of the system.Aims. To explore the orbital parameters of the planets, their dynamical history, and the planet-to-disk interaction, we made follow-up observations of the system during the VLT/SPHERE guaranteed time observation program. We obtained 21 observations, most of them in favorable conditions. In addition, we observed HR 8799 with the instrument LUCI at the Large Binocular Telescope (LBT).Methods. All the observations were reduced with state-of-the-art algorithms implemented to apply the spectral and angular differential imaging method. We re-reduced the SPHERE data obtained during the commissioning of the instrument and in three open-time programs to have homogeneous astrometry. The precise position of the four planets with respect to the host star was calculated by exploiting the fake negative companions method. We obtained an astrometric precision of the order of 6 mas in the worst case and 1 mas in the best case. To improve the orbital fitting, we also took into account all of the astrometric data available in the literature. From the photometric measurements obtained in different wavelengths, we estimated the masses of the planets following the evolutionary models.Results. We obtained updated parameters for the orbits with the assumption of coplanarity, relatively small eccentricities, and periods very close to the 2:1 resonance. We also refined the dynamical mass of each planet and the parallax of the system (24.49 ± 0.07 mas), which overlap with the recent Gaia eDR3/DR3 estimate. Hydrodynamical simulations suggest that inward migration of the planets caused by the interaction with the disk might be responsible for the planets being locked in resonance. We also conducted detailed N-body simulations indicating possible positions of a putative fifth planet with a mass below the present detection limits of ≃3 MJup.
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| 7. |
- Chanda, Somen, et al.
(författare)
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Seven-quasiparticle bands in Ce-139
- 2009
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 79:5
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Tidskriftsartikel (refereegranskat)abstract
- The high spin states in the Ce-139 nucleus have been studied by in-beam gamma-spectroscopic techniques using the reaction Te-130(C-12,3n)Ce-139 at E-beam=65 MeV. A gamma detector array, consisting of five Compton-suppressed Clover detectors was used for coincidence measurements. 15 new levels have been proposed and 28 new gamma transitions have been assigned to Ce-139 on the basis of gamma gamma coincidence data. The level scheme of Ce-139 has been extended above the known 70 ns 19/2 isomer up to similar to 6.1 MeV in excitation energy and 35/2h in spin. The spin-parity assignments for most of the newly proposed levels have been made using the deduced Directional Correlation from Oriented states of nuclei (DCO ratio) and the Polarization Directional Correlation from Oriented states (PDCO ratio) for the de-exciting transitions. The observed level structure has been compared with a large basis shell model calculation and also with the predictions from cranked Nilsson-Strutinsky (CNS) calculations. A general consistency has been observed between these two different theoretical approaches.
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| 8. |
- Islam, A. B. M. R., et al.
(författare)
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Arsenic mineral dissolution and possible mobilization in mineral-microbe-groundwater environment
- 2013
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 262, s. 989-996
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic (As) is widely distributed in the nature as ores or minerals. It has been attracted much attention for the global public health issue, especially for groundwater As contamination. The aim of this study was to elucidate the characteristics of microbes in groundwater where As-minerals were dissolved. An ex situ experiment was conducted with 7 standard As-minerals in bacteria-free groundwater and stored in experimental vessels for 1 year without supplementary nutrients. The pH (6.7-8.4) and EhS.H.E. (24-548mV) changed between initial (0 day) and final stages (365 days) of experiment. The dissolution of As was detected higher from arsenolite (4240±8.69mg/L) and native arsenic (4538±9.02mg/L), whereas moderately dissolved from orpiment (653±3.56mg/L) and realgar (319±2.56mg/L) in compare to arsenopyrite (85±1.25mg/L) and tennantite (3±0.06mg/L). Optical microscopic, scanning electron microscopic observations and flurometric enumeration revealed the abundance of As-resistant bacillus, coccus and filamentous types of microorganisms on the surface of most of As-mineral. 4'-6-Diamidino-2-phenylindole (DAPI)-stained epifluorescence micrograph confirmed the presence of DNA and carboxyfluorescein diacetate (CFDA) staining method revealed the enzymatically active bacteria on the surface of As-minerals such as in realgar (As4S4). Therefore, the microbes enable to survive and mobilize the As in groundwater by dissolution/bioweathering of As-minerals.
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