15 research outputs found
Use of Remote Sensing Data in Assessing the Impact of Climate and Land Use Land Cover Change on Groundwater Dynamics in Semi-Arid Regions
No full textThis study examined how Land Use Land Cover (LULC) and climate affect groundwater dynamics in Southern India's semi-arid region (Chitravathi River basin) and identified the suitable sites for constructing the artificial recharge structures using geographical information systems (GIS). Coupled Model Intercomparison Project Phase6-Global Circulation Models (CMIP6-GCMs) climatic data is used to generate climate projections for the future. The GCMs are ranked for precipitation and temperatures using the Taylor Skill Score (TSS). Rating Metric (RM) was preferred to establish the final rank of the GCMs. Ensemble of projections from the top four ranked GCMs (MPI-ESM1-2-LR, EC-Earth3, MPI-ESM1-2-HR, and INM-CM5-0) were used as they estimated the most reliable forecasts for all the three considered parameters. MPI-ESM1-2-LR was the top-ranked GCM with an RM of 0.92. By using the ensemble GCMs, the six extreme precipitation indices, namely, consecutive dry days (CDD), consecutive wet days (CWD), total wet-day precipitation (PRCPTOT), R10mm (days), R95p (very wet days in mm), RX1day (maximum 1-day precipitation in mm) were calculated as per Expert Team on Climate Change Detection and Indices (ETCCDI) recommendations. Trend analysis of all the above parameters was calculated using Mann-Kendall (MK) and Spearman's rho tests. The future LULC map was produced using cellular automata and artificial neural networks (CA-ANN). Using standard modelling techniques, the SWAT model was used to evaluate the individual impact of climate change on groundwater recharge and the combined impacts of LULC and climate change. The SWAT model was calibrated for discharge data on a monthly basis at a gauging station. The overall accuracy of the SWAT was R2 = 0.83 and NSE = 0.81. The SWAT groundwater module estimates recharge for baseline (1985 - 2014), near-future (2015 - 2030), mid-future (2031 - 2060), and far-future (2061 - 2100) under the moderate SSP2-4.5 and extreme SSP5-8.5 emission scenarios. MODFLOW steady-state groundwater flow model was employed to predict future groundwater levels. Calibration of the model was performed based on seasonal groundwater level data spanning the years 2014 - 2022, and validation was carried out using data from 2020 - 2022. MODFLOW model exhibited good overall accuracy, with R2 values of 0.96 during calibration and 0.94 during validation. Based on the projected groundwater recharge and levels, a resiliency map of the basin was developed. Results revealed that recharge during constant LULC conditions ranged from 135 to 215 mm/year under SSP2-4.5 and 149 to 316 mm/year under the SSP5-8.5 scenario. Compared to baseline recharge (116.4 mm), the future groundwater recharge under both SSPs increased. The results also indicated that by the year 2060, under the SSP2-4.5 scenario, groundwater levels in the basin would decrease by 54 m, while under the SSP5-8.5 scenario, the decrease would be 62 m. By 2060, both SSPs indicate poor groundwater resiliency. Observations from the study highlight the non-resilient state of groundwater. In response, a study was conducted to identify locations conducive to artificial recharge of the groundwater system. Using remotely sensed data and GIS tools, thematic maps incorporating soil type, geology, topography, and groundwater information were overlaid. The Weighted Overlay Analysis (WOA) with assigned weighted scores and the Analytical Hierarchy Process (AHP) identified favourable sites for groundwater recharge. The resultant map guides the spatial distribution of these sites, offering valuable insights to safeguard and sustain the basin's groundwater resources
Stochastic PDES, regularity structures, and interacting particle systems
No full textThese lecture notes grew out of a series of lectures given by the
second named author in short courses in Toulouse, Matsumoto, and Darmstadt. The main aim is to explain some aspects of the theory of “Regularity structures”developed recently by Hairer in [26]. This theory gives a way to study wellposednessfor a class of stochastic PDEs that could not be treated previously.Prominent examples include the KPZ equation as well as the dynamic Φ43model.Such equations can be expanded into formal perturbative expansions.Roughly speaking the theory of regularity structures provides a way to truncate this expansion after finitely many terms and to solve a fixed point problem for the “remainder”. The key ingredient is a new notion of “regularity” which is based on the terms of this expansion.
Resum ´ e. ´ Ces notes sont bas´ees sur trois cours que le deuxi`eme auteur a donn´es `a Toulouse, Matsumoto et Darmstadt. L’objectif principal est d’expliquer certains aspects de la th´eorie des “structures de r´egularit´e” d´evelopp´ee r´ecemment par Hairer [26]. Cette th´eorie permet de montrer que certaines EDP stochastiques,
qui ne pouvaient ˆetre trait´ees auparavant, sont bien pos´ees. Parmi les exemples se trouvent l’´equation KPZ et le mod`ele Φ4
2 dynamique. De telles ´equations peuvent ˆetre d´evelopp´ees en s´eries perturbatives formelles. La th´eorie des structures de r´egularit´e permet de tronquer ce d´eveloppement apr´es un nombre fini de termes, et de r´esoudre un probl`eme de point fixe pour le reste. L’id´ee principale est une nouvelle notion de r´egularit´e des distributions,
qui d´epend des termes de ce d´eveloppement
Sustainable e-bike charging station that enables ac, dc andwireless charging from solar energy
No full textIf electric vehicles have to be truly sustainable, it is essential to charge them from sustainable sources of electricity, such as solar or wind energy. In this paper, the design of solar powered e-bike charging station that provides AC, DC and wireless charging of e-bikes is investigated. The charging station has integrated battery storage that enables for both grid-connected and off-grid operation. The DC charging uses the DC power from the photovoltaic panels directly for charging the e-bike battery without the use of an AC charging adapter. For the wireless charging, the e-bike can be charged through inductive power transfer via the bike kickstand (receiver) and a specially designed tile (transmitter) at the charging station, which provides maximum convenience to the user.DC systems, Energy conversion & StoragePhotovoltaic Materials and Device
Writing from the shadowlands: how cross-cultural literature negotiates the legacy of Edward Said
No full textThis thesis examines the impact of Edward Said's influential work Orientalism and its legacy in respect of contemporary reading and writing across cultures. It also questions the legitimacy of Said's retrospective stereotyping of early examples of cross-cultural representation in literature as uncompromisingly 'orientalist'.
It is well known that the release of Edward Said's Orientalism in 1978 was responsible for the rise of a range of cultural and critical theories from multiculturalism to postcolonialism. It was a study that not only polarized critics and forced scholars to re-examine orientalist archives, but persuaded creative writers to re-think their ethnographic positions when it came to the literary representations of cultures other than their own. Without detracting from the enormous impact of Said, this thesis isolates gaps and silences in Said that need correcting. Furthermore, there is an element of intransigence, an uncompromising refusal to fine-tune what is essentially a binary discourse of the West and its other in Said's work, that encourages the continued interrogation of power relations but which, because of its very boldness, paradoxically disallows the extent to which the conflict of cultures indeed produced new, hybrid social and cultural formations.
In an attempt to challenge the severity of Said's claim that 'every European, in what he could say about the Orient, was consequently a racist, an imperialist, and almost totally ethnocentric', the thesis examines a number of different discursive contexts in which such a presumption is challenged. Thus while the second chapter discusses the 'traditional' profession-based orientalism of nineteenth-century E. G. Browne, the third considers the anti-imperialism of colonial administrator Leonard Woolf. The fourth chapter provides a reflection on the difficulties of diasporic 'orientalism' through the works of Michael Ondaatje while chapter five demonstrates the effects of the dialogism used by Amitav Ghosh as a defence against 'orientalism'. The thesis concludes with an examination of contemporary writing by Andrea Levy that appositely illustrates the legacy of Said's influence.
While the restrictive parameters of Said's work make it difficult to mount a thorough-going critique of Said, this thesis shows that, indeed, it is within the restraints of these parameters and in the very discourse that Said employs that he traps himself. This study claims that even Said is susceptible to 'orientalist' criticism in that he is as much an 'orientalist' as those at whom he directs his polemic
Representations of migrant and nation in selected works of Rohinton Mistry and Salman Rushdie
No full textThis thesis explores the representations of, and the relationship between. the migrant and the nation in selected works of the Bombay-born novelists Rohinton Mistry and Salman Rushdie. I explore each writer's engagement with contemporary debates surrounding the material, political, social and imaginative consequences of the crisis in secularism in India during the 1970s, 1980s and 1990s, and consider how this engagement is informed by their
migrant positions beyond India's borders. A primary concern is the way in which Mistry's and Rushdie's representations of the nation, and of migrant and diasporic subjects, intersects with the representation of Bombay in their work.
This thesis is divided into five chapters. The first two chapters concentrate on Mistry's fiction, the remaining three on Rushdie's work. Published between 1988 and 2002, the central novels examined are situated within debates regarding the founding principles of the Indian nation, and notions of Indianness, the rise of communalism in general and Hindu nationalism in particular, and the renaming of Bombay as Mumbai. My readings foreground the necessity of a
close understanding of the historical and political transformations taking place within Bombay and India during the 1970s, 1980s and 1990s, but also during the 1950s and 1960s. I argue that Mistry's and Rushdie's work is informed by a deepening anxiety over these socio-political transformations, and over how reconfigurations of Indianness increasingly position minority communities, and migrant and diasporic subjects, outside of definitions of national identity.
This anxiety extends into the negotiation of their own migrant positions. My reading of the differing representations of the migrant in Mistry's and Rushdie's work engages with ideas of accountability, political responsibility, and with notions of cosmopolitanism. In doing so, I question familiar assumptions regarding the migrant condition as one of predominantly empowering political agency. I argue that, while both authors emphasise the importance of the migrant sustaining a critical engagement with India's politics, they also foreground the anxious difficulties of doing so. This difficulty informs Mistry's and Rushdie's divergent negotiation of their own position as migrant writers, and I examine how their fiction is marked by an anxiety over the adequacy of writing as a mode of political engagement with the crisis in secularism and the parochialisation of Bombay, and as a means of negotiating the politics of migrancy
First Detection of Polarization in X-Rays for PSR B0540-69 and Its Nebula
No full textXie, Fei et al.--Full list of authors: Xie, Fei; Wong, Josephine; La Monaca, Fabio; Romani, Roger W.; Heyl, Jeremy; Kaaret, Philip; Di Marco, Alessandro; Bucciantini, Niccolò; Liu, Kuan; Ng, Chi-Yung; Di Lalla, Niccolò; Weisskopf, Martin C.; Costa, Enrico; Soffitta, Paolo; Muleri, Fabio; Bachetti, Matteo; Pilia, Maura; Rankin, John; Fabiani, Sergio; Agudo, Iván; Antonelli, Lucio A.; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Capitanio, Fiamma; Castellano, Simone; Cavazzuti, Elisabetta; Chen, Chien-Ting; Ciprini, Stefano; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Donnarumma, Immacolata; Doroshenko, Victor; Dovčiak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kislat, Fabian; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, Henric; Latronico, Luca; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marin, Frédéric; Marinucci, Andrea; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Matt, Giorgio; Mitsuishi, Ikuyuki; Mizuno, Tsunefumi; Negro, Michela; O'Dell, Stephen L.; Omodei, Nicola; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Perri, Matteo; Pesce-Rollins, Melissa; Petrucci, Pierre-Olivier; Possenti, Andrea; Poutanen, Juri; Puccetti, Simonetta; Ramsey, Brian D.; Ratheesh, Ajay; Roberts, Oliver J.; Sgrò, Carmelo; Slane, Patrick; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Vink, Jacco; Wu, Kinwah; Zane, Silvia; Wadiasingh, Zorawar; Ho, Wynn C. G.; Harding, Alice K.; Gendreau, Keith C.; Arzoumanian, Zaven; IXPE CollaborationWe report on X-ray polarization measurements of the extragalactic Crab-like PSR B0540-69 and its Pulsar Wind Nebula (PWN) in the Large Magellanic Cloud, using a ∼850 ks Imaging X-ray Polarimetry Explorer (IXPE) exposure. The PWN is unresolved by IXPE. No statistically significant polarization is detected for the image-averaged data, giving a 99% confidence polarization upper limit (MDP99) of 5.3% in the 2–8 keV energy range. However, a phase-resolved analysis detects polarization for both the nebula and pulsar in the 4–6 keV energy range. For the PWN defined as the off-pulse phases, the polarization degree (PD) of (24.5 ± 5.3)% and polarization angle (PA) of (78.1 ± 6.2)° is detected at 4.6σ significance level, consistent with the PA observed in the optical band. In a single on-pulse window, a hint of polarization is measured at 3.8σ with PD of (50.0 ± 13.1)% and PA of (6.2 ± 7.4)°. A "simultaneous" PSR/PWN analysis finds two bins at the edges of the pulse exceeding 3σ PD significance, with PD of (68 ± 20)% and (62 ± 20)%; intervening bins at 2–3σ significance have lower PD, hinting at additional polarization structure. © 2024. The Author(s). Published by the American Astronomical Society.The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2022-13-I.0, agreements ASI-INAF-2022-19-HH.0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). F.X. is supported by National Key R&D Program of China (grant No. 2023YFE0117200) and National Natural Science Foundation of China (grant No. 12373041) and K.L. is supported by National Natural Science Foundation of China (grant No. 12133003). C.Y.N. and Y.J.Y. are supported by a GRF grant of the Hong Kong Government under HKU 17305419. Funding for this work was provided in part by contract NNM17AA26C from the MSFC to Stanford and 80MSFC17C0012 to MIT in support of the IXPE project. N.B. is supported by the INAF MiniGrant "PWNnumpol—Numerical Studies of Pulsar Wind Nebulae in The Light of IXPE." I.L. is supported by the NASA Postdoctoral Program at the Marshall Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA. W.C.G.H. acknowledges support through grant 80NSSC23K0078 from NASA. This research has made use of NICER data. We thank NICER staff for the scheduling of these observations. This paper employs a list of Chandra data sets, obtained by the Chandra X-ray Observatory, contained in doi:10.25574/cdc.177.Peer reviewe
Analysis of Crab X-Ray Polarization Using Deeper Imaging X-Ray Polarimetry Explorer Observations
No full textWong, Josephine et al.--Full list of authors: Wong, Josephine; Mizuno, Tsunefumi; Bucciantini, Niccoló; Romani, Roger W.; Yang, Yi-Jung; Liu, Kuan; Deng, Wei; Goya, Kazuho; Xie, Fei; Pilia, Maura; Kaaret, Philip; Weisskopf, Martin C.; Silvestri, Stefano; Ng, C. -Y.; Chen, Chien-Ting; Agudo, Iván; Antonelli, Lucio A.; Bachetti, Matteo; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Capitanio, Fiamma; Castellano, Simone; Cavazzuti, Elisabetta; Ciprini, Stefano; Costa, Enrico; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Di Lalla, Niccoló; Di Marco, Alessandro; Donnarumma, Immacolata; Doroshenko, Victor; Dovčiak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Heyl, Jeremy; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kislat, Fabian; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, Henric; La Monaca, Fabio; Latronico, Luca; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marin, Frédéric; Marinucci, Andrea; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Matt, Giorgio; Mitsuishi, Ikuyuki; Muleri, Fabio; Negro, Michela; O'Dell, Stephen L.; Omodei, Nicola; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel Lawrence; Perri, Matteo; Pesce-Rollins, Melissa; Petrucci, Pierre-Olivier; Possenti, Andrea; Poutanen, Juri; Puccetti, Simonetta; Ramsey, Brian D.; Rankin, John; Ratheesh, Ajay; Roberts, Oliver J.; Sgró, Carmelo; Slane, Patrick; Soffitta, Paolo; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey; Turolla, Roberto; Vink, Jacco; Wu, Kinwah; Zane, SilviaWe present Crab X-ray polarization measurements using Imaging X-Ray Polarimetry Explorer (IXPE) data with a total exposure of 300 ks, three times more than the initial 2022 discovery paper. Polarization is detected in three times more pulsar phase bins, revealing an S-shaped +40° polarization angle sweep in the main pulse and >1σ departures from the OPTIMA optical polarization in both pulses, suggesting different radiation mechanisms or sites for the polarized emission at the two wavebands. Our polarization map of the inner nebula reveals a toroidal magnetic field, as seen in prior IXPE analyses. Along the southern jet, the magnetic field orientation relative to the jet axis changes from perpendicular to parallel and the polarization degree decreases by ∼6%. These observations may be explained by kink instabilities along the jet or a collision with a dense, jet-deflecting medium at the tip. Using spectropolarimetric analysis, we find asymmetric polarization in the four quadrants of the inner nebula, as expected for a toroidal field geometry, and a spatial correlation between polarization degree and photon index. © 2024. The Author(s). Published by the American Astronomical Society.This work was supported in part through NASA grant NNM17AA26C administered by the Marshall Space Flight Center. The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2022-13-I.0, agreements ASI-INAF-2022-19-HH.0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at the NASA Goddard Space Flight Center (GSFC). N.B. was supported by the INAF MiniGrant "PWNnumpol—Numerical Studies of Pulsar Wind Nebulae in The Light of IXPE." F.X. is supported by the National Natural Science Foundation of China (grant No. 12373041). T. M. was supported by JSPS KAKENHI grant No. 23K25882. I.L. was supported by the NASA Postdoctoral Program at the Marshall Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA. This paper employs the Chandra data set, obtained by the Chandra X-ray Observatory, contained in doi:10.25574/cdc.264.Peer reviewe
Epilepsy surgery in a pediatric population: a retrospective study of 129 children from a tertiary care hospital in a developing country along with assessment of quality of life
No full textPurpose: To assess the outcome of a pediatric population operated for drug-resistant epilepsy from a large tertiary care center in India. Methods: Retrospectively: quality of life (QOL); prospectively: preoperative assessment included interictal EEG, MRI (as per epilepsy protocol), video-EEG. Ictal SPECT (with subtraction) and PET were performed when required. QOL scores were assessed using the HASS or SSQ for seizure severity, Quality of Life in Childhood Epilepsy (QOLCE) for QOL, and Child Behavior Check List (CBCL) for behavior. Results: 142 were operated from January 2000 to June 2011 by the senior author. 118 patients with at least 1 year of follow-up were included in the study. Mean age at surgery was 9.8 ± 4.3 years. In addition, 40 patients underwent QOL assessment prospectively both before and after surgery. Mean duration of epilepsy was 5.3 ± 3.3 years. A class I outcome (Engel’s) was seen in 79.5% patients, class II in 8.6%, class III in 10.7%, and class IV in 1 patient. As per surgical procedures, class I outcome in patients who underwent temporal resection, hemispherotomy and extratemporal resection was 76, 87 and 72%, respectively. QOL scores correlated with duration of seizures, epileptic encephalopathy and outcome of surgery, but not with side of surgery, age and sex. Conclusions: This study, the largest reported from India, has demonstrated satisfactory results for epilepsy surgery in children
X-Ray Polarization Detection of Cassiopeia A with IXPE
No full textFull list of authors: Vink, Jacco; Prokhorov, Dmitry; Ferrazzoli, Riccardo; Slane, Patrick; Zhou, Ping; Asakura, Kazunori; Baldini, Luca; Bucciantini, Niccolo; Costa, Enrico; Di Marco, Alessandro; Heyl, Jeremy; Marin, Frederic; Mizuno, Tsunefumi; Ng, C-Y; Pesce-Rollins, Melissa; Ramsey, Brian D.; Rankin, John; Ratheesh, Ajay; Sgro, Carmelo; Soffitta, Paolo; Swartz, Douglas A.; Tamagawa, Toru; Weisskopf, Martin C.; Yang, Yi-Jung; Bellazzini, Ronaldo; Bonino, Raffaella; Cavazzuti, Elisabetta; Costamante, Luigi; Di Lalla, Niccolo; Latronico, Luca; Maldera, Simone; Manfreda, Alberto; Massaro, Francesco; Mitsuishi, Ikuyuki; Omodei, Nicola; Oppedisano, Chiara; Zane, Silvia; Agudo, Ivan; Antonelli, Lucio A.; Bachetti, Matteo; Baumgartner, Wayne H.; Bianchi, Stefano; Bongiorno, Stephen D.; Brez, Alessandro; Capitanio, Fiamma; Castellano, Simone; Ciprini, Stefano; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Donnarumma, Immacolata; Doroshenko, Victor; Dovciak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, Henric; La Monaca, Fabio; Liodakis, Ioannis; Marinucci, Andrea; Marscher, Alan P.; Marshall, Herman L.; Matt, Giorgio; Muleri, Fabio; O'Dell, Stephen L.; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Perri, Matteo; Pilia, Maura; Possenti, Andrea; Poutanen, Juri; Puccetti, Simonetta; Romani, Roger W.; Spandre, Gloria; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicolas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey; Turolla, Roberto; Wu, Kinwah; Xie, Fei.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.We report on a ∼5σ detection of polarized 3–6 keV X-ray emission from the supernova remnant Cassiopeia A (Cas A) with the Imaging X-ray Polarimetry Explorer (IXPE). The overall polarization degree of 1.8% ± 0.3% is detected by summing over a large region, assuming circular symmetry for the polarization vectors. The measurements imply an average polarization degree for the synchrotron component of ∼2.5%, and close to 5% for the X-ray synchrotron-dominated forward shock region. These numbers are based on an assessment of the thermal and nonthermal radiation contributions, for which we used a detailed spatial-spectral model based on Chandra X-ray data. A pixel-by-pixel search for polarization provides a few tentative detections from discrete regions at the ∼ 3σ confidence level. Given the number of pixels, the significance is insufficient to claim a detection for individual pixels, but implies considerable turbulence on scales smaller than the angular resolution. Cas A's X-ray continuum emission is dominated by synchrotron radiation from regions within ≲1017 cm of the forward and reverse shocks. We find that (i) the measured polarization angle corresponds to a radially oriented magnetic field, similar to what has been inferred from radio observations; (ii) the X-ray polarization degree is lower than in the radio band (∼5%). Since shock compression should impose a tangential magnetic-field structure, the IXPE results imply that magnetic fields are reoriented within ∼1017 cm of the shock. If the magnetic-field alignment is due to locally enhanced acceleration near quasi-parallel shocks, the preferred X-ray polarization angle suggests a size of 3 × 1016 cm for cells with radial magnetic fields. © 2022. The Author(s). Published by the American Astronomical Society.The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC), and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). J.V. and D.P. are supported by funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 101004131 (SHARP). The research at Boston University was supported in part by National Science Foundation grant AST-2108622. We thank Dawoon Kim for kindly providing us with his script for making polar plots of polarization degree and angle.With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.Peer reviewe
