Nicholas E. Thomas
A5088480492- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Solar and Space Plasma Dynamics
- Gamma-ray bursts and supernovae
- Mechanics and Biomechanics Studies
- Astro and Planetary Science
- High-pressure geophysics and materials
- Radio Astronomy Observations and Technology
- Astronomical Observations and Instrumentation
- Particle Accelerators and Free-Electron Lasers
- Ionosphere and magnetosphere dynamics
- Advanced X-ray Imaging Techniques
- Particle Detector Development and Performance
- Nuclear Physics and Applications
- Planetary Science and Exploration
- Neutrino Physics Research
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- X-ray Spectroscopy and Fluorescence Analysis
- Calibration and Measurement Techniques
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Advanced X-ray and CT Imaging
- Magnetic confinement fusion research
Marshall Space Flight Center
2021-2024
University of Maryland, College Park
2023
Istituto Nazionale di Fisica Nucleare
2023
Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata
2023
Louisiana State University
2023
Goddard Space Flight Center
2012-2022
University of Maryland, Baltimore County
2013-2018
Both heliophysics and planetary physics seek to understand the complex nature of solar wind's interaction with system obstacles like Earth's magnetosphere, ionospheres Venus Mars, comets. Studies this objective are frequently conducted help single or multipoint in situ electromagnetic field particle observations, guided by predictions both local global numerical simulations, placed context observations from far extreme ultraviolet (FUV, EUV), hard X-ray, energetic neutral atom imagers (ENA)....
We report on the first detection of linearly polarized x-ray emission from an ultra-magnetized neutron star with Imaging X-ray Polarimetry Explorer (IXPE). The IXPE 35 observations anomalous pulsar 4U 0142+61 reveal a linear polarization degree $(12\pm 1)\%$ throughout 2--8 keV band. detect substantial variation energy: is $(14\pm at 2--4 and $(41\pm 7)\%$ 5.5--8 keV, while it drops below instrumental sensitivity around 4--5 where angle swings by $\sim 90^\circ$. give us completely new...
Abstract The launch of the Imaging X-ray Polarimetry Explorer (IXPE) on 2021 December 9 has opened a new window in astronomy. We report here results first IXPE observation weakly magnetized neutron star, GS 1826−238, performed 2022 March 29–31 when source was high soft state. An upper limit (99.73% confidence level) 1.3% for linear polarization degree is obtained over 2–8 keV energy range. Coordinated INTEGRAL and NICER observations were carried out simultaneously with IXPE. spectral...
Abstract The Lunar Environment heliospheric X-ray Imager (LEXI) is a wide field-of-view soft telescope developed to study solar wind-magnetosphere coupling. LEXI part of the Blue Ghost 1 mission comprised 10 payloads be deployed on lunar surface. monitors dayside magnetopause position and shape as function time by observing X-rays (0.1–2 keV) emitted from wind charge-exchange between exospheric neutrals high charge-state plasma in magnetosheath. Measurements are used test temporal models...
Abstract Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric ∼16.6 day orbit. There are also the spectral state, and it has historically shown both atoll Z state properties. We observed source with Imaging Polarimetry Explorer two orbital segments, 6 days apart, for total of 263 ks. find an polarization degree these segments 1.6% ± 0.3% 1.4% at angles 37° 5° −12° 7°, respectively. Thus, we rotation angle 49° 8° along Because accretion flow,...
We report on the first observation of a radio-quiet Active Galactic Nucleus (AGN) using polarized X-rays: Seyfert 1.9 galaxy MCG-05-23-16. This source was pointed with Imaging X-ray Polarimetry Explorer (IXPE) starting May 14, 2022 for net observing time 486 ks, simultaneously XMM-Newton (58 ks) and NuSTAR (83 ks). A polarization degree smaller than $\Pi<4.7\%$ (at 99% c.l.) is derived in 2-8 keV energy range, where emission dominated by primary component ascribed to hot corona. The...
Cen X-3 is the first X-ray pulsar discovered 50 years ago. Radiation from such objects expected to be highly polarized due birefringence of plasma and vacuum associated with propagation photons in presence strong magnetic field. Here we present results observations performed Imaging Polarimetry Explorer. The source exhibited significant flux variability was observed two states different by a factor ~20 flux. In low-luminosity state no polarization found either pulse phase-averaged (with...
ABSTRACT We report spectro-polarimetric results of an observational campaign the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER, and INTEGRAL. Consistently with previous results, broad-band spectrum is characterized a lower-energy component, attributed to accretion disc kTin ≈ 1 keV, plus unsaturated Comptonization in thermal plasma temperature kTe = 3 keV optical depth τ 4, assuming slab geometry. measure polarization degree 2–8 band P 1.8 ± 0.3 per...
ABSTRACT We report on the Imaging X-ray Polarimetry Explorer (IXPE) observation of closest and brightest Compton-thick active galactic nucleus (AGN), Circinus galaxy. find source to be significantly polarized in 2–6 keV band. From previous studies, spectrum is known dominated by reflection components, both neutral (torus) ionized (ionization cones). Our analysis indicates that polarization degree 28 ± 7 per cent (at 68 confidence level) for reflector, with a angle 18° 5°, roughly...
ABSTRACT We report on the second observation of radio-quiet active galactic nucleus MCG-05-23-16 performed with Imaging X-ray Polarimetry Explorer (IXPE). The started 2022 November 6 for a net observing time 640 ks, and was partly simultaneous NuSTAR (86 ks). After combining these data those obtained in first IXPE pointing May (simultaneous XMM–Newton NuSTAR) we find 2–8 keV polarization degree Π = 1.6 ± 0.7 (at 68 per cent confidence level), which corresponds to an upper limit 3.2 99...
Abstract Magnetars are the most strongly magnetized neutron stars, and one of promising targets for X-ray polarimetric measurements. We present here first Imaging Polarimetry Explorer observation magnetar 1RXS J170849.0-400910, jointly analyzed with a new Swift archival NICER data. The total (energy- phase-integrated) emission in 2–8 keV energy range is linerarly polarized, at ∼35% level. phase-averaged polarization signal shows marked increase energy, ranging from ∼20% 2–3 up to ∼80% 6–8...
Abstract We present the first X-ray polarimetric study of dipping accreting neutron star 4U 1624−49 with Imaging Polarimetry Explorer. report a detection polarization in nondip time intervals confidence level 99.99%. find an average degree (PD) 3.1% ± 0.7% and angle 81° 6° east north 2–8 keV band. upper limit on PD 22% during dips 95% confidence. The increases energy, reaching from 3.0% 0.9% 4–6 band to 6% 2% 6–8 This indicates likely arises Comptonization. high observed is unlikely be...
Context. NGC 1068 is the most observed radio-quiet active galactic nucleus (AGN) in polarimetry, yet its high-energy polarization has never been probed before due to a lack of dedicated polarimeters. Aims. Using first X-ray polarimeter sensitive enough measure AGNs, we want probe orientation and geometric arrangement (sub)parsec-scale matter around source. Methods. We used Imaging Polarimetry Explorer (IXPE) satellite measure, for time, 2–8 keV 1068. pointed IXPE at target net exposure time...
Abstract Supernova remnants are commonly considered to produce most of the Galactic cosmic rays via diffusive shock acceleration. However, many questions regarding physical conditions at fronts, such as magnetic-field morphology close particle acceleration sites, remain open. Here we report detection a localized polarization signal from some synchrotron X-ray emitting regions Tycho’s supernova remnant made by Imaging Polarimetry Explorer. The derived degree emission is 9% ± 2% averaged over...
X-ray polarimetry is a unique way to probe the geometrical configuration of highly magnetized accreting neutron stars (X-ray pulsars). GRO J1008−57 first transient pulsar observed at two different flux levels by Imaging Polarimetry Explorer (IXPE) during its outburst in November 2022. We find polarization properties be independent luminosity, with degree varying between nondetection and about 15% over pulse phase. Fitting phase-resolved spectro-polarimetric data rotating vector model allowed...
Abstract The radiation from accreting X-ray pulsars was expected to be highly polarized, with some estimates for the polarization degree of up 80%. However, phase-resolved and energy-resolved polarimetry is required in order test different models shed light on emission processes geometry region. Here we present first results observations pulsar Vela X-1 performed Imaging Polarimetry Explorer. considered archetypal example a wind-accreting, high-mass binary system, consisting magnetized...
ABSTRACT X Persei is a persistent low-luminosity X-ray pulsar of period ≈ 835 s in Be binary system. The field strength at the neutron star surface not known precisely, but indirect signs indicate magnetic above 1013 G, which makes object one most magnetized pulsars. Here we present results observations performed with Imaging Polarimetry Explorer (IXPE). polarization signal was found to be strongly dependent on spin phase pulsar. energy-averaged degree 3–8 keV band varied from several ∼20...
Abstract Recent observations with the Imaging X-ray Polarimetry Explorer (IXPE) of two anomalous pulsars provided evidence that emission from magnetar sources is strongly polarized. Here we report on joint IXPE and XMM-Newton soft γ -repeater SGR 1806–20. The spectral timing properties 1806–20 derived data are in broad agreement previous measurements; however, found source at an all-time low persistent flux level. No significant polarization was measured apart 4–5 keV energy range, where a...
The mean production factor, or broadband averaged cross-section, for solar wind charge-exchange (SWCX) with hydrogen producing emission in the ROSAT 1 4 keV (R12) band is (3.8 0.2) 10 20 ´count degree -2 cm .The factor expected to be temporally variable, and that variation roughly 15%.These values are derived from a comparison of long-term (background) enhancements All-Sky Survey magnetohysdrodynamic simulations magnetosheath.This value 1.8-4.5 times higher than limited atomic data,...
ABSTRACT Diffuse X-rays from the Local Galaxy ( DXL ) is a sounding rocket mission designed to quantify and characterize contribution of Solar Wind Charge eXchange (SWCX) X-ray Background study properties Hot Bubble (LHB). Based on results mission, we quantified removed SWCX diffuse background measured by ROSAT All Sky Survey. The “cleaned” maps were used investigate physical LHB. Assuming thermal ionization equilibrium, highly uniform temperature distributed around kT = 0.097 keV ± 0.013...
The phase- and energy-resolved polarization measurements of accreting X-ray pulsars (XRPs) allow us to test different theoretical models their emission, they also provide an avenue determine the emission region geometry. We present results observations XRP GX 301−2 performed with Imaging Polarimetry Explorer (IXPE). A persistent XRP, has one longest spin periods known: ∼680 s. massive hyper-giant companion star Wray 977 supplies mass neutron via powerful stellar winds. did not detect...
Abstract We report on X-ray polarization measurements of the extragalactic Crab-like PSR B0540-69 and its Pulsar Wind Nebula (PWN) in Large Magellanic Cloud, using a ∼850 ks Imaging Polarimetry Explorer (IXPE) exposure. The PWN is unresolved by IXPE. No statistically significant detected for image-averaged data, giving 99% confidence upper limit (MDP 99 ) 5.3% 2–8 keV energy range. However, phase-resolved analysis detects both nebula pulsar 4–6 For defined as off-pulse phases, degree (PD)...
Three recent results related to the heliosphere and local interstellar medium (ISM) have provided an improved insight into distribution conditions of material in solar neighborhood. These are measurement magnetic field outside by Voyager 1, mapping three-dimensional structure neutral surrounding Local Cavity using extensive ISM absorption line reddening data, a sounding rocket flight which observed heliospheric helium focusing cone X-rays robust estimate contribution wind charge exchange...
We describe the development, launch into space, and initial results from a prototype wide field-of-view soft X-ray imager that employs lobster-eye optics targets heliophysics, planetary, astrophysics science. The sheath transport observer for redistribution of mass is first instrument using this type launched space provides proof-of-concept future flight instruments capable imaging structures such as terrestrial cusp, entire dayside magnetosheath outside magnetosphere, comets, Moon, solar...