Evidence of Particle Acceleration in the Superbubble 30 Doradus C with NuSTAR

We present evidence of diffuse, non-thermal X-ray emission from the superbubble 30 Doradus C (30 Dor C) using hard X-ray images and spectra from NuSTAR observations. For this analysis, we utilize data from a 200 ks targeted observation of 30 Dor C as well as 2.8 Ms of serendipitous off-axis observations from the monitoring of nearby SN 1987A. The complete shell of 30 Dor C is detected up to 20 keV, and the young supernova remnant MCSNR J0536-6913 in the southeast of 30 Dor C is not detected above 8 keV. Additionally, six point sources identified in previous Chandra and XMM-Newton investigations have hard X-ray emission coincident with their locations. Joint spectral fits to the NuSTAR and XMM-Newton spectra across the 30 Dor C shell confirm the non-thermal nature of the diffuse emission. Given the best-fit rolloff frequencies of the X-ray spectra, we find maximum electron energies of 70-110 TeV (assuming a B-field strength of 4$\mu$G), suggesting 30 Dor C is accelerating particles. Particles are either accelerated via diffusive shock acceleration at locations where the shocks have not stalled behind the H$\alpha$ shell, or cosmic-rays are accelerated through repeated acceleration of low-energy particles via turbulence and magnetohydrodynamic waves in the bubble's interior.Comment: 14 pages, 8 figures, ApJ, in pres

NuSTAR observations of the young, energetic radio pulsar PSR B1509-58

We report on Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of the young rotation-powered radio pulsar PSR B1509$-$58 in the supernova remnant MSH 15$-$52. We confirm the previously reported curvature in the hard X-ray spectrum, showing that a log parabolic model provides a statistically superior fit to the spectrum compared with the standard power law. The log parabolic model describes the NuSTAR data, as well as previously published gamma-ray data obtained with COMPTEL and AGILE, all together spanning 3 keV through 500 MeV. Our spectral modelling allows us to constrain the peak of the broadband high energy spectrum to be at 2.6$\pm$0.8 MeV, an improvement of nearly an order of magnitude in precision over previous measurements. In addition, we calculate NuSTAR spectra in 26 pulse phase bins and confirm previously reported variations of photon indices with phase. Finally, we measure the pulsed fraction of PSR B1509$-$58 in the hard X-ray energy band for the first time. Using the energy resolved pulsed fraction results, we estimate that the pulsar's off-pulse emission has a photon index value between 1.26 and 1.96. Our results support a model in which the pulsar's lack of GeV emission is due to viewing geometry, with the X-rays originating from synchrotron emission from secondary pairs in the magnetosphere.Comment: 10 pages, 8 figures, 6 tables, ApJ accepte

Arcus: the soft x-ray grating explorer

Arcus provides high-resolution soft X-ray spectroscopy in the 12-50 Å bandpass with unprecedented sensitivity, including spectral resolution < 2500 and effective area < 250 cm^2. The three top science goals for Arcus are (1) to measure the effects of structure formation imprinted upon the hot baryons that are predicted to lie in extended halos around galaxies, (2) to trace the propagation of outflowing mass, energy, and momentum from the vicinity of the black hole to extragalactic scales as a measure of their feedback, and (3) to explore how stars form and evolve. Arcus uses the same 12 m focal length grazing-incidence Silicon Pore X-ray Optics (SPOs) that ESA has developed for the Athena mission; the focal length is achieved on orbit via an extendable optical bench. The focused X-rays from these optics are diffracted by high-efficiency Critical-Angle Transmission (CAT) gratings, and the results are imaged with flight-proven CCD detectors and electronics. Combined with the high-heritage NGIS LEOStar-2 spacecraft and launched into 4:1 lunar resonant orbit, Arcus provides high sensitivity and high efficiency observing of a wide range of astrophysical sources

Optimizations of Pt/SiC and W/Si multilayers for the Nuclear Spectroscopic Telescope Array

The Nuclear Spectroscopic Telescope Array, NuSTAR, is a NASA funded Small Explorer Mission, SMEX, scheduled for launch in mid 2011. The spacecraft will fly two co-aligned conical approximation Wolter-I optics with a focal length of 10 meters. The mirrors will be deposited with Pt/SiC and W/Si multilayers to provide a broad band reflectivity from 6 keV up to 78.4 keV. To optimize the mirror coating we use a Figure of Merit procedure developed for gazing incidence optics, which averages the effective area over the energy range, and combines an energy weighting function with an angular weighting function to control the shape of the desired effective area. The NuSTAR multilayers are depth graded with a power-law, d_i = a/(b + i)^c, and we optimize over the total number of bi-layers, N, c, and the maximum bi-layer thickness, d_(max). The result is a 10 mirror group design optimized for a flat even energy response both on and off-axis

Observational Artifacts of NuSTAR: Ghost Rays and Stray Light

The Nuclear Spectroscopic Telescope Array (NuSTAR), launched in June 2012, flies two conical approximation Wolter-I mirrors at the end of a 10.15m mast. The optics are coated with multilayers of Pt/C and W/Si that operate from 3--80 keV. Since the optical path is not shrouded, aperture stops are used to limit the field of view from background and sources outside the field of view. However, there is still a sliver of sky (~1.0--4.0 degrees) where photons may bypass the optics altogether and fall directly on the detector array. We term these photons Stray-light. Additionally, there are also photons that do not undergo the focused double reflections in the optics and we term these Ghost Rays. We present detailed analysis and characterization of these two components and discuss how they impact observations. Finally, we discuss how they could have been prevented and should be in future observatories.Comment: Published in Journal of Astronomical Telescopes, Instruments, and Systems. Open Access. http://dx.doi.org/10.1117/1.JATIS.3.4.04400

X-ray polarimetry with the Polarization Spectroscopic Telescope Array (PolSTAR)

This paper describes the Polarization Spectroscopic Telescope Array (PolSTAR), a mission proposed to NASA’s 2014 Small Explorer (SMEX) announcement of opportunity. PolSTAR measures the linear polarization of 3–50 keV (requirement; goal: 2.5–70 keV) X-rays probing the behavior of matter, radiation and the very fabric of spacetime under the extreme conditions close to the event horizons of black holes, as well as in and around magnetars and neutron stars. The PolSTAR design is based on the technology developed for the Nuclear Spectroscopic Telescope Array (NuSTAR) mission launched in June 2012. In particular, it uses the same X-ray optics, extendable telescope boom, optical bench, and CdZnTe detectors as NuSTAR. The mission has the sensitivity to measure ∼1% linear polarization fractions for X-ray sources with fluxes down to ∼5 mCrab. This paper describes the PolSTAR design as well as the science drivers and the potential science return

Measuring the Evolution of the NuSTAR Detector Gains

The memo describes the methods used to track the long-term gain variations in the NuSTAR detectors. It builds on the analysis presented in Madsen et al. (2015) using the deployable calibration source to measure the gain drift in the NuSTAR CdZnTe detectors. This is intended to be a live document that is periodically updated as new entries are required in the NuSTAR gain CALDB files. This document covers analysis up through early-2022 and the gain v011 CALDB file released in version 20240226.Comment: 11 page, 7 figures. Intended as a living, easy-to-find document. No intention of submitting this to a journa

Effective area calibration of the nuclear spectroscopic telescope array (NuSTAR)

The Nuclear Spectroscopic Telescope ARray (NuSTAR) has been in orbit for 6 years, and with the calibration data accumulated over that period we have taken a new look at the effective area calibration. The NuSTAR 10-m focal length is achieved using an extendible mast, which flexes due to solar illumination. This results in individual observations sampling a range of off-axis angles rather than a particular off-axis angle. In our new approach, we have split over 50 individual Crab observations into segments at particular off-axis angles. We combine segments from different observations at the same off-axis angle to generate a new set of synthetic spectra, which we use to calibrate the vignetting function of the optics against the canonical Crab spectrum