The level and uncertainty of the particle induced background in CCD detectors plays a crucial role for future X-ray instruments, such as the Wide Field Imager (WFI) onboard Athena. To mitigate the background systematic uncertainties, which will limit the Athena science goals, we aim to understand the relationship between the energetic charged particles interacting in the detector and satellite, and the instrumental science background to an unprecedented level. These particles produce easily identified "cosmic-ray tracks" along with less easily identified signals produced by secondary particles, e.g., X-rays generated by particle interactions with the instrument and indistinguishable from genuine sky X-rays. We utilize the Small Window Mode of the PN camera onboard XMM-Newton to understand the time, spatial and energy dependence of the various background components, particularly the particle induced background. While the distribution of particle events follows expected detector readout patterns, we find a particle track length distribution inconsistent with the simple, isotropic model. We also find that the detector mode-specific readout results in a shifted Cu fluorescent line. We illustrate that on long timescales the variability of the particle background correlates well with the solar cycle. This 20-year lightcurve, can be reproduced by a particle detector onboard Chandra, the HRC anti-coincidence shield. We conclude that the self-anti-coincidence method of removing X-ray-like events near detected particle tracks in the same frame can be optimized with the inclusion of additional information, such as the energy of the X-ray. The results presented here are relevant for any future pixelated X-ray imaging detector, and could allow the WFI to probe to truly faint X-ray surface brightness.

Hybrid CMOS detectors (HCDs) have several excellent features as high-performance X-ray detectors, including rapid readout, deep-depletion silicon for high quantum efficiency, radiation hardness, and low power. Random telegraph noise (RTN) is a type of noise that can reduce the performance of HCDs and other CMOS sensors. After finding and quantifying RTN in the recently developed engineering grade Speedster-EXD550 HCDs, this form of noise has also been found in other X-ray HCDs. We aim to investigate its presence and characteristics in the relatively mature H2RG X-ray HCD and to compare it with that of the Speedster-EXD550. We use archival data taken with an H2RG X-ray HCD at two different temperatures to determine the percentage of pixels that are being impacted by RTN. We identify RTN in 0.42% of pixels when the detector is operated at 140 K, but we are only able to identify RTN in 0.060% of pixels when the detector is operated at 160 K. We characterize RTN in two Speedster-EXD550 detectors, identifying 5.1% of pixels with RTN in one detector and 7.1% in another, which is significantly more than the H2RG. These results verify the difference between two different HCDs and provide techniques that can be applied to future HCDs. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License.Distribution or reproduction of this work in whole or in part requires full attribution of the originalpublication, including its DOI.

We report the results of an extensive set of simulations exploring the sensitivity of the BlackCAT CubeSat to long-duration gamma-ray bursts (GRBs). BlackCAT is a NASA APRA-funded CubeSat mission for the detection and real-time subarcminute localization of high-redshift ( z ≳ 3.5) GRBs. Thanks to their luminous and long-lived afterglow emissions, GRBs are uniquely valuable probes of high-redshift star-forming galaxies and the intergalactic medium. In addition, each detected GRB with a known redshift serves to localize a region of high-redshift star formation in three dimensions, enabling deep follow-on searches for host galaxies and associated local and large-scale structures. We explore two distinct models for the GRB redshift distribution and luminosity function, both consistent with Swift observations. We find that, for either model, BlackCAT is expected to detect a mean of 42 bursts per year on orbit, with 6.7% to 10% of these at z > 3.5. BlackCAT bursts will be localized to an r _90 ≲ 55″ precision and reported to the community within seconds. Due to the mission orbit and pointing scheme, bursts will be located in the night sky and well placed for deep multiwavelength follow-up observations. BlackCAT is on schedule to achieve launch readiness in 2025.

BlackCAT is a NASA-funded 6U CubeSat mission planned to be launch-ready in 2025. BlackCAT will use its wide field-of-view and arcminute-scale localization to identify gamma-ray bursts (GRBs), gravitational-wave counterparts, and other high-energy transient events. The mission will send rapid alerts after detection of a transient event, enabling prompt follow-up from other ground- and space-based observatories. The science instrument is a coded aperture telescope, using a focal plane with four Speedster-EXD550 event-driven X-ray hybrid CMOS detectors (HCDs) and a gold-plated nickel coded mask to localize source positions. We describe methods for the calibration of the detectors and the assembled coded-aperture instrument. We also briefly discuss plans for in-flight commissioning and calibration.

The BlackCAT CubeSat is an X-ray coded-aperture-telescope observatory that is expected to launch in 2025. It is designed for observations of bright X-ray sources in the 0.5-20 keV band. The instrument will have a wide field of view (0.85 steradian) and be capable of catching gamma ray bursts (GRBs) from the distant universe, galactic transients, and flares from blazars, while monitoring the X-ray sky. In addition to the primary high-redshift GRB science, BlackCAT can monitor known source variability and search for rare and exciting events including gravitational-wave X-ray counterparts, magnetar flares, supernova shock breakouts, and tidal disruption events. The mission will thus function as a multi-wavelength and multi-messenger complement to present and future facilities including LIGO, VIRGO, KAGRA, IceCube, KM3NET, LSST, LOFAR, SKA, and CTA. Rapid notifications of burst positions will be transmitted to the ground via satellite network and then relayed to the GCN. The name BlackCAT is derived from its scientific emphasis on black-hole-related transient events being observed with a coded aperture telescope (CAT). BlackCAT will serve as the scientific payload aboard a commercial 6U CubeSat spacecraft provided by NanoAvionics US. Novel event-driven X-ray hybrid CMOS detectors will form the focal plane array. In addition to carrying out science programs related to distant GRBs, transients, and X-ray sky monitoring, BlackCAT will also serve as a pathfinder for future economical missions combining multiple BlackCAT modules on either a single small satellite or on multiple CubeSats. BlackCAT will also serve as a platform for new X-ray hybrid CMOS detector development. An overview of BlackCAT in its current development state and its current status will be presented.

Based on our Chandra imaging-spectroscopic observations, we present the latest evolution of the X-ray remnant of SN 1987A. Recent changes in the electron temperatures and volume emission measures suggest that the blast wave in SN 1987A is moving out of the dense inner ring structure, also called the equatorial ring (ER). The 0.5-2.0 keV X-ray light curve shows a linearly declining trend (by $\sim$4.5 % yr$^{-1}$) between 2016 and 2020, as the blast wave heats the hitherto unknown circumstellar medium (CSM) outside the ER. While the peak X-ray emission in the latest 0.3-8.0 keV image is still within the ER, the radial expansion rate in the 3.0-8.0 keV images suggests an increasing contribution of the X-ray emission from less dense CSM since 2012, at least partly from beyond the ER. It is remarkable that, since 2020, the declining soft X-ray flux has stabilized around $\sim$7 $\times$ 10$^{-12}$ erg s$^{-1}$ cm$^{-2}$, which may signal a contribution from the reverse-shocked outer layers of ejecta as predicted by the 3-D magneto-hydrodynamic (MHD) models. In the latest ACIS spectrum of supernova remnant (SNR) 1987A in 2022 we report a significant detection of the Fe K line at $\sim$6.7 keV, which may be due to changing thermal conditions of the X-ray emitting CSM and/or the onset of reverse shock interactions with the Fe-ejecta.

The Penn State University High-Energy Astrophysics Detector and Instrumentation (HEADI) Lab, in collaboration with Teledyne Imaging Sensors (TIS), has continued its efforts to improve soft x-ray Hybrid CMOS detectors (HCDs) on several fronts. We report on the read noise and energy resolution for the H1RG and the H2RG using a cryogenic SIDECAR (TM), which gained TRL 9 and flight heritage through the Water Recovery X-ray Rocket Mission in 2018. We also describe the 40-mu m event-driven Speedster-EXD HCD, which has been scaled up from a 64x64 array to an 550x550 array. The readout circuitry within the ROIC for the Speedster-EXD contains a high-gain capacitive transimpedance amplifier (CTIA) to negate pixel cross-talk, in-pixel correlated double sampling (CDS) for correction of reset noise variations, and an in-pixel comparator enabling event-driven readout. Here we report on read noise and energy resolution measurements for the Speedster-EXD and discuss the upcoming BlackCAT CubeSAT, on which the Speedster-EXD550 will fly, raising the TRL of these HCDs. Further, to meet the requirements of future high-throughput and high spatial resolution Lynx-like x-ray observatories, HCDs with fast readout and small pixel sizes have been developed. Here we report on the energy resolution and the lowest measured read noise of any x-ray HCD to-date for the 12.5-mu m 128x128 prototype Small-pixel HCD, as well as present the current results for the newest x-ray HCD, the Small-pixel1024. The Small-pixel1024 is a 12.5 mu m 1024x1024 HCD utilizing a high-gain CTIA and in-pixel CDS. Finally, we report on the development efforts between Penn State and Teledyne on a new event-driven HCD, which will retain the low read noise of the Small-pixel HCD while having event-driven capabilities like the Speedster-EXD.

Much of the baryonic matter in the Universe, including the most active and luminous sources, are best studied in the X-ray band. Key advances in X-ray optics and detectors have paved the way for the Advanced X-ray Imaging Satellite (AXIS), a Probe-class mission that is a major improvement over Chandra, which has generated a steady stream of important discoveries for the past 2 decades. AXIS can be launched in the late 2020s and will transform our understanding in several major areas of astrophysics, including the growth and fueling of supermassive black holes, galaxy formation and evolution, the microphysics of cosmic plasmas, the time-variable universe, and a wide variety of cutting-edge studies. Relative to Chandra, the AXIS PSF is nearly twice as sharp on-axis; its field of view for subarcsecond imaging 70 times larger by area; its effective area at 1 keV is 10 times larger. The low-Earth orbit ensures a low and stable detector background, resulting in 50 times greater sensitivity than Chandra for extended sources. AXIS has a rapid repointing response with operations similar to Swift, but is 100 times more sensitive for time-domain science. These capabilities open up a vast discovery space and complement the next generation of astronomical observatories. A high-spectral-resolution mission (Athena) operating at the same time as a high-angular-resolution mission (AXIS) greatly increases the range of scientific discovery. AXIS will use lightweight X-ray optics made of thin single-crystal silicon mirrors developed at NASA Goddard. The detector array builds on a long legacy of X-ray CCD and provides improved photon localization, much faster readout time, and broader energy band. The estimated mission costs are consistent with the $1B Probe mission cost guideline.

Future x-ray observatories will require imaging detectors with fast readout speeds that simultaneously achieve or exceed the other high performance parameters of x-ray charge-coupled devices (CCDs) used in many missions over the past three decades. Fast readout will reduce the impact of pile-up in missions with large collecting areas while also improving performance in other respects like timing resolution. Event-driven readout, in which only pixels with charge from x-ray events are read out, can be used to achieve these faster operating speeds. Speedster-EXD550 detectors are hybrid complementary metal-oxide semiconductor (CMOS) detectors capable of event-driven readout, developed by Teledyne Imaging Sensors and Penn State University. We present initial results from measurements of the first of these detectors, demonstrating their capabilities and performance in both full-frame and event-driven readout modes. These include dark current, read noise, gain variation, and energy resolution measurements from the first two engineering-grade devices.

BlackCAT is a NASA CubeSat mission planned to be launch-ready in early 2025. Using a wide-field telescope, this 6U CubeSat will monitor the soft x-ray sky, searching for high-redshift Gamma-Ray Bursts (GRBs), gravitational-wave counterparts, and other transient events. After detecting burst events, BlackCAT will be capable of transmitting rapid alerts to enable prompt follow-up observations. The instrument is composed of a coded-aperture telescope using an array of event-driven x-ray Hybrid CMOS Detectors (HCDs) in its focal plane. In this paper, we provide a brief update on the design and status of the mission.

The novel Speedster-EXD550 is a 550×550-pixel x-ray Hybrid CMOS Detector (HCD) with event-driven readout capabilities and 40-micron pixel pitch. In event-driven readout mode, only the pixels that contain sufficient liberated charge from the absorption of an x-ray will be read out. Event-driven readout allows for even faster readout speed than other HCDs, reaching readout speeds up to 10,000 frames/sec. The high frame rate of the Speedster-EXD550 is desirable for future missions as the effects of dark current and x-ray pile-up will be reduced. The readout circuitry within the ROIC for the Speedster-EXD550 contains a high-gain capacitive transimpedance amplifier, in-pixel correlated double sampling, and an in-pixel comparator enabling event-driven readout. The Speedster-EXD550 also utilizes column-parallel on-chip digitization. The ability of the Speedster-EXD550 will be demonstrated on BlackCAT, a funded NASA CubeSat mission. Testing and characterization of the Speedster-EXD550 has been done by the Penn State High Energy Astrophysics Detector and Instrumentation lab in both full-frame and event-driven readout modes. A radioactive 55Fe source was used for the measurements presented. Here, we discuss the methods and recent results for the characterization of the Speedster-EXD550 dark current, read noise, gain, and gain variation.

A science goal of many future x-ray observatories is mapping the cosmic web through deep exposures of faint diffuse sources. Such observations require low background and the best possible knowledge of the remaining unrejected background. The dominant contribution to the background above 1-2 keV is from Galactic cosmic ray protons. Their flux and spectrum are modulated by the solar cycle but also by solar activity on shorter timescales. Understanding this variability may prove crucial to reducing background uncertainty for ESA's Athena x-ray observatory and other missions with large collecting area. We examine the variability of the particle background as measured by ACIS on the Chandra x-ray observatory and compare that variability to that measured by the alpha magnetic spectrometer (AMS), a precision particle detector on the ISS. We show that cosmic ray proton variability measured by AMS is well matched to the ACIS background and can be used to estimate proton energies responsible for the background. We discuss how this can inform future missions.

We present our velocity measurements of 59 clumpy, metal-rich ejecta knots in the supernova remnant (SNR) of SN 1572 (Tycho). We use our 450 ks Chandra High Energy Transmission Grating Spectrometer observation to measure the Doppler shift of the He-like Si K alpha line-center wavelength emitted from these knots to find their line-of-sight (radial) velocities (nu(r)). We find nu(r) up to similar to 5500 km s(-1), with roughly consistent speeds between blueshifted and redshifted ejecta knots. We also measure the proper motions (PMs) for our sample based on archival Chandra Advanced CCD Imaging Spectrometer data taken from 2003, 2009, and 2015. We estimate PMs up to 0.'' 35 yr(-1), which corresponds to a transverse velocity of about 5800 km s(-1) for the distance of 3.5 kpc to Tycho. Our nu(r) and transverse velocity measurements imply space velocities of similar to 1900-6000 km s(-1) for the ejecta knots in Tycho. We estimate a new expansion center of R.A.(J2000) = 00(h)25(m)18(s).725 +/- 1(s).157 and decl.(J2000) = +64 degrees 08'02.'' 5 +/- 11.'' 2 from our PM measurements, consistent to within similar to 13 '' of the geometric center. The distribution of space velocities throughout the remnant suggests that the southeast quadrant generally expands faster than the rest of the SNR. We find that blueshifted knots are projected more in the northern shell, while redshifted knots are more in the southern shell. The previously estimated reverse shock position is consistent with most of our estimated ejecta distribution; however, some ejecta show deviations from the 1D picture of the reverse shock.

The BlackCAT CubeSat will monitor the soft X-ray sky, searching for high-redshift gamma-ray bursts (GRBs), gravitational-wave counterparts, and other high-energy transient events. BlackCAT will utilize a coded-aperture mask to localize sources to sub-arcminute precision. We investigate the primary forms of background that will affect this mission and present different methods to suppress these sources in order to increase the sensitivity of this mission. In the absence of mitigation, the optical and ultraviolet backgrounds could increase noise in the hybrid CMOS detectors (HCDs) used in this mission and potentially trigger spurious events. We plan to use a polyimide filter to suppress extreme ultraviolet emission produced by the geocorona. The HCDs and polyimide filter will be coated with a thin aluminum layer to block optical light. We estimate the magnitude of the observed cosmic and galactic X-ray backgrounds. Additionally, we investigate the impact of trapped particles on the sensitivity and duty cycle of the mission. We discuss the effect of these various sources of background on the sensitivity of BlackCAT to GRBs and other transient events.

The BlackCAT observatory makes use of a 6U CubeSat platform with an x-ray coded aperture telescope payload. BlackCAT, utilizing its wide field-of-view (0.9 steradians), will monitor deep space for a variety of x-ray transients and flares, with a primary focus on high redshift gamma-ray bursts. The payload consists of a detector module (DM), a dedicated electronics package, mechanical mounts, and thermal straps for passive cooling. The DM includes the DM housing, coded aperture mask, optical blocking filter (OBF), and a focal plane array (FPA) consisting of four x-ray hybrid CMOS detectors (HCDs). Each of these four detectors is a 550×550-pixel Speedster-EXD silicon sensor with a molybdenum package to provide a low-strain thermal and mechanical mounting structure. The primary purpose of the electronics package is reading out and processing data from the HCDs. For optimal scientific performance, the FPA must be maintained at a temperature of -40°C or below. The detectors have an aluminum OBF directly deposited because the silicon detectors are sensitive to optical light. For additional optical blocking against the brightest optical background and UV light, a separate OBF will be mounted in front of the detector surface. The coded aperture mask is a wire mesh made of nickel with a thin layer of gold coating all sides. The mask allows approximately 40% of incident x-rays to strike the detector in a unique pattern that is dependent upon source position and the open cell geometry. This allows for the angular position of the source to be determined to sub-arcminute precision. To prevent deformation due to thermal strain, the mask is required to maintain a set temperature between 10°C and 20°C. The DM housing acts as the primary support structure for the payload and is thick enough to provide shielding from off-axis x-rays and optical/UV light. The OBF is directly connected to the DM housing, while the mask and FPA are both thermally isolated via standoffs to meet respective temperature requirements. Additionally, the DM housing is the interface between the payload components and the chassis. We present an overview of the mechanical and thermal payload requirements, as well as design constraints imposed by the 6U CubeSat form factor. We describe the designs used to meet these requirements and present analyses to demonstrate the efficacy of these designs. The mechanical requirements and information from thermal analyses will drive the overall design of the BlackCAT CubeSat to achieve the science goals throughout the mission lifetime.

The Wide Field Imager (WFI) flying on Athena will usher in the next era of studying the hot and energetic Universe. WFI observations of faint, diffuse sources will be limited by uncertainty in the background produced by high-energy particles. These particles produce easily identified "cosmic-ray tracks" along with signals from secondary photons and electrons generated by particle interactions with the instrument. The signal from these secondaries is identical to the X-rays focused by the optics, and cannot be filtered without also eliminating these precious photons. As part of a larger effort to understand the WFI background, we here present results from a study of background-reduction techniques that exploit the spatial correlation between cosmic-ray particle tracks and secondary events. We use Geant4 simulations to generate a realistic particle background, sort this into simulated WFI frames, and process those frames in a similar way to the expected flight and ground software to produce a WFI observation containing only particle background. The technique under study, Self Anti-Coincidence or SAC, then selectively filters regions of the detector around particle tracks, turning the WFI into its own anti-coincidence detector. We show that SAC is effective at improving the systematic uncertainty for observations of faint, diffuse sources, but at the cost of statistical uncertainty due to a reduction in signal. If sufficient pixel pulse-height information is telemetered to the ground for each frame, then this technique can be applied selectively based on the science goals, providing flexibility without affecting the data quality for other science. The results presented here are relevant for any future silicon-based pixelated X-ray imaging detector, and could allow the WFI and similar instruments to probe to truly faint X-ray surface brightness.

Next-generation X-ray observatories, such as the Lynx X-ray Observatory Mission Concept or other similar concepts in the coming decade, will require detectors with high quantum efficiency (QE) across the soft X-ray band to observe the faint objects that drive their mission science objectives. Hybrid CMOS Detectors (HCDs), a form of active-pixel sensor, are promising candidates for use on these missions because of their fast read-out, low power consumption, and intrinsic radiation hardness. In this work, we present QE measurements of a Teledyne H2RG HCD, performed using a gas-flow proportional counter as a reference detector. We find that this detector achieves high QE across the soft X-ray band, with an effective QE of 94.6 ± 1.1 % at the Mn Kα/Kβ energies (5.90/6.49 keV), 98.3 ± 1.9 % at the Al Kα energy (1.49 keV), 85.6 ± 2.8 % at the O Kα energy (0.52 keV), and 61.3 ± 1.1 % at the C Kα energy (0.28 keV). These values are in good agreement with our model, based on the absorption of detector layers. We find similar results in a more restrictive analysis considering only high-quality events, with only somewhat reduced QE at lower energies.

Astrometry is a powerful technique in astrophysics to measure three-dimensional positions of stars and other astrophysical objects, including exoplanets and the gravitational influence they have on each other.Interferometric astrometry is presented here as just one in a suite of powerful astrometric techniques, which include space-based, seeing-limited and wide-angle adaptive optics techniques.Fundamental limits are discussed, demonstrating that even ground-based techniques have the capability for astrometry at the single micro-arcsecond level, should sufficiently sophisticated instrumentation be constructed for both the current generation of single telescopes and long-baseline optical interferometers.