The x-ray polarization of compact objects in x-ray binaries allows us to understand the complex spacetimes surrounding these sources. XL-Calibur is a state-of-the-art, balloon-borne telescope that measures the linear polarization of stellar-mass black holes, neutron stars, and nebulae in the 15-80 keV energy band. The selected energy range allows for observing coronal emission from black holes while also enabling us to narrow down on emission models from neutron stars, pulsars, and magnetars. Early in 2024, XL-Calibur will be launched from Kiruna, Sweden for approximately 10 days to observe Cyg X-1 and Cyg X-3, or other sources chosen based on flux levels at the time of flight. Observations might be coordinated with the recently launched Imaging x-ray Polarimetry Explorer mission which measures polarization in the complimentary 2-8 keV band. Combined XL-Calibur and IXPE observations will yield information on both soft and hard x-rays allowing us to decompose the total emission from black holes into thermal disk and coronal. We discuss the characterization of the XL-Calibur CdZnTe detectors, the telescope mirror and truss setup, and preliminary results from our most recent flight.
We present the detector performance and early science results from GRBAlpha, a 1U CubeSat mission, which is a technological pathfinder to a future constellation of nanosatellites monitoring gamma-ray bursts (GRBs). GRBAlpha was launched in March 2021 and operates on a 550 km altitude sun-synchronous orbit. The gamma-ray burst detector onboard GRBAlpha consists of a 75×75×5 mm CsI(Tl) scintillator, read out by a dual-channel multi-pixel photon counter (MPPC) setup. It is sensitive in the ∼30−900 keV range. The main goal of GRBAlpha is the in-orbit demonstration of the detector concept, verification of the detector’s lifetime, and measurement of the background level on low-Earth orbit, including regions inside the outer Van Allen radiation belt and in the South Atlantic anomaly. GRBAlpha has already detected five, both long and short, GRBs and two bursts were detected within a time-span of only 8 hours, proving that nanosatellites can be used for routine detection of gamma-ray transients. For one GRB, we were able to obtain a high resolution spectrum and compare it with measurements from the Swift satellite. We find that, due to the variable background, the time fraction of about 67% of the low-Earth polar orbit is suitable for gamma-ray burst detection. One year after launch, the detector
The super DIOS mission is a candidate of Japanese future satellite program after 2030’s and this scientific concept has been approved to establish an ISAS/JAXA research group. The main aim of the super DIOS is a x-ray survey to quantify of baryons, over several scales, from the circumgalactic medium around galaxies, cluster outskirts to the warm-hot intergalactic medium along the large cosmic structure by detections of the redshifted emission lines from OVII, OVIII and other ions, for investigating the dynamical state of baryons, including energy flow and metal cycles, in the universe. The super DIOS will have a resolution of 15 arcseconds and 3 kilo-pixels of transition edge sensor (TES) and its micro-wave SQUID multiplexer read-out system. This performance resolves most contaminating x-ray sources and reduces the level of diffuse x-ray background after subtracting point-like sources. The technical achievements of on-board cooling system reached by the Hitomi (ASTRO-H) and XRISM for microcalorimeter provide baseline technology for Super DIOS. We will also have a large scale collaborations with multi wave-length survey projects such as optical and radio survey observations.
This paper introduces a second-generation balloon-borne hard X-ray polarimetry mission, XL-Calibur. X-ray polarimetry promises to give qualitatively new information about high-energy astrophysical sources, such as pulsars and binary black hole systems. The XL-Calibur contains a grazing incidence X-ray telescope with a focal plane detector unit that is sensitive to linear polarization. The telescope is very similar in design to the ASTRO-H HXT telescopes that has the world’s largest effective area above ~10 keV. The detector unit combines a low atomic number Compton scatterer with a CdZnTe detector assembly to measure the polarization making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation. It also contains a CdZnTe imager at the bottom. The detector assembly is surrounded by the improved anti-coincidence shielding, giving a better sensitivity. The pointing system with arcsecond accuracy will be achieved.
CFRP is a composite material composed of carbon fiber and resin. CFRP is commonly applied to the aerospace industry which requires lightweight and intensity. Thanks to superior formability of CFRP, we can form shape of Wolter-1 optics, which consists of paraboloid and hyperboloid, to a monolithic substrate. Since the surface roughness of a CFRP substrate is a few µm, we have to make the smooth surface for reflecting X-rays on the CFRP substrate. We have developed a new method of shaping the reflective surface instead of the replica method used in lightweight X-ray mirrors such as Astro-H. In the new method, the reflective surface is formed by pasting thin sheet-glasses with 100 µm thick onto the CFRP substrate. The thin sheet-glass has a surface roughness about 0.4 nm as measured by Zygo. We fabricated a CFRP mirror pasting thin sheet-glasses, and then coated tungsten on the mirror in June 2020. The figure error (s) of the CFRP mirror was achieved to be about 1-2 μm by stacking the CFRP mirror on the housing module. X-ray imaging quality of the CFRP mirror was measured at Spring-8 in July 2020. The half-power diameter of the CFRP mirror was estimated to be about 150 arcsec, which was nearly equal to the prediction from a distribution of the slope error deduced from the surface profile. We describe a future plan to improve the image quality of the CFRP mirror.
The X-Ray Imaging and Spectroscopy Mission (XRISM) is the successor to the 2016 Hitomi mission that ended prematurely. Like Hitomi, the primary science goals are to examine astrophysical problems with precise highresolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. XRISM carries a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly and a co-aligned X-ray CCD camera that covers the same energy band over a large field of view. XRISM utilizes Hitomi heritage, but all designs were reviewed. The attitude and orbit control system were improved in hardware and software. The number of star sensors were increased from two to three to improve coverage and robustness in onboard attitude determination and to obtain a wider field of view sun sensor. The fault detection, isolation, and reconfiguration (FDIR) system was carefully examined and reconfigured. Together with a planned increase of ground support stations, the survivability of the spacecraft is significantly improved.
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