System performance of a cryogenic test-bed for the time-division multiplexing readout for NewAthena X-IFU
Authors:
Davide Vaccaro,
Jan van der Kuur,
Paul van der Hulst,
Tobias Vos,
Martin de Wit,
Luciano Gottardi,
Kevin Ravensberg,
Emanuele Taralli,
Joseph Adams,
Simon Bandler,
Douglas Bennet,
James Chervenak,
Bertrand Doriese,
Malcolm Durkin,
Johnathon Gard,
Carl Reintsema,
Kazuhiro Sakai,
Steven Smith,
Joel Ullom,
Nicholas Wakeham,
Jan-Willem den Herder,
Brian jackson,
Pourya Khosropanah,
Jian-Rong Gao,
Peter Roelfsema
, et al. (1 additional authors not shown)
Abstract:
The X-ray Integral Field Unit (X-IFU) is an instrument of ESA's future NewAthena space observatory, with the goal to provide high-energy resolution ($<$ 4 eV at X-ray energies up to 7 keV) and high-spatial resolution (9") spectroscopic imaging over the X-ray energy range from 200 eV to 12 keV, by means of an array of about 1500 transition-edge sensors (TES) read out via SQUID time-division multipl…
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The X-ray Integral Field Unit (X-IFU) is an instrument of ESA's future NewAthena space observatory, with the goal to provide high-energy resolution ($<$ 4 eV at X-ray energies up to 7 keV) and high-spatial resolution (9") spectroscopic imaging over the X-ray energy range from 200 eV to 12 keV, by means of an array of about 1500 transition-edge sensors (TES) read out via SQUID time-division multiplexing (TDM). A TDM-based laboratory test-bed has been assembled at SRON, hosting an array of $75\times 75\ \upmu$m$^2$ TESs that are read out via 2-column $\times$ 32-row TDM. A system component that is critical to high-performance operation is the wiring harness that connects the room-temperature electronics to the cryogenic readout componentry. We report here on our characterization of such a test-bed, whose harness has a length close to what envisioned for X-IFU, which allowed to achieve a co-added energy resolution at a level of 2.7~eV FWHM at 6~keV via 32-row readout. In addition, we provide an outlook on the integration of TDM readout into the X-IFU Focal-Plane Assembly Development Model.
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Submitted 5 November, 2024; v1 submitted 9 September, 2024;
originally announced September 2024.
Fitting the light curves of Sagittarius A* with a hot-spot model
Authors:
A. I. Yfantis,
M. A. Mościbrodzka,
M. Wielgus,
J. T. Vos,
A. Jimenez-Rosales
Abstract:
Sagittarius A* exhibits frequent flaring activity across the electromagnetic spectrum. Signatures of an orbiting hot spot have been identified in the polarized millimeter wavelength light curves observed with ALMA in 2017 immediately after an X-ray flare. The nature of these hot spots remains uncertain. We expanded existing theoretical hot-spot models created to describe the Sgr A* polarized emiss…
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Sagittarius A* exhibits frequent flaring activity across the electromagnetic spectrum. Signatures of an orbiting hot spot have been identified in the polarized millimeter wavelength light curves observed with ALMA in 2017 immediately after an X-ray flare. The nature of these hot spots remains uncertain. We expanded existing theoretical hot-spot models created to describe the Sgr A* polarized emission at millimeter wavelengths. We sampled the posterior space, identifying best-fitting parameters and characterizing uncertainties. Using the numerical radiative transfer code ipole, we defined a semi-analytical model describing a ball of plasma orbiting Sgr A*, threaded with a magnetic field and emitting synchrotron radiation. We then explored the posterior space in the Bayesian framework of dynesty. We fit the static background emission separately, using a radiatively inefficient accretion flow model. We considered eight models with a varying level of complexity, distinguished by choices regarding dynamically important cooling, non-Keplerian motion, and magnetic field polarity. All models converge to realizations that fit the data, but one model without cooling, non-Keplerian motion, and magnetic field pointing toward us improved the fit significantly and also matched the observed circular polarization. Our models represent observational data well and allow testing various effects in a systematic manner. From our analysis, we have inferred an inclination of $155-160$ deg, which corroborates previous estimates, a preferred period of 90 minutes, and an orbital radius of $9-12$ gravitational radii. Our non-Keplerian models indicate a preference for an orbital velocity of $0.6-0.9$ times the Keplerian value. Last, all our models agree on a high dimensionless spin value ($a_{*}>0.8$), but the impact of spin on the corresponding light curves is subdominant with respect to other parameters.
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Submitted 5 March, 2024; v1 submitted 11 October, 2023;
originally announced October 2023.