Field Scanner Design for MUSTANG of the Green Bank Telescope

MUSTANG is a bolometer camera for the Green Bank Telescope (GBT) working at a frequency of 90 GHz. The detector has a field of view of 40 arcseconds. To cancel out random emission change from atmosphere and other sources, requires a fast scanning reflecting system with a few arcminute ranges. In this paper, the aberrations of an off-axis system are reviewed. The condition for an optimized system is provided. In an optimized system, as additional image transfer mirrors are introduced, new aberrations of the off-axis system may be reintroduced, resulting in a limited field of view. In this paper, different scanning mirror arrangements for the GBT system are analyzed through the ray tracing analysis. These include using the subreflector as the scanning mirror, chopping a flat mirror and transferring image with an ellipse mirror, and chopping a flat mirror and transferring image with a pair of face-to-face paraboloid mirrors. The system analysis shows that chopping a flat mirror and using a well aligned pair of paraboloids can generate the required field of view for the MUSTUNG detector system, while other systems all suffer from larger off-axis aberrations added by the system modification. The spot diagrams of the well aligned pair of paraboloids produced is only about one Airy disk size within a scanning angle of about 3 arcmin.Comment: 7 pages, 9 figure

Le regole del gioco: Primo incontro con l'ingegneria strategica

Cu particles decorated carbon composite microspheres (CCMs) with a unique sesame ball structure have been prepared by combining the mass-producible spray drying technique with calcinations. The conventional cuprammonium cellulose complex solution obtained by dissolving cellulose in a cuprammonia solution has been applied as raw materials for the preparation of Cu­(NH₃)₄²⁺/cellulose complex microspheres via a spray drying process. The resulted Cu­(NH₃)₄²⁺/cellulose complex microspheres are then transformed into the Cu particles homogeneously decorated porous carbon spheres <i>in situ</i> by calcinations at 450 or 550 °C. The coordination effect between the Cu­(NH₃)₄²⁺ species and the hydroxyl groups of the cellulose macromolecules has been exploited for directing the dispersion of the Cu particles in the resultant composite CCMs. The antimicrobial effects of the CCMs are evaluated by determining the minimum growth inhibitory concentrations using Staphylococcus aureus and Escherichia coli as representatives, respectively. The CCMs show high efficiency catalytic properties to the conversion of 4-nitrophenol to 4-aminophenol using NaBH₄ as a reductant in a mild condition. The recyclability and stability of the CCM catalysts have also been studied

AT2023lli: A Tidal Disruption Event with Prominent Optical Early Bump and Delayed Episodic X-ray Emission

High-cadence, multiwavelength observations have continuously revealed the diversity of tidal disruption events (TDEs), thus greatly advancing our knowledge and understanding of TDEs. In this work, we conducted an intensive optical-UV and X-ray follow-up campaign of TDE AT2023lli, and found a remarkable month-long bump in its UV/optical light curve nearly two months prior to maximum brightness. The bump represents the longest separation time from the main peak among known TDEs to date. The main UV/optical outburst declines as $t^{-4.10}$, making it one of the fastest decaying optically selected TDEs. Furthermore, we detected sporadic X-ray emission 30 days after the UV/optical peak, accompanied by a reduction in the period of inactivity. It is proposed that the UV/optical bump could be caused by the self-intersection of the stream debris, whereas the primary peak is generated by the reprocessed emission of the accretion process. In addition, our results suggest that episodic X-ray radiation during the initial phase of decline may be due to the patched obscurer surrounding the accretion disk, a phenomenon associated with the inhomogeneous reprocessing process. The double TDE scenario, in which two stars are disrupted in sequence, is also a possible explanation for producing the observed early bump and main peak. We anticipate that the multicolor light curves of TDEs, especially in the very early stages, and the underlying physics can be better understood in the near future with the assistance of dedicated surveys such as the deep high-cadence survey of the 2.5-meter Wide Field Survey Telescope (WFST).Comment: 14 pages, 8 figures,accepted for publication by ApJ