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1. A close quasar pair in a disk–disk galaxy merger at z = 2.17

   https://doi.org/10.1038/s41586-023-05766-6  

   Chen, Yu-Ching ; Liu, Xin ; Foord, Adi ; Shen, Yue ; Oguri, Masamune ; Chen, Nianyi ; Di Matteo, Tiziana ; Holgado, Miguel ; Hwang, Hsiang-Chih ; Zakamska, Nadia ( April 2023 , Nature)
2. A Circumplanetary Disk around PDS70c

   https://doi.org/10.3847/2041-8213/ac0f83  

   Benisty, Myriam ; Bae, Jaehan ; Facchini, Stefano ; Keppler, Miriam ; Teague, Richard ; Isella, Andrea ; Kurtovic, Nicolas T. ; Pérez, Laura M. ; Sierra, Anibal ; Andrews, Sean M. ; et al ( July 2021 , The Astrophysical Journal Letters)
3. A triple-star system with a misaligned and warped circumstellar disk shaped by disk tearing

   https://doi.org/10.1126/science.aba4633  

   Kraus, Stefan ; Kreplin, Alexander ; Young, Alison K. ; Bate, Matthew R. ; Monnier, John D. ; Harries, Tim J. ; Avenhaus, Henning ; Kluska, Jacques ; Laws, Anna S. E. ; Rich, Evan A. ; et al ( September 2020 , Science)

   Young stars are surrounded by a circumstellar disk of gas and dust, within which planet formation can occur. Gravitational forces in multiple star systems can disrupt the disk. Theoretical models predict that if the disk is misaligned with the orbital plane of the stars, the disk should warp and break into precessing rings, a phenomenon known as disk tearing. We present observations of the triple-star system GW Orionis, finding evidence for disk tearing. Our images show an eccentric ring that is misaligned with the orbital planes and the outer disk. The ring casts shadows on a strongly warped intermediate region of the disk. If planets can form within the warped disk, disk tearing could provide a mechanism for forming wide-separation planets on oblique orbits.

    

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4. Damping and Stiffness Mistuning Effects in a Bladed Disk With Varied Disk Coupling

   https://doi.org/10.1115/1.4063542  

   Krizak, Troy ; Kurstak, Eric ; D'Souza, Kiran ( January 2024 , Journal of Engineering for Gas Turbines and Power)

   Component mode mistuning (CMM) is a well-known, well documented reduced order modeling technique that effectively models small variations in blade-to-blade stiffness for bladed disks. In practice, bladed disks always have variations, referred to as mistuning, and are a focus of a large amount of research. One element that is commonly ignored from small mistuning implementations is the variation within the blade-to-blade damping values. This work seeks to better understand the effects of damping mistuning by utilizing both structural and proportional damping formulations. This work builds from previous work that implemented structural damping mistuning reduced order models formulated based on CMM. A similar derivation was used to create reduced order models with a proportional damping formulation. The damping and stiffness mistuning values investigated in this study were derived using measured blade natural frequencies and damping ratios from high-speed rotating experiments on freestanding blades. The two separate damping formulations that are presented give very similar results, enabling the user to select their preferred method for a given application. A key parameter investigated in this work is the significance of blade-to-blade coupling. The blade-to-blade coupling study investigates how the level of coupling impacts damping mistuning effects versus applying average damping to the bladed disk model. Also, the interaction of stiffness and damping mistuning is studied. Monte Carlo simulations were carried out to determine amplification factors, or the ratio of mistuned blade responses to tuned blade responses, for various mistuning levels and patterns.

    

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5. How Large Is a Disk—What Do Protoplanetary Disk Gas Sizes Really Mean?

   https://doi.org/10.3847/1538-4357/ace7d1  

   Trapman, Leon ; Rosotti, Giovanni ; Zhang, Ke ; Tabone, Benoît ( August 2023 , The Astrophysical Journal)

   It remains unclear what mechanism is driving the evolution of protoplanetary disks. Direct detection of the main candidates, either turbulence driven by magnetorotational instabilities or magnetohydrodynamical disk winds, has proven difficult, leaving the time evolution of the disk size as one of the most promising observables able to differentiate between these two mechanisms. But to do so successfully, we need to understand what the observed gas disk size actually traces. We studied the relation betweenR_CO,90%, the radius that encloses 90% of the¹²CO flux, andR_c, the radius that encodes the physical disk size, in order to provide simple prescriptions for conversions between these two sizes. For an extensive grid of thermochemical models, we calculateR_CO,90%from synthetic observations and relate properties measured at this radius, such as the gas column density, to bulk disk properties, such asR_cand the disk massM_disk. We found an empirical correlation between the gas column density atR_CO,90%and disk mass:$N_{\mathrm{gas}}{(R_{\mathrm{CO},90\%})\approx 3.73\times {10}^{21}(M_{\mathrm{disk}}/M_{\odot })}^{0.34}{\mathrm{cm}}^{-2}$. Using this correlation we derive an analytical prescription ofR_CO,90%that only depends onR_candM_disk. We deriveR_cfor disks in Lupus, Upper Sco, Taurus, and the DSHARP sample, finding that disks in the older Upper Sco region are significantly smaller (〈R_c〉 = 4.8 au) than disks in the younger Lupus and Taurus regions (〈R_c〉 = 19.8 and 20.9 au, respectively). This temporal decrease inR_cgoes against predictions of both viscous and wind-driven evolution, but could be a sign of significant external photoevaporation truncating disks in Upper Sco.

    

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