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1. A Comparison of Outflow Properties in AGN Dwarfs versus Star-forming Dwarfs

   https://doi.org/10.3847/1538-4357/acca7c  

   Aravindan, Archana ; Liu, Weizhe ; Canalizo, Gabriela ; Veilleux, Sylvain ; Bohn, Thomas ; Sexton, Remington O. ; Rupke, David S. N. ; U, Vivian ( June 2023 , The Astrophysical Journal)

   Feedback likely plays a crucial role in resolving discrepancies between observations and theoretical predictions of dwarf galaxy properties. Stellar feedback was once believed to be sufficient to explain these discrepancies, but it has thus far failed to fully reconcile theory and observations. The recent discovery of energetic galaxy-wide outflows in dwarf galaxies hosting active galactic nuclei (AGNs) suggests that AGN feedback may have a larger role in the evolution of dwarf galaxies than previously suspected. In order to assess the relative importance of stellar versus AGN feedback in these galaxies, we perform a detailed Keck/KCWI optical integral field spectroscopic study of a sample of low-redshift star-forming (SF) dwarf galaxies that show outflows in ionized gas in their Sloan Digital Sky Survey spectra. We characterize the outflows and compare them to observations of AGN-driven outflows in dwarfs. We find that SF dwarfs have outflow components that have comparable widths (W₈₀) to those of outflows in AGN dwarfs, but are much less blueshifted, indicating that SF dwarfs have significantly slower outflows than their AGN counterparts. Outflows in SF dwarfs are spatially resolved and significantly more extended than those in AGN dwarfs. The mass-loss, momentum, and energy rates of star-formation-driven outflows are much lower than those of AGN-driven outflows. Our results indicate that AGN feedback in the form of gas outflows may play an important role in dwarf galaxies and should be considered along with SF feedback in models of dwarf galaxy evolution.

    

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2. Kinetic description of stable white dwarfs

   https://doi.org/10.3934/krm.2021033  

   Jang, Juhi ; Seok, Jinmyoung ( January 2022 , Kinetic and Related Models)

   In this paper, we study fermion ground states of the relativistic Vlasov-Poisson system arising in the semiclassical limit from relativistic quantum theory of white dwarfs. We show that fermion ground states of the three dimensional relativistic Vlasov-Poisson system exist for subcritical mass, the mass density of such fermion ground states satisfies the Chandrasekhar equation for white dwarfs, and that they are orbitally stable as long as solutions exist.

    

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3. Rapidly rotating white dwarfs

   https://doi.org/10.1088/1361-6544/ab8d13  

   Strauss, Walter A ; Wu, Yilun ( September 2020 , Nonlinearity)

   null (Ed.)
4. The merger fraction of ultramassive white dwarfs

   https://doi.org/10.1093/mnras/stac3182  

   Kilic, Mukremin ; Moss, Adam G. ; Kosakowski, Alekzander ; Bergeron, P. ; Conly, Annamarie A. ; Brown, Warren R. ; Toonen, Silvia ; Williams, Kurtis A. ; Dufour, P. ( November 2022 , Monthly Notices of the Royal Astronomical Society)

   We search for merger products among the 25 most massive white dwarfs in the Montreal White Dwarf Database 100 pc sample through follow-up spectroscopy and high-cadence photometry. We find an unusually high fraction, 40 per cent, of magnetic white dwarfs among this population. In addition, we identify four outliers in transverse velocity and detect rapid rotation in five objects. Our results show that $56^{+9}_{-10}$ per cent of the $M\approx 1.3\, {\rm M}_{\odot }$ ultramassive white dwarfs form through mergers. This fraction is significantly higher than expected from the default binary population synthesis calculations using the α prescription (with αλ = 2), and provides further support for efficient orbital shrinkage, such as with low values of the common-envelope efficiency.

    

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5. The POKEMON Speckle Survey of Nearby M Dwarfs. III. The Stellar Multiplicity Rate of M Dwarfs within 15 pc

   https://doi.org/10.3847/1538-3881/ad267d  

   Clark, Catherine A. ; van Belle, Gerard T. ; Horch, Elliott P. ; Ciardi, David R. ; von Braun, Kaspar ; Skiff, Brian A. ; Winters, Jennifer G. ; Lund, Michael B. ; Everett, Mark E. ; Hartman, Zachary D. ; et al ( March 2024 , The Astronomical Journal)

   M dwarfs are ubiquitous in our Galaxy, and the rate at which they host stellar companions, and the properties of these companions, provide a window into the formation and evolution of the star(s), and of any planets that they may host. The Pervasive Overview of “Kompanions” of Every M dwarf in Our Neighborhood (POKEMON) speckle survey of nearby M dwarfs is volume limited from M0V through M9V out to 15 pc, with additional targets at larger distances. In total, 1125 stars were observed, and 455 of these are within the volume-limited, 15 pc sample of M-dwarf primaries. When we combine the speckle observations with known companions from the literature, we find that the stellar multiplicity rate of M dwarfs within 15 pc is 23.5% ± 2.0%, and that the companion rate is 28.8% ± 2.1%. We also find that the projected separation distribution for multiples that are known to host planets peaks at 198 au, while the distribution for multiples that are not yet known to host planets peaks at 5.57 au. This result suggests that the presence of close-in stellar companions inhibits the formation of M-dwarf planetary systems, similar to what has been found for FGK stars.

    

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