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1. Multiprobe cosmology from the abundance of SPT clusters and DES galaxy clustering and weak lensing

   https://doi.org/10.1103/PhysRevD.111.063533  

   Bocquet, S; Grandis, S; Krause, E; To, C; Bleem, L E; Klein, M; Mohr, J J; Schrabback, T; Alarcon, A; Alves, O; et al (March 2025, Physical Review D)

   Cosmic shear, galaxy clustering, and the abundance of massive halos each probe the large-scale structure of the Universe in complementary ways. We present cosmological constraints from the joint analysis of the three probes, building on the latest analyses of the lensing-informed abundance of clusters identified by the South Pole Telescope (SPT) and of the auto- and cross-correlation of galaxy position and weak lensing measurements ( $3\times 2\mathrm{pt}$ ) in the Dark Energy Survey (DES). We consider the cosmological correlation between the different tracers and we account for the systematic uncertainties that are shared between the large-scale lensing correlation functions and the small-scale lensing-based cluster mass calibration. Marginalized over the remaining $\mathrm{\Lambda }$ cold dark matter ( $\mathrm{\Lambda }\mathrm{CDM}$ ) parameters (including the sum of neutrino masses) and 52 astrophysical modeling parameters, we measure ${\mathrm{\Omega }}_{\mathrm{m}}=0.300\pm 0.017$ and ${\sigma }_8=0.797\pm 0.026$ . Compared to constraints from primary cosmic microwave background (CMB) anisotropies, our constraints are only 15% wider with a probability to exceed of 0.22 ( $1.2\sigma$ ) for the two-parameter difference. We further obtain $S_8\equiv {\sigma }_8({\mathrm{\Omega }}_{\mathrm{m}}/0.3{)}^{0.5}=0.796\pm 0.013$ which is lower than the measurement at the $1.6\sigma$ level. The combined SPT cluster, DES $3\times 2\mathrm{pt}$ , and datasets mildly prefer a nonzero positive neutrino mass, with a 95% upper limit $\sum m_{\nu }<0.25\mathrm{eV}$ on the sum of neutrino masses. Assuming a $w\mathrm{CDM}$ model, we constrain the dark energy equation of state parameter $w=-1.15_{-0.17}^{+0.23}$ and when combining with primary CMB anisotropies, we recover $w=-1.20_{-0.09}^{+0.15}$ , a $1.7\sigma$ difference with a cosmological constant. The precision of our results highlights the benefits of multiwavelength multiprobe cosmology and our analysis paves the way for upcoming joint analyses of next-generation datasets. Published by the American Physical Society2025 

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2. A 1.9 solar-mass neutron star candidate in a 2-year orbit

   https://doi.org/10.33232/001c.116675  

   El-Badry, Kareem; Simon, Joshua D.; Reggiani, Henrique; Rix, Hans-Walter; Latham, David W.; Bieryla, Allyson; Buchhave, Lars A.; Shahaf, Sahar; Mazeh, Tsevi; Chakrabarti, Sukanya; et al (January 2024, The Open Journal of Astrophysics)

   We report discovery and characterization of a main-sequence G star orbiting a dark object with mass $1.90\pm 0.04M_{\odot }$ . The system was discovered via Gaia astrometry and has an orbital period of 731 days. We obtained multi-epoch RV follow-up over a period of 639 days, allowing us to refine the Gaia orbital solution and precisely constrain the masses of both components. The luminous star is a $\gtrsim 12$ ,Gyr-old, low-metallicity halo star near the main-sequence turnoff (,K; ; ; $M\approx 0.79M_{\odot }$ ) with a highly enhanced lithium abundance. The RV mass function sets a minimum companion mass for an edge-on orbit of $M_2>1.67M_{\odot }$ , well above the Chandrasekhar limit. The Gaia inclination constraint, $i=68.7\pm 1.4$ ,deg, then implies a companion mass of $M_2=1.90\pm 0.04M_{\odot }$ . The companion is most likely a massive neutron star: the only viable alternative is two massive white dwarfs in a close binary, but this scenario is disfavored on evolutionary grounds. The system’s low eccentricity ( $e=0.122\pm 0.002$ ) disfavors dynamical formation channels and implies that the neutron star likely formed with little mass loss ( $\lesssim 1M_{\odot }$ ) and with a weak natal kick (). Stronger kicks with more mass loss are not fully ruled out but would imply that a larger population of similar systems with higher eccentricities should exist. The current orbit is too small to have accommodated the neutron star progenitor as a red supergiant or super-AGB star. The simplest formation scenario – isolated binary evolution – requires the system to have survived unstable mass transfer and common envelope evolution with a donor-to-accretor mass ratio $>10$ . The system, which we call Gaia NS1, is likely a progenitor of symbiotic X-ray binaries and long-period millisecond pulsars. Its discovery challenges binary evolution models and bodes well for Gaia’s census of compact objects in wide binaries. 

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3. Atacama Cosmology Telescope: Multiprobe cosmology with unWISE galaxies and ACT DR6 CMB lensing

   https://doi.org/10.1103/PhysRevD.111.083516  

   Farren, Gerrit S; Krolewski, Alex; Qu, Frank J; Ferraro, Simone; Calabrese, Erminia; Dunkley, Jo; Embil_Villagra, Carmen; Hill, J Colin; Kim, Joshua; Madhavacheril, Mathew S; et al (April 2025, Physical Review D)

   We present a joint analysis of the cosmic microwave background (CMB) lensing power spectra measured from the Data Release 6 of the Atacama Cosmology Telescope (ACT) and PR4, cross-correlations between the ACT and lensing reconstruction and galaxy clustering from unWISE, and the unWISE clustering auto-spectrum. We obtain 1.5% constraints on the matter density fluctuations at late times parametrized by the best constrained parameter combination $S_8^{3\mathrm{x}2\mathrm{pt}}\equiv {\sigma }_8({\mathrm{\Omega }}_m/0.3{)}^{0.4}=0.815\pm 0.012$ . The commonly used $S_8\equiv {\sigma }_8({\mathrm{\Omega }}_m/0.3{)}^{0.5}$ parameter is constrained to $S_8=0.816\pm 0.015$ . In combination with baryon acoustic oscillation (BAO) measurements we find ${\sigma }_8=0.815\pm 0.012$ . We also present sound-horizon-independent estimates of the present day Hubble rate of $H_0={66.4}_{-3.7}^{+3.2}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ from our large scale structure data alone and $H_0={64.3}_{-2.4}^{+2.1}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ in combination with uncalibrated supernovae from . Using parametric estimates of the evolution of matter density fluctuations, we place constraints on cosmic structure in a range of high redshifts typically inaccessible with cross-correlation analyses. Combining lensing cross- and autocorrelations, we derive a 3.3% constraint on the integrated matter density fluctuations above $z=2.4$ , one of the tightest constraints in this redshift range and fully consistent with a $\mathrm{\Lambda }$ cold dark matter ( $\mathrm{\Lambda }\mathrm{CDM}$ ) model fit to the primary CMB from . Finally, combining with primary CMB observations and using the extended low redshift coverage of these combined datasets we derive constraints on a variety of extensions to the $\mathrm{\Lambda }\mathrm{CDM}$ model including massive neutrinos, spatial curvature, and dark energy. We find in flat $\mathrm{\Lambda }\mathrm{CDM}\sum m_{\nu }<0.12\mathrm{eV}$ at 95% confidence using the large scale structure data, BAO measurements from Sloan Digital Sky Survey, and primary CMB observations. 

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4. Zooming In On The Multi-Phase Structure of Magnetically-Dominated Quasar Disks: Radiation From Torus to ISCO Across Accretion Rates

   https://doi.org/10.33232/001c.137296  

   Hopkins, Philip F; Su, Kung-Yi; Murray, Norman; Steinwandel, Ulrich P; Kaaz, Nicholas; Ponnada, Sam B; Bardati, Jaeden; Piotrowska, Joanna M; Wang, Hai-Yang; Shi, Yanlong; et al (January 2025, The Open Journal of Astrophysics)

   Recent radiation-thermochemical-magnetohydrodynamic simulations resolved formation of quasar accretion disks from cosmological scales down to ~300 gravitational radii $R_g$ , arguing they were ‘hyper-magnetized’ (plasma $\beta \ll 1$ supported by toroidal magnetic fields) and distinct from traditional $\alpha$ -disks. We extend these, refining to $\approx 3R_g$ around a BH with multi-channel radiation and thermochemistry, and exploring a factor of 1000 range of accretion rates ( $\dot{m}\sim 0.01-20$ ). At smaller scales, we see the disks maintain steady accretion, thermalize and self-ionize, and radiation pressure grows in importance, but large deviations from local thermodynamic equilibrium and single-phase equations of state are always present. Trans-Alfvenic and highly-supersonic turbulence persists in all cases, and leads to efficient vertical mixing, so radiation pressure saturates at levels comparable to fluctuating magnetic and turbulent pressures even for $\dot{m}\gg 1$ . The disks also become radiatively inefficient in the inner regions at high $\dot{m}$ . The midplane magnetic field remains primarily toroidal at large radii, but at super-Eddington $\dot{m}$ we see occasional transitions to a poloidal-field dominated state associated with outflows and flares. Large-scale magnetocentrifugal and continuum radiation-pressure-driven outflows are weak at $\dot{m}<1$ , but can be strong at $\dot{m}\gtrsim 1$ . In all cases there is a scattering photosphere above the disk extending to $\gtrsim 1000R_g$ at large $\dot{m}$ , and the disk is thick and flared owing to magnetic support (with $H/R$ nearly independent of $\dot{m}$ ), so the outer disk is strongly illuminated by the inner disk and most of the inner disk continuum scatters or is reprocessed at larger scales, giving apparent emission region sizes as large as . 

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5. Narrowline Laser Cooling and Spectroscopy of Molecules via Stark States

   https://doi.org/10.1103/9v1s-d6bd  

   Mehling, Kameron; Burau, Justin J; Hillberry, Logan E; Chen, Mengjie; Aggarwal, Parul; Cheng, Lan; Ye, Jun; Scheidegger, Simon (December 2025, PRX Quantum)

   The electronic energy level structure of yttrium monoxide (YO) provides a long-lived, low-lying ${}^2\mathrm{\Delta }$ state ideal for high-precision molecular spectroscopy, narrowline laser cooling at the single photon-recoil limit, and studying dipolar physics with unprecedented interaction strength. High-resolution laser spectroscopy of ultracold laser-cooled YO molecules is used to study the Stark effect in the ${\mathrm{A}}^{\mathrm{\prime }}{}^2{\mathrm{\Delta }}_{3/2}J=3/2$ state. An immediate onset of the linear Stark effect is observed in the presence of weak applied electric fields due to the near-degenerate $\mathrm{\Lambda }$ doublet and the large electric dipole moment. By applying a small electric field the Stark-insensitive state is spectroscopically isolated and the absolute transition frequency to the $\mathrm{X}{}^2{\mathrm{\Sigma }}^{+}$ electronic ground state is determined with a fractional frequency uncertainty of $9\times {10}^{-12}$ . This electric field control is necessary to implement a quasi-closed photon-cycling scheme that preserves parity. With this scheme the first narrowline laser cooling of a molecule is demonstrated, reducing the temperature of sub-Doppler cooled YO in two dimensions. 

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