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1. CLASS Angular Power Spectra and Map-component Analysis for 40 GHz Observations through 2022

   https://doi.org/10.3847/1538-4357/ad1abf  

   Eimer, Joseph R; Li_李, Yunyang 云炀; Brewer, Michael K; Shi_时, Rui 瑞; Ali, Aamir; Appel, John W; Bennett, Charles L; Bruno, Sarah Marie; Bustos, Ricardo; Chuss, David T; et al (March 2024, The Astrophysical Journal)

   Abstract Measurement of the largest angular scale (ℓ< 30) features of the cosmic microwave background (CMB) polarization is a powerful way to constrain the optical depth to reionization and search for the signature of inflation through the detection of primordialB-modes. We present an analysis of maps covering 73.6% of the sky made from the 40 GHz channel of the Cosmology Large Angular Scale Surveyor (CLASS) from 2016 August to 2022 May. Taking advantage of the measurement stability enabled by front-end polarization modulation and excellent conditions from the Atacama Desert, we show this channel achieves higher sensitivity than the analogous frequencies from satellite measurements in the range 10 <ℓ< 100. Simulations show the CLASS linear (circular) polarization maps have a white noise level of $125\left(130\right)\mu \mathrm{K}\mathrm{arcmin}$. We measure the Galaxy-maskedEEandBBspectra of diffuse synchrotron radiation and compare to space-based measurements at similar frequencies. In combination with external data, we expand measurements of the spatial variations of the synchrotron spectral energy density (SED) to include new sky regions and measure the diffuse SED in the harmonic domain. We place a new upper limit on a background of circular polarization in the range 5 <ℓ< 125 with the first bin showingD_ℓ< 0.023 $\mu {\mathrm{K}}_{\mathrm{CMB}}^2$at 95% confidence. These results establish a new standard for recovery of the largest-scale CMB polarization from the ground and signal exciting possibilities when the higher sensitivity and higher-frequency CLASS channels are included in the analysis. 

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2. Inside the Stagnation Radius of the Nearest Billion-solar-mass Black Hole

   https://doi.org/10.3847/1538-4357/adfa93  

   Wrobel, J M; Pesce, D W; Nyland, K E (September 2025, The Astrophysical Journal)

   Abstract We used the NSF Jansky Very Large Array at a frequencyν = 22 GHz to study the nearest billion-solar-mass black hole (BH), in the early-type galaxy NGC 3115 at a distance of 9.7 Mpc. We localize a faint continuum nucleus, with flux densityS_{22 GHz} = 48.2 ± 6.4μJy, to a FWHM diameterd_{22 GHz} < 59 mas (2.8 pc). We find no evidence for adjacent emission within a stagnation region of radiusR_sta ∼ 360 mas (17 pc) identified in a recent hydrodynamic simulation tailored to NGC 3115. Within that region, the simulated gas flow developed into an advection-dominated accretion flow (ADAF). The nucleus’ luminosity densityL_{22 GHz} = 5.4 × 10¹⁷W Hz⁻¹is about 60 times that of Sagittarius A^⋆. The nucleus’ spectral index ${\alpha }_{10\mathrm{GHz}}^{22\mathrm{GHz}}=-1.85\pm 0.18$(S_ν ∝ ν^α) indicates optically thin synchrotron emission. The spectral energy distribution of the nucleus peaks nearν_peak = 9 GHz. Modeling this radio peak as an ADAF implies a BH massM_ADAF = (1.2 ± 0.2) × 10⁹M_⊙, consistent with previous estimates of (1–2) × 10⁹M_⊙from stellar or hot-gas dynamics. Also, the Eddington-scaled accretion rate for NGC 3115, ${\dot{M}}_{\mathrm{ADAF}}/{\dot{M}}_{\mathrm{Edd}}=1.2_{-0.6}^{+1.0}\times 10^{-8}$, is about 4–8 times lower than recent estimates for Sagittarius A^⋆. 

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3. A Measurement of the Largest-scale CMB E -mode Polarization with CLASS

   https://doi.org/10.3847/1538-4357/adc723  

   Li_李, Yunyang 云炀; Eimer, Joseph R; Appel, John W; Bennett, Charles L; Brewer, Michael K; Bruno, Sarah Marie; Bustos, Ricardo; Chan, Carol_Yan Yan; Chuss, David T; Cleary, Joseph; et al (June 2025, The Astrophysical Journal)

   Abstract We present measurements of large-scale cosmic microwave backgroundE-mode polarization from the Cosmology Large Angular Scale Surveyor 90 GHz data. Using 115 det-yr of observations collected through 2024 with a variable-delay polarization modulator, we achieved a polarization sensitivity of $82\mu \mathrm{K}\mathrm{arcmin}$, comparable to Planck at similar frequencies (100 and 143 GHz ). The analysis demonstrates effective mitigation of systematic errors and addresses challenges to large-angular-scale power recovery posed by time-domain filtering in maximum-likelihood map-making. A novel implementation of the pixel-space transfer matrix is introduced, which enables efficient filtering simulations and bias correction in the power spectrum using the quadratic cross-spectrum estimator. Overall, we achieved an unbiased time-domain filtering correction to recover the largest angular scale polarization, with the only power deficit, arising from map-making nonlinearity, being characterized as <3%. Through cross-correlation with Planck, we detected the cosmic reionization at 99.4% significance and measured the reionization optical depth $\tau =0.053_{-0.019}^{+0.018}$, marking the first ground-based attempt at such a measurement. At intermediate angular scales (ℓ > 30), our results, both independently and in cross-correlation with Planck, remain fully consistent with Planck’s measurements. 

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4. Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars

   https://doi.org/10.3847/1538-4357/ade0bc  

   Ocker, Stella Koch; Chen, Mandy C; Oh, S Peng; Sharma, Prateek (July 2025, The Astrophysical Journal)

   Abstract The circumgalactic medium (CGM) is poorly constrained at the subparsec scales relevant to turbulent energy dissipation and regulation of multiphase structure. Fast radio bursts are sensitive to small-scale plasma density fluctuations, which can induce multipath propagation (scattering). The amount of scattering depends on the density fluctuation spectrum, including its amplitude $C_{\mathrm{n}}^2$, spectral indexβ, and dissipation scalel_i. We use quasar observations of CGM turbulence at ≳pc scales to infer $C_{\mathrm{n}}^2$, finding it to be $10^{-16}\lesssim C_{\mathrm{n}}^2\lesssim 10^{-9}$m^−20/3for hot (T> 10⁶K) gas and $10^{-8}\lesssim C_{\mathrm{n}}^2\lesssim 10^{-4}$m^−20/3for cool (10⁴≲T≲ 10⁵K) gas, depending on the gas sound speed and density. These values of $C_{\mathrm{n}}^2$are much smaller than those inferred in the interstellar medium at similar physical scales. The resulting scattering delays from the hot CGM are negligible (≪1μs at 1 GHz), but they are more detectable from the cool gas as either radio pulse broadening or scintillation, depending on the observing frequency and sightline geometry. Joint quasar-FRB observations of individual galaxies can yield lower limits onl_i, even if the CGM is not a significant scattering site. An initial comparison between quasar and FRB observations (albeit for different systems) suggestsl_i≳ 750 km in ∼10⁴K gas in order for the quasar and FRB constraints to be consistent. If a foreground CGM is completely ruled out as a source of scattering along an FRB sightline, thenl_imay be comparable to the smallest cloud sizes (≲pc) inferred from photoionization modeling of quasar absorption lines. 

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5. Measurement of the branching fractions of $$ \overline{B} $$ → D(*)K−$$ {K}_{(S)}^{\left(\ast \right)0} $$ and $$ \overline{B} $$ → D(*)$$ {D}_s^{-} $$ decays at Belle II

   https://doi.org/10.1007/JHEP08(2024)206  

   Adachi, I; Aggarwal, L; Aihara, H; Akopov, N; Aloisio, A; Althubiti, N; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, T; et al (August 2024, Journal of High Energy Physics)

   Abstract We present measurements of the branching fractions of eight$$ {\overline{B}}^0 $$ ${\overline{B}}^0$→D^(*)+K⁻$$ {K}_{(S)}^{\left(\ast \right)0} $$ $K_{\left(S\right)}^{\left(\ast \right)0}$,B⁻→D^(*)0K⁻$$ {K}_{(S)}^{\left(\ast \right)0} $$ $K_{\left(S\right)}^{\left(\ast \right)0}$decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Υ(4S) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362 fb⁻¹. The event yields are extracted from fits to the distributions of the difference between expected and observedBmeson energy, and are efficiency-corrected as a function ofm(K⁻$$ {K}_{(S)}^{\left(\ast \right)0} $$ $K_{\left(S\right)}^{\left(\ast \right)0}$) andm(D^(*)$$ {K}_{(S)}^{\left(\ast \right)0} $$ $K_{\left(S\right)}^{\left(\ast \right)0}$) in order to avoid dependence on the decay model. These results include the first observation of$$ {\overline{B}}^0 $$ ${\overline{B}}^0$→D⁺K⁻$$ {K}_S^0 $$ $K_S^0$,B⁻→D*⁰K⁻$$ {K}_S^0 $$ $K_S^0$, and$$ {\overline{B}}^0 $$ ${\overline{B}}^0$→D*⁺K⁻$$ {K}_S^0 $$ $K_S^0$decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of theK⁻$$ {K}_{(S)}^{\left(\ast \right)0} $$ $K_{\left(S\right)}^{\left(\ast \right)0}$systems are compatible with quasi-two-body decays via a resonant transition with spin-parityJ^P= 1⁻for theK⁻$$ {K}_S^0 $$ $K_S^0$systems andJ^P= 1⁺for theK⁻K*⁰systems. We also present measurements of the branching fractions of four$$ {\overline{B}}^0 $$ ${\overline{B}}^0$→D^(*)+$$ {D}_s^{-} $$ $D_s^{-}$,B⁻→D^(*)0$$ {D}_s^{-} $$ $D_s^{-}$decay channels with a precision compatible to the current world averages. 

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