We present a toy model for the thermal optical/UV/Xray emission from tidal disruption events (TDEs). Motivated by recent hydrodynamical simulations, we assume that the debris streams promptly and rapidly circularize (on the orbital period of the most tightly bound debris), generating a hot quasispherical pressuresupported envelope of radius
We explore the effects of rapid rotation on the properties of neutrinoheated winds from protoneutron stars (PNS) formed in corecollapse supernovae or neutronstar mergers by means of threedimensional generalrelativistic hydrodynamical simulations with M0 neutrino transport. We focus on conditions characteristic of a few seconds into the PNS cooling evolution when the neutrino luminosities obey
 Award ID(s):
 2002577
 NSFPAR ID:
 10486133
 Publisher / Repository:
 DOI PREFIX: 10.3847
 Date Published:
 Journal Name:
 The Astrophysical Journal
 Volume:
 931
 Issue:
 2
 ISSN:
 0004637X
 Format(s):
 Medium: X Size: Article No. 104
 Size(s):
 ["Article No. 104"]
 Sponsoring Org:
 National Science Foundation
More Like this

Abstract R _{v} ∼ 10^{14}cm (photosphere radius ∼10^{15}cm) surrounding the supermassive black hole (SMBH). As the envelope cools radiatively, it undergoes Kelvin–Helmholtz contractionR _{v} ∝t ^{−1}, its temperature risingT _{eff}∝t ^{1/2}while its total luminosity remains roughly constant; the optical luminosity decays as . Despite this similarity to the mass fallback rate $\nu {L}_{\nu}\propto \phantom{\rule{0.50em}{0ex}}{R}_{v}^{2}{T}_{\mathrm{eff}}\propto {t}^{3/2}$ , envelope heating from fallback accretion is subdominant compared to the envelope cooling luminosity except near optical peak (where they are comparable). Envelope contraction can be delayed by energy injection from accretion from the inner envelope onto the SMBH in a regulated manner, leading to a latetime flattening of the optical/Xray light curves, similar to those observed in some TDEs. Eventually, as the envelope contracts to near the circularization radius, the SMBH accretion rate rises to its maximum, in tandem with the decreasing optical luminosity. This coolinginduced (rather than circularizationinduced) delay of up to several hundred days may account for the delayed onset of thermal Xrays, latetime radio flares, and highenergy neutrino generation, observed in some TDEs. We compare the model predictions to recent TDE lightcurve correlation studies, finding both agreement and points of tension. ${\stackrel{\u0307}{M}}_{\mathrm{fb}}\propto {t}^{5/3}$ 
Abstract We measure the thermal electron energization in 1D and 2D particleincell simulations of quasiperpendicular, lowbeta (
β _{p}= 0.25) collisionless ion–electron shocks with mass ratiom _{i}/m _{e}= 200, fast Mach number –4, and upstream magnetic field angle ${\mathcal{M}}_{\mathrm{ms}}=1$θ _{Bn}= 55°–85° from the shock normal . It is known that shock electron heating is described by an ambipolar, $\stackrel{\u02c6}{\mathit{n}}$ parallel electric potential jump, ΔB ϕ _{∥}, that scales roughly linearly with the electron temperature jump. Our simulations have –0.2 in units of the preshock ions’ bulk kinetic energy, in agreement with prior measurements and simulations. Different ways to measure $\mathrm{\Delta}{\varphi}_{\parallel}/(0.5{m}_{\mathrm{i}}{{u}_{\mathrm{sh}}}^{2})\sim 0.1$ϕ _{∥}, including the use of de Hoffmann–Teller frame fields, agree to tensofpercent accuracy. Neglecting offdiagonal electron pressure tensor terms can lead to a systematic underestimate ofϕ _{∥}in our lowβ _{p}shocks. We further focus on twoθ _{Bn}= 65° shocks: a ( ${\mathcal{M}}_{\mathrm{s}}\phantom{\rule{0.25em}{0ex}}=\phantom{\rule{0.25em}{0ex}}4$ ) case with a long, 30 ${\mathcal{M}}_{\mathrm{A}}\phantom{\rule{0.25em}{0ex}}=\phantom{\rule{0.25em}{0ex}}1.8$d _{i}precursor of whistler waves along , and a $\stackrel{\u02c6}{\mathit{n}}$ ( ${\mathcal{M}}_{\mathrm{s}}\phantom{\rule{0.25em}{0ex}}=\phantom{\rule{0.25em}{0ex}}7$ ) case with a shorter, 5 ${\mathcal{M}}_{\mathrm{A}}\phantom{\rule{0.25em}{0ex}}=\phantom{\rule{0.25em}{0ex}}3.2$d _{i}precursor of whistlers oblique to both and $\stackrel{\u02c6}{\mathit{n}}$ ;B d _{i}is the ion skin depth. Within the precursors,ϕ _{∥}has a secular rise toward the shock along multiple whistler wavelengths and also has localized spikes within magnetic troughs. In a 1D simulation of the , ${\mathcal{M}}_{\mathrm{s}}\phantom{\rule{0.25em}{0ex}}=\phantom{\rule{0.25em}{0ex}}4$θ _{Bn}= 65° case,ϕ _{∥}shows a weak dependence on the electron plasmatocyclotron frequency ratioω _{pe}/Ω_{ce}, andϕ _{∥}decreases by a factor of 2 asm _{i}/m _{e}is raised to the true proton–electron value of 1836. 
Abstract We present cosmological constraints from a gravitational lensing mass map covering 9400 deg^{2}reconstructed from measurements of the cosmic microwave background (CMB) made by the Atacama Cosmology Telescope (ACT) from 2017 to 2021. In combination with measurements of baryon acoustic oscillations and big bang nucleosynthesis, we obtain the clustering amplitude
σ _{8}= 0.819 ± 0.015 at 1.8% precision, , and the Hubble constant ${S}_{8}\equiv {\sigma}_{8}{({\mathrm{\Omega}}_{\mathrm{m}}/0.3)}^{0.5}=0.840\pm 0.028$H _{0}= (68.3 ± 1.1) km s^{−1}Mpc^{−1}at 1.6% precision. A joint constraint with Planck CMB lensing yieldsσ _{8}= 0.812 ± 0.013, , and ${S}_{8}\equiv {\sigma}_{8}{({\mathrm{\Omega}}_{\mathrm{m}}/0.3)}^{0.5}=0.831\pm 0.023$H _{0}= (68.1 ± 1.0) km s^{−1}Mpc^{−1}. These measurements agree with ΛCDM extrapolations from the CMB anisotropies measured by Planck. We revisit constraints from the KiDS, DES, and HSC galaxy surveys with a uniform set of assumptions and find thatS _{8}from all three are lower than that from ACT+Planck lensing by levels ranging from 1.7σ to 2.1σ . This motivates further measurements and comparison, not just between the CMB anisotropies and galaxy lensing but also between CMB lensing probingz ∼ 0.5–5 on mostly linear scales and galaxy lensing atz ∼ 0.5 on smaller scales. We combine with CMB anisotropies to constrain extensions of ΛCDM, limiting neutrino masses to ∑m _{ν}< 0.13 eV (95% c.l.), for example. We describe the mass map and related data products that will enable a wide array of crosscorrelation science. Our results provide independent confirmation that the universe is spatially flat, conforms with general relativity, and is described remarkably well by the ΛCDM model, while paving a promising path for neutrino physics with lensing from upcoming groundbased CMB surveys. 
Abstract The conventional accretion disk lore is that magnetized turbulence is the principal angular momentum transport process that drives accretion. However, when dynamically important largescale magnetic fields thread an accretion disk, they can produce mass and angular momentum outflows, known as winds
, that also drive accretion. Yet, the relative importance of turbulent and winddriven angular momentum transport is still poorly understood. To probe this question, we analyze a longduration (1.2 × 10^{5}r _{g}/c ) simulation of a rapidly rotating (a = 0.9) black hole feeding from a thick (H /r ∼ 0.3), adiabatic, magnetically arrested disk (MAD), whose dynamically important magnetic field regulates mass inflow and drives both uncollimated and collimated outflows (i.e., winds and jets, respectively). By carefully disentangling the various angular momentum transport processes within the system, we demonstrate the novel result that disk winds and disk turbulence both extract roughly equal amounts of angular momentum from the disk. We find cumulative angular momentum and mass accretion outflow rates of and $\stackrel{\u0307}{L}\propto {r}^{0.9}$ , respectively. This result suggests that understanding both turbulent and laminar stresses is key to understanding the evolution of systems where geometrically thick MADs can occur, such as the hard state of Xray binaries, lowluminosity active galactic nuclei, some tidal disruption events, and possibly gammaray bursts. $\stackrel{\u0307}{M}\propto {r}^{0.4}$ 
Abstract The repeating fast radio burst FRB 20190520B is localized to a galaxy at
z = 0.241, much closer than expected given its dispersion measure DM = 1205 ± 4 pc cm^{−3}. Here we assess implications of the large DM and scattering observed from FRB 20190520B for the host galaxy’s plasma properties. A sample of 75 bursts detected with the Fivehundredmeter Aperture Spherical radio Telescope shows scattering on two scales: a mean temporal delayτ (1.41 GHz) = 10.9 ± 1.5 ms, which is attributed to the host galaxy, and a mean scintillation bandwidth Δν _{d}(1.41 GHz) = 0.21 ± 0.01 MHz, which is attributed to the Milky Way. Balmer line measurements for the host imply an Hα emission measure (galaxy frame) EM_{s}= 620 pc cm^{−6}× (T /10^{4}K)^{0.9}, implying DM_{Hα}of order the value inferred from the FRB DM budget, pc cm^{−3}for plasma temperatures greater than the typical value 10^{4}K. Combining ${\mathrm{DM}}_{\mathrm{h}}={1121}_{138}^{+89}$τ and DM_{h}yields a nominal constraint on the scattering amplification from the host galaxy , where $\tilde{F}G\phantom{\rule{0.50em}{0ex}}=\phantom{\rule{0.50em}{0ex}}{1.5}_{0.3}^{+0.8}{({\mathrm{pc}}^{2}\phantom{\rule{0.25em}{0ex}}\mathrm{km})}^{1/3}$ describes turbulent density fluctuations and $\tilde{F}$G represents the geometric leverage to scattering that depends on the location of the scattering material. For a twoscreen scattering geometry whereτ arises from the host galaxy and Δν _{d}from the Milky Way, the implied distance between the FRB source and dominant scattering material is ≲100 pc. The host galaxy scattering and DM contributions support a novel technique for estimating FRB redshifts using theτ –DM relation, and are consistent with previous findings that scattering of localized FRBs is largely dominated by plasma within host galaxies and the Milky Way.