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3C84 is a nearby radio source with a complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates the use of VLBI above the hitherto available maximum frequency of 86GHz. Using ultrahigh resolution VLBI observations at the highest available frequency of 228GHz, we aim to directly detect compact structures and understand the physical conditions in the compact region of 3C84. We used EHT 228GHz observations and, given the limited (u,v)-coverage, applied geometric model fitting to the data. We also employed quasi-simultaneously observed, multi-frequency VLBI data for the source in order to carry out a comprehensive analysis of the core structure. We report the detection of a highly ordered, strong magnetic field around the central, SMBH of 3C84. The brightness temperature analysis suggests that the system is in equipartition. We determined a turnover frequency of $\nu_m=(113\pm4)$GHz, a corresponding synchrotron self-absorbed magnetic field of $B_{SSA}=(2.9\pm1.6)$G, and an equipartition magnetic field of $B_{eq}=(5.2\pm0.6)$G. Three components are resolved with the highest fractional polarisation detected for this object ($m_\textrm{net}=(17.0\pm3.9)$%). The positions of the components are compatible with those seen in low-frequency VLBI observations since 2017-2018. We report a steeply negative slope of the spectrum at 228GHz. We used these findings to test models of jet formation, propagation, and Faraday rotation in 3C84. The findings of our investigation into different flow geometries and black hole spins support an advection-dominated accretion flow in a magnetically arrested state around a rapidly rotating supermassive black hole as a model of the jet-launching system in the core of 3C84. However, systematic uncertainties due to the limited (u,v)-coverage, however, cannot be ignored., Comment: 15 pages, 6 figures, published in A&A

Starting from the observing campaign in April 2018, the Greenland Telescope (GLT) has been added as a new station of the Event Horizon Telescope (EHT) array. Visibilities on baselines to the GLT, particularly in the North-South direction, potentially provide valuable new constraints for the modeling and imaging of sources such as M87*. The GLT's location at high Northern latitudes adds unique challenges to its calibration strategies. Additionally, the performance of the GLT was not optimal during the 2018 observations due to it being only partially commissioned at the time. This document describes the steps taken to estimate the various parameters (and their uncertainties) required for the absolute flux calibration of the GLT data as part of the EHT. In particular, we consider the non-optimized status of the GLT in 2018, as well as its improved performance during the 2021 EHT campaign., Comment: 17 pages, 4 figures, EHT Memo Series 2023-L1-02

We present an absolute $^3$He polarimetry method based on thermal neutron transmission for a double-chambered cell. This method utilizes the fact that a $^3$He nucleus has a large absorption cross section and a spin dependence for thermal neutrons. The cell had a pumping chamber and a target chamber. Polarized $^3$He gas was produced in the pumping chamber by SEOP and then diffused into the target chamber. The $^3$He polarization in the target chamber was determined by comparing the neutron transmissions with the polarized and unpolarized targets. The measurement was performed at the RIKEN Accelerator-Driven Compact Neutron Source. The $^3$He polarization in the target chamber was determined with a statistical error of 1.8% and systematic uncertainty of 0.6%. This method can be used to obtain high-precision data of spin observables in few-nucleon scattering for the investigation of nuclear forces., Comment: 15 pages, 7 figures

We study the dynamics of the spin system that consist of a positively charged II-VI semiconductor quantum dot doped with a single Cr$^+$ ion. The resonant photoluminescence (PL) of the positively charged exciton coupled with the Cr$^+$ spin is used to analyze the main spin relaxation channels. The intensity of the resonant PL is reduced by an optical pumping of the spin of the resident hole-Cr$^+$ complex that can be seen as a nano-magnet. The spin memory can be partially erased by a non-resonant optical excitation. This leads to an increase of the resonant PL signal. The resonant PL is co-circularly polarized and corresponds to relaxation channels that conserve the Cr$^+$ spin $\vert S_z \vert$. The observation in the resonant-PL excitation spectra of optical transitions with a change of the Cr$^+$ spin permits to determine the magnetic anisotropy of the magnetic atom. Optical pumping, auto-correlation measurements and the power dependence of the PL intensity distribution show that the effective temperature of the hole-Cr$^+$ spin system is affected by the optical excitation through the local generation of phonons.

We present a precise measurement of the cross section, proton and $\rm ^3He$ analyzing powers, and spin correlation coefficient $C_{y,y}$ for $p$-$\rm ^3He$ elastic scattering near 65 MeV, and a comparison with rigorous four-nucleon scattering calculations based on realistic nuclear potentials and a model with $\Delta$-isobar excitation. Clear discrepancies are seen in some of the measured observables in the regime around the cross section minimum. Theoretical predictions using scaling relations between the calculated cross section and the $\rm ^3 He$ binding energy are not successful in reproducing the data. Large sensitivity to the $NN$ potentials and rather small $\Delta$-isobar effects in the calculated cross section are noticed as different features from those in the deuteron-proton elastic scattering. The results obtained above indicate that $p$-$\rm ^3He$ scattering at intermediate energies is an excellent tool to explore nuclear interactions not accessible by three-nucleon scattering., Comment: 22 pages, 6 figures

Realistic synthetic observations of theoretical source models are essential for our understanding of real observational data. In using synthetic data, one can verify the extent to which source parameters can be recovered and evaluate how various data corruption effects can be calibrated. These studies are important when proposing observations of new sources, in the characterization of the capabilities of new or upgraded instruments, and when verifying model-based theoretical predictions in a comparison with observational data. We present the SYnthetic Measurement creator for long Baseline Arrays (SYMBA), a novel synthetic data generation pipeline for Very Long Baseline Interferometry (VLBI) observations. SYMBA takes into account several realistic atmospheric, instrumental, and calibration effects. We used SYMBA to create synthetic observations for the Event Horizon Telescope (EHT), a mm VLBI array, which has recently captured the first image of a black hole shadow. After testing SYMBA with simple source and corruption models, we study the importance of including all corruption and calibration effects. Based on two example general relativistic magnetohydrodynamics (GRMHD) model images of M87, we performed case studies to assess the attainable image quality with the current and future EHT array for different weather conditions. The results show that the effects of atmospheric and instrumental corruptions on the measured visibilities are significant. Despite these effects, we demonstrate how the overall structure of the input models can be recovered robustly after performing calibration steps. With the planned addition of new stations to the EHT array, images could be reconstructed with higher angular resolution and dynamic range. In our case study, these improvements allowed for a distinction between a thermal and a non-thermal GRMHD model based on salient features in reconstructed images., Comment: 20 pages, 15 figures, accepted for publication in A&A

Proton-3He scattering is one of the good probes to study the T=3/2 channel of three--nucleon forces. We have measured 3He analyzing powers for p-3He elastic scattering with the polarized 3He target at 70 and 100 MeV. The data are compared with the theoretical predictions based on the modern nucleon--nucleon potentials. Large discrepancies are found between the data and the calculations at the angles where the 3He analyzing power takes the minimum and maximum values, which are not explained by taking into account Delta-isobar degrees of freedom., Comment: 7pages, 3 figures Submission to SciPost

Inflation is the leading theory of the first instant of the universe. Inflation, which postulates that the universe underwent a period of rapid expansion an instant after its birth, provides convincing explanation for cosmological observations. Recent advancements in detector technology have opened opportunities to explore primordial gravitational waves generated by the inflation through B-mode (divergent-free) polarization pattern embedded in the Cosmic Microwave Background anisotropies. If detected, these signals would provide strong evidence for inflation, point to the correct model for inflation, and open a window to physics at ultra-high energies. LiteBIRD is a satellite mission with a goal of detecting degree-and-larger-angular-scale B-mode polarization. LiteBIRD will observe at the second Lagrange point with a 400 mm diameter telescope and 2,622 detectors. It will survey the entire sky with 15 frequency bands from 40 to 400 GHz to measure and subtract foregrounds. The U.S. LiteBIRD team is proposing to deliver sub-Kelvin instruments that include detectors and readout electronics. A lenslet-coupled sinuous antenna array will cover low-frequency bands (40 GHz to 235 GHz) with four frequency arrangements of trichroic pixels. An orthomode-transducer-coupled corrugated horn array will cover high-frequency bands (280 GHz to 402 GHz) with three types of single frequency detectors. The detectors will be made with Transition Edge Sensor (TES) bolometers cooled to a 100 milli-Kelvin base temperature by an adiabatic demagnetization refrigerator.The TES bolometers will be read out using digital frequency multiplexing with Superconducting QUantum Interference Device (SQUID) amplifiers. Up to 78 bolometers will be multiplexed with a single SQUID amplidier. We report on the sub-Kelvin instrument design and ongoing developments for the LiteBIRD mission., Comment: 7 pages 2 figures Journal of Low Temperature Physics - Special edition - LTD17 Proceeding

The Atacama Millimeter/submillimeter Array (ALMA) Phasing Project (APP) has developed and deployed the hardware and software necessary to coherently sum the signals of individual ALMA antennas and record the aggregate sum in Very Long Baseline Interferometry (VLBI) Data Exchange Format. These beamforming capabilities allow the ALMA array to collectively function as the equivalent of a single large aperture and participate in global VLBI arrays. The inclusion of phased ALMA in current VLBI networks operating at (sub)millimeter wavelengths provides an order of magnitude improvement in sensitivity, as well as enhancements in u-v coverage and north-south angular resolution. The availability of a phased ALMA enables a wide range of new ultra-high angular resolution science applications, including the resolution of supermassive black holes on event horizon scales and studies of the launch and collimation of astrophysical jets. It also provides a high-sensitivity aperture that may be used for investigations such as pulsar searches at high frequencies. This paper provides an overview of the ALMA Phasing System design, implementation, and performance characteristics., Comment: Accepted to PASP; 23 pages

This White Paper details the intentions and plans of the East Asian Very Long Baseline Interferometry (VLBI) community for pushing the frontiers of millimeter/submillimeter VLBI. To this end, we shall endeavor to actively promote coordinated efforts in the East Asia region. Our goal is to establish firm collaborations among the East Asia VLBI community in partnership with related institutes in North America and Europe and to expand existing global mm/submm VLBI arrays for (a) exploring the vicinity of black holes with an ultimate angular resolution down to 1~R$_{S}$ (Schwarzschild radius) and (b) investigating the dynamics of circumstellar gas in star-forming regions and late-type stars, and circumnuclear gas around active galactic nuclei (AGNs). In the first half of this White Paper, we highlight scientific accomplishments of the East Asia (EA) VLBI community. Various VLBI research results on M87, Sgr A*, blazars, narrow-line Seyfert~1 galaxies, and compact symmetric objects are described, and future visions of our VLBI science are briefly presented. Maser science of star formation, stellar evolution, and physics of accretion disks around AGNs are also discussed. A new vision for conducting multi-transition maser studies using mm/submm VLBI together with the Atacama Large Millimeter/Submillimeter Array (ALMA) is described. In the second half of this White Paper, we describe the EA community's vision for using mm/submm VLBI arrays in the framework or extended version of the Event Horizon Telescope (EHT) and the Global Millimeter VLBI Array (GMVA). The accomplishment of the aforementioned goal will maximize the overall scientific outcomes of mm/submm VLBI in the world., Comment: 93 pages, 54 figures. White Paper from East Asia VLBI community

In heterogeneous cohorts and those where censoring by non-primary risks is informative many conventional survival analysis methods are not applicable; the proportional hazards assumption is usually violated at population level and the observed crude hazard rates are no longer estimators of what they would have been in the absence of other risks. In this paper, we develop a fully Bayesian survival analysis to determine the probabilistically optimal description of a heterogeneous cohort and we propose a novel means of recovering hazard rates and survival functions `decontaminated' of the effects of any competing risks. Most competing risks studies implicitly assume that risk correlations are induced by cohort or disease heterogeneity that is not captured by covariates. We additionally assume that proportional hazards hold at the level of individuals, for all risks, leading to a generic statistical description that allows us to decontaminate the effects of informative censoring, and from which Cox regression, frailty and random effects models, and latent class models can all be recovered as special cases. Synthetic data confirm that our approach can map a cohort's substructure, and remove heterogeneity-induced false protectivity and false aetiology effects. Application to survival data from the ULSAM cohort leads to plausible alternative explanations for previous counter-intuitive inferences to prostate cancer. The importance of managing cardiovascular disease as a comorbidity in women diagnosed with breast cancer is suggested on application to survival data from the AMORIS study., Comment: 23 pages, 8 figures

We report about a 230 GHz very long baseline interferometry (VLBI) fringe finder observation of blazar 3C 279 with the APEX telescope in Chile, the phased submillimeter array (SMA), and the SMT of the Arizona Radio Observatory (ARO). We installed VLBI equipment and measured the APEX station position to 1 cm accuracy (1 sigma). We then observed 3C 279 on 2012 May 7 in a 5 hour 230 GHz VLBI track with baseline lengths of 2800 M$\lambda$ to 7200 M$\lambda$ and a finest fringe spacing of 28.6 micro-arcseconds. Fringes were detected on all baselines with SNRs of 12 to 55 in 420 s. The correlated flux density on the longest baseline was ~0.3 Jy/beam, out of a total flux density of 19.8 Jy. Visibility data suggest an emission region <38 uas in size, and at least two components, possibly polarized. We find a lower limit of the brightness temperature of the inner jet region of about 10^10 K. Lastly, we find an upper limit of 20% on the linear polarization fraction at a fringe spacing of ~38 uas. With APEX the angular resolution of 230 GHz VLBI improves to 28.6 uas. This allows one to resolve the last-photon ring around the Galactic Center black hole event horizon, expected to be 40 uas in diameter, and probe radio jet launching at unprecedented resolution, down to a few gravitational radii in galaxies like M 87. To probe the structure in the inner parsecs of 3C 279 in detail, follow-up observations with APEX and five other mm-VLBI stations have been conducted (March 2013) and are being analyzed., Comment: accepted for publication in A&A

A 12-m diameter radio telescope will be deployed to the Summit Station in Greenland to provide direct confirmation of a Super Massive Black Hole (SMBH) by observing its shadow image in the active galaxy M87. The telescope (Greenland Telescope: GLT) is to become one of the Very Long Baseline Interferometry (VLBI) stations at sub-millimeter (submm) regime, providing the longest baseline > 9,000 km to achieve an exceptional angular resolution of 20 micro arc sec at 350 GHz, which will enable us to resolve the shadow size of ~40 micro arc sec. The triangle with the longest baselines formed by the GLT, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and the Submillimeter Array (SMA) in Hawaii will play a key role for the M87 observations. We have been working on the image simulations based on realistic conditions for a better understanding of the possible observed images. In parallel, retrofitting of the telescope and the site developments are in progress. Based on three years of opacity monitoring at 225 GHz, our measurements indicate that the site is excellent for submm observations, comparable to the ALMA site. The GLT is also expected to make single-dish observations up to 1.5 THz., Comment: 15 pages, 6 figures, accepted by Radio Science journal

We present the first constraint on Faraday rotation measure (RM) at submillimeter wavelengths for the nucleus of M 87. By fitting the polarization position angles ($\chi$) observed with the SMA at four independent frequencies around $\sim$230 GHz and interpreting the change in $\chi$ as a result of \emph{external} Faraday rotation associated with accretion flow, we determine the rotation measure of the M 87 core to be between $-$7.5$\times$10$^{5}$ and 3.4$\times$10$^{5}$ rad/m$^{2}$. Assuming a density profile of the accretion flow that follows a power-law distribution and a magnetic field that is ordered, radial, and has equipartition strength, the limit on the rotation measure constrains the mass accretion rate $\dot{M}$ to be below 9.2$\times$10$^{-4}$ M$_{\odot}$~yr$^{-1}$ at a distance of 21 Schwarzchild radii from the central black hole. This value is at least two orders of magnitude smaller than the Bondi accretion rate, suggesting significant suppression of the accretion rate in the inner region of the accretion flow. Consequently, our result disfavors the classical \emph{advection dominated accretion flow} (ADAF) and prefers the \emph{adiabatic inflow-outflow solution} (ADIOS) or \emph{convection-dominated accretion flow} (CDAF) for the hot accretion flow in M 87., Comment: 11 pages, 4 figures, accepted by ApJL

The GLT project is deploying a new submillimeter (submm) VLBI station in Greenland. Our primary scientific goal is to image a shadow of the supermassive black hole (SMBH) of six billion solar masses in M87 at the center of the Virgo cluster of galaxies. The expected SMBH shadow size of 40-50 $\mu$as requires superbly high angular resolution, suggesting that the submm VLBI would be the only way to obtain the shadow image. The Summit station in Greenland enables us to establish baselines longer than 9,000 km with ALMA in Chile and SMA in Hawaii as well as providing a unique $u$--$v$ coverage for imaging M87. Our VLBI network will achieve a superior angular resolution of about 20 $\mu$as at 350 GHz, corresponding to $\sim2.5$ times of the Schwarzschild radius of the supermassive black hole in M87. We have been monitoring the atmospheric opacity at 230 GHz since August. 2011; we have confirmed the value on site during the winter season is comparable to the ALMA site thanks to high altitude of 3,200 m and low temperature of $-50\degr$C. We will report current status and future plan of the GLT project towards our expected first light on 2015--2016., Comment: 4 pages, 5 figures; to appear in the conference proceedings of "Innermost Regions of Relativistic Jets and Their Magnetic Fields", June 10-14, 2013, Granada, Spain