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Very few detections have been made of optical flashes contemporaneous with prompt high-energy emission from a gamma-ray burst (GRB). In this work, we present and analyze light curves of GRB-associated optical flashes and afterglows from the Transiting Exoplanet Survey Satellite (TESS). Our sample consists of eight GRBs with arcsecond-level localizations from the X-Ray Telescope on board the Neil Gehrels Swift Observatory (Swift). For each burst, we characterize the prompt optical emission and any observed afterglow, and constrain physical parameters for four of these bursts using their TESS light curves. This work also presents a straightforward method to correct for TESS's cosmic-ray mitigation strategy on 20 s timescales, which allows us to estimate the "true" brightness of optical flashes associated with prompt GRB emission. We also highlight TESS's continuous wide-field monitoring capability, which provides an efficient means of identifying optical emission from GRBs and characterizing early time afterglow light curves. Based on empirical detection rates from Swift and the Fermi Gamma-ray Space Telescope, up to 10 GRBs per year may fall within the contemporaneous TESS field of view. [ABSTRACT FROM AUTHOR]

We introduce a 0.7 m telescope system at the Miryang Arirang Astronomical Observatory (MAAO), a public observatory in Miryang, Korea. System integration and a scheduling program enable the 0.7 m telescope system to operate completely robotically during nighttime, eliminating the need for human intervention. Using the 0.7 m telescope system, we obtain atmospheric extinction coefficients and the zero-point magnitudes by observing standard stars. As a result, we find that atmospheric extinctions are moderate but they can sometimes increase depending on the weather conditions. The measured 5 σ limiting magnitudes reach down to BVRI = 19.4–19.6 AB mag for a point source with a total integrated time of 10 minutes under clear weather conditions, demonstrating comparable performance with other observational facilities operating under similar specifications and sky conditions. We expect that the newly established MAAO 0.7 m telescope system will contribute significantly to the observational studies of astronomy. Particularly, with its capability for robotic observations, this system, although its primary duty is for public viewing, can be extensively used for the time-series observation of transients. [ABSTRACT FROM AUTHOR]

We performed a rigorous reverberation-mapping analysis of the broad-line region (BLR) in a highly accreting (L / L Edd = 0.74–3.4) active galactic nucleus, Markarian 142 (Mrk 142), for the first time using concurrent observations of the inner accretion disk and the BLR to determine a time lag for the H β λ 4861 emission relative to the ultraviolet (UV) continuum variations. We used continuum data taken with the Niel Gehrels Swift Observatory in the UVW 2 band, and the Las Cumbres Observatory, Dan Zowada Memorial Observatory, and Liverpool Telescope in the g band, as part of the broader Mrk 142 multiwavelength monitoring campaign in 2019. We obtained new spectroscopic observations covering the H β broad emission line in the optical from the Gemini North Telescope and the Lijiang 2.4 m Telescope for a total of 102 epochs (over a period of 8 months) contemporaneous to the continuum data. Our primary result states a UV-to-H β time lag of 8.68 − 0.72 + 0.75 days in Mrk 142 obtained from light-curve analysis with a Python-based running optimal average algorithm. We placed our new measurements for Mrk 142 on the optical and UV radius–luminosity relations for NGC 5548 to understand the nature of the continuum driver. The positions of Mrk 142 on the scaling relations suggest that UV is closer to the "true" driving continuum than the optical. Furthermore, we obtain log (M • / M ⊙) = 6.32 ± 0.29 assuming UV as the primary driving continuum. [ABSTRACT FROM AUTHOR]

Observations of long-duration gamma-ray bursts (GRBs) with TeV emission during their afterglow have been on the rise. Recently, GRB 221009A, the most energetic GRB ever observed, was detected by the Large High Altitude Air Shower Observatory experiment in the energy band 0.2–7 TeV. Here, we interpret its afterglow in the context of a hybrid model in which the TeV spectral component is explained by the proton-synchrotron process while the low-energy emission from optical to X-ray is due to synchrotron radiation from electrons. We constrained the model parameters using the observed optical, X-ray, and TeV data. By comparing the parameters of this burst and of GRB 190114C, we deduce that the VHE emission at energies ≥1 TeV in the GRB afterglow requires large explosion kinetic energy, E ≳ 1054 erg and a reasonable circumburst density, n ≳ 10 cm−3. This results in a small injection fraction of particles accelerated to a power law, ∼10−2. A significant fraction of shock energy must be allocated to a near equipartition magnetic field, ϵ B ∼ 10−1, while electrons should only carry a small fraction of this energy, ϵ e ∼ 10−3. Under these conditions required for a proton-synchrotron model, namely ϵ B ≫ ϵ e , the SSC component is substantially subdominant over proton-synchrotron as a source of TeV photons. These results lead us to suggest that proton-synchrotron process is a strong contender for the radiative mechanisms explaining GRB afterglows in the TeV band. [ABSTRACT FROM AUTHOR]

The Pierre Auger Observatory (PAO) and Telescope Array (TA) collaborations report significant differences in the observed energy spectra of ultra-high-energy cosmic rays (UHECRs) above 30 EeV. In this work we present a joint fit of TA and PAO data using the rigidity-dependent maximum energy model, including a full marginalization over all relevant parameters. We test two possible scenarios to explain these differences. One is that they are due to complex energy-dependent experimental systematics; the other is the presence of a local astrophysical source in the Northern Hemisphere, which is only visible by the TA experiment. We show that the astrophysical and systematic scenarios improve the explanation of the data equally well, compared to the scenario where both experiments observe the same UHECR flux from a cosmological source distribution and have energy-independent systematics. We test different mass compositions emitted from the local source and conclude that the data are best described by a source lying at a distance below 26 Mpc that emits cosmic rays dominated by the silicon mass group. We also discuss possible source candidates and the possible role of the putative local UHECR source in the observed TA anisotropy and in the differences in TA spectral data from different decl. bands. [ABSTRACT FROM AUTHOR]

Extremely large telescopes (ELTs) present an unparalleled opportunity to study the magnetism, atmospheric dynamics, and chemistry of very-low-mass (VLM) stars, brown dwarfs, and exoplanets. Instruments such as the Giant Magellan Telescope–Consortium Large Earth Finder (GMT/GCLEF), the Thirty Meter Telescope's Multi-Objective Diffraction-limited High-Resolution Infrared Spectrograph (TMT/MODHIS), and the European Southern Observatory's Mid-Infrared ELT Imager and Spectrograph (ELT/METIS) provide the spectral resolution and signal-to-noise ratio necessary to Doppler image ultracool targets' surfaces based on temporal spectral variations due to surface inhomogeneities. Using our publicly available code, Imber, developed and validated in Plummer & Wang, we evaluate these instruments' abilities to discern magnetic starspots and cloud systems on a VLM star (TRAPPIST-1), two L/T transition ultracool dwarfs (VHS J1256−1257 b and SIMP J0136+0933), and three exoplanets (Beta Pic b and HR 8799 d and e). We find that TMT/MODHIS and ELT/METIS are suitable for Doppler imaging the ultracool dwarfs and Beta Pic b over a single rotation. Uncertainties for longitude and radius are typically ≲10°, and latitude uncertainties range from ∼10° to 30°. TRAPPIST-1's edge-on inclination and low υ sin i provide a challenge for all three instruments, while GMT/GCLEF and the HR 8799 planets may require observations over multiple rotations. We compare the spectroscopic technique, photometry-only inference, and the combination of the two. We find combining spectroscopic and photometric observations can lead to improved Bayesian inference of surface inhomogeneities and offers insight into whether ultracool atmospheres are dominated by spotted or banded features. [ABSTRACT FROM AUTHOR]

The Vera C. Rubin Observatory will undertake the Legacy Survey of Space and Time, providing an unprecedented, volume-limited catalog of star clusters in the Southern Sky, including Galactic and extragalactic star clusters. The Star Clusters subgroup of the Stars, Milky Way and Local Volume Working Group has identified key areas where Rubin Observatory will enable significant progress in star cluster research. This roadmap represents our science cases and preparation for studies of all kinds of star clusters from the Milky Way out to distances of tens of megaparsecs. [ABSTRACT FROM AUTHOR]

Axion-like particles (ALPs) are well-motivated extensions of the Standard Model of Particle Physics and a generic prediction of some string theories. X-ray observations of bright active galactic nuclei (AGNs) hosted by rich clusters of galaxies are excellent probes of very-light ALPs, with masses log (m a / eV) < − 12.0. We evaluate the potential of future X-ray observatories, particularly Athena and the proposed AXIS, to constrain ALPs via observations of cluster-hosted AGNs, taking NGC 1275 in the Perseus cluster as our exemplar. Assuming perfect knowledge of the instrument calibration, we show that a modest exposure (200 ks) of NGC 1275 by Athena permits us to exclude all photon–ALP couplings g a γ > 6.3 × 10−14 GeV−1 at the 95% confidence level, as previously shown by Conlon et al., representing a factor of 10 improvement over current limits. We then proceed to assess the impact of realistic calibration uncertainties on the Athena projection by applying a standard Cash likelihood procedure, showing the projected constraints on g a γ weaken by a factor of 10 (back to the current most sensitive constraints). However, we show how the use of a deep neural network can disentangle the energy-dependent features induced by instrumental miscalibration and those induced by photon–ALP mixing, allowing us to recover most of the sensitivity to the ALP physics. In our explicit demonstration, the machine learning applied allows us to exclude g a γ > 2.0 × 10−13 GeV−1, complementing the projected constraints of next-generation ALP dark matter birefringent cavity searches for very-light ALPs. Finally, we show that a 200 ks AXIS/on-axis observation of NGC 1275 will tighten the current best constraints on very-light ALPs by a factor of 3. [ABSTRACT FROM AUTHOR]

The transient optical sky has remained largely unexplored on very short timescales. While there have been some experiments searching for optical transients from minutes to years, none have had the capability to distinguish millisecond fast optical bursts (FOBs). Such very fast transients could be the optical counterparts of fast radio bursts, the prompt emission from γ -ray bursts, or other previously unknown phenomena. Here, we investigate a novel approach to the serendipitous detection of FOBs, which relies on searching for anomalous spatial images. In particular, due to their short duration, the seeing-distorted images of FOBs should look characteristically different than those of steady sources in a standard optical exposure of finite duration. We apply this idea to simulated observations with the Vera C. Rubin Observatory, produced by tracing individual photons through a turbulent atmosphere, and down through the optics and camera of the Rubin telescope. We compare these simulated images to steady-source star simulations in 15 s integrations, the nominal Rubin exposure time. We report the classification accuracy results of a neural network classifier for distinguishing FOBs from steady sources. From this classifier, we derive constraints in duration–intensity parameter space for unambiguously identifying FOBs in Rubin observations. We conclude with estimates of the total number of detections of FOB counterparts to FRBs expected during the 10 yr Rubin Legacy Survey of Space and Time. [ABSTRACT FROM AUTHOR]

This study is the first attempt to generate a three-dimensional (3D) coronal electron density distribution based on the pix2pixHD model, whose computing time is much shorter than that of the magnetohydrodynamic (MHD) simulation. For this, we consider photospheric solar magnetic fields as input, and electron density distribution simulated with the MHD Algorithm outside a Sphere (MAS) at a given solar radius is taken as output. We consider 155 pairs of Carrington rotations as inputs and outputs from 2010 June to 2022 April for training and testing. We train 152 deep-learning models for 152 solar radii, which are taken up to 30 solar radii. The artificial intelligence (AI) generated 3D electron densities from this study are quite consistent with the simulated ones from lower radii to higher radii, with an average correlation coefficient 0.97. The computing time of testing data sets up to 30 solar radii of 152 deep-learning models is about 45.2 s using the NVIDIA TITAN XP graphics-processing unit, which is much less than the typical simulation time of MAS. We find that the synthetic coronagraphic images estimated from the deep-learning models are similar to the Solar Heliospheric Observatory (SOHO)/Large Angle and Spectroscopic Coronagraph C3 coronagraph data, especially during the solar minimum period. The AI-generated coronal density distribution from this study can be used for space weather models on a near-real-time basis. [ABSTRACT FROM AUTHOR]

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies. [ABSTRACT FROM AUTHOR]

The application of a sodium laser guide star is the key difference between a modern adaptive optics system and traditional adaptive optics system. Especially in system such as multiconjugate adaptive optics, a sodium laser guide star asterism that is formed by several laser guide stars in a certain pattern is required to probe more atmospheric turbulence in different directions. To achieve this, a sodium laser guide star asterism launching platform is required. In this paper, we introduce the sodium laser guide star asterism launching platform built and tested on the 1.8 m telescope of Gaomeigu Observatory. The platform has two functions: one function is to compare the performance of sodium laser guide stars generated by different lasers at the same place, and the other function is to generate a sodium laser guide star asterism with an adjustable shape. The field test results at the beginning of 2021 verified the important role of the platform, which is also the first time that a sodium laser guide star asterism was realized in China. [ABSTRACT FROM AUTHOR]

The Kodaikanal Observatory has made synoptic observations of the Sun in white light since 1904, and these images are sketched on the Stonyhurst grids called Sun charts. These continuous hand-drawn data sets are used for long-term studies of the Sun. This article investigates temporal and periodic variations of the monthly hemispheric sunspot number and sunspot group area for 1905â€"2016, covering solar cycles 14â€"24. We find that the temporal variations of the sunspot number and group area are different in each hemisphere and peak at different times of the solar cycle in the opposite hemisphere. For both data sets, Cycle 19 shows maximum amplitude. For the sunspot number time series, Cycle 24 was the weakest, and Cycle 15 for the group area. The existence of double peaks and violation of the “oddâ€"even rule” was found in both data sets. We have studied the periodic and quasiperiodic variations in both time series using the wavelet technique. We noticed that, along with the fundamental mode of the ∼11 yr cycle and polarity reversal period of 22 yr, the sunspot activity data also exhibited several midterm periodicities in the opposite hemispheres, in particular the Rieger-group, and quasi-biennial periodicities. The temporal evolution of these detected quasi-periodicities also differs in the northern and southern hemispheres. We analyzed the data set statistically to understand the bulk properties and coupling between the opposite hemispheres. The study indicates that the two hemispheric data sets differ, but some dependency could be present. [ABSTRACT FROM AUTHOR]

SPECULOOS is a ground-based transit survey consisting of six identical 1 m robotic telescopes. The immediate goal of the project is to detect temperate terrestrial planets transiting nearby ultracool dwarfs (late M-dwarf stars and brown dwarfs), which could be amenable for atmospheric research with the next generation of telescopes. Here, we report the developments of the northern counterpart of the projectâ€"SPECULOOS Northern Observatory, and present its performance during the first three years of operations from mid-2019 to mid-2022. Currently, the observatory consists of one telescope, which is named Artemis. The Artemis telescope demonstrates remarkable photometric precision, allowing it to be ready to detect new transiting terrestrial exoplanets around ultracool dwarfs. Over the period of the first three years after the installation, we observed 96 objects from the SPECULOOS target list for 6000 hr with a typical photometric precision of 0.5%, and reaching a precision of 0.2% for relatively bright non-variable targets with a typical exposure time of 25 s. Our weather downtime (clouds, high wind speed, high humidity, precipitation and/or high concentration of dust particles in the air) over the period of three years was 30% of overall night time. Our actual downtime is 40% because of additional time loss associated with technical problems. [ABSTRACT FROM AUTHOR]

We discuss the idea of a measurement that, making use of data from space interferometers, could detect the gravito-magnetic field generated by the rotation of the Milky Way, including the possible contribution of the dark matter halo. The galactic signal would be superposed to the gravito-magnetic field of the Sun. The proposed technique is based on the asymmetric propagation of light along the closed contour of the space interferometer, in a Sagnac-like approach. We discuss the principles of detection as well as some practical aspects of the proposed experiment using, as a case study, LISA, the most mature project to date. Both gravito-magnetic signals will be modulated thanks to the annual oscillation of the plane of the interferometer with respect to the galactic plane and to the spin axis of the Sun. Although larger than the detector intrinsic noise, these signals will be superposed to a much larger kinematic modulation due to orbital motion, making them very hard to be observed. We also mention a second phenomenon, where the gravito-magnetic field rotates the polarization of the propagating electromagnetic beams: the effect will be present in LISA, although exceedingly small and out of reach of present technology. [ABSTRACT FROM AUTHOR]

Many gamma-ray bursts (GRBs) have been observed from radio wavelengths, and a few at very high energies (VHEs, >100 GeV). The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is well suited to study transient phenomena at VHEs owing to its large field of view and duty cycle. These features allow for searches of VHE emission and can probe different model assumptions of duration and spectra. In this paper, we use data collected by HAWC between 2014 December and 2020 May to search for emission in the energy range from 80 to 800 GeV coming from a sample of 47 short GRBs that triggered the Fermi, Swift, and Konus satellites during this period. This analysis is optimized to search for delayed and extended VHE emission within the first 20 s of each burst. We find no evidence of VHE emission, either simultaneous or delayed, with respect to the prompt emission. Upper limits (90% confidence level) derived on the GRB fluence are used to constrain the synchrotron self-Compton forward-shock model. Constraints for the interstellar density as low as 10âˆ'2 cmâˆ'3 are obtained when assuming z = 0.3 for bursts with the highest keV fluences such as GRB 170206A and GRB 181222841. Such a low density makes observing VHE emission mainly from the fast-cooling regime challenging. [ABSTRACT FROM AUTHOR]

Changing-look active galactic nucleus NGC 4151, which has attracted a lot of attention, is undergoing the second dramatic outburst stage in its evolutionary history. To investigate the geometry and kinematics of the broad-line region (BLR), and measure the mass of supermassive black hole in NGC 4151, we perform a 7 month photometric and spectroscopic monitoring program in 2020â€"2021, using the 2.4 m telescope at Lijiang Observatory. We successfully measure the time lags of the responses from broad H α, H β, H Îł, He i, and He ii emission lines to continuum variation, which are 7.63 âˆ' 2.62 + 1.85 , 6.21 âˆ' 1.13 + 1.41 , 5.67 âˆ' 1.94 + 1.65 , 1.59 âˆ' 1.11 + 0.86 , and 0.46 âˆ' 1.06 + 1.22 days, respectively, following radial stratification. The ratios of time lags among these lines are 1.23: 1.00: 0.91: 0.26: 0.07. We find that the continuum lag between the ultraviolet and optical bands can significantly affect the lag measurements of He i and He ii. Virial and infalling gas motions coexist in this campaign, which is different from previous results, implying the evolutionary kinematics of BLR. Based on our measurements and previous ones in the literature, we confirm that the BLR of NGC 4151 is basically virialized. Finally, we compute the black hole mass through multiple lines, and the measurement from H β to be 3.94 âˆ' 0.72 + 0.90 Ă— 10 7 M ⊙ , which is consistent with previous results. The corresponding accretion rate is 0.02 âˆ' 0.01 + 0.01 L Edd c âˆ' 2 , implying a sub-Eddington accretor. [ABSTRACT FROM AUTHOR]

We detail the follow-up and characterization of a transiting exo-Venus identified by TESS, GJ 3929b (TOI-2013b), and its nontransiting companion planet, GJ 3929c (TOI-2013c). GJ 3929b is an Earth-sized exoplanet in its star’s Venus zone (P b = 2.616272 ± 0.000005 days; S b = 17.3 âˆ' 0.7 + 0.8 S ⊕) orbiting a nearby M dwarf. GJ 3929c is most likely a nontransiting sub-Neptune. Using the new, ultraprecise NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak National Observatory, we are able to modify the mass constraints of planet b reported in previous works and consequently improve the significance of the mass measurement to almost 4 σ confidence (M b = 1.75 ± 0.45 M ⊕). We further adjust the orbital period of planet c from its alias at 14.30 ± 0.03 days to the likely true period of 15.04 ± 0.03 days, and we adjust its minimum mass to m sin i = 5.71 ± 0.92 M ⊕. Using the diffuser-assisted ARCTIC imager on the ARC 3.5 m telescope at Apache Point Observatory, in addition to publicly available TESS and LCOGT photometry, we are able to constrain the radius of planet b to R p = 1.09 ± 0.04 R ⊕. GJ 3929b is a top candidate for transmission spectroscopy in its size regime (TSM = 14 ± 4), and future atmospheric studies of GJ 3929b stand to shed light on the nature of small planets orbiting M dwarfs. [ABSTRACT FROM AUTHOR]

We describe observations of the white-light structures in the low corona following the X8.2 flare SOL 2017-09-10, as observed in full Stokes parameters by the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory. These data show both bright loops and a diffuse emission region above them. We interpret the loops as the white-light counterpart of a classical loop-prominence system, intermediate between the hot X-ray loops and coronal rain. The diffuse emission external to the loops is linearly polarized and has a natural interpretation in terms of Thomson scattering from the hot plasma seen prior to its cooling and recombination. The polarimetric data from HMI enable us to distinguish this contribution of scattering from the HMI pseudocontinuum measurement, and to make a direct estimation of the coronal mass in the polarized source. For a snapshot at 16:19 UT, we estimate a mass 8 Ă— 1014 g. We further conclude that the volumetric filling factor of this source is near unity. [ABSTRACT FROM AUTHOR]

An observation simulator is established, on an event-by-event basis, for the Polarimetry Focusing telescope Array (PFA) on board the planned enhanced X-ray Timing and Polarimetry observatory (eXTP). An event generator, based on XIMPOL, is used to sample the parameters of the X-rays reaching the aperture of the telescope. The trajectories and interactions of X-rays through the telescope and the corresponding secondaries are calculated using the optics and detector simulation model built in GEANT4, before being translated into signals in the pixelated readout electronics. It is shown that mirror deformation is required for the optics simulation model, and transportation of ionization electrons is required for the detector simulation model to reproduce the overall performance of the telescope. The developed tool is useful in different mission phases, such as payload optimization in the design phase, discrimination of new phenomena against known physics models in the calibration phases, and sensitivity studies of potential polarized X-ray sources in observation planning. The sensitivity of PFA to the Crab Nebula and Crab pulsar is investigated to demonstrate the application of the tool. Even with the dilution effect, space-resolved and phase-resolved polarimetry can reveal important aspects of the Crab Nebula and Crab pulsar and help break the degeneracy between different models. [ABSTRACT FROM AUTHOR]

Stellar image motion measured differentially with small telescopes can be converted to image quality predictions for large telescopes at the same site. To demonstrate this methodology, multi-wavelength seeing distributions are predicted for Las Campanas Observatory based on the Differential Image Motion Monitor (DIMM) results from the Giant Magellan Telescope site survey. The observed seeing distribution at 0.5 μ m is used to compute a family of predicted seeing distributions from 0.32 to 4.7 μ m. Tokovinin’s formula is used to transform the DIMM seeing distributions (based on Kolmogorov theory) to the large telescope image sizes expected in the von Karman theory. The latter framework includes an outer scale, or largest size, for the turbulent eddies above a telescope. The impact of seeing distributions on site selection and on telescope and instrument design are discussed. Other considerations in selecting an excellent site are also listed and explained. [ABSTRACT FROM AUTHOR]

Coronal plumes are long, ray-like, open structures that have been considered as possible sources of the solar wind. Their origin in the largely unipolar coronal holes has long been a mystery. Earlier spectroscopic and imaging observations revealed blueshifted plasma and propagating disturbances (PDs) in plumes that are widely interpreted in terms of flows and/or propagating slow-mode waves, but these interpretations (flows versus waves) remain under debate. Recently we discovered an important clue about plume internal structure: dynamic filamentary features called plumelets, which account for most of the plume emission. Here we present high-resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly and the Interface Region Imaging Spectrograph that revealed numerous, quasi-periodic, tiny jets (so-called jetlets) associated with transient brightening, flows, and plasma heating at the chromospheric footpoints of the plumelets. By analogy to larger coronal jets, these jetlets are most likely produced within the plume base by magnetic reconnection between closed and open flux at stressed 3D null points. The jetlet-associated brightenings are in phase with plumelet-associated PDs, and vary with a period of ∼3â€"5 minutes, which is remarkably consistent with the photospheric/chromospheric p-mode oscillation. This reconnection at the open-closed boundary in the chromosphere/transition region is likely modulated or driven by local manifestations of the global p-mode waves. The jetlets extend upward to become plumelets, contribute mass to the solar wind, and may be sources of the switchbacks recently detected by the Parker Solar Probe. [ABSTRACT FROM AUTHOR]

We study the evolution of rapid neutron-capture process (r-process) isotopes in the galaxy. We analyze relative contributions from core-collapse supernovae (CCSNe), neutron star mergers, and collapsars under a range of astrophysical conditions and nuclear input data. Here we show that, although the r-process in each of these sites can lead to a similar (universal) elemental distribution, the detailed isotopic abundances can differ from one site to another. These differences may allow for the identification of which sources contributed to the early evolution of r-process material in the galaxy. Our simulations suggest that the early evolution was dominated by CCSNe and collapsar r-process nucleosynthesis. This conclusion may be testable if the next generation of observatories can deduce isotopic r-process abundances. [ABSTRACT FROM AUTHOR]

Parametric instability (PI), induced by the interaction between the cavity optical modes and acoustic modes of a mirror, is an inherent risk in interferometric gravitational wave detectors. The instability can result in exponential growth in acoustic mode amplitude and the saturation of detectors control systems. In this paper we analyse PI in the neutron star extreme matter observatory, a proposed high optical power (4.5 MW) detector, operating at cryogenic temperatures with silicon test masses (TMs), targeting high sensitivity between 1 and 4 kHz. Our results show that with current design parameters, approximately 16 unstable modes will arise per TM with maximum parametric gain ∼10. Varying the TM radius of curvature from the nominal values could eliminate PI, however not with current manufacture or actuator capability. PI mitigation will be required to suppress all unstable modes. This analysis identifies four optical modes and 16 acoustic modes dominating PI in NEMO paves the way for the design of PI mitigation strategies. [ABSTRACT FROM AUTHOR]

The Dark Energy Spectroscopic Instrument (DESI) survey is a spectroscopic survey of tens of millions of galaxies at 0 < z < 3.5 covering 14,000 sq. deg. of the sky. In its first 1.1 yr of survey operations, it has observed more than 14 million galaxies and 4 million stars. We describe the processes that govern DESI’s observations of the 15,000 fields composing the survey. This includes the planning of each night’s observations in the afternoon; automatic selection of fields to observe during the night; real-time assessment of field completeness on the basis of observing conditions during each exposure; reduction, redshifting, and quality assurance of each field of targets in the morning following observation; and updates to the list of future targets to observe on the basis of these results. We also compare the performance of the survey with historical expectations and find good agreement. Simulations of the weather and of DESI observations using the real field-selection algorithm show good agreement with the actual observations. After accounting for major unplanned shutdowns, the dark time survey is progressing about 7% faster than forecast, which is good agreement given approximations made in the simulations.

We report TeV gamma-ray observations of the ultra-high-energy source MGRO J1908+06 using data from the High Altitude Water Cherenkov Observatory. This source is one of the highest-energy known gamma-ray sources, with emission extending past 200 TeV. Modeling suggests that the bulk of the TeV gamma-ray emission is leptonic in nature, driven by the energetic radio-faint pulsar PSR J1907+0602. Depending on what assumptions are included in the model, a hadronic component may also be allowed. Using the results of the modeling, we discuss implications for detection prospects by multi-messenger campaigns. [ABSTRACT FROM AUTHOR]

The “equal-contrast technique” (ECT) methodology, developed by Singh et al. to generate uniform long time series of Ca-K images obtained during the 20th century from the Kodaikanal Observatory (KO), improved the correlation between the plage area and sunspot parameters. The same methodology can also be used on other observatory data taken with different instruments. We can combine such ECT-corrected images to reduce the gaps in the observations and make a long uniform data set to study short- and long-term variations. We apply this procedure to Mount Wilson Observatory (MWO) historical Ca-K data and recent Ca-K filtergrams obtained using narrowband filters at KO and the Mauna Loa Solar Observatory (MLSO). To determine the success of this method, the results of the analysis of the ECT images obtained from KO, MWO, and MLSO are compared. A comparison of the plage and active areas derived from KO and MWO images before and after the ECT procedure indicates an improvement in the correlation coefficients (CCs) between all the data sets after the ECT application. The CC for the combined monthly mean Ca-K plage area derived from the KO, MWO, and Precision Solar Photometric Telescope (at the MLSO) data with sunspot numbers is 0.96 for the period 1905â€"2015. The paper demonstrates that the time series of Ca-K data obtained from different instruments after applying the ECT procedure becomes uniform in contrast. The combined time series of KO and MWO spectroheliograms has 12 hr intervals compared to the ≈24 hr gap for a time series from a single observatory. [ABSTRACT FROM AUTHOR]

In this paper, we present photometric and spectroscopic observations of the subluminous Type Ia supernova (SN Ia) 2012ij, which has an absolute B -band peak magnitude M B , max = âˆ' 17.95 ± 0.15 mag. The B -band light curve exhibits a fast postpeak decline with Î" m 15(B) = 1.86 ± 0.05 mag. All the R - and I / i -band light curves show a weak secondary peak/shoulder feature at about 3 weeks after the peak, like some transitional subclass of SNe Ia, which could result from an incomplete merger of near-infrared (NIR) double peaks. The spectra are characterized by Ti ii and strong Si ii λ 5972 absorption features that are usually seen in low-luminosity objects like SN 1999by. The NIR spectrum before maximum light reveals weak carbon absorption features, implying the existence of unburned materials. We compare the observed properties of SN 2012ij with those predicted by the sub-Chandrasekhar-mass and the Chandrasekhar-mass delayed-detonation models and find that both optical and NIR spectral properties can be explained to some extent by these two models. By comparing the secondary maximum features in the I and i bands, we suggest that SN 2012ij is a transitional object linking normal SNe Ia to typical 91bg-like ones. From the published sample of SNe Ia from the Carnegie Supernova Project II, we estimate that the fraction of SN 2012ijâ€"like SNe Ia is not lower than ∼2%. [ABSTRACT FROM AUTHOR]

The repeating FRB 20201124A was first discovered by CHIME/FRB in November of 2020, after which it was seen to repeat a few times over several months. It entered a period of high activity in April of 2021, at which time several observatories recorded tens to hundreds more bursts from the source. These follow-up observations enabled precise localization and host-galaxy identification. In this paper, we report on the CHIME/FRB-detected bursts from FRB 20201124A, including their best-fit morphologies, fluences, and arrival times. The large exposure time of the CHIME/FRB telescope toward the location of this source allows us to constrain its rates of activity. We analyze the repetition rates over different spans of time, constraining the rate prior to discovery to <3.4 dayâˆ'1 (at 3 σ), and demonstrate a significant change in the event rate following initial detection. Lastly, we perform a maximum-likelihood estimation of a power-law luminosity function, finding a best-fit index α = âˆ'4.6 ± 1.3 ± 0.6, with a break at a fluence threshold of F min ∼ 16.6 Jy ms, consistent with the fluence completeness limit of the observations. This index is consistent within uncertainties with those of other repeating FRBs for which it has been determined. [ABSTRACT FROM AUTHOR]

Gravitational-wave (GW) astrophysics is a rapidly expanding field, with plans to enhance the global ground-based observatory network through the addition of larger, more sensitive observatories: the Einstein Telescope and Cosmic Explorer. These observatories will allow us to peer deeper into the sky, collecting GW events from farther away and earlier in the universe. Within our own Galaxy, there is a plethora of interesting GW sources, including core-collapse supernovae, phenomena in isolated neutron stars and pulsars, and potentially novel sources. As GW observatories are directionally sensitive, their placement on the globe will affect the observation of Galactic sources. We analyze the performance of one-, two-, and three-observatory networks, both for sources at the Galactic center, as well as for a source population distributed over the Galactic disk. We find that, for a single Cosmic Explorer or Einstein Telescope observatory, placement at near-equatorial latitudes provides the most reliable observation of the Galactic center. When a source population distributed over the Galactic disk is considered, the observatory location is less impactful, although equatorial observatories still confer an advantage over observatories at more extreme latitudes. For two- and three-node networks, the longitudes of the observatories additionally become important for consistent observation of the Galaxy. [ABSTRACT FROM AUTHOR]

In this paper, we aim to use the DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO), a future Japanese space gravitational-wave antenna sensitive to the frequency range between LISA and ground-based detectors, to provide gravitational-wave constraints on the cosmic curvature at z ∼ 5. In the framework of the well-known distance sum rule, the perfect redshift coverage of the standard sirens observed by DECIGO, compared with lensing observations including the source and lens from LSST, makes such cosmological-model-independent tests more natural and general. Focusing on three kinds of spherically symmetric mass distributions for the lensing galaxies, we find that the cosmic curvature is expected to be constrained with the precision of ΔΩK ∼ 10−2 in the early universe (z ∼ 5.0), improving the sensitivity of ET constraints by about a factor of 10. However, in order to investigate this further, the mass-density profiles of early-type galaxies should be properly taken into account. Specifically, our analysis demonstrates the strong degeneracy between the spatial curvature and the lens parameters, especially the redshift evolution of the power-law lens index parameter. When the extended power-law mass-density profile is assumed, the weakest constraint on the cosmic curvature can be obtained, whereas the addition of DECIGO to the combination of LSST+DECIGO does improve significantly the constraint on the luminosity–density slope and the anisotropy of the stellar velocity dispersion. Therefore, our paper highlights the benefits of synergies between DECIGO and LSST in constraining new physics beyond the standard model, which could manifest themselves through accurate determination of the cosmic curvature. [ABSTRACT FROM AUTHOR]

The third generation of gravitational wave detectors like the Einstein telescope or the cosmic explorer will be Michelson interferometers with Fabryâ€"Perot cavities in the arms, using mirror test masses with diameter at the limit of technical feasibility. Unlike other detectors, the Einstein telescope will have a 60° angle between the arms. Because of its larger incidence angle, at any given beam size, it would require beam splitters almost double in size and much heavier than the 90° case. It is proposed here to install beam expander telescopes with angled mirrors located inside the Michelson interferometer between the Fabryâ€"Perot cavities and the beam splitter. In addition to reducing the beam sizes and the beam splitter to manageable sizes, the proposed solution allows to bring the optimal recombination angle to 90°. The proposed geometry also offers a natural way to separate the beam splitters of different detectors into individual, smaller and more stable caverns thus improving observatory observation-time efficiency, to provide needed beam diagnostic points and convenient degrees of freedom for beam alignment into both the Fabry Perot cavities and the beam splitter, as well as to provide a method for maintaining optimal mode matching of the two arms onto the beam splitter without thermal compensation plates. [ABSTRACT FROM AUTHOR]

The optical light curves of quiescent black hole low-mass X-ray binaries often exhibit significant nonellipsoidal variabilities, showing the photospheric radiation of the companion star is veiled by other sources of optical emission. Assessing this “veiling” effect is critical to the black hole mass measurement. Here in this work, we carry out a strictly simultaneous spectroscopic and photometric campaign on the prototype of black hole low-mass X-ray binary A0620-00. We find that for each observation epoch, the extra optical flux beyond a pure ellipsoidal modulation is positively correlated with the fraction of veiling emission, indicating the accretion disk contributes most of the nonellipsoidal variations. Meanwhile, we also obtain a K2V spectral classification of the companion, as well as the measurements of the companion’s rotational velocity v sin i = 83.8 ± 1.9 km sâˆ'1 and the mass ratio between the companion and the black hole q = 0.063 ± 0.004. [ABSTRACT FROM AUTHOR]

The Kodaikanal Observatory has provided long-term synoptic observations of chromospheric activities in the Ca ii K line (393.34 nm) since 1907. This article investigates temporal and periodic variations of the hemispheric Caâ€"K-index time series in the low-latitude zone (±40°), utilizing the recently digitized photographic plates of Caâ€"K images from the Kodaikanal Observatory for the period of 1907â€"1980. We find that the temporal evolution of the Caâ€"K index differs from one hemisphere to another, with the solar cycle peaking at different times in the opposite hemisphere, except for cycles 14, 15, and 21, when the phase difference between the two hemispheres was not significant. The monthly averaged data show a higher activity in the northern hemisphere during solar cycles 15, 16, 18, 19, and 20, and in the southern hemisphere during cycles 14, 17, and 21. We notice an exponentially decaying distribution for each hemisphere’s Caâ€"K index and the whole solar disk. We explored different midterm periodicities of the measured Caâ€"K index using the wavelet technique, including Rieger-type and quasi-biennial oscillations on different timescales present in the time series. We find a clear manifestation of the Waldmeier effect (stronger cycles rise faster than the weaker ones) in both the hemispheres separately and the whole disk in the data. Finally, we have found the presence of the Gnevyshev gap (time interval between two cycle maxmima) in both the hemispheric data during cycles 15 to 20. Possible interpretations of our findings are discussed with the help of existing theoretical models and observations. [ABSTRACT FROM AUTHOR]

The Large High Altitude Air Shower Observatory (LHAASO) detected 12 gamma-ray sources above 100 TeV, which are the possible origins of Galactic cosmic-rays. We summarize the neutrino measurements by IceCube and ANTARES in the vicinity of LHAASO sources to constrain the contribution of hadronic gamma-rays in these sources. We find that the current observations constrain hadronic gamma-rays to contribute no more than ∼60% of the gamma-rays from the Crab Nebula. Gamma-rays from two LHAASO sources, LHAASO J1825âˆ'1326 and LHAASO J1907+0626, are dominated by leptonic components up to ∼200 TeV, under the hypotheses in the analysis by IceCube. The uncertainties of the constraint on the hadronic gamma-ray emission are discussed. We also constrain the total 100 TeV gamma-ray emission from TeV pulsar wind nebulae by relying on the remarkable sensitivity of LHAASO at that energy. [ABSTRACT FROM AUTHOR]

In this study, we present an observational analysis of a coronal hole (CH) observed on 2018 November 1 and solar wind (SW) that originated from it, using the Solar Dynamics Observatory, the Parker Solar Probe (PSP) observations at 68 solar radii, ACE and WIND data at 1 au, and interplanetary scintillation (IPS) observations from 0.2 to 1 au. The CH-originated SW stream was observed by L1 on 2018 November 4 and by PSP on 2018 November 15. We examined the CH for nine Carrington Rotations (CR) and find that the SW stream to reach L1 varied from one CR to other. We find that the pressure, temperature, and magnetic fields increase as the speed of the SW increases and the density decreases with distance. We noticed suprathermal particle enhancement at and after the stream interaction region in both PSP and L1 observations, but the enhancement lasted longer in PSP compared to measurements made at L1. The multiple-rotation observations of the CH imply that any differences in observations between PSP and spacecraft at L1 are due to the radial evolution of the solar wind stream rather than of the CH or the source plasma itself. In addition, IPS measured the radio signal irregularities driven by the SW. Furthermore, we employed a standard analytical model to extrapolate the magnetic field at larger heights. We find that the extrapolated magnetic field at 68 R ⊙ and 1 au matches well with the magnetic field measured by PSP and OMNI. [ABSTRACT FROM AUTHOR]

The dominant uncertainty in the current measurement of the Hubble constant (H 0) with strong gravitational lensing time delays is attributed to uncertainties in the mass profiles of the main deflector galaxies. Strongly lensed supernovae (glSNe) can provide, in addition to measurable time delays, lensing magnification constraints when knowledge about the unlensed apparent brightness of the explosion is imposed. We present a hierarchical Bayesian framework to combine a data set of SNe that are not strongly lensed and a data set of strongly lensed SNe with measured time delays. We jointly constrain (i) H 0 using the time delays as an absolute distance indicator, (ii) the lens model profiles using the magnification ratio of lensed and unlensed fluxes on the population level, and (iii) the unlensed apparent magnitude distribution of the SN population and the redshiftâ€"luminosity relation of the relative expansion history of the universe. We apply our joint inference framework on a future expected data set of glSNe and forecast that a sample of 144 glSNe of Type Ia with well-measured time series and imaging data will measure H 0 to 1.5%. We discuss strategies to mitigate systematics associated with using absolute flux measurements of glSNe to constrain the mass density profiles. Using the magnification of SN images is a promising and complementary alternative to using stellar kinematics. Future surveys, such as the Rubin and Roman observatories, will be able to discover the necessary number of glSNe, and with additional follow-up observations, this methodology will provide precise constraints on mass profiles and H 0. [ABSTRACT FROM AUTHOR]

We study the stellar binary black holes (BBHs) inspiraling/merging in galactic nuclei based on our numerical method GNC. We find that 3%â€"40% of all newborn BBHs will finally merge due to various dynamical effects. In a five-year mission, up to 104, 105, and ∼100 of BBHs inspiraling/merging in galactic nuclei can be detected with signal-to-noise ration >8 in Advanced LIGO (aLIGO), Einstein / DECIGO, and TianQin/LISA/TaiJi, respectively. Roughly tens are detectable in both LISA/TaiJi/TianQin and aLIGO. These BBHs have two unique characteristics. (1) Significant eccentricities: 1%â€"3%, 2%â€"7%, or 30%â€"90% of them have e i > 0.1 when they enter into aLIGO, Einstein, or space observatories, respectively. Such high eccentricities provide a possible explanation for that of GW190521. Most highly eccentric BBHs are not detectable in LISA/Tianqin/TaiJi before entering into aLIGO/Einstein, as their strain becomes significant only at f GW ≳ 0.1 Hz. DECIGO becomes an ideal observatory to detect those events, as it can fully cover the rising phase. (2) Up to 2% of BBHs can inspiral/merge at distances ≲103 r SW from the massive black hole, with significant accelerations, such that the Doppler phase drift of ∼10â€"105 of them can be detected with signal-to-noise ratio >8 in space observatories. The energy density of the gravitational-wave backgrounds (GWBs) contributed by these BBHs deviates from the power-law slope of 2/3 at f GW ≲ 1 mHz. The high eccentricity, significant accelerations, and the different profile of the GWB of these sources make them distinguishable, and thus interesting for future gravitational-wave detections and tests of relativities. [ABSTRACT FROM AUTHOR]

Space-based observatories at the second Sunâ€"Earth Lagrange Point (L2) offer a unique opportunity to efficiently determine the orbits of distant solar system objects by taking advantage of the parallax effect that arises from nearly simultaneous ground- and space-based observations. Given the typical orbit of an observatory about L2, the observational baseline of ∼1.5 Ă— 106 km between L2 and Earth results in an instantaneous parallax of ∼10″â€"100″, even for the most distant of detectable trans-Neptunian objects (TNOs) in our solar system. Current ground-based strategies for measuring the orbits of TNOs are very expensive and require multiple years of observations. We show that the direct constraint on the distance to a TNO, afforded by near-simultaneous ground- and space-based observations, allows us to confidently determine orbits with as few as three ground-based observations spanning 24 hr combined with a single observational epoch from an observatory orbiting L2. [ABSTRACT FROM AUTHOR]

We present a study of the detection and recovery efficiency of the Rubin Observatory for detached eclipsing binaries (EBs) in the galactic field, globular clusters (GCs), and open clusters (OCs), with a focus on comparing two proposed observing strategies: a standard cadence (baseline) and a cadence that samples the galactic plane more evenly (colossus). We generate realistic input binary populations in all observing fields of the Rubin Observatory, simulate the expected observations in each filter, and attempt to characterize the EBs using these simulated observations. In our models, we predict that the baseline cadence will enable the Rubin Observatory to observe about three million EBs; our technique could recover and characterize nearly one million of these in the field and thousands within star clusters. If the colossus cadence is used, the number of recovered EBs would increase by an overall factor of about 1.7 in the field and in globular clusters, and a factor of about 3 in open clusters. Including semidetached and contact systems could increase the number of recovered EBs by an additional factor of about 2.5 to 3. Regardless of the cadence, observations from the Rubin Observatory could reveal statistically significant physical distinctions between the distributions of EB orbital elements between the field, GCs, and OCs. Simulations such as these can be used to bias correct the sample of Rubin Observatory EBs to study the intrinsic properties of the full binary populations in the field and star clusters. [ABSTRACT FROM AUTHOR]

We discuss the largest and most homogeneous spectroscopic data set of field RR Lyrae variables (RRLs) available to date. We estimated abundances using both high-resolution and low-resolution (Î" S method) spectra for fundamental (RRab) and first overtone (RRc) RRLs. The iron abundances for 7941 RRLs were supplemented with similar estimates that are available in the literature, ending up with 9015 RRLs (6150 RRab, 2865 RRc). The metallicity distribution shows a mean value of 〈[Fe/H]〉 = âˆ'1.51 ± 0.01, and σ (standard deviation) = 0.41 dex with a long metal-poor tail approaching [Fe/H] ≃ âˆ' 3 and a sharp metal-rich tail approaching solar iron abundance. The RRab variables are more metal-rich (〈[Fe/H]〉ab = âˆ'1.48 ± 0.01, σ = 0.41 dex) than RRc variables (〈[Fe/H]〉c = âˆ'1.58 ± 0.01, σ = 0.40 dex). The relative fraction of RRab variables in the Bailey diagram (visual amplitude versus period) located along the short-period (more metal-rich) and the long-period (more metal-poor) sequences are 80% and 20%, while RRc variables display an opposite trend, namely 30% and 70%, respectively. We found that the pulsation period of both RRab and RRc variables steadily decreases when moving from the metal-poor to the metal-rich regime. The visual amplitude shows the same trend, but RRc amplitudes are almost two times more sensitive than RRab amplitudes to metallicity. We also investigated the dependence of the population ratio (N c /Ntot) of field RRLs on the metallicity and we found that the distribution is more complex than in globular clusters. The population ratio steadily increases from ∼0.25 to ∼0.36 in the metal-poor regime, it decreases from ∼0.36 to ∼0.18 for âˆ'1.8 ≤ [Fe/H] ≤ âˆ'0.9 and it increases to a value of ∼0.3 approaching solar iron abundance. [ABSTRACT FROM AUTHOR]

It is not yet fully understood how planet formation affects the properties of host stars, in or out of a cluster; however, abundance trends can help us understand this process. We present a detailed chemical abundance analysis of six stars in Praesepe, a planet-hosting open cluster. Pr0201 is known to host a close-in (period of 4.4 days) giant planet (mass of 0.54 M J), while the other five cluster members in our sample (Pr0133, Pr0081, Pr0208, Pr0051, and Pr0076) have no detected planets according to measurements of radial velocity. Using high-resolution echelle spectra with high signal-to-noise ratio obtained with Keck/HIRES and a novel approach to measurements of equivalent width (XSpect-EW), we derived abundances of up to 20 elements spanning a range of condensation temperatures (T C). We find a mean cluster metallicity of [Fe/H] = +0.21 ± 0.02 dex, in agreement with most previous determinations. We find most of our elements show an [X/Fe] scatter of ∼0.02â€"0.03 dex and conclude that our stellar sample is chemically homogeneous. The T C slope for the cluster mean abundances is consistent with zero and none of the stars in our sample exhibit individually a statistically significant T C slope. Using a planet engulfment model, we find that the planet host, Pr0201, shows no evidence of significant enrichment in its refractory elements when compared to the cluster mean that would be consistent with a planetary accretion scenario. [ABSTRACT FROM AUTHOR]

In this study, we investigate an extreme ultraviolet (EUV) wave event on 2010 February 11, which occurred as a limb event from the Earth viewpoint and a disk event from the Solar Terrestrial Relations Observatory-Behind viewpoint. We use the data obtained by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory in various EUV channels. The EUV wave event was launched by a partial prominence eruption. Compared with some EUV wave events in previous works, this EUV wave event contains a faster wave with a speed of ∼445 ± 6 km s−1, which we call a coronal Moreton wave, and a slower wave with a speed of ∼298 ± 5 km s−1, which we call the Extreme Ultraviolet Imaging Telescope (EIT) wave. The coronal Moreton wave is identified as a fast-mode wave and the EIT wave is identified as an apparent propagation due to successive field-line stretching. We also observe a stationary front associated with the fast-mode EUV wave. This stationary front is explained as mode conversion from the coronal Moreton wave to a slow-mode wave near a streamer. [ABSTRACT FROM AUTHOR]

As the signal-to-noise of Sunyaev–Zeldovich (SZ) cross-correlation measurements of galaxies improves our ability to infer properties about the circumgalactic medium (CGM), we will transition from being limited by statistical uncertainties to systematic uncertainties. Using thermodynamic profiles of the CGM created from the IllustrisTNG (The Next Generation) simulations we investigate the importance of specific choices in modeling the galaxy sample. These choices include different sample selections in the simulation (stellar versus halo mass, color selections) and different fitting models (matching by the shape of the mass distribution, inclusion of a two-halo term). We forward model a mock galaxy sample into projected SZ observable profiles and fit these profiles to a generalized Navarro–Frenk–White profile using forecasted errors of the upcoming Simons Observatory experiment. We test the number of free parameters in the fits and show that this is another modeling choice that yields different results. Finally, we show how different fitting models can reproduce parameters of a fiducial profile, and show that the addition of a two-halo term and matching by the mass distribution of the sample are extremely important modeling choices to consider. [ABSTRACT FROM AUTHOR]

Recent observations made with advanced LIGO and advanced Virgo have initiated the era of gravitational-wave astronomy. The number of events detected by these '2nd generation' (2G) ground-based observatories is partially limited by noise arising from temperature-induced position fluctuations of the test mass (TM) mirror surfaces used for probing spacetime dynamics. The design of next-generation gravitational-wave observatories addresses this limitation by using cryogenically cooled test masses; current approaches for continuously removing heat (resulting from absorbed laser light) rely on heat extraction via black-body radiation or conduction through suspension fibres. As a complementing approach for extracting heat during observational runs, we investigate cooling via helium gas impinging on the TM in free molecular flow. We establish a relation between cooling power and corresponding displacement noise, based on analytical models, which we compare to numerical simulations. Applying this theoretical framework with regard to the conceptual design of the Einstein telescope (ET), we find a cooling power of 10 mW at 18 K for a gas pressure that exceeds the ET design strain noise goal by at most a factor of ∼3 in the signal frequency band from 3 to 11 Hz. A cooling power of 100 mW at 18 K corresponds to a gas pressure that exceeds the ET design strain noise goal by at most a factor of ∼11 in the band from 1 to 28 Hz. [ABSTRACT FROM AUTHOR]

We present a preview of the faint dwarf galaxy discoveries that will be possible with the Vera C. Rubin Observatory and Subaru Hyper Suprime-Cam in the next decade. In this work, we combine deep ground-based images from the Panoramic Imaging Survey of Centaurus and Sculptor and extensive image simulations to investigate the recovery of faint, resolved dwarf galaxies in the Local Volume with a matched-filter technique. We adopt three fiducial distances (1.5, 3.5, and 5 Mpc) and quantitatively evaluate the effects on dwarf detection of varied stellar backgrounds, ellipticity, and Milky Way foreground contamination and extinction. We show that our matched-filter method is powerful for identifying both compact and extended systems, and near-future surveys will be able to probe at least ∼4.5 mag below the tip of the red giant branch (TRGB) for a distance of up to 1.5 Mpc and ∼2 mag below the TRGB at 5 Mpc. This will push the discovery frontier for resolved dwarf galaxies to fainter magnitudes, lower surface brightnesses, and larger distances. Our simulations show the secure census of dwarf galaxies down to MV ≈ −5, −7, and −8 will soon be within reach, out to 1.5, 3.5, and 5 Mpc, respectively, allowing us to quantify the statistical fluctuations in satellite abundances around hosts and parse environmental effects as a function of host properties. [ABSTRACT FROM AUTHOR]

The recent discovery of electromagnetic signals in coincidence with neutron-star mergers has solidified the importance of multimessenger campaigns in studying the most energetic astrophysical events. Pioneering multimessenger observatories, such as LIGO/Virgo and IceCube, record many candidate signals below the detection significance threshold. These sub-threshold event candidates are promising targets for multimessenger studies, as the information provided by them may, when combined with contemporaneous gamma-ray observations, lead to significant detections. Here we describe a new method that uses such candidates to search for transient events using archival very-high-energy gamma-ray data from imaging atmospheric Cherenkov telescopes (IACTs). We demonstrate the application of this method to sub-threshold binary neutron star (BNS) merger candidates identified in Advanced LIGO's first observing run. We identify eight hours of archival VERITAS observations coincident with seven BNS merger candidates and search them for TeV emission. No gamma-ray emission is detected; we calculate upper limits on the integral flux and compare them to a short gamma-ray burst model. We anticipate this search method to serve as a starting point for IACT searches with future LIGO/Virgo data releases as well as in other sub-threshold studies for multimessenger transients, such as IceCube neutrinos. Furthermore, it can be deployed immediately with other current-generation IACTs, and has the potential for real-time use that places a minimal burden on experimental operations. Lastly, this method may serve as a pilot for studies with the Cherenkov Telescope Array, which has the potential to observe even larger fields of view in its divergent pointing mode. [ABSTRACT FROM AUTHOR]

The most common way to discover extragalactic fast transients, which fade within a few nights in the optical, is via follow-up of gamma-ray burst and gravitational-wave triggers. However, wide-field surveys have the potential to identify rapidly fading transients independently of such external triggers. The volumetric survey speed of the Zwicky Transient Facility (ZTF) makes it sensitive to objects as faint and fast fading as kilonovae, the optical counterparts to binary neutron star mergers, out to almost 200 Mpc. We introduce an open-source software infrastructure, the ZTF REaltime Search and Triggering, ZTFReST , designed to identify kilonovae and fast transients in ZTF data. Using the ZTF alert stream combined with forced point-spread-function photometry, we have implemented automated candidate ranking based on their photometric evolution and fitting to kilonova models. Automated triggering, with a human in the loop for monitoring, of follow-up systems has also been implemented. In 13 months of science validation, we found several extragalactic fast transients independently of any external trigger, including two supernovae with post-shock cooling emission, two known afterglows with an associated gamma-ray burst (ZTF20abbiixp, ZTF20abwysqy), two known afterglows without any known gamma-ray counterpart (ZTF20aajnksq, ZTF21aaeyldq), and three new fast-declining sources (ZTF20abtxwfx, ZTF20acozryr, ZTF21aagwbjr) that are likely associated with GRB200817A, GRB201103B, and GRB210204A. However, we have not found any objects that appear to be kilonovae. We constrain the rate of GW170817-like kilonovae to R < 900 Gpc−3 yr−1 (95% confidence). A framework such as ZTFReST could become a prime tool for kilonova and fast-transient discovery with the Vera Rubin Observatory. [ABSTRACT FROM AUTHOR]

We statistically estimate the conversion rate of the energy released during an active region transient brightening to Doppler motion and thermal and nonthermal energies. We used two types of data sets for the energy estimation and detection of transient brightenings. One includes spectroscopic images of Fe xiv , Fe xv , and Fe xvi lines observed by the Hinode/EUV Imaging Spectrometer. The other includes images obtained from the 211 Å channel of the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA). The observed active region was NOAA 11890 on 2013 November 9 and 10. As a result, the released Doppler motion and nonthermal energies were found to be approximately 0.1%–1% and 10%–100% of the change in the amount of thermal energy in each enhancement, respectively. Using this conversion rate, we estimated the contribution of the total energy flux of AIA transient brightenings to the active region heating to be at most 2% of the conduction and radiative losses. [ABSTRACT FROM AUTHOR]

LIN 358 and SMC N73 are two symbiotic binaries in the halo of the Small Magellanic Cloud, each composed of a hot white dwarf accreting from a cool giant companion. In this work, we characterize these systems using a combination of spectral energy distribution (SED)-fitting to the extant photometric data spanning a broad wavelength range (X-ray/ultraviolet to near-infrared), detailed analysis of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra for the giant stars, and orbit fitting to high quality radial velocities from the APOGEE database. Using the calculated Roche lobe radius for the giant component and the mass ratio for each system, it is found that LIN 358 is likely undergoing mass transfer via wind Roche lobe overflow, while the accretion mechanism for SMC N73 remains uncertain. This work presents the first orbital characterization for both of these systems (yielding periods of >270 and >980 days, respectively, for SMC N73 and LIN 358) and the first global SED fitting for SMC N73. In addition, variability was identified in APOGEE spectra of LIN 358 spanning 17 epochs over two years that may point to a time variable accretion rate as the product of an eccentric orbit. [ABSTRACT FROM AUTHOR]