bluuebunny/crossref_metadata_2025_split huggingface dataset:
GASKAP-OH: A New Deep Survey of Ground-State OH Masers and Absorption in the Southern Sky
Authors: Dawson J. R. , Breen S. L. ,   the GASKAP-OH Team
Published: February 2024

AbstractThe Galactic ASKAP survey of OH (GASKAP-OH) is surveying the Milky Way Fourth Quadrant, the Galactic Centre, the Galactic Bulge and the Large Magellanic Cloud (LMC) in the 18-cm ground-state lines of the hydroxyl radical (OH), using Australia’s Square Kilometre Array Pathfinder (ASKAP) telescope. With an expected per-channel rms sensitivity of 36 mJy/beam in its shallowest regions, and a velocity channel width of 0.1 km s-1, GASKAP-OH is expected to discover hundreds of new star-formation and evolved star OH masers, as well as extensive absorption from quasi-thermal OH throughout the Galactic Plane. We here summarise the science goals and technical specifications of the survey, and report initial detection results from test observations. GASKAP-OH is expected to run for several years and is an open collaboration. Data products will be made available to the wider community as soon as they are verified.
A comprehensive model of maser polarization
Authors: Lankhaar Boy 
Published: February 2024

AbstractMaser polarization observations have been successfully used to characterize magnetic fields towards a variety of astrophysical objects. Circular polarization yields the magnetic field strength of the maser source, and linear polarization yields information on the magnetic field morphology. Linear polarization can be produced when the maser saturates or through its anisotropic pumping. We present a comprehensive model of the polarization of masers. In contrast to regular excitation modeling, we relax the assumption of isotropically populated level populations, and model both the total population and level alignments. Through this approach, we obtain quantitative estimates on the anisotropic pumping of a variety of maser sources. In this way, the maser polarization may be related to the gas density, temperature, geometry and the magnetic field. Using the results of our modeling, we discuss, and give predictions, of the polarization of SiO, methanol, and water (mega)masers.
IC 485 : A candidate for a new disk-maser galaxy
Authors: Ladu Elisabetta , Tarchi Andrea , Castangia Paola , Surcis Gabriele , Braatz James A. , Panessa Francesca , Pesce Dominic 
Published: February 2024

AbstractFundamental physical quantities of the nuclear regions of the Active Galactic Nuclei can be obtained using megamaser studies. In particular, disk-masers associated with accretion disks around the supermassive black holes are used, through high angular resolution measurements, to trace the disk geometry, to estimate the BH mass and to measure accurate distances to their host galaxies. In this contribution, we present the first results in continuum and spectral-line mode of a high-sensitivity, multi-epoch VLBI study of the nuclear region of the megamaser LINER galaxy IC 485.
High-cadence 6.7 GHz methanol maser monitoring observations by Hitachi 32-m radio telescope
Authors: Yonekura Yoshinori , Tanabe Yoshihiro , Moriizumi Ren 
Published: February 2024

AbstractWe started high-cadence monitoring observations of 6.7 GHz methanol masers from Dec. 2012 using Hitachi 32-m radio telescope (Yonekura et al.(2016). Observations have been conducted basically every day. On average, 13 hours of observations have been made per day, amounting to 4000–5000 hours per year. The cadence varies by sources: one observation in 1–50 days. In addition to already known 29 sources (Tanabe et al. 2023 and references therein), we have newly identified ∼20 sources with periodic flux variability. We have also detected 5 sources with sudden flux rises in 2019–2022, including G358.93–0.03 which was confirmed to be associated with the accretion burst.
Megamaser Cosmology Project II : The prospects for measuring a 1% Ho and distances to high-z galaxies
Authors: Kuo Cheng-Yu , Pesce Dominic , Impellizzeri Violetta , Braatz James , Reid Mark 
Published: February 2024

AbstractH2O megamaser emission from sub-parsec circumnuclear disks at the center of active galaxies allows a single-step, direct distance measurements to galaxies in the Hubble flow without any external calibration. Based on accurate distance determinations of six maser galaxies within 150 Mpc, the Megamaser Cosmology Project (MCP) team recently obtained H0 = 73.9± 3.0 km/s/Mpc (‘∼ 4% accuracy), independent of distance ladders and the cosmic microwave background. To further applying the megamaser technique to attain a 1% Ho measurement, detecting more high-quality disk maser systems is crucial. In this conference proceeding, we update the status of the MCP and discuss strategies of detecting additional high-quality disk maser galaxies within z ∼ 0.1. In addition, we show the prospects of reaching a 1% Ho measurement with the supreme sensitivity of the ngVLA. Finally, we demonstrate that applying the maser technique to distance measurements of high-z galaxies with future submm VLBI systems is promising and this will allow for investigation of the new tension between the ΛCDM model and the high-z Hubble diagram.
(Sub)mm Observations of Evolved Stars
Authors: Humphreys Elizabeth , Randall Suzanna , Asaki Yoshiharu , Bergman Per 
Published: February 2024

AbstractEvolved stars on the asymptotic giant branch and red supergiants have multiple processes that can be studied in the (sub)mm, including stellar surfaces, circumstellar thermal gas and dust, and masers. Telescopes such as APEX and ALMA have opened the possibility to perform studies that are revealing new information on these, as well as on the role of binaries in shaping stellar winds and the evolution to planetary nebulae. Here, we discuss some recent results for (sub)mm observations towards evolved stars focusing particularly on masers. This includes SiO and water masers, as well as ALMA high angular resolution observations of HCN masers towards a carbon-rich star.
High resolution VLBI observations of 6.7GHz periodic methanol masers
Authors: Olech Mateusz 
Published: February 2024

AbstractIn the last 20 years a small group of 6.7GHz methanol maser sources displaying periodic variability have been identified. This variability is thought to reflect local processes linked to star formation. A number of models have been proposed e.g. colliding wind binary, protostellar pulsation, accretion on binary system. Recent studies of known sources as well as non-periodic flaring masers suggest an episodic accretion as a driving mechanism. We present the results of VLBI observation program aimed at studying known periodic methanol maser sources. High resolution maps of emission, source morphology and evolution in time will be discussed. Those results will help us fully understand the nature of maser periodicity in star forming regions.
Water megamaser emission in hard X-ray selected, highly obscured AGNs
Authors: Castangia Paola , Tarchi Andrea , Della Ceca Roberto , Caccianiga Alessandro , Severgnini Paola , Surcis Gabriele , Melis Andrea , Panessa Francesca , Malizia Angela , Bassani Loredana 
Published: February 2024

AbstractWe took profit of the availability of large catalogs of active galact nuclei (AGNs) selected in the hard X-ray from satellite missions (e. g., INTEGRAL, Swift/BAT) to investigate the relation between the occurrence of water maser emission and the X-ray properties of the nuclei on a statistically meaningful basis. Our studies demonstrate that the hard X-ray selection may significantly enhance the maser detection rate over comparably large optical or infrared surveys. Here, we report on a recent survey to search for water maser emission with the Sardinia Radio Telescope (SRT) in a sample of heavily absorbed AGN taken from the 70 months Swift/BAT catalog.
Torun methanol maser monitoring program
Authors: Wolak P. , Szymczak M. , Bartkiewicz A. , Durjasz M. , Kobak A. , Olech M. 
Published: February 2024

AbstractSince 2009, the Torun 32 m radio telescope has been used to monitor a sample of ∼140 sources of the 6.7 GHz methanol maser emission. In 2022, the sample was extended to about 250 targets. Approximately three-quarters show variability greater than 10% on timescales of a few weeks to several years. The most significant results are detecting a few flare events and discovering about a dozen periodic variables with periods ranging from a month to a few years. Here, we present the preliminary analysis of the properties of periodic masers.
Annual parallax measurement of extreme OH/IR candidate star OH39.7+1.5
Authors: Watanabe Ryosuke 
Published: February 2024

AbstractOH/IR stars are low- to intermediate-mass stars (about 0.5-8 solar masses) in the AGB phase, and are considered to be in the process of evolving from Mira variables to planetary nebulae. We aim to understand the evolutionary stages of these AGB stars by approaching them from astrometric VLBI observations with VERA. In 2017, we have started VLBI observations of several OH/IR stars including OH39.7+1.5 presented in this poster. We observed the H2O maser of OH39.7+1.5 and obtained an annual parallax of 0.55 ± 0.03 mas (distance D = 1.81 ± 0.12 kpc). Using this annual parallax, we revealed distribution (about 35 au square), internal motions, and expansion velocities (average about 15.4 ± 5.1 km s-1) of the maser spots. We compared expansion velocity of H2O maser with that of OH maser and found to be consistent across the error range. This suggests that the radial velocity of H2O gas around OH39.7+1.5 has reached a terminal velocity. OH39.7+1.5 has not data on annual parallax or proper motion in Gaia DR3, and this is the first time that annual parallax has been measured.
Maser Science with the African VLBI Network and MeerKAT
Authors: Chibueze James O. 
Published: February 2024

AbstractThe African VLBI Network (AVN) is slowly becoming a reality. A couple of successful fringe test observations have been conducted even as single-dish maser monitoring observations constitute the main activity on the telescopes (HartRAO 26 m and Ghana 32 m). Some of the recent observational results from the AVN telescopes includes detection of velocity drifts in masers. Although MeerKAT is largely designed for high sensitivity continuum and HI science, its bands cover some masers and is already making impressive discoveries. The need to grow the critical mass of radio astronomers in the African continent persists. The NWU 4-dish interferometer, the Nigeria 3.7 m radio telescope and the African Millimeter Telescope (AMT) are some of the initiatives that will significantly improve the statistics of radio astronomers in Africa.
H2O masers and host environments of FU Orionis and EX Lupi type low-mass eruptive YSOs
Authors: Marianna Szabó Zsófia , Gong Yan , Yang Wenjin , Menten Karl M. , Bayandina Olga S. , Cyganowski Claudia J. , Kóspál Ágnes , Ábrahám Péter , Belloche Arnaud , Wyrowski Friedrich 
Published: February 2024

AbstractThe FU Orionis (FUor) and EX Lupi (EXor) type objects are rare pre-main sequence low-mass stars undergoing accretion outbursts. Maser emission is widespread and is a powerful probe of mass accretion and ejection on small scales in star forming region. However, very little is known about the overall prevalence of water masers towards FUors/Exors. We present results from our survey using the Effelsberg 100-m telescope to observe the largest sample of FUors and EXors, plus additional Gaia alerted sources (with the potential nature of being eruptive stars), a total of 51 targets, observing the 22.2 GHz H2O maser, while simultaneously covering the NH3 23 GHz.
The Dynamics of the Outflow Structure in W49 N
Authors: Asanok Kitiyanee , Gray M.D. , Hirota T. , Sugiyama K. , Phetra M. , Kramer B.H. , Liu T. , Kim K.T. , Pimpanuwat B. 
Published: February 2024

AbstractIn this current study, we report only the preliminary result of the SiO v=0 Ј=5→4 emission toward W49 N at 230 GHz, observed using the ALMA telescope on September 29, 2018. The position–velocity diagram of the SiO emission shows a structure of a bipolar outflow and has a face-on orientation with an inclination angle of 36.4±0.4 degrees with respect to the line of sight. Here we summarize the calculated physical properties of its outflow.
The water and methanol masers in the face-on accretion system around the high-mass protostar G353.273+0.641
Authors: Motogi Kazuhito , Hirota Tomoya , Machida Masahiro N. , Tanaka Kei E. I. , Yonekura Yoshinori 
Published: February 2024

AbstractWe report on a direct comparison of VLBI maser data and ALMA thermal-emission data for the high-mass protostar G353.273+0.641. We detected a gravitationally-unstable disk by dust and a high-velocity jet traced by a thermal CO line by ALMA long-baselines (LB). 6.7 GHz CH3OH masers trace infalling streamlines inside the disk. The innermost maser ring indicates another compact accretion disk of 30 au. Such a nested system could be caused by angular momentum transfer by the spiral arms. 22 GHz H2O masers trace the jet-accelerating region, which are directly connecting the CO jet and the protostar. The recurrent maser flares imply episodic jet ejections per 1–2 yr, while typical separation of CO knots indicates a variation of outflow rate per 100 yr. Our study demonstrates that VLBI maser observations are still a powerful tool to explore detailed structures nearby high-mass protostars by combining ALMA LB.
Closing Remarks of the International Astronomical Union Symposium 380
Authors: Bartkiewicz Anna , Pihlström Ylva 
Published: February 2024

AbstractWe are pleased to summarise the IAU Symposium 380, Cosmic Masers: Proper Motion toward the Next-Generation Large Projects held on March 2023 March 20-24 in Kagoshima City, Japan. It is the sixth symposium focusing on astrophysical masers broadly used in research of star formation and evolved stars, astrometric measurements of the Milky Way galaxy, as well as studies of extragalactic environments.
Early Star Formation Traced by Water Masers
Authors: Ladeyschikov Dmitry 
Published: February 2024

AbstractIn this study, the correlation between 22 GHz water masers and other maser species with far infrared/submillimeter (FIR/sub-mm) sources is investigated. Comparing luminosity to mass ratio (L/M) of FIR/sub-mm clumps linked to different maser species, 22 GHz water masers have significantly lower L/M values than 6.7 GHz methanol and 1665 MHz OH masers. This suggests 22 GHz water masers may precede them in the evolution timeline of SFRs. The close association between water masers and FIR/sub-mm sources provides insight into maser pumping conditions and evolutionary stages.
Overview of the Maser Monitoring Organisation
Authors: Burns Ross A. , Kobak Agnieszka , Caratti o Garatti Alessio , Tolmachev Alexander , Volvach Alexandr , Alakoz Alexei , Wootten Alwyn , Bisyarina Anastasia , Dzodzomenyo Andrews , Sobolev Andrey , Bartkiewicz Anna , Aberfelds Artis , Stecklum Bringfried , Kramer Busaba , Macdonald Callum , Cyganowski Claudia , Colomer Fransisco , Miro Cristina Garcia , Brogan Crystal , Li Dalei , Smits Derck , Engels Dieter , Ladeyschikov Dmitry , Johnstone Doug , Popova Elena , Proven-Adzri Emmanuel , van den Heever Fanie , Orosz Gabor , Surcis Gabriele , Wu Gang , MacLeod Gordon , Linz Hendrik , Imai Hiroshi , van Langevelde Huib , Valtts Irina , Shmeld Ivar , Chibueze James O. , Brand Jan , Kumar Jayender , Green Jimi , Vorster Job , Eislöffel Jochen , Kim Jungha , Sugiyama Koichiro , Menten Karl , Immer Katharina , Rygl Kazi , Sunada Kazuyoshi , Kim Kee-Tae , Volvach Larisa , Moscadelli Luca , Jordan Lucas , Uscanga Lucero , Gray Malcolm , Szymczak Marian , Olech Mateusz , Hoare Melvin , Durjasz Michał , Uchiyama Mizuho , Shakhvorostova Nadya , Bayandina Olga , Wolak Pawel , Gulyaev Sergei , Khaibrakhmanov Sergey , Breen Shari , Goedhart Sharmila , Casu Silvia , Ellingsen Simon , Paulson Sonu Tabitha , Kurtz Stan , Weston Stuart , Yoshihiro Tanabe , Natusc Tim , Hunter Todd , Hirota Tomoya , Baan Willem , Vlemmings Wouter , Chen Xi , Gong Yan , Yonekura Yoshinori , Szabó Zsófia Marianna , Abraham Zulema 
Published: February 2024

AbstractThe Maser Monitoring Organisation is a collection of researchers exploring the use of time-variable maser emission in the investigation of astrophysical phenomena. The forward directed aspects of research primarily involve using maser emission as a tool to investigate star formation. Simultaneously, these activities have deepened knowledge of maser emission itself in addition to uncovering previously unknown maser transitions. Thus a feedback loop is created where both the knowledge of astrophysical phenomena and the utilised tools of investigation themselves are iteratively sharpened. The project goals are open-ended and constantly evolving, however, the reliance on radio observatory maser monitoring campaigns persists as the fundamental enabler of research activities within the group.
Fine structure and refractive scattering of the H2O maser in star-forming region W49N
Authors: Shakhvorostova N. N. , Moran J. M. , Alakoz A. V. , Imai H. , Gwinn C. R. , Sobolev A. M. 
Published: February 2024

AbstractWe used the unprecedented resolution of ∼25 μas of the VLBI array formed with the RadioAstron satellite to study the structures of H2O maser spots in the star forming region W49N. We found that anisotropic diffractive scattering of the ISM dominates the images of the maser spot, but does not completely blur them. The refractive scattering floor is about 0.001 in visibility at a baseline of 8 Gλ.
Maser polarization simulation in an evolving star: effect of magnetic field on SiO maser in the circumstellar envelope
Authors: Phetra M. , Gray M. D. , Asanok K. , Kramer B. H. , Sugiyama K. , Etoka S. , Nuntiyakul W. 
Published: February 2024

AbstractMaser polarization changes during a pulsation in the CSE of an AGB star are related in a complicated way to the magnetic field structure. 43 GHz SiO maser transitions are useful for polarization study because of their relatively simple Zeeman splitting structure and their location. This work uses 3D maser simulation to investigate the effect of the magnetic field on maser polarization with different directions. The results show that linear polarization depends on the magnetic direction while circular polarization is less significant. The EVPA changes through π/2 at an angle of around 50 degrees, approximately the Van Vleck angle. The EVPA rotation result from 3D maser simulation is consistent with results from 1D simulations, and may explain the 90 degree change of the EVPA within a single cloud in the observational cases of TX Cam and R Cas.
Ocean Coupling Limits Rupture Velocity of Fastest Observed Ice Shelf Rift Propagation Event
Authors: Olinger Stephanie D. , Lipovsky Bradley P. , Denolle Marine A. 
Published: February 2024

AbstractThe Antarctic ice sheet is buttressed by floating ice shelves that calve icebergs along large fractures called rifts. Despite the significant influence exerted by rifting on ice shelf geometry and buttressing, the scarcity of in situ observations of rift propagation contributes considerable uncertainty to understanding rift dynamics. Here, we report the first‐ever seismic recording of a multiple‐kilometer rift propagation event. Remote sensing and seismic recordings reveal that a rift in the Pine Island Glacier Ice Shelf extended 10.53 km at a speed of 35.1 m/s, the fastest known ice fracture at this scale. We simulate ocean‐coupled rift propagation and find that the dynamics of water flow within the rift limit the propagation rate, resulting in rupture two orders of magnitude slower than typically predicted for brittle fracture. Using seismic recordings of the elastic waves generated during rift propagation, we estimate that ocean water flows into the rift at a rate of at least 2,300 m3/s during rift propagation and causes mixing in the subshelf cavity. Our observations support the hypotheses that large ice shelf rift propagation events are brittle, hydrodynamically limited, and exhibit sensitive coupling with the surrounding ocean.
Capturing the Relative‐Humidity‐Sensitive Gas–Particle Partitioning of Organic Aerosols in a 2D Volatility Basis Set
Authors: Serrano Damha Camilo , Cummings Bryan E. , Schervish Meredith , Shiraiwa Manabu , Waring Michael S. , Zuend Andreas 
Published: February 2024

AbstractAerosol water affects the physicochemical properties and mass concentration of organic aerosols (OA), but it is typically omitted by air quality, weather, and climate models. We compare two classes of simplified models to estimate the OA water uptake and gas–particle partitioning of organic compounds. One class uses a single‐hygroscopicity‐parameter (κ) approach while the other is based on the reduced‐complexity Binary Activity Thermodynamics (BAT) model. We show that a BAT‐based two‐dimensional volatility basis set (VBS) model always predicts a higher OA mass concentration at elevated relative humidity (RH), for example, ∼16% at 80% RH, than any variation of the κ‐based method considered—even when BAT‐VBS predicts a lower water uptake. The main reason being that the BAT‐VBS model captures variations in effective saturation mass concentration of organics (C*) with RH, a feature that other VBS methods lack. The BAT‐VBS framework offers an efficient, RH‐sensitive treatment for reduced‐complexity OA modeling.
Submesoscale Variability and Basal Melting in Ice Shelf Cavities of the Amundsen Sea
Authors: Shrestha Kalyan , Manucharyan Georgy E. , Nakayama Yoshihiro 
Published: February 2024

AbstractMelting of ice shelves can energize a wide range of ocean currents, from three‐dimensional turbulence to relatively large‐scale boundary currents. Here, we conduct high‐resolution simulations of the western Amundsen Sea to show that submesoscale eddies are prevalent inside ice shelf cavities. The simulations indicate energetic submesoscale eddies at the top and bottom ocean boundary layers, regions with sharp topographic slopes and strong lateral buoyancy gradients. These eddies play a substantial role in the vertical and lateral (along‐isopycnal) heat advection toward the ice shelf base, enhancing the basal melting in all simulated cavities. In turn, the meltwater provides strong buoyancy gradients that energize the submesoscale variability, forming a positive loop that could affect the overall efficiency of heat exchange between the ocean and the ice shelf cavity. Our study implies that submesoscale‐induced enhancement of basal melting may be a ubiquitous process that needs to be parameterized in coarse‐resolution climate models.
First Results From REPTile‐2 Measurements Onboard CIRBE
Authors: Li Xinlin , Selesnick Richard , Mei Yang , O’Brien Declan , Hogan Benjamin , Xiang Zheng , Khoo Lengying , Zhao Hong , Schiller Quintin , Temerin Michael , Baker Daniel N. 
Published: February 2024

AbstractCIRBE (Colorado Inner Radiation Belt Experiment), a 3U CubeSat, was launched on 15 April 2023 into a sun synchronous orbit (97.4° inclination and 509 km altitude). The sole science payload onboard is REPTile‐2 (Relativistic Electron and Proton Telescope integrated little experiment—2), an advanced version of REPTile which operated in space between 2012 and 2014. REPTile‐2 has 60 channels for electrons (0.25–6 MeV) and 60 channels for protons (6.5–100 MeV). It has been working well, capturing detailed dynamics of the radiation belt electrons, including several orders of magnitude enhancements of the outer belt electrons after an intense magnetic storm, multiple “wisps”‐ an electron precipitation phenomenon associated with human‐made very low frequency (VLF) waves in the inner belt, and “drift echoes” of 0.25–1.4 MeV electrons across the entire inner belt and part of the outer belt. These new observations provide opportunities to test the understanding of the physical mechanisms responsible for these features.