bluuebunny/crossref_metadata_2025_split huggingface dataset:
Results of KVN Key Science Program for evolved stars
Authors: Yun Youngjoo , Cho Se-Hyung , Yoon Dong-Hwan , Yang Haneul , Dodson Richard , Rioja María J. , Imai Hiroshi 
Published: February 2024

AbstractWe present the results of KVN Key Science Program (KSP) for evolved stars, which was launched in 2014. The first phase of KSP ended in June 2020 and the second phase started in October 2020. The goal of KSP is to study the physical characteristics of the evolved stars by observing the spatial distribution and temporal variability of the stellar masers at four frequency-bands (K, Q, W and D bands). The 22 GHz H2O maser is usually observed from the outer part of circumstellar envelopes compared to the 43, 86, 129 GHz SiO masers, thus the kinematic links between these regions can be studied by the multi-frequency simultaneous observations of KSP along the stellar pulsation cycles. This eventually enable us to study the enormous mass-loss rate of evolved stars, and the accumulated results from KSP are expected to shed light on the study of the late stage of the stellar evolution.
A sensitive search for SiO maser emission in planetary nebulae
Authors: Gómez José F. , Cala Roldán A. , Miranda Luis F. , Imai Hiroshi , Osorio Mayra , Anglada Guillem 
Published: February 2024

AbstractEight planetary nebulae (PNe) are known to emit OH and/or H2O masers, but there is no report of an SiO maser in this type of objects. We present a search for SiO masers in 16 confirmed and candidate PNe, carried out with the Australia Telescope Compact Array. We found no evidence of association between SiO masers and PNe in our data. Previous detections of thermal SiO emission in PNe show that these molecules can be present in gas phase in this type of objects, but it is not yet clear whether they can be found where the physical conditions are appropriate for maser pumping. We suggest that the best candidates for a new search would be PNe showing high-velocity outflows.
Kinematics in the Galactic Center with SiO masers
Authors: Paine Jennie , Darling Jeremy 
Published: February 2024

AbstractStellar SiO masers are found in the atmospheres of asymptotic giant branch (AGB) stars with several maser transitions observed around 43 and 86 GHz. At least 28 SiO maser stars have been detected within ∼2 pc projected distance from Sgr A* by the Very Large Array (VLA) and Atacama Millimeter/submillimeter Array (ALMA). A subset of these masers have been studied for several decades and form the basis of the radio reference frame that anchors the reference frame for infrared stars in the Galactic Center (GC). We present new observations of the GC masers from VLA and ALMA. These new data combined with extant maser astrometry provide 3D positions, velocities, and acceleration limits. The proper motions and Doppler velocities are measured with unprecedented precision for these masers. We further demonstrate how these measurements may be used to trace the stellar and dark matter mass distributions within a few pc of Sgr A*.
Fully 3D modelling of masers towards AGB stars - latest development and early results
Authors: Pimpanuwat B. , M. D.  , Gray  , S.  , Etoka  , W.  , Homan  , A. M. S.  , Richards  
Published: February 2024

AbstractWe present new results from a 3D modelling code for maser flares which provides the user with control over the physical conditions; maser cloud geometry and orientation; and fast runtime via parallelisation. The statistics of simulated observables suggest that achievable amplification may be dependent on viewpoints of the source and that a randomly placed observer is likely to detect an unremarkable blue- or red-shifted maser unless the line-of-sight direction is optimal for maser amplification. A preliminary model of masers towards π1 Gru based on SPH simulations also shows promising consistency with ALMA observations of high-j SiO transitions from the source.
Monitoring of the polarized H2O maser emission around the massive protostars W75N(B)-VLA 1 and W75N(B)-VLA 2
Authors: Surcis Gabriele , Vlemmings Wouter H.T. , Goddi Ciriaco , Torrelles José-María 
Published: February 2024

AbstractSeveral radio sources have been detected in the high-mass star-forming region W75N(B), among them the massive young stellar objects VLA 1 and VLA 2 are of great interest. These are thought to be in different evolutionary stages. In particular, VLA 1 is at the early stage of the photoionization and it is driving a thermal radio jet, while VLA 2 is a thermal, collimated ionized wind surrounded by a dusty disk or envelope. In both sources 22 GHz H2O masers have been detected in the past. Those around VLA 1 show a persistent linear distribution along the thermal radio jet and those around VLA 2 have instead traced the evolution from a non-collimated to a collimated outflow over a period of ∼20 years. The magnetic field inferred from the H2O masers showed a rotation of its orientation according to the direction of the major-axis of the shell around VLA 2, while it is immutable around VLA 1.We further monitored the polarized emission of the 22 GHz H2O masers around both VLA 1 and VLA 2 over a period of six years with the European VLBI Network for a total of four epochs separated by two years from 2014 to 2020. We here present the results of our monitoring project by focusing on the evolution of the maser distribution and of the magnetic field around the two massive young stellar objects.
SiO maser line ratios in the BAaDE Survey
Authors: Lewis Megan O. , Pihlström Ylva M. , Sjouwerman Loránt O. 
Published: February 2024

AbstractMulti-transition SiO maser emission has been detected in over 10 thousand evolved stars across the plane of the Milky Way by the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey. In addition to the large source catalog of the survey, the frequency coverage is also unprecedented: the J=1-0 (43 GHz) data cover seven separate transitions of SiO, and the J=2-1 (86 GHz) data cover ten SiO transitions. In contrast, most other SiO maser data only probe the SiO v=1 and v=2 at 43 GHz and/or the v=1 at 86 GHz. Our extended range allows for the derivation of SiO line ratios for a huge population of evolved stars, including those derived from rare transitions associated with 29SiO and 30SiO isotopologues. We examine how these ratios are affected by the specific combinations of transitions that are detected in a single source. Furthermore, we present a class of ‘isotopologue dominated’ sources where the 29SiO transitions are the brightest in the 43 GHz spectrum. Finally, using Optical Gravitational Lensing Experiment (OGLE) light curves of our maser stars, changes in line ratios as a function of stellar phase are discussed.
The origin of the Perseus-arm gap revealed with VLBI astrometry
Authors: Sakai Nobuyuki , Nakanishi Hiroyuki , Kurahara Kohei , Sakai Daisuke , Hachisuka Kazuya , Kim Jeong-Sook , Kameya Osamu 
Published: February 2024

AbstractThe Perseus arm has a gap in Galactic longitudes (l) between 50° and 80° where the arm has little star formation activity. To understand the gap, we conducted VERA (VLBI Exploration of Radio Astrometry) astrometry and analyzed archival H <SC>I</SC> data. We report on parallax and proper motion results from four star-forming regions, of which G050.28–00.39 and G070.33+01.59 are associated with the gap. Perseus-arm sources G049.41+00.32 and G050.28–00.39 lag relative to a Galactic rotation by 77 ± 17 km s-1 and 31 ± 10 km s-1, respectively. The noncircular motion of G049.41+00.32 cannot be explained by the gravitational potential of the arm. We discovered rectangular holes with integrated brightness temperatures less than 30 K arcdeg in l vs. VLSR of the H <SC>I</SC> data. Also, we found extended H <SC>I</SC> emission on one side of the Galactic plane when integrating the H <SC>I</SC> data over the velocity range covering the hole. G049.41+00.32 and G050.28–00.39 are moving toward the emission. The Galactic H <SC>I</SC> disk at the same velocity range showed an arc structure, indicating that the disk was pushed from the lower side of the disk. All the observational results might be explained by a cloud collision with the Galactic disk.
ALMA explores the inner wind of evolved O-rich stars with two widespread vibrationally excited transitions of water
Authors: Baudry Alain , Wong Ka Tat , Etoka Sandra , Richards Anita M.S. , Gray Malcolm D. , Herpin Fabrice , Danilovich Taïssa , Wallström Sofia , Decin Leen , Gottlieb Carl A. ,   the ATOMIUM consortium
Published: February 2024

AbstractALMA observations with angular resolution in the range ∼20–200 mas demonstrate that emission at 268.149 and 262.898 GHz in the (0,2,0) and (0,1,0) vibrationally excited states of water are widespread in the inner envelope of O-rich AGB stars and red supergiants. These transitions are either quasi-thermally excited, in which case they can be used to estimate the molecular column density, or show signs of maser emission with a brightness temperature of ∼103–107 K in a few stars. The highest spatial resolution observations probe the inner few stellar radii environment, up to ∼10–12 R* in general, while the mid resolution data probe more thermally excited gas at larger extents. In several stars, high velocity components are observed at 268.149 GHz which may be caused by the kinematic perturbations induced by a companion. Radiative transfer models of water are revisited to specify the physical conditions leading to 268.149 and 262.898 GHz maser excitation.
Methanol and excited OH masers in W49N as observed using EVN
Authors: Bartkiewicz Anna , Szymczak Marian , Kobak Agnieszka , Aramowicz Mirosława 
Published: February 2024

AbstractWe imaged the excited OH maser line at 6.035 GHz associated with the 6.7 GHz methanol masers in a selected sample of high-mass young stellar objects using the European VLBI Network. The excited OH emission was found in a survey of methanol maser sources carried out since 2018 with the Torun 32-m telescope. The overlap of radial velocities of spectral features of methanol and excited OH suggested that both lines arose in the same volume of gas, therefore, we verified this hypothesis with the interferometric data. Here, we present the first images at the milliarcsecond scale of both maser transitions and identify the Zeeman pairs at the ex-OH line estimating the strength of the magnetic field in G43.149+00.013 (W49N).
Study of Active Galactic Nuclei using the Water Vapour Masers
Authors: Deepshikha  , Naomasa Nakai , Madoka Yamazaki , Aya Yamauchi 
Published: February 2024

AbstractThe mass of the black hole separated from the mass of the maser disk is calculated using the mega-maser technique for 15 maser-galaxies and the corresponding Magorrian relationship (inline1) is analysed.
A database of circumstellar OH masers update
Authors: Engels Dieter , López-Martí Belen 
Published: February 2024

AbstractThe database of circumstellar OH masers by Engels & Bunzel (2015) was updated to include new 1612, 1665, and 1667 MHz OH maser observations published between 2015 and 2022. A cross-correlation of the database was made with infrared catalogues (AllWISE and 2MASS) and with GAIA DR3. This led frequently to significantly improved coordinates and identified contaminations with non-stellar sources. About 40% of all OH maser-detected stars were not detected by GAIA. These are mostly representatives of the population of highly obscured stars at the end of AGB or at the beginning of post-AGB evolution.
Galactic Astrometry with VLBI
Authors: Rygl Kazi L. J. 
Published: February 2024

AbstractAstrometric very long baseline interferometry (VLBI) observations of stellar masers are an excellent method to determine distances and proper motions in our Galaxy. Large maser astrometry surveys, the Bar and Spiral Structure Legacy survey and the VLBI Exploration for Radio Astrometry, allowed astronomers to determine fundamental Galactic parameters, such as the rotation curve and the distance to the Galactic centre, as well as to trace the spiral arms. In this review, the results of these surveys will be summarised and compared with astrometric measurements using other methods.
The Astrometric Animation of Water Masers toward the Mira Variable BX Cam
Authors: Xu Shuangjing , Imai Hiroshi , Yun Youngjoo , Zhang Bo , Rioja María J. , Dodson Richard , Cho Se-Hyung , Kim Jaeheon , Cui Lang , Sobolev Andrey M. , Chibueze James O. , Kim Dong-Jin , Amada Kei , Nakashima Jun-ichi , Orosz Gabor , Oyadomari Miyako , Oh Sejin , Yonekura Yoshinori , Sun Yan , Mai Xiaofeng , Zhang Jingdong , Wen Shiming , Jung Taehyun 
Published: February 2024

AbstractWe report VLBI monitoring observations of the 22 GHz H2O masers toward the Mira variable BX Cam. Data from 37 epochs spanning ∼3 stellar pulsation periods were obtained between May 2018 and June 2021 with a time interval of 3–4 weeks. In particular, the VERA dual-beam system was used to measure the kinematics and parallaxes of the H2O maser features. The obtained parallax, 1.79±0.08 mas, is consistent with Gaia EDR3 and previous VLBI measurements. The position of the central star was estimated relied on Gaia EDR3 data and the center position of the 43 GHz SiO maser ring imaged with KVN. Analysis of the 3D maser kinematics revealed an expanding circumstellar envelope with a velocity of 13±4 km s−1 and significant spatial and velocity asymmetries. The H2O maser animation achieved by our dense monitoring program manifests the propagation of shock waves in the circumstellar envelope of BX Cam.
Maser Tracers of Gas Dynamics near Young Stars New Perspectives
Authors: Sanna Alberto , Moscadelli Luca 
Published: February 2024

AbstractThe protostellar environment where young stars form has physical conditions suitable to excite a number of molecular maser lines that have traditionally provided an unique probe of star formation kinematics, at the highest angular resolution of radio very long baseline interferometry (VLBI) observations. In the following, we will discuss a number of recent results on our understanding of the gas dynamics traced by masers in the vicinity of young forming stars. These findings provide direct clues on how our community can substantially contribute to the field of star formation in the next decade.
Estimating distances to AGB stars using IR data
Authors: Bhattacharya Rajorshi , Pihlström Ylva M. , Sjouwerman Loránt O. 
Published: February 2024

AbstractWe present a method to estimate distances to AGB stars, utilizing the rich infrared data sets available for these infrared-bright targets. The method is based on the assumption that stars with intrinsically similar properties (metallicity, initial mass, etc.) produce similar spectral energy distributions (SEDs) and similar luminosities. We here discuss the results for AGB stars belonging to the BAaDE survey sample whose distances were calibrated using the template SEDs of stars with their VLBI parallaxes. As VLBI parallaxes are only known for a handful of sources, the resulting templates only cover a small subset of the BAaDE sample. Additional methods to derive suitable templates will therefore also be required. The work on expanding the template set is promising, although more fine tuning is still needed.
HINOTORI and Maser Observations
Authors: Nakashima Keisuke , Shum Ka-Yiu , Imai Hiroshi ,   HINOTORI Collaboration
Published: February 2024

AbstractHINOTORI (Hybrid Integration Project in Nobeyama, Triple-band Oriented) has constructed a higher sensitivity 22/43 GHz and a 22/43/86 GHz simultaneous observation systems in the Nobeyama 45-m telescope by introducing new frequency separation filters in the telescope’s quasi-optics. The performance of the observation systems, such as the beam squint, the aperture efficiency, the system noise temperature when inserting the filters, and the phase stability of the signal path have been evaluated. It is indicated that the established systems have sufficient performance for single-dish and VLBI observations. The single-dish observation demonstrations using the triple-band system were successfully conducted in acquiring scientific data including multiple maser lines.
Trigonometric parallax, proper motion, and structure of three southern hemisphere methanol masers
Authors: Hyland Lucas J. , Ellingsen Simon P. , Reid Mark J. , Kumar Jayender , Orosz Gabor 
Published: February 2024

AbstractWe present the trigonometric parallax, proper motion, and structure of three methanol masers from the Southern Hemisphere Parallax Interferometric Radio Astrometry Legacy Project (SπRALS). All three masers have better than 5% parallax accuracy, which we attribute to the new inverse MultiView calibration technique.
Properties of pulsating OH/IR stars revealed from astrometric VLBI observation
Authors: Nakagawa Akiharu , Kurayama Tomoharu , Sudou Hiroshi , Orosz Gabor 
Published: February 2024

AbstractWe aim to reveal properties of evolution stages in AGB phase; Mira, OH/IR stars, and non-variable OH/IR stars. We presented results of our VLBI observations of four stars; NSV17351, OH39.7+1.5, IRC–30363, and AW Tau. We used the VERA VLBI array to observe 22 GHz H2O masers. Parallaxes of the four sources were obtained to be 0.247±0.035 mas (4.05±0.59 kpc), 0.54±0.03 mas (1.85±0.10 kpc), 0.562±0.201 mas (1.78±0.73 kpc), and 0.449±0.032 mas (2.23±0.16 kpc). Determination of pulsation period of NSV17351 was done for the first time. We revealed the position and kinematics of NSV17351 in our Galaxy and found that NSV17351 is located in an interarm region. A new period-magnitude relationship was indicated in the infrared region. Various other properties based on the distance measurements are also discussed. We have to emphasize that the VLBI astrometry is effective and the only way for parallax measurements of dust obscured OH/IR stars.
Sub-mm spectral astrometric VLBI with the ngEHT
Authors: Dodson Richard , Rioja Maria J. 
Published: February 2024

AbstractWe present the prospects from astrometric spectral line VLBI in the era of ngEHT. We review the potential targets, that span many interesting science cases. We summarise the approaches that have been demonstrated to work at lower frequencies and touch on the simulations that give us great confidence that these same approaches will continue to work at sub-mm wavelengths. We conclude that this is a worthwhile pursuit with a high probability of success.
Water masers high resolution measurements of the diverse conditions in evolved star winds
Authors: Richards A. M. S. , Asaki Y. , Baudry A. , Brand J. , Decin L. , Etoka S. , Gray M. D. , Herpin F. , Humphreys R. , Pimpanuwat B. , Singh A. P. , Yates J. A. , Ziurys L. M. 
Published: February 2024

AbstractWe compare detailed observations of multiple H2O maser transitions around the red supergiant star VY CMa with models to constrain the physical conditions in the complex outflows. The temperature profile is consistent with a variable mass loss rate but the masers are mostly concentrated in dense clumps. High-excitation lines trace localised outflows near the star.
Astrometric observations of water maser sources toward the Galactic Center with VLBI
Authors: Sakai Daisuke , Oyama Tomoaki , Kobayashi Hideyuki , Honma Mareki 
Published: February 2024

AbstractThe Central Molecular Zone (CMZ) in the Galactic Center region shows outstanding non-circular motion unlike the Galactic disk. While several models describing this non-circular motion have been proposed, a uniform kinematic model of the CMZ orbit has not yet emerged. To uncover the dynamics of the Galactic center region, we conducted VLBI astrometric observations of 22GHz water maser sources towards the Galactic center using VERA. By measuring parallaxes and proper motions, we can determine whether each source is actually located in the CMZ or not, and identify the three-dimensional positions and velocities in the non-circular orbit if the source is indeed located in the CMZ. We present the results of our astrometric study for several maser sources associated with molecular clouds towards the Galactic center. The astrometric observations toward Sgr B2(M) indicated that Sgr B2 complex is moving toward the positive Galactic longitude relative to Sgr A*.
Observations of Possibly New OH Excited Rotational State Masers
Authors: Shmeld Ivar , Aberfelds Artis , Patoka Oleksey 
Published: February 2024

AbstractIn order to search for new 6.035 GHz excited OH masers 272 star-forming regions visible from the northern hemisphere with known active methanol masers were observed with the 32 m and 16 m radio telescopes of the Ventspils International Radio Astronomy Center (VIRAC). Three possibly new excited OH maser sources at 6.035 GHz were seen.
OH megamaser emission in the outflow of the luminous infrared galaxy Zw049.057
Authors: Aalto Susanne , Lankhaar Boy , Wethers Clare , Moldon Javier , Beswick Robert 
Published: February 2024

AbstractHigh resolution (0."26 × 0."13 (70 × 35 pc)) L-band (18 cm) OH megamaser (OHM) e-Merlin observations of the LIRG Zw049.057 show that the emission is emerging from a low velocity outflowing structure - which is foreground to a fast, dense and collimated molecular outflow detected by ALMA. The extremely dusty compact obscured nucleus (CON) of Zw049.057 has no (or only little) OHM emission associated with it - possibly because of too high number densities that quench the OHM. In contrast we detect 6 cm H2CO emission primarily from the CON-region. We suggest that the OHM-region of Zw049.057 is not directly associated with star formation, but instead occurs in a wide-angle, slow outflow that surrounds the fast and dense outflow. The OHM is pumped by IR emission that likely stems from activities in the nucleus. We briefly discuss how OHM emission can be used as a probe of LIRG-CON galaxies.
Jet and Outflows in Massive Star Forming Region: G10.34-0.14
Authors: Kang Jihyun , Kim Mikyoung , Kim Kee-Tae , Hirota Tomoya ,   KaVA SF team
Published: February 2024

AbstractThe ALMA observations of the high-mass star-forming region G10.34-0.14 reveal the existence of three massive hot cores. The most massive of these cores, core S1, exhibits both high and low-velocity jet/outflow in the CO, SiO, and CH3OH. It is associated with water and Class I methanol masers. The core N shows a low-velocity CO outflow and is associated with an Extended Green Object, along with Class I and II methanol masers. The characteristics of the outflows and masers in these two cores suggest they are in different stage of evolution and varying physical conditions.
HMSFR G024.33+0.14: A possible new discovery in the making
Authors: van den Heever S. P. , Szymczak M. , Durjasz M. , Bartkiewicz A. , Olech M. , Wolak P. 
Published: February 2024

AbstractSince 2017, and the formation of the maser monitoring organisation (M2O), we have observed several intriguing events. These events have included possible accretion bursts, strong jets, periodicity after a flare, a heat-wave of radiation travelling outward at a fraction of the speed of light, to name a few. In September 2019 the M2O was notified of another source showing flaring behavior, and here we present the possibility of the first discovery of long-term maser periodicity from the high-mass star formation region (HMSFR) G024.33+0.14, with a period of about 3000 days.
Discovery of circular polarization of the 6.7 GHz methanol maser in G33.641-0.228
Authors: Fujisawa Kenta 
Published: February 2024

AbstractThe 6.7 GHz methanol maser emitted by a high-mass star forming region G33.641-0.228 is known to exhibit fast flux density variability on timescales of less than one day. The mechanism of this variability, called burst, has not been known. We observed the circular polarization of this maser. As a result, we found that only the spectral components representing burst exhibit strong circular polarization exceeding 10%. This suggests that the two phenomena of the burst and circular polarization are related to each other.