We present a study of the expanding molecular ring G35.28+0.04. Based on 6.7 GHz methanol maser data, we determine its distance to be 8.85(+1.15) (-0.91) kpc. Using CO (J = 1-0) observations from the Purple Mountain Observatory 13.7 m telescope together with multiwavelength archival data, we investigate the kinematic properties of the ring and its potential role in multigeneration star formation. The molecular gas shows clear expansion signatures, and the probability density function of N-H2 exhibits a typical double lognormal distribution, consistent with turbulence and feedback-driven compression. H ii regions inside and outside the ring show a bimodal age distribution, which is suggestive of sequential or hierarchical star formation, with younger regions potentially associated with later stages of feedback. Spectral energy distribution fitting of point sources reveals no clear age gradient among young stellar objects. ClassIII sources are radially concentrated toward regions of strong molecular compression; however, these sources may largely trace an earlier stellar population or the ambient field rather than being directly produced by the current expansion of the ring. Infrared and radio continuum data further indicate that the ionizing feedback from the original exciting source has significantly weakened, although the ring structure still preserves dynamical imprints of its long-term evolution. Taken together, our results are consistent with a scenario in which G35.28+0.04 has experienced feedback-influenced, possibly multigenerational star formation over the past similar to 21-28 Myr, providing new insight into the evolution of molecular rings and hierarchical star formation processes.

Accretion-driven outbursts are a fundamental process in star formation, determining the final masses of stars and the chemistry of protoplanetary disks, yet their detection in the youngest, deeply embedded protostars remains challenging. Radiatively pumped methanol masers, to date associated exclusively with high-mass young stellar objects, exhibit flares that are interpreted as signatures of accretion bursts and serve as beacons to identify massive protostellar outbursts. Indeed, for all such methanol maser flares studied thus far, the driving source has been identified as the associated high mass protostar. By combining James Webb Space Telescope (JWST) and Atacama Large Millimeter/submillimeter Array (ALMA) observations, we prove that the recent methanol maser flare in the massive star-forming region IRAS 18134-194216 was driven by a nearby lower-mass protostar undergoing a strong accretion outburst, rather than the central massive object. Our infrared spectroscopy captures the physical and chemical response of the protostellar core to the accretion burst. Our results demonstrate that methanol masers flares can uncover the hidden population of embedded low-mass bursting protostars in massive clusters, and challenge the standard paradigm where such maser activity is exclusively attributed to massive protostars, demonstrating that cavities opened by low-mass companions can provide a radiative path for triggering flares of pre-existing masers excited by massive protostars.

G34 is an active star-forming region with complex velocity components. Within the 38-63 km s(-1) velocity range, we identify a possible cloud-cloud collision at a distance of '3 kpc. Using the( 12)CO ( J = 1-0) line from the Purple Mountain Observatory 13.7-m millimeter telescope to trace the diffuse gas structures associated with the collision. The gas components at 38-50 and 53-63 km s(-1) exhibit a U-shaped complementary distribution and a bridge feature in the position-velocity diagram. At the collision interface, the velocity dispersion of (CO)-C-12 is significantly enhanced, which may result from the impact of the collision. We analyse the spatial distributions of 6.7 GHz CH3OH masers, APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) clumps, H II regions, young stellar objects, and O-type stars, finding that most are concentrated near the collision interface. This supports a strong coupling between cloud-cloud collisions and star formation. In addition, we detect H I self-absorption features and molecular outflows at the interface. Based on observations of 6 and 2 cm H2CO lines from the Effelsberg 100 m and Tianma Radio Telescope 64 m telescopes, along with NH(3 )lines from the Nanshan 26 m telescope, we derive an H 2 volume density of 10( 4)-10( 5 )cm(-3 )in the compressed region. Finally, we compare the collision time-scales (greater than or similar to 0.35 Myr), the dynamical age of the HII region G34.26 + 0.15 (greater than or similar to 0.33 Myr), and the outflow time-scale ( '7.5 Myr). The results suggest that gas at the base of the U-shaped structure was compressed during the collision and driven into the outflow. After millions of years of evolution, the gas density increased, potentially triggering star formation.

The prestellar core Barnard 68 (B68) is a prototypical source to study the initial conditions and chemical processes of star formation. A previous numerical simulation suggested the southeastern bullet is impacting on the main body of B68. In order to obtain more observational evidence, mapping observations of the ground state SO (1 _0 –0 _1 ) emission line at 30 GHz were made with the Effelsberg 100 m telescope. Based on the velocity field and channel maps derived from SO, three velocity components were clearly detected. The velocity field of the main body indicates rotation and is well fitted by a solid-body rotation model. The measured radial velocity difference between the bullet and the main core is about 0.4 km s ^−1 , which is almost equal to the velocity obtained by the previous numerical simulation. Therefore, the bullet is most likely impacting on the rotating main body of B68. A 1D spherical non–local thermodynamic equilibrium Monte Carlo radiation transfer RATRAN code is performed to derive the radial abundance profile of SO by analyzing the observed velocity-integrated intensity. SO is depleted inside a 60″ (0.02 pc) radius from the core. The abundance stays constant at 2.0 × 10 ^−9 for radii larger than 60″ from the center of the main core. The abundance is enhanced at the interface of the bullet and the main core, indicating that shock waves were produced by the collision between the bullet and the main core. In conclusion, based on the kinematical and chemical analysis, our observational results support the previously proposed core–core collision scenario in B68.

We confirmed the existence of a massive protocluster in G23.43-0.18 from our Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum and molecular line observations. We resolved the region into one main massive protostellar object, G23.43-0.18 A, one intermediate mass protostellar object, G23.43-0.18 B, and three low mass objects, G23.43-0.18 C1, G23.43-0.18 C2, and G23.43-0.18 C3. A spiral arm structure is observed in G23.43-0.18 B. G23.43-0.18 A 1.3 mm dust continuum emission showed a 'butterfly' morphology with clear evidence of the existence of a cavity and bipolar outflow with an inclination angle of 50$<^>\circ$. G23.43-0.18 B presents a compact rotating structure, and possibly an inner Keplerian disc, traced with methanol lines and powers a jet revealed by multiple compact emission peaks in CO, indicating episodic ejections every 300 yr. The presence of 6.7 GHz methanol masers in G23.43-0.18 A and G23.43-0.18 B are strong indications that both objects host massive protostars and are good sites to test some theories of the early evolutionary phases of massive stars.

We present the survey results of the S255IR star-forming region in the 210-250 GHz range observed with the SMA interferometric array. We have constructed 115 channel maps and integrated intensity maps in the emission lines of various molecules. Complex organic molecules are observed mainly in the direction of the hot core SMA1. Exceptions are methanol and methylacetylene, which are seen in the direction of the SMA2 core and bipolar outflows as well. Spectra in the direction of the SMA1 and SMA2 cores were obtained and 59 molecules were detected, including complex molecules of 8-10 atoms.

We study the structure, interstellar absorption, color-magnitude diagrams, kinematics, and dynamical state of embedded star clusters in the star-forming region associated with the giant molecular cloud G174+2.5. Our investigation is based on photometric data from the UKIDSS Galactic Plane Survey catalog and astrometric data from the Gaia DR3 catalogs. First, we recover all the known embedded clusters and candidate clusters in the region using surface density maps. Then, for the detected clusters, we determine their general parameters: the center positions, radii, number of stars, and reddening. To evaluate the reddening, we use both the NICEST algorithm and the Q-method. Both methods produce consistent extinction maps in the regions of the four studied clusters. However, the Q-method yields a much smaller color scatter in the CMD. For four clusters in particular (S235 North-West, S235 A-B-C, S235 Central, and S235 East1+East2), we were able to compute individual membership probabilities, the cluster distances, the cluster masses, and their average proper motions. By building on these results, we have studied the clusters' kinematics and dynamics. Moreover, we estimate the mass of the gas component and the star formation efficiency (SFE) in the regions of these four clusters. Finally, we provide an estimate of the total energy of the stellar and gas components in the area of these four clusters to determine whether the clusters are bound (here we consider a `cluster' as the system `stars + gas'). The gravitational bound strongly depends on the region for which we estimate the gas mass. If we consider the mass of the entire cloud, all these four clusters turn out to be bound.

Magnetic reconnection, a critical process in astrophysical luminosity outbursts like solar flares, may also underpin such events in high-mass young stellar objects (HMYSOs). Despite theoretical predictions, observational evidence linking luminosity outbursts to magnetic reconnection in HMYSOs is still lacking. Our study examines the bursting HMYSO G36.11+0.55, where we find a significant correlation between the variability of 6.668 GHz CH3OH maser and the magnetic field strength inferred from 6.035 GHz ex-OH masers. This aligns with models of accretion-driven magnetic flux accumulation and reconnection-driven ejection, proposed for low-mass protostellar flares in theoretical studies. The CH3OH maser light curve closely resembles those observed or expected in other luminosity outbursts linked to magnetic reconnection. Furthermore, CH3OH maser flare regions coincide with jets from the source, also supporting the model of reconnection-driven magnetic flux ejection. These observational results underscore the essential role of magnetic fields in HMYSO outburst dynamics and material accretion near HMYSOs.

We present the results of the ongoing spectral and photometric study at the Kourovka Observatory of the young variable star V645 Cyg, which is an Ae/Be Herbig object and is located in a region of active star formation. The increase in brightness and reddening of the color of V645 Cyg, previously discovered by the authors and continuing to this day, as well as the increase in the absorption component of the blue wing of the Hα line profile are interpreted within the framework of the assumption of a decrease in the optical thickness of the expanding gas-dust cocoon and an increase in the visibility of regions of the gas-dust envelope heated by the radiation of the star. New results obtained during 2024 are presented.

Preliminary results of the study of molecular spectra of three regions of the massive protostellar object G12.89+0.49, observed with the ALMA interferometer in the frequency range of 216-234 GHz, are presented. Regions of size 0.15ʺ × 0.15ʺ are identified along the disk plane (MM1-1, MM1-2 and MM1-3). In the region MM1-1, which is the richest with lines, 28 methanol lines are identified in the spectra. A significant difference was revealed in the widths of the methanol lines: in MM1-1 FWHM = 5-7 km/s, in MM1-2 and MM1-3 3- 4 km/s, and in the radial velocities: in MM1-1 and MM1-2 Vlsr = 31-32 km/s, in MM1-3 35-36 km/s. Based on the estimates of the physical parameters of the regions under consideration, carried out using the large velocity gradient approximation, it was concluded that most of the observed methanol lines correspond to transitions that are excited, with a probability of 95 %, in the outer parts of the disk with the parameters: gas kinetic temperature ≥ 140 K, gas number density ≥ 105 cm−3, methanol column density ≥ 1018 cm−2, methanol abundance ≥ 10−6. At the same time, in MM1-1 and MM1-2, lines are observed corresponding to transitions of the J6−J7 Evt = 1 series, which, according to our estimates, are excited in a hotter ≥ 190 K and, possibly, denser part of the disk.

The molecular cloud complex G34 is located at a distance of 2.12 +/- 0.38 kpc and contains two giant filaments, F1 and F2. It is considered a good example of colliding filaments. We mapped these two filaments using the (CO)-C-13 and (CO)-C-12 (J = 1-0) lines that were observed with the 13.7 m millimeter-wavelength telescope of the Purple Mountain Observatory. The fraction of high-column density gas N-H2 > 1.0 x 10(22) cm(-2) in F1 and F2 is 4.16% and 8.33%, respectively, which is lower than the typical value of 10% for giant molecular filaments. Moreover, only one of the 13 dense clumps identified in F1 and F2 correlates with the infrared dust cores traced by the NASA Wide-field Infrared Survey Explorer (WISE) 22 mu m emission. This suggests that F1 and F2 may be in early stages of their evolution and might be forming low-mass stars. We also observe large-scale velocity gradients in F1 and F2. Along the spine of F1, the velocity and line mass increase from the ends toward the center, while in F2, they increase from the northwest to the southeast. These parameters are inversely correlated with the gravitational potential, which may indicate a transformation between kinetic energy and gravitational potential energy between F1 and F2. Furthermore, no H II regions correlate with F1 and F2 in the WISE data of galactic H II regions, which indicates that the gas distribution within F1, as well as the V-shaped structure of F1, is unaffected by feedback from H II regions, but is instead caused by gravitational effects. The material in F1 and F2 is not concentrated at the ends of the filaments, but rather in the middle of F1 and at one end of F2 and therefore does not lead to the edge-collapse effect. The collapse and merging timescales thus do not compete. Finally, we calculated the merging time of F1 and F2. When the angle between the line-of-sight velocity and the direction of the relative velocity between F1 and F2 is 45 degrees, the average relative velocity between F1 and F2 is 1.39 km s(-1). The resulting merging timescale is approximately 4.62 +/- 1.12 Myr. This process might be influenced by additional stellar feedback from ongoing star formation within the filaments.

We study the structure, kinematics, and star-forming activity of filamentary cloud F-NE associated with AGAL323.444+0.096 using ^13 CO ( J = 2–1) molecular line and continuum data from the far-infrared to near-infrared. The cloud comprises two elongated subfilaments, F-NE-north and F-NE-south, each spanning 25 pc, with systemic velocities of −65.25 and −67.38 km s ^−1 , respectively. F-NE-north and F-NE-south seem to be merging by collision. They exhibit signatures of cloud–cloud collisions, including U-shaped and arc-like morphologies, complementary components, and bridge features, suggesting ongoing collisions. The interacting zones show enhanced column densities and elevated velocity dispersion, further supporting the collision scenario. All these features are consistent with the “fray and gather” model. Dense clumps and young stellar objects are predominantly concentrated in these collision regions, implying that filament merging and localized collisions drive the formation of massive dusty clumps capable of nurturing massive stars. These results demonstrate that filament merging by collision is crucial for both filament structural evolution and the formation of massive stars and clusters.

Context. Maser flares are particularly significant in the study of massive star formation as they not only signal but also provide unique insights into transient phenomena such as accretion bursts. Aims. With this project, we aim to investigate the context of the ongoing 6.7 GHz methanol maser flare in the little-known massive star-forming region G11.497-1.485. Methods We carried out two epochs of the Karl G. Jansky Very Large Array (VLA) observation for 6.7 GHz and 12 GHz class II methanol, 22 GHz water masers, and continuum in the C , Ku , and K bands. Results. The VLA overview revealed the presence of five distinct radio-continuum sources (CM1-4 and N) in G11.497-1.485. The central source, CM1, is found to show signs of accretion disc fragmentation, highlighted by the centimetre-continuum-traced fragments, and is found to drive a high-energy jet, the ends of which are marked by non-thermal knots CM2 and CM3. CM1 showed a gradual flaring of methanol masers and a fading of a 22 GHz water maser, which might be signalling an accretion burst. The two remaining sources of the region, CM4 and N, make up one of the most compact jet and disc–jet systems found to date. Conclusions. The obtained data reveal, for the first time, the structure of the G11.497-1.485 region. The change in fluxes of the maser and the continuum emission confirm a transient event and reveal its impact on multiple sources in the region.

The high-mass young stellar object G358.93-0.03-MM1 underwent a rapid accretion burst event from 2019 January to June, resulting in flares observed in most class II methanol maser transitions starting in mid-January. In contrast, the 22.235 GHz water maser flare started in mid-April. To investigate the physical origin of this significant difference, we made the Karl G. Jansky Very Large Array observations toward the G358.93-0.03 region on 2019 March 23 and April 4 and obtained the intensity and spatial distribution images of the water maser as well as the continuum emissions at Ku and K bands on the epoch close to the water maser flare. A comparative analysis, incorporating previously reported detections in February (pre-water maser flare) and June (post-water maser flare), reveals the time lag between the accretion burst and water maser flare. These observations confirm the variations of the propagation speed of a heatwave induced by the accretion burst in different directions: the heatwave is decelerated in dense regions (e.g., the disk and jet), whereas in directions from G358-MM1 to water maser components, the heatwave speed is supposed to be close to the speed of light. Variations in flux density and spatial positions were detected for water masers and continuum emissions, indicating that the accretion burst event originating from G358-MM1 affects not only the immediate environment within a dense structure of 0.″2 (1400 au at a source distance of 6.75 kpc) around MM1 itself, but also exerts influence on broader-scale regions extending up to approximately 3″ (21,000 au).

Context . The effect of accretion bursts on massive young stellar objects (MYSOs) represents a new research field in the study of young stars and their environment. The impact of such bursts on the disk and envelope has been observed and plays the role of a “smoking gun” providing information about the properties of the burst itself. Aims . We aim to investigate the impact of an accretion burst on massive disks with different types of envelopes and to study the effects of an accretion burst on the temperature structure and the chemistry of the disk. We focus on water and methanol as chemical species for this paper. Methods . The thermochemical code of ProDiMo (PROtoplanetary DIsk MOdel) is used to perform simulations of high-mass protoplanetary-disk models with different types of envelopes in the presence of an accretion burst. The models in question represent different evolutionary stages of protostellar objects. We calculated and show the chemical abundances in three phases of the simulation (pre-burst, burst, and post-burst). Results . More heavily embedded disks show higher temperatures. The impact of the accretion burst is mainly characterized by the desorption of chemical species present in the disk and envelope from the dust grains to the gas phase. When the post-burst phase starts, the sublimated species freeze out again. The degree of sublimation depends strongly on the type of envelope the disk is embedded in. An accretion burst in more massive envelopes produces stronger desorption of the chemical species. However, our models show that the timescale for the chemistry to reach the pre-burst state is independent of the type of envelope. Conclusions . The study shows that the disk’s temperature increases with a more massive envelope enclosing it. Thus, the chemistry of MYSOs in earlier stages of their evolution reacts stronger to an accretion burst than at later stages where the envelope has lost most of its mass or has been dissipated. The study of the impact of accretion bursts could also provide helpful theoretical context to the observation of methanol masers in massive disks.

The Maser Monitoring Parkes Project (M2P2) is an ongoing project to observe masers towards high-mass star-forming regions (HMSFRs) using the 64 m CSIRO Parkes radio telescope, Murriyang. In this paper, we outline the project and introduce Stokes-I data from the first two years of observations. For the 63 sightlines observed in this project we identify a total of 1 514 individual maser features: 14.4% of these (203) towards 27 sightlines show significant variability. Most of these (160/203) are seen in the main-line transitions of OH at 1665 and 1667 MHz, but this data set also includes a significant number of variable features in the satellite lines at 1 612 and 1 720 MHz (33 and 10, respectively), most of which (24 and 9, respectively) appear to be associated with the HMSFRs. We divide these features into 4 broad categories based on the behaviour of their intensity over time: flares (6%), periodic (11%), long-term trends (33%), and 'other' (50%). Variable masers provide a unique laboratory for the modelling of local environmental conditions of HMSFRs, and follow-up publications will delve into this in more detail.

ABSTRACT Multi-epoch very long baseline interferometry (VLBI) observations measure three-dimensional water maser motions in protostellar outflows, enabling analysis of inclination and velocity. However, these analyses assume that water masers and shock surfaces within outflows are co-propagating. We compare VLBI data on maser-traced bow shocks in the high-mass protostar AFGL 5142-MM1, from seven epochs of archival data from the VLBI Exploration of Radio Astrometry (VERA), obtained from 2014 April to 2015 May, and our newly conducted data from the KVN and VERA Array (KaVA), obtained in 2016 March. We find an inconsistency between the expected displacement of the bow shocks and the motions of individual masers. The separation between two opposing bow shocks in AFGL 5142-MM1 was determined to be 337.17 ± 0.07 mas in the KaVA data, which is less than an expected value of 342.1 ± 0.7 mas based on extrapolation of the proper motions of individual maser features measured by VERA. Our measurements imply that the bow shock propagates at a velocity of 24 ± 3 km s−1, while the individual masing gas clumps move at an average velocity of 55 ± 5 km s−1; that is ,the water masers are moving in the outflow direction at double the speed at which the bow shocks are propagating. Our results emphasize that investigations of individual maser features are best approached using short-term high-cadence VLBI monitoring, while long-term monitoring on timescales comparable to the lifetimes of maser features is better suited to tracing the overall evolution of shock surfaces. Observers should be aware that masers and shock surfaces can move relative to each other, and that this can affect the interpretation of protostellar outflows.

HMYSOs gain most of their mass in short bursts of accretion. Maser emission is an invaluable tool in discovering and probing accretion bursts. We observed the 22 GHz water maser response induced by the accretion burst in NGC6334I-MM1B and identified the underlying maser variability mechanisms. We report seven epochs of VLBI observations of 22 GHz water masers in NGC6334I with the VERA array, from 2014 to 2016, spanning the onset of the accretion burst in 2015.1. We also report 2019 ALMA observations of 321 GHz water masers and 22 GHz maser monitoring by HartRAO. We analyze variability patterns and use proper motions with the 22 GHz to 321 GHz line ratio to distinguish between masers in C-shocks and J-shocks. We also calculated the burst-to-quiescent variance ratio of the single-dish time series. The constant mean proper motion before and after the burst indicates that maser variability is due to excitation effects from variable radiation rather than jet ejecta. We find that the flux density variance ratio in the single-dish time series can identify maser efficiency variations in 22 GHz masers. The northern region, CM2-W2, is excited in C-shocks and showed long-term flaring with velocity-dependent excitation of new maser features. We propose that radiative heating of H2 due to high-energy radiation from the accretion burst be the mechanism for the flaring in CM2-W2. The southern regions are excited by J-shocks and have short-term flaring and dampening of water masers. We attributed the diverse variability patterns in the southern regions to the radiative transfer of the burst energy in the source. Our results indicate that the effects of source geometry, shock type, and incident radiation spectrum are fundamental factors affecting 22 GHz maser variability. Investigating water masers in irradiated shocks will improve their use as a diagnostic in time-variable radiation environments.

Context. High-mass young stellar objects gain most of their mass in short intense bursts of accretion. Maser emission is an invaluable tool in discovering and probing these accretion bursts. Aims. Our aim was to observe the 22 GHz water maser response induced by the accretion burst in NGC6334I-MM1B and to identify the underlying maser variability mechanisms. Methods. We report seven epochs of very long baseline interferometry (VLBI) observations of 22 GHz water masers in NGC6334I with the VLBI Exploration of Radio Astrometry (VERA) array, from 2014 to 2016, spanning the onset of the accretion burst in 2015.1. We also report 2019 Atacama Large Millimeter/submillimeter Array (ALMA) observations of 321 GHz water masers and 22 GHz single-dish maser monitoring by the Hartebeesthoek Radio Astronomical Observatory (HartRAO). We analysed long-term variability patterns and used proper motions with the 22 GHz to 321 GHz line ratio to distinguish between masers in non-dissociative C-shocks and dissociative J-shocks. We also calculated the burst-to-quiescent variance ratio of the single-dish time series. Results. We detected a water maser distribution resembling a bipolar outflow morphology. The constant mean proper motion before and after the burst indicates that maser variability is due to excitation effects from variable radiation rather than jet ejecta. For the whole region, we find that the flux density variance ratio in the single-dish time series can identify maser efficiency variations in 22 GHz masers. The northern region, CM2-W2, is excited in C-shocks and showed long-term flaring with velocity-dependent excitation of new maser features after the onset of the burst. We propose that radiative heating of H2 due to high-energy radiation from the accretion burst be the main mechanism for the flaring in CM2-W2. The southern regions are excited by J-shocks, which have shown short-term flaring and dampening of water masers. We attribute the diverse variability patterns in the southern regions to the radiative transfer of the burst energy in the complex source geometry. Conclusions. Our results indicate that the effects of source geometry, shock type, and incident radiation spectrum are fundamental factors affecting 22 GHz maser variability. Investigating water masers in irradiated shocks will improve their use as a diagnostic in time-variable radiation environments, such as accretion bursting sources.

We have conducted a systematic line survey, primarily focused on transitions of the methanol and ammonia molecules, and monitoring observations of masers toward the high-mass star-forming region NGC 6334I. These observations were undertaken between 2019 and 2022 in the C, K, Ka , and Q bands with the Tianma Radio Telescope. In total, 63 CH 3 OH (including 11 class I and nine class II maser or maser candidate), 18 13 CH 3 OH, and 34 NH 3 (including seven maser or maser candidate) transitions were detected. The emission is likely associated with the luminosity outburst source MM1. Rotation diagram analysis of multiple ammonia transitions shows that the gas temperature in the molecular core was a factor of 2 higher than that measured in previous observations in the pre-burst stage. This suggests that the molecular core has likely been heated by radiation originating from the luminosity outburst. Maser variability in the methanol and excited-state OH masers shows a general trend that the maser components associated with the luminosity outburst have decreased in their intensity since 2020. The decay in the maser luminosity indicates that the outburst is possibly declining, and as a result, the duration of the MM1 luminosity outburst may be shorter than the predicted 40 yr duration. Compared to the masers detected toward another luminosity outburst source, G358.93-0.03, abundant class I methanol masers and strong water maser flares were also detected toward NGC 633I, but masers from rare class II methanol transitions and new molecules were absent toward NGC 6334I. The large number of detections of maser transitions toward the two burst sources provided a database for further maser modeling to explore the physical environments associated with accretion burst events.