Aayushi Verma

We present a detailed analysis of the long-term photometric and spectroscopic evolution of V1180 Cas over a decade, aiming to identify the dominant mechanisms behind its variability. We combine multiband light curves from 1999 to 2025 with over 30 epochs of optical to near-infrared (NIR) spectroscopy (0.5–2.5 μ m), analyzing variability patterns, color behavior, and emission line diagnostics. We investigate the temporal evolution of accretion and outflow indicators and their correlation with photometric states. The light curve reveals a transition from sporadic early dimming events to a quasi-periodic pattern since 2018, with 11 major dips showing asymmetry and stochastic substructure. Color–magnitude diagrams show classic UXor-like blueing during deep minima, while NIR and mid-infrared color changes indicate thermal evolution of the disk. Spectroscopic analysis reveals persistent hydrogen, Ca II , He I , and forbidden line emission. Accretion diagnostics track photometric variability, and forbidden lines often intensify during dips, implying a physical link between extinction and outflows. Estimated accretion rates range from ∼10 ⁻⁸ to 10 ⁻⁷ M _⊙ yr ⁻¹ ; the outflow rate and density diagnostics are consistent with disk winds and shock-excited jets. V1180 Cas demonstrates dual-mode variability driven by both variable circumstellar extinction and episodic accretion events. The hybrid UXor/EXor behavior, combined with evolving disk signatures and persistent outflows, suggests a young stellar object undergoing coupled accretion–extinction–outflow evolution. Continued monitoring will be essential to fully resolve the physical processes shaping its variability.

We explore the physical environment of the Galactic mid-infrared (MIR) bubble [HKS2019] E71 (hereafter E71) through a multiwavelength approach. E71 is located at the edge of a filamentary structure, as traced in Herschel images (250–500 μm), Herschel column density map, and molecular maps in the velocity range [−20, −14] km s⁻¹. It hosts a stellar cluster (radius ∼ 1.26 pc, distance ∼1.81 ± 0.15 kpc) associated with radio continuum emission, including a centrally positioned B1.5-type massive star (hereafter “m2”), along with an enhanced population of evolved low-mass stars and young stellar objects. MIR images and molecular line maps reveal a photodissociation region surrounding “m2,” exhibiting an arc-like structure along the edges of E71. Regularly spaced molecular and dust condensations are identified along this structure. The position–velocity map of ¹²CO (1–0) emission suggests an expansion of molecular gas concentrated at the periphery of E71. Near-infrared spectroscopic observations with TANSPEC confirm the presence of the accretion process in a massive young stellar object (MYSO) located near the edge of the bubble. High-resolution uGMRT radio continuum maps uncover substructures in the ionized emission, both toward the MYSO and the center of E71. These findings support that “m2” has shaped an arc-like morphology through its feedback processes. The pressure exerted by “m2” and the velocity structure of the ^12/13CO (1–0) emission suggest that the stellar feedback has likely driven out molecular material, leading to the formation of the expanding E71 bubble. Our overall investigation infers that the “collect and collapse” process might be a possible mechanism that can describe the ongoing star formation activities around the E71 bubble.

We explore the physical environment of the Galactic mid-infrared (MIR) bubble [HKS2019] E71 (hereafter E71) through a multi-wavelength approach. E71 is located at the edge of a filamentary structure, as traced in Herschel images (250-500 $μ$m), Herschel column density map, and molecular maps in the velocity range [-20,-14] km/s. It hosts a stellar cluster (radius~1.26 pc, distance~1.81+/-0.15 kpc) associated with radio continuum emission, including a centrally positioned B1.5-type massive star (hereafter 'm2'), along with an enhanced population of evolved low-mass stars and young stellar objects. MIR images and molecular line maps reveal a PDR surrounding 'm2', exhibiting an arc-like structure along the edges of E71. Regularly spaced molecular and dust condensations are identified along this structure. The position-velocity map of 12CO emission suggests an expansion of molecular gas concentrated at the periphery of E71. Near-infrared spectroscopic observations with TANSPEC confirm the presence of the accretion process in a massive young stellar object (MYSO) located near the edge of the bubble. High-resolution uGMRT radio continuum maps uncover substructures in the ionized emission, both toward the MYSO and the center of E71. These findings support that 'm2' has shaped an arc-like morphology through its feedback processes. The pressure exerted by 'm2' and the velocity structure of the 12/13CO(1-0) emission suggest that the stellar feedback has likely driven out molecular material, leading to the formation of the expanding E71 bubble. Our overall investigation infers that the "collect and collapse" process might be a possible mechanism that can describe the ongoing star formation activities around the E71 bubble.

We present an observational study of the S284-RE region, a low-metallicity area associated with the extended S284 H ii region. A thermally supercritical filament (mass ∼2402 M _⊙ and length ∼8.5 pc) is investigated using the Herschel column density map. The Spitzer ratio 4.5 μm/3.6 μm map traces the H₂ outflows in this filament, where previously reported young stellar objects (YSOs) are spatially distributed. Analysis of the YSO distribution has revealed three active star-forming clusters (YCl1, YCl2, and YCl3) within the filament. YCl3 seems to be the most evolved and YCl2 the youngest, while YCl1 displays signs of nonthermal fragmentation. The JWST (F470N+F444W)/F356W ratio map reveals at least seven bipolar H₂ outflows, with four (olc1–olc4) in YCl1 and three (ol1–ol3) in YCl2. The driving sources of these outflows are identified based on outflow geometry, Atacama Large Millimeter/submillimeter Array (ALMA) continuum peaks, and YSO positions. Two ALMA continuum sources—#2 and #3—from the M–R _eff plot are recognized as potential massive star formation candidates. ALMA continuum source #2 hosts at least three outflow-driving sources, whereas ALMA continuum source #3 contains two. The bipolar outflow olc1, driven by an embedded object within continuum source #2, is likely a massive protostar, as indicated by the Br-α and PAH emissions depicted in the JWST (F405N+F444W)/F356W ratio map. The presence of H₂ knots in the outflows olc1 and ol1 suggests episodic accretion. Overall, the study investigates a massive protostar candidate, driving the ∼2.7 pc H₂ outflow olc1 and undergoing episodic accretion.

We aim to investigate the global star formation scenario in star-forming sites AFGL 5157, [FSR2007] 0807 (hereafter FSR0807), [HKS2019] E70 (hereafter E70), [KPS2012] MWSC 0620 (hereafter KPS0620), and IRAS 05331+3115 in the outer Galactic arm. The distribution of young stellar objects in these sites coincides with a higher extinction and H₂ column density, which agrees with the notion that star formation occurs inside the dense molecular cloud cores. We have found two molecular structures at different velocities in this direction; one contains AFGL 5157 and FSR0807, and the other contains E70, [KPS2012] MWSC 0620, and IRAS 05331+3115. All these clusters in our target region are in different evolutionary stages and might form stars through different mechanisms. The E70 cluster seems to be the oldest in our sample; AFGL 5157 and FSR0807 formed later, and KPS0620 and IRAS 05331+3115 are the youngest sites. AFGL 5157 and FSR0807 are physically connected and have cold filamentary structures and dense hub regions. Additionally, the near-infrared photometric analysis shows signatures of massive star formation in these sites. KPS0620 also seems to have cold filamentary structures with the central hub but lacks signatures of massive stars. Our analysis suggests molecular gas flow and the hub filamentary star formation scenario in these regions. IRAS 05331+3115 is a single clump of molecular gas favoring low-mass star formation. Our study suggests that the selected area is a menagerie of star-forming sites where the formation of the stars happens through different processes.

We present a multiwavelength analysis of the star cluster NGC 2316 and its surroundings. We estimated the physical parameters of the NGC 2316 cluster, including its shape (elongated), size (R _cluster = 0.4 pc), distance (1.3 ± 0.3 kpc), and minimum reddening (A _V = 1.55 mag). We discovered two massive stars (B2.0V-B1.5V, age ∼12 Myr) embedded (A _V = 4 mag) within this cluster. The cluster region still forms young stars even though the most massive star was born ∼12 Myr ago. We also found evidence of positive feedback from these massive stars. We identified a cold gas/dust lane extending westward from the cluster. The western end of the dust lane seems to favor low-mass star formation, whereas the cluster end favors bit massive star formation, which seems to have started earlier than the western end. We found an elongated molecular cloud in this region, characterized by numerous filamentary structures. The morphology of the filaments, along with position–velocity maps, velocity dispersion maps, channel maps, etc., indicate a coalescence of filaments and a potential longitudinal flow of matter toward the cluster through the western end of the gas/dust lane. This entire region seems to be a Hub-filamentary system (HFS), in which the NGC 2316 cluster is probably the hub and the dark lane is the main filamentary structure. Being the gravity well of this HFS, star formation started first in the NGC 2316 region and went on to the other filamentary nodes.

We have carried out a quantitative analysis of the 1°×1° region near star-forming site AFGL 5157 using ’Minimal Spanning Tree’ (MST). The analysis reveals that this region consists of five major clusters. The cluster radii of the cores and active regions were found to be varying between 0.75-2.62 pc and 2.77-4.58 pc, respectively, for these regions, while the aspect ratio varies between 0.71 to 7.17. This hints towards the clumpy as well as elongated clusters in the region. We calculated structure parameter Q for each region which varies between 0.41-0.62 and 0.23-0.81 for the cores and ARs, respectively. This shows the existence of fractal distribution in all the cores and ARs except the core of the [HKS2019] E70 bubble.

We present here the results of 8 yr of our near-simultaneous optical–near-infrared spectro-photometric monitoring of the bona fide FU Ori (FUor)-type candidate V2493 Cygnus (V2493 Cyg) starting from 2013 September to 2021 June. During our optical monitoring period (between 2015 October 16 and 2019 December 30), the V2493 Cyg is slowly dimming with an average dimming rate of ∼26.6 ± 5.6 mmag yr⁻¹ in the V band. Our optical photometric colors show a significant reddening of the source post the second outburst pointing toward a gradual expansion of the emitting region post the second outburst. The mid-infrared colors, on the contrary, exhibit a blueing trend, which can be attributed to the brightening of the disk due to the outburst. Our spectroscopic monitoring shows a dramatic variation of the Hα line as it transitioned from absorption feature to the emission feature and back. Such transition can possibly be explained by the variation in the wind structure in combination with accretion. Combining our time evolution spectra of the Ca ii infrared triplet lines with the previously published spectra of V2493 Cyg, we find that the accretion region has stabilized compared to the early days of the outburst. The evolution of the O i λ7773 Å line also points toward the stabilization of the circumstellar disk post the second outburst.

We present a comprehensive analysis of the Galactic mid-infrared bubble [HKS2019] E70 (E70) by adopting a multiwavelength approach to understand the physical environment and star formation scenario around it. We identified a small (radius ∼1.7 pc) stellar cluster inside the E70 bubble, and its distance is estimated as 3.26 ± 0.45 kpc. This cluster is embedded in the molecular cloud and hosts massive stars, as well as young stellar objects (YSOs), suggesting active star formation in the region. The spectral type of the brightest star (M1) of the E70 cluster is estimated as O9V, and a circular ring/shell of gas and dust is found around it. The diffuse radio emission inside this ring/shell, the excess pressure exerted by the massive star M1 at the YSO’s core, and the distribution of photodissociation regions, a class I YSO, and two ultracompact H ii regions on the rim of this ring/shell clearly suggest positive feedback of the massive star M1 in the region. We also found a low-density shell-like structure in the ¹²CO(J = 1–0) molecular emission along the perimeter of the E70 bubble. The velocity structure of the ¹²CO emission suggests that the feedback from the massive star appears to have expelled the molecular material, and the subsequent swept-up material is what appears as the E70 bubble.