IIA SAILI KESHRIKinematics of the lens host S0 galaxy NGC 1553: Role of secular processes
We investigated the central structure of the S0 galaxy NGC 1553, to understand its origin and the underlying dynamical processes that shape it. The high-resolution integral field spectroscopic data from the Multi Unit Spectroscopic Explorer (MUSE) reveal a well-ordered rotation pattern, consisting of a (i) rapidly rotating nuclear disc that is somewhat decoupled from the main disc, and (ii) an inner lens; we collectively refer to these structures as the 'disc-lens'. The central peak in the velocity dispersion indicates the presence of a classical bulge. The nuclear disc is dynamically colder than the surrounding disc, while the lens is dynamically hotter. The higher-order Gauss─Hermite moments, h3 and h4, further characterise the stellar kinematics. An anti-correlation between the line-of-sight velocity and skewness (h3) is consistent with regular rotation. In contrast, the ring-like increase in kurtosis (h4) confirms the presence of the nuclear disc component. Unsharp masking of HST images has previously revealed a nuclear bar and faint spiral structures within the central ∼10 arcsec, supporting the role of secular evolution. The mass-weighted stellar age map reveals an old stellar population in the central regions, with a high metallicity that suggests the in situ formation of the disc─lens from disc material. We discuss possible formation scenarios for the disc─lens, including both minor mergers and secular processes, and examine the influence of the Dorado group environment on NGC 1553. Our findings suggest that the disc─lens in NGC 1553 formed during the early stages of the galaxy's evolution. However, its subsequent development has been shaped by internal and external processes. These results provide new insights into the origin and evolution of kinematically distinct substructures in S0 galaxies.
IIA ARKAPRABHA SARANGIJWST observations of sn 2023ixf. II. The panchromatic evolution between 250 and 720 days after the explosion
We present the nebular phase spectroscopic and photometric observations of the nearby hydrogen-rich core-collapse supernova (CCSN) SN 2023ixf, obtained through our JWST programs. These observations, combined with ground-based optical and near-infrared spectra, cover +252.67–719.96 days, creating a comprehensive, panchromatic time-series data set spanning 0.32–30 μm. In this second paper of the series, we focus on identifying key spectral emission features and tracking their evolution through the nebular phase. The JWST data reveal hydrogen emission from the Balmer to Humphreys series, as well as prominent forbidden lines from Ne, Ar, Fe, Co, and Ni. NIRSpec observations display strong emission from the first-overtone and fundamental bands of carbon monoxide, which weaken with time as the ejecta cools and dust emission dominates. The spectral energy distribution shows a clear infrared excess emerging by +252.67 days peaking around 10.0 μm, with a secondary bump at 18.0 μm developing by +719.96 days. We suggest that this evolution could arise from multiple warm dust components. In upcoming papers in this series, we will present detailed modeling of the molecular and dust properties. Overall, this work provides the community with a unique data set that can be used to advance our understanding of the mid-infrared properties of CCSNe, offering an unprecedented resource for studying their late-time line, molecular, and dust emission.
IIA DIPANKAR BANERJEEPolar Filaments Capture High-latitude Solar Poloidal Field Interactions and Can Foretell the Future Sunspot Cycle Amplitude before Polar Field Precursors
Polar fields at the minimum of a sunspot cycle—which are a manifestation of the radial component of the Sun’s poloidal field—are deemed to be the best indicator of the strength of the toroidal component and hence, the amplitude of the future sunspot cycle. However, the Sun’s polar magnetic fields are difficult to constrain with ground-based or space-based observations from near the plane of ecliptic. In this context, polar filaments— dark, elongated structures that overlie polarity inversion lines—are known to offer critical insights into solar polar field dynamics. Through investigations of the long-term evolution of polar filament areas and length acquired from the Meudon Observatory and complimentary solar surface flux transport simulations, here, we establish the common physical foundation connecting the Babcock–Leighton solar dynamo mechanism of solar polar field reversal and buildup with the origin and evolution of polar filaments. We discover a new relationship connecting the residual filament area of adjacent solar cycles with the amplitude of the next sunspot cycle—which can serve as a new tool for solar cycle forecasts—advancing the forecast window to earlier than polar-field-based precursors. We conclude that polar filament properties encapsulate the physics of interaction of the poloidal magnetic field of the previous and current sunspot cycles, the result of which is the net poloidal magnetic field at the end of the current cycle, thus encoding as a precursor the strength of the upcoming solar cycle.
IIA ARUN, RDiscovery of fullerenes in the shell of candidate luminous blue variable WRAY 16-232
We report the discovery of fullerene in the circumstellar environment of WRAY 16-232, a strong candidate luminous blue variable. Multiple pointings of archival Spitzer Infrared Spectrograph spectra reveal, for the first time, the presence of prominent vibrational bands of C60 at 17.4 and 18.9 μm in a luminous blue variable (LBV) envelope, along with the strong polycyclic aromatic hydrocarbon features. These observations suggest that, despite the harsh radiative conditions, large carbonaceous molecules can form, process, and survive in the ejecta of massive stars. Complementary optical spectroscopy with South African Large Telescope High-Resolution Spectrograph shows multiple P Cygni profiles in H α, He I, and Fe II lines, which are indicative of a dense, expanding wind and substantial mass-loss. Furthermore, analysis of decade long photometric data shows short-term brightness variations of ∼0.5 mag. These results not only reinforce the classification of WRAY 16-232 as a strong LBV candidate but also provide new insights into the mechanisms of dust formation and the chemical enrichment of the interstellar medium by massive stars. We discuss various scenarios for fullerene formation in such environments, and find that shock processing due to wind-wind interactions could be playing a vital role. The shell of WRAY 16-232 has an ideal UV field strength and the time-scales appear to match with shock processing time-scales. The results highlight the need for further high spatial/spectral resolution and temporal observations to confirm the formation and survival scenario of C60 in its shell.
IIA RAMESH, RSpectroscopic Observations of Temporal Changes in the 5303 Å Solar Coronal Emission Line During a Flare
We report long duration observations of changes in the 5303 Å (Fe XIV) solar coronal emission line parameters at heliocentric distance r≈1.07R⊙, using data obtained with the Visible Line Emission Coronagraph (VELC) onboard Aditya-L1 in the sit and stare mode. The observed changes are due to a flare near the east limb of the Sun. The intensity and width of the line are enhanced during the event. There is no change in the Doppler velocity. Our analysis indicates that the increase in line width is most likely due to an increase in temperature due to flare heating
IIA ARVIND K DATTATREYUnveiling dynamics and variability in open clusters: insights from a comprehensive analysis of six galactic clusters
We present a kinematic and dynamical analysis of six Galactic open clusters – NGC 2204, NGC 2660, NGC 2262, Czernik 32, Pismis 18, and NGC 2437, using Gaia DR3. We used Bayesian and Gaussian Mixture Model (GMM) methods to identify cluster members, but chose GMM because it is more appropriate for low-massstars. Estimated distancesrange from 1.76 to 4.20 kpc and ages from 0.199 to 1.95 Gyr, confirming their intermediate-age nature. King model fits indicate compact morphologies, with core radii of 1–10 arcmin and cluster radii of 5–24 arcmin. We identify 13 blue straggler stars and 3 yellow straggler stars members, whose central concentrations suggest origins via masstransfer orstellar collisions. The massfunction slopes(0.96–1.19) are flatter than the Salpeter value, which indicates that these clusters have undergone dynamical mass segregation. Orbit integration within a Galactic potential indicates nearly circular orbits (eccentricities 0.02–0.10), vertical excursions within ±132 pc, and guiding radii near the solar circle, suggesting disc confinement. These clusters likely formed in the thin disc and are shaped by Galactic tidal perturbations, facilitating the rapid loss of low-mass members. Additionally, 12 variable stars were found across 4 clusters using Transiting Exoplanet Survey Satellite (TESS) light curves, including γ Doradus and SPB pulsators, eclipsing binaries, and a yellow straggler candidate. Periods were derived via Lomb–Scargle analysis. Two eclipsing binaries (TIC 94229743 and TIC 318170024) were modelled using PHOEBE, yielding mass ratios of 1.37 and 2.16, respectively. Our findings demonstrate that integrating orbital dynamics and variable star studies presents valuable insights into the evolutionary pathways of open clusters
IIA SHANTIKUMAR, N. SDependence of water vapor radiative forcing on aerosol loading: Analyses over the densely populated and highly polluted Indo-Gangetic Plain region
This study analyzes the aerosol and precipitable water vapor (PWV) properties at six sites in the Indo-Gangetic Plains (IGP), a densely populated and highly polluted region. The main objective is to explore how the columnar PWV is related to the attenuation of shortwave solar radiation (SWR), as well as the combined role of aerosol properties and PWV on radiative forcing based on AERONET data and model (SBDART) simulations. The analysis revealed high aerosol optical depth (AOD) values (0.4–0.6) throughout the year in all the sites, associated with increased PWV (4–5 cm) during the summer monsoon. Comprehensive investigation shows that changes in PWV levels also affect aerosols’ size distribution, optical properties and radiation balance in a similar way - but in different magnitudes - between the examined sites. The water vapor radiative effect (WVRE) is highly dependent on aerosol presence, with its magnitude for both surface (− 130 to − 140 Wm− 2) and atmospheric forcing becoming higher under clean atmospheres (without aerosols). Aerosol presence is also considered in the computations of the WVRE. In that case, the WVRE becomes more pronounced at the top of the atmosphere (TOA) (30 to 35 Wm− 2) but exhibits a lower forcing impact on the surface (about − 45 Wm− 2) and within the atmosphere (70–80 Wm− 2), suggesting important aerosol-PWV interrelations. The atmospheric heating rate due to PWV is more than double (3.5–4.5 K Day− 1) that of aerosols (1–1.9 K Day− 1), highlighting its essential role in radiative effects and climate implications over the IGP region. The radiative impacts of PWV and aerosols are further examined as a function of the single scattering albedo, solar zenith angle, and absorbing AOD at the different sites, revealing dependence on both astronomical and atmospheric variables related to aerosol absorption, thus unravelling the combined role of aerosols and PWV in climate implications.
IIA ARKAPRABHA SARANGITwo Decades of Dust Evolution in SN 2005af through JWST, Spitzer, and Chemical Modeling
The evolution of dust in core-collapse supernovae (SNe), in general, is poorly constrained owing to a lack of infrared observations a few years after explosion. Most theories of dust formation in SNe heavily rely only on SN 1987A. In the last two years, the James Webb Space Telescope (JWST) has enabled us to probe the dust evolution in decades-old SNe, such as SN 2004et, SN 2005ip, and SN 1980K. In this paper, we present two decades of dust evolution in SN 2005af, combining early-time infrared observations with the Spitzer Space Telescope and recent detections by the JWST. We have used a chemical kinetic model of dust synthesis in SN ejecta to develop a template of dust evolution in SN 2005af. Moreover, using this approach, for the first time, we have separately quantified the dust formed in the pre-explosion wind that survived after the explosion and the dust formed in the metal-rich SN ejecta post-explosion. We report that in SN 2005af, predominantly carbon-rich dust formed in the ejecta, with a total mass of at least 0.02 M⊙. In the circumstellar medium, the surviving oxygen-rich dust amounts to about (3–6) × 10−3 M⊙, yielding a total dust mass of at least 0.025 M⊙.
IIA ANUPAMA, G. CThe Most Luminous Known Fast Blue Optical Transient AT 2024wpp: Unprecedented Evolution and Properties in the X-Rays and Radio
We present X-ray (0.3─79 keV) and radio (0.25─203 GHz) observations of the most luminous fast blue optical transient (LFBOT) AT 2024wpp at z = 0.0868, spanning 2─280 days after first light. AT 2024wpp shows luminous (LX ≍ 1.5 × 1043 erg s−1), variable X-ray emission with a Compton hump peaking at δt ≍ 50 days. The X-ray spectrum evolves from a soft (Fν ∝ ν−0.6) to an extremely hard state (Fν ∝ ν1.26) accompanied by a rebrightening at δt ≍ 50 days. The X-ray emission properties favor an embedded high-energy source shining through asymmetric expanding ejecta. We detect radio emission peaking at L9 GHz ≍ 1.7 × 1029 erg s−1 Hz−1 at δt ≍ 73 days. The spectral evolution is unprecedented: the early millimeter fluxes rise nearly an order of magnitude during δt ≍ 17─32 days, followed by a decline in spectral peak fluxes. We model the radio emission as synchrotron radiation from an expanding blast wave interacting with a dense environment ( Ṁ∼10−3M⊙yr−1 for vw = 1000 km s−1). The inferred outflow velocities increase from Γβc ≍ 0.07c to 0.42c during δt ≍ 32─73 days, indicating an accelerating blast wave. We interpret these observations as a shock propagating through a dense shell of radius ≍1016 cm and then accelerating into a steep density profile ρCSM(r) ∝ r−3.1. All radio-bright LFBOTs exhibit similar circumstellar medium (CSM) density profiles (ρCSM ∝ r−3), suggesting similar progenitor processes. The X-ray and radio properties favor a progenitor involving super-Eddington accretion onto a compact object launching mildly relativistic disk wind outflows.
IIA SANTANU MONDALDistinct Fe K Line Complexes in MAXI J1744−294 Revealed by XRISM High-resolution Spectroscopy
The newly discovered Galactic transient MAXI J1744−294 went into its first X-ray outburst in 2025. We study the spectral properties of this source in the 2–10 keV energy band during this outburst using X-ray data from the XRISM satellite for both of its Resolve and Xtend instruments, taken on 2025 March 3. High-resolution spectroscopy has revealed, for the first time, complex iron line features in this source, corresponding to distinct components of Fe XXV emission and Fe XXVI absorption lines. Such a detailed structure has not been reported in other low-mass X-ray binaries to date, prior to the XRISM era. Our analysis shows that the line complexes arise from two highly ionized plasmas with an ionization rate ∼103 erg cm s −1 with distinct turbulent velocities—one broad (vturb ≈ 2513 km s −1) from hot gas at the inner accretion disk and one narrow (vturb ≈ 153 km s−1) scattered by nearby photoionized gas. These results offer new insight into the reprocessing of continuum in stratified media, either in the accretion disk or winds, or both, for X-ray binaries in the soft state. The data are well described by models with spin, mass of the black hole, and accretion disk inclination 0.63─0.70, 7.9 ± 2.2 M⊙, and 19°─24°. The fitted spectral model parameters suggest that the source is in the soft spectral state. The source is situated in a crowded field near the Galactic center, resulting in a large hydrogen column density.