http://hdl.handle.net/2248/1 Publications from IIAP are submitted here Sun, 18 Oct 2026 22:26:27 GMT 2026-10-18T22:26:27Z http://hdl.handle.net/2248/9074 Investigating the young stellar populations and hierarchies in nearby galaxies with the UVIT. II. presenting the properties of ~25,000 UV-detected star-forming clumps Shashank, Gairola; Subramanian, S; Mondal, Chayan; Menon, Shyam H; Subramaniam, A Studying young stellar populations within galaxies can help refine our understanding of recent star formation in galaxies and their evolution. With this motivation, we present a catalog of ~25,000 recently formed (within 400 Myr) star-forming clumps (SFCs) in 17 morphologically diverse nearby galaxies, including 8 massive, classic spirals, 6 intermediate-mass, flocculent spirals, and 3 dwarf irregulars. We used far- (FUV) and near-UV observations from the Ultraviolet Imaging Telescope, whose ~ 1.″5 angular resolution and 28' field of view allow us to probe SFCs at a mean physical scale of ~54 pc, within the full extent of our galaxies. We adopted a homogeneous SFC detection criterion, corrected for spatially varying dust attenuation (using 6″ resolution AV maps, made by combining FUV with archival infrared observations), and estimated the SFC ages by comparing the observed UV color--magnitude diagrams with Starburst99 simple stellar population models. Using our SFC catalog, we studied the age demographic of the recently formed stellar populations across different galaxy morphologies and observed age trends consistent with several well-known phenomena, such as the inside-out formation of disk galaxies, local gravitational instabilities leading to flocculent spiral arms, and the stochastic nature of star formation in dwarf galaxies. Leveraging full galaxy coverage and FUV data, our catalog complements existing optically identified star cluster catalogs in the literature toward improving our understanding of star formation across a wide range of galaxy morphologies, masses, and environments. We make the SFC catalog and AV maps of our 17 galaxies publicly available with this paper. Open Access; Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Tue, 01 Sep 2026 00:00:00 GMT http://hdl.handle.net/2248/9074 2026-09-01T00:00:00Z http://hdl.handle.net/2248/9073 CHIME/slow overview and pilot survey: A new backend to search for second-duration radio transients with the CHIME telescope Mate, Sujay; Luke, Kevin; Bhusare, Yash; Balasubramanian, Arvind; Pleunis, Ziggy; Scholz, Paul; Tendulkar, Shriharsh; Bhardwaj, Mohit; Brar, Charanjot; Dong, Fengqiu Adam; Fonseca, Emmanuel; Gaensler, B. M; Hessels, Jason; Huang, Jeff; Jain, Naman; Joseph, Ronniy C; Kaspi, Victoria M; Khan, Afrokk; Main, Robert; Meyers, Bradley W; Milutinovic, Nikola; Nimmo, Kenzie; Shin, Kaitlyn; Spear, David; Stairs, Ingrid; Tan, Chia Min We present an overview of CHIME/Slow, a real-time transient search backend under development to search for second-duration radio transients using the CHIME telescope, and results obtained from a pilot survey carried out using the prototype version of the search pipeline. The prototype CHIME/Slow pipeline was tested on archival data obtained in 2022 December, 2023 January, and 2023 February with a total on-sky time of 17 days with an instantaneous field of view of ~13 deg2. In this pilot survey, we detected nine bursts, one from a new nonrepeating source, FRB 20230204C, and eight from the known hyperactive repeating source FRB 20220912A. Out of these nine bursts, two bursts from the repeater were not detected by CHIME/FRB, while the nonrepeater was detected in the side-lobe of a beam in CHIME/FRB, exhibiting shorter burst width and narrower bandwidth compared to the CHIME/Slow detection. Here we report properties of the bursts, discuss the sensitivity and completeness of the current version of the CHIME/Slow pipeline, and outline future development to improve its performance. Finally, based on these results, we report the all-sky rate (95% credible region) of radio transients with burst widths between 16 ms and 5 s, fluence above 5 Jy ms, and observing frequency of 600 MHz to be between 184 and 4556 bursts sky-1 day-1. Open Access; Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Tue, 01 Sep 2026 00:00:00 GMT http://hdl.handle.net/2248/9073 2026-09-01T00:00:00Z http://hdl.handle.net/2248/9072 The ALMA-QUARKS survey: Properties of hot molecular fragments in the massive protocluster IRAS 17233-3606 Chen, Li; Qin, Sheng-Li; Yang, Dongting; Jiao, Wenyu; Liu, Tie; Goldsmith, Paul F; Zhang, Zhenying; Li, Chuanshou; Xu, Feng-Wei; Dib, S; Gupta, Shivani; Tang, Xindi; Peng, Yaping; Tang, Mengyao; Juvela, Mika; Li, Di; Yang, A.Y; Liu, Meizhu; Zhen, Lingmin; Chibueze, J. O; Toth, L. Viktor; Hoque, Ariful; Stutz, Amelia M; Bronfman, Leonardo; Das, Swagat; Garcia, Pablo; Kim, Kee-Tae; Lee, Chang Won; Hwang, Jihye; Zou, Jia-Hang; Guo, Yongqi; Kou, Zhiping To investigate the physical mechanisms of fragmentation within the hot molecular core of the massive protocluster IRAS 17233-3606 (G351.78-0.54), we carried out a detailed analysis of continuum and lines using the Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 data from the ATOMS survey and Band 6 data from the QUARKS survey. The low-resolution 3 mm data reveal a massive hot core millimeter source 1 (MM1) with a mass of ~81.3 M⊙, and a prominent ultracompact (UC) H II region, millimeter source 2 (MM2), while the high-resolution data resolve MM1 into 11 hot molecular fragments (HMFs). These HMFs exhibit hot (Trot = 100--310 K) CH3CN and CH3OH emission and high column densities (N H2 > 1023 cm-2), indicating their potential to form massive stars. Based on outflows, masers, H II regions, and f[CH3CN/CH3OH] abundance ratios, the evolutionary sequences of the 11 HMFs are categorized as Phases I to IV. The mean minimum-spanning tree (MST) separation (~1.8 × 103 au) of the HMFs is nearly half of the thermal Jeans length (~3.3 × 103 au). Together with the Q parameter Q = 0.77 and virial parameter αvir = 0.84 of MM1, these results suggest an evolutionary scenario in which fragmentation is initially driven by thermal instability, followed by global gravitational contraction and growth through active accretion. Meanwhile, feedback from the B2-type zero-age main-sequence (ZAMS) star and the UC H II region significantly influence the morphology and chemical properties of MM1 and MM2. This heterogeneity highlights the role of diverse physical processes taking place in high-mass protoclusters. Open Access; Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Thu, 10 Sep 2026 00:00:00 GMT http://hdl.handle.net/2248/9072 2026-09-10T00:00:00Z http://hdl.handle.net/2248/9070 Multiband optical photometric variability of the blazar OJ 287 from 2015 to 2025 Gupta, A. C; Dogra, Karan; Kidger, M; Valtonen, Mauri J; Wiita, P. J; Kushwaha, Pankaj; Savchenko, S. S; Kurtanidze, S. O; Jorstad, S; Marscher, A; Matsumoto, K; Poyner, G; Rahmatullaeva, F; Rajkumar, N; Ribes, N. G; Semkov, E; Shishkina, E. V; Stojanovic, M; Strigachev, A; Tripathi, Tushar; Troitskaya, Y. V; Troitskiy, I. S; Valero, J; Vasilyev, A. A; Villarroel, B; Volvach, A. E; Volvach, L. N; Wagner, S. J; Weaver, Z. R; Yang, Wen Xin; Zhang, Zhongli; Zhovtan, A. V; Zuo, Wenwen; Kojiguchi, N; Sugiura, Y; Cui, Lang; Hu, Shao Ming; Damljanovic, G; Bachev, R; Vince, O; Liao, M; Wang, Zhongxiang; Darriba, A; Haque, S; Alfaro, F. S; Amatller, J. B; Andujar, J. M. F; Arnold, S; Arranz, T; Bachini, M; Barcelo, C. L; Boeva, S; Borman, G. A; Boyd, D; Buczinski, D; Casal, J. D; Chen, X; Cores, J. M; Cucarella, F. C; Devanand, P. U; Dhiman, V; Espasa, L. T; Fan, J. H; Farfan, R. G; Fernandez, J. R; Garcia, F; Garcia, R. C; Gaur, H; Gomez, J. C; Gonzalez, J. L. S; Gonzalez-Carballo, J. L; Grishina, T. S; Grondona, F. H; Gu, M. F; Guo, H; Hagen-Thorn, V. A; Hurst, G; Ibryamov, S. I; Ivanidze, R. Z; James, N; Jardine, B; Johnstone, S; Jovanovic, M. D; Kalita, N; Karge, S; Kishore, Shubham; Kopatskaya, E. N; Kurtanidze, O. M; Kurtenkov, A; Larionova, Elena G; Lorenz, E. R; Lozano, J; Mananes, E. F; Martinez, F. L; Mobberley, M; Morales-Aimar, M; Morozova, D. A; Nikolashvili, M. G; Nikolov, Y; Nogues, R. Naves; Novikova, P. A; Penas, L. M; Perez, A. Escartin; Perello, C; Pickard, R; Pinilla, F. G We present the most densely sampled multiband optical photometric observations of the peculiar BL Lacertae object OJ 287 from 2015 to 2025 with a focus on its optical activity on diverse timescales. We present a total of 2296, 10,927, 11,484, and 2982 data points in B, V, R, and I bands, respectively. The densely sampled observations allow us to keep track of the source evolution that it has exhibited since the start of the predicted major optical flaring activity at the end of 2015. The study reveals clear and persistent bluer-when-brighter trends in both the long-term and short-term variations. Different bands were cross-correlated with discrete correlation functions, which peak at zero lag, implying cospatial emission. Using eight optical spectra in the low-flux states of OJ 287 taken from 2017 October 21 to 2017 November 22, from Steward Observatory, we estimate the central black hole mass to be at least 3.89 × 109 M⊙ from the [O III] line width. The emission mechanism of the binary black hole blazar, and its possible implication in various aspects of multimessenger astronomy, are briefly discussed. Open Access; Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Tue, 01 Sep 2026 00:00:00 GMT http://hdl.handle.net/2248/9070 2026-09-01T00:00:00Z