IIAP Publications

A consistency check for the calibration of 5303Å solar coronal emission line observations with Aditya-L1/VELC

Mon, 01 Jun 2026 00:00:00 GMT

A consistency check for the calibration of 5303Å solar coronal emission line observations with Aditya-L1/VELC Priyal, M; Ramesh, R; Singh, J; Sasikumar Raja, K; Savarimuthu, P We carried out radiometric calibration of the Visible Emission Line Coronagraph (VELC) onboard Aditya-L1 at 5303Å using observations of the Sun itself, a novel approach compared to the calibration using bright stars in the other currently operational space solar coronagraphs. The measured VELC detector count corresponding to the center of Sun’s disk is ≈ (1.70±0.12)×108 sec−1Å −1, which relates to Sun’s flux at 1AU in 5303Å, ≈ 3.0456× 106 erg sec−1cm−2Å −1. We verified the above calibration using observations of the bright star Sirius-A whose estimated flux at 1AU in 5303Å is ≈ 1.44 × 10−8 erg sec−1cm−2Å −1. The expected detector count with VELC in this case is ≈ 19 ± 1.4sec−1Å −1, and the measured count is ≈ 23 ± 0.4sec−1Å −1. The reasonable agreement between the expected and observed values for Sirius-A in this initial consistency check after two years of observations with VELC, indicates that measurements of coronal brightness at 5303Å with the VELC and its conversion into absolute physical units using observations of the Sun disk light are in order. Using the Sirius-A observations we measured the point spread function (PSF) of the VELC in its 5303Å channel also. Its full width at half maximum (FWHM) is ≈ 3.8′′. Restricted Access; The original publication is available at springerlink.com.

Dwarf and intermediate-mass galaxies in MaNGA: Evidence for different evolutionary trends

Sat, 20 Jun 2026 00:00:00 GMT

Dwarf and intermediate-mass galaxies in MaNGA: Evidence for different evolutionary trends Chandan, Watts; Gothai, L; Barway, Sudhanshu We investigate the interplay between morphology, specific star formation rate (sSFR), and local environment using a sample of 7408 galaxies from the fourth-generation Sloan Digital Sky Survey Mapping Nearby Galaxies at Apache Point Observatory survey. Our analysis spans stellar masses from dwarf to massive galaxies, enabling a unified view of how stellar mass and environment regulate galaxy evolution. Galaxies are classified by morphology (ellipticals (E), lenticulars (S0s), early-type spirals (ETS), and late-type spirals (LTS)) and local environmental density, with star formation activity traced using sSFR. Low-mass galaxies (log(M /M ) < 10) are predominantly star-forming and dominated by LTS, whereas high-mass galaxies (log(M /M ) 10) are dominated by ETS and are largely quenched. By separating dwarf (log(M /M ) 9.5) and intermediate-mass galaxies (9.5 < log(M /M ) < 10), we find that dwarf galaxies remain predominantly star-forming with only weak environmental dependence, whereas intermediate-mass galaxies exhibit clearer environmental trends toward quenching. Using the D4000 index as a tracer of long-term stellar population aging, we further show that dwarf E and S0s host systematically younger stellar populations than their intermediate-mass counterparts, implying reduced quenching efficiency and more gradual environmental processing in the dwarf regime. This distinction is not evident among spiral galaxies, whose stellar population properties are comparatively insensitive to the dwarf versus nondwarf classification. Overall, these results indicate that the commonly defined low-mass galaxy population is not homogeneous and that dwarf and intermediate-mass galaxies show systematically different evolutionary trends. Treating them separately is therefore essential for interpreting galaxy evolution in the lowmass regime. 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.

The VMC survey: LV. the coherent expansion of the SMC

Mon, 01 Jun 2026 00:00:00 GMT

The VMC survey: LV. the coherent expansion of the SMC Vijayasree, S; Niederhofer, Florian; Cioni, Maria-Rosa L; van Loon, Jacco Th; Bekki, K; de Grijs, R; Subramanian, S; Kacharov, N; Omkumar, Abinaya O; Cullinane, L. R; Ivanov, Valentin D Context. The Small Magellanic Cloud (SMC) exhibits significant kinematic disequilibrium due to interactions with the Large Magellanic Cloud (LMC). Aims. Here, we investigate the two-dimensional stellar kinematics of the SMC to understand the dynamical effects of these interactions by exploiting the increased time baseline of 6−11 years from the VISTA Survey of the Magellanic Clouds (VMC) data release 7. Methods. We derive proper motions with a threefold improvement in precision compared to previous studies based on VMC data. We used a geometric framework accounting for perspective effects from line-of-sight motion to model the systemic motion across the SMC and construct a residual proper motion map. We further introduce an anisotropic linear velocity gradient model to quantify the stretching of the galaxy. Results. For the first time across all stellar populations, the residual proper motion map reveals expansion along the south-east and north-west directions, consistent with LMC-induced tidal forces, detectable even in the central regions. The gradient-corrected residuals show predominantly radial motions towards the SMC centre with no evidence of rotation. Velocity maps for different stellar populations, without assuming a rotating-disk model, reveal a coherent northward motion away from the centre exclusively in older red giant branch stars, interpreted as a kinematic signature of a past (>2 Gyr ago) interaction. Conclusions. This study highlights the inadequacy of simple rotating-disk models in capturing the internal kinematics of the galaxy. Open Access; Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Detection of an optical quasiperiodic oscillation in the Blazar 3C 454.3

Mon, 01 Jun 2026 00:00:00 GMT

Detection of an optical quasiperiodic oscillation in the Blazar 3C 454.3 Dogra, Karan; Gupta, A. C; Raiteri, C. M; Villata, M; Wiita, P. J; Valtonen, Mauri J; Kurtanidze, S. O; Jorstad, S; Bachev, R; Damljanovic, G; Lorey, C; Savchenko, S. S; Vince, O; Abdelkareem, M; Aceituno, F. J; Acosta-Pulido, J. A; Agudo, I; Andreuzzi, G; Ata, S. A; Baida, G. V; Barbieri, L; Blinov, D; Bonnoli, G; Borman, G. A; Carnerero, M. I; Carosati, D; Casanova, V; Chen, W. P; Cui, Lang; Devanand, P. U; Elhosseiny, E. G; Elsaesser, D; Escudero, J; Fan, J. H; Feige, M; Gazeas, K; Grishina, T. S; Gu, Minfeng; Hagen-Thorn, V. A; Hemrich, F; Hsiao, H. Y; Ismail, M; Ivanidze, R. Z; Jovanovic, M. D; Kamel, T. M; Kimeridze, G. N; Kishore, Shubham; Kopatskaya, E. N; Kuberek, D; Kurtanidze, O. M; Kurtenkov, A; Larionov, V. M; Larionova, Elena G; Larionova, L. V; Lin, H. C; Marchini, A; Marinelli, C; Marscher, A; Morcuende, D; Morozova, D. A; Nazarov, S. V; Nikolashvili, M. G; Reinhart, D; Otero-Santos, J; Scherbantin, A; Semkov, E; Shishkina, E. V; Sigua, L. A; Singh, Ajay Kumar; Sota, A; Steineke, R; Stojanovic, M; Strigachev, A; Takey, Ali; Tawfeek, Amira A; Tripathi, Tushar; Troitskiy, I. S; Troitskaya, Y. V; Tsai, An-Li; Vasilyev, A. A; Vrontaki, K; Zhang, Zhongli; Zhovtan, A. V; Zottmann, N; Zuo, Wenwen We analyzed 19 yr of R-band data of the blazar 3C 454.3 from the Whole Earth Blazar Telescope archive, along with new data from its members and from public archives such as those provided by the Small and Moderate Aperture Research Telescope System and the Steward Observatory projects to search for quasiperiodic oscillations (QPOs). We detected a QPO of ∼433 days using Lomb─Scargle periodogram, which lasted from MJD 54980─58450 as detected by the weighted wavelet Z-transform technique, making it one of the most persistent QPOs ever detected in the optical regime. The phase dispersion minimization technique was also performed to further validate this QPO claim. We detected this signal at a global significance of 2.53σ across all methodologies. To explain the observed QPO, we have considered both models focused on the accretion disk around a supermassive black hole (SMBH), and those based purely on jet emissions. Plausible jet-based models involve a shock moving down the jet in a helical magnetic field, whereas the SMBH models could involve Lense─Thirring-effect-induced jet precession or dual jets in a binary SMBH system. We introduce a novel approach to distinguish genuine QPOs from spurious signals arising from annual seasonal gaps, a common limitation of ground-based observations. 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.