Dr. Raya Dastidar

Email: rdastidr (at) gmail (dot) com

I am an observational astrophysicist and FONDECYT post-doctoral fellow specializing in the study of supernovae. Currently based in Chile, home to some of the world's most powerful telescopes, my research focuses on unraveling the mysteries of stellar explosions through the capture and analysis of their light curves and spectra.

My primary research focus is on supernovae, particularly the progenitors and environments of these stellar explosions. I have a specific interest in hydrogen-rich Type II supernovae, ejecta–circumstellar medium interactions, and the metallicity of supernova ejecta and their environments. My work combines analytical and hydrodynamical modeling of light curves with spectral modeling, aiming to better understand their underlying physics and evolutionary pathways.

• CV

During my PhD, I focused primarily on characterizing supernovae through detailed observational analysis. In recent years, however, I have developed a strong interest in simulating light curves and spectra, which offers deeper insights into these cosmic events. I use open-source codes such as SNEC, TARDIS, MESA in my research to model the physical processes behind supernovae. I also use photometric and spectroscopic data of supernovae to measure distances to their host galaxies. Find my list of publications below:

• Publications

SN 2019nyk: a rapidly declining Type II supernova with early interaction signatures.
R. Dastidar, G. Pignata et al. A&A, 685, A44 (2024)

Early spectra of SN 2019nyk exhibit high-ionisation emission features and narrow H Balmer lines, persisting until 4.1 days after explosion, indicating the presence of circumstellar material (CSM) in close proximity. A comparison of the early spectra with literature models indicated a mass-loss rate of 10^-3 M_⊙ yr^-1. A discrepancy arises between the CSM density derived from spectral model comparisons, which is lower than that obtained through hydrodynamical modeling with SNEC in our work. This could be resolved by introducing a low-density material above the high-density CSM inferred from the SNEC modelling.

SN 2018is: a low-luminosity Type IIP supernova with narrow hydrogen emission lines at early phases.
R. Dastidar, K. Misra, et al. A&A, 694, A260 (2025)

SN 2018is contributes to the diversity observed within the population of low-luminosity Type II supernovae, with an atypically steep decline during the photospheric phase and remarkably narrow emission lines at early phases. We used the expanding photosphere method (EPM) to obtain a redshift independent distance to its host galaxy, utilising the early photometric and spectroscopic data of SN 2018is. By performing linear fit to t vs θ/v_ph for the three filter combinations {BV}, {BVI} and {VI}, the explosion epoch (t₀) and distance (D) were determined from the intercept and slope, respectively.

The fast rise of the unusual type IIL/IIb SN 2018ivc.
A. Reguitti, R. Dastidar et al. A&A, 692, A26 (2024)

With our high-cadence data, we observed the SN rising very rapidly by nearly three magnitudes in five hours (or 18 mag d⁻¹). From the comparison of the light curves and the late spectrum of SN 2018ivc with those of type IIL and IIb SNe, we found some aspects in common with both typologies; thus, we propose that SN 2018ivc may be a transitional object between the two families of events: a type IIL/IIb SN. Modelling of the early light curve with SNEC indicated a stripped progenitor with hydrogen envelope mass of 0.74 M_⊙, which is also intermediate to those of IIb and IIL progenitors.

Signatures of the shock interaction as an additional power source in the nebular spectra of SN 2023ixf.
A. Kumar, R. Dastidar et al. MNRAS, 538, 659 (2025)

We analysed the nebular spectrum of the famous SN 2023ixf, observed one year post-explosion (at +363 d) with the recently commissioned WEAVE instrument on the 4.2m William Herschel Telescope. The +363 d spectrum exhibits a complex H𝛼 profile, a hallmark of ongoing interaction between the SN ejecta and CSM. Detailed multi-Gaussian decomposition of this profile reveals that the central broad feature spanning ±4000 km s⁻¹ can be decomposed into three Gaussian components: a red-shifted feature near 12 km s⁻¹ and two symmetric components peaking at ±1950 km s⁻¹. This indicates that an ongoing interaction with the inner CSM, expelled within a decade before the explosion, leads to the broadening of the H 𝛼 emission. Furthermore, two broader components peaking at ±5650 km s⁻¹ indicate shock interactions with CSM expelled 350 – 640 years before the explosion. The observed slanted wings in the H𝛼 profile, unlike the sharp boxy shapes predicted by models, suggest a less dense CSM around SN 2023ixf.

Comparison of the +363 d spectrum of SN 2023ixf with the +350 d nebular spectra models from Dessart et al. (2023). The models, representing various injected shock powers ranging from 1 × 10⁴⁰ to 1 × 10⁴¹ erg s⁻¹, are indicated in the figure legend. The inset provides a close-up view of the [O I] doublet and H𝛼 regions. For comparison, the +259 d spectrum of SN 2023ixf is also shown in the inset. The extent of the central H𝛼 component in the models (±2000 km s⁻¹) is marked with dashed lines, while the green shaded region highlights its extent in SN 2023ixf.

I’m a Bengali from Kolkata, India, but unlike many other Bengalees who are naturally gifted in music and art, I lack those talents. Instead, I channel my creativity into sleeping during the day (remember, I am an astronomer!), watching the sky (which led to a few accidents!), experimenting in the kitchen, capturing nature through photography, tending to my plants, and, most importantly, indulging in the joy of eating!