arXiv subjects

Klára Lelkes

Publications and source records attributed to Klára Lelkes.

4 recordsLinked to original sources

arXiv2026

SN 2026dix: a nearby, transitional Type IIb/Ib supernova consistent with a warm supergiant progenitor

Understanding the final evolution stages of (very) massive stars and their explosive outcomes, stripped-envelope supernovae (SESNe), represent a long-term challenge for astrophysics. The latest results support a continuous distribution within the traditional SESN subclasses (IIb, Ib, Ic). The nearby ($D \approx 17.5$ Mpc) SN 2026dix seems to be another member of the recently identified group of transitional Type IIb/Ib explosions. A point source is located at the SN position within the uncertainties on multiple pre-explosion {\it HST} images. Together with post-explosion photometry and spectroscopy, it provides a good opportunity to study a rare type of SN in detail. We carried out a thorough comparative light-curve (LC) and spectral analysis of SN 2026dix. We also constructed its bolometric LC and modeled it semi-analytically. In addition, we constructed the spectral energy distribution of the presumed progenitor and compared this to model stellar atmospheres and binary stellar evolution tracks. We infer that SN 2026dix arose from an explosion in an interacting binary system, consistent with the properties of a warm ($T_\textrm{eff} \approx 6750-$7750 K; spectral type F2 to A7), luminous ($\log(L_{\rm bol}/L_{\odot})\approx 4.9-5.3$) supergiant primary and a less luminous, less massive hot dwarf companion. The nature of the identified progenitor closely resembles that of some other known cases of SNe IIb and also well aligns with both the results of our semi-analytical LC modeling and the comparison of the LCs and spectra of SN 2026dix with the output of radiative-transfer models of an exploding star with $M_\textrm{ini}$ = 18 $M_{\odot}$.

astro-ph.SR↗

arXiv2026

Long-term optical and near-infrared photometric evolution of SN 2019vxm, an interacting Type IIn supernova

The diversity of Type IIn supernovae is largely driven by the properties of the circumstellar material (CSM) they explode into. We examine the temporal evolution of SN 2019vxm, an interacting supernova that belongs to the class of long-lasting Type IIn events, using multicolor photometry spanning the ultraviolet, optical and near-infrared wavelengths, including over 650 days of optical and 1500 days of IR coverage. The evolution of the spectral energy distribution and bolometric luminosity, as well as the effective temperature and radius of the photosphere, indicates that the supernova was initially surrounded by an optically thick CSM, which was heated and pushed outward by the forward shock of the impacting ejecta. About 80-100 days after the explosion the forward shock and the photosphere decouples, and we observe the receding photosphere of the H-recombination front within the now thinned CSM. Near-IR measurements reveal long-lasting, slowly cooling emission from circumstellar dust around SN 2019vxm and an IR rebrightening about one year after explosion, which we tentatively identify as a signature of an outer CSM region. We find that due to the moving photosphere and the transition from optically thick to partially thin inner CSM, modeling the explosion and subsequent interaction of the ejecta with the CSM to infer progenitor and CSM masses faces difficulties. Nevertheless, the inferred high masses and extremely high mass-loss rates point to a massive progenitor undergoing intense pre-supernova mass loss.

astro-ph.HE↗

arXiv2026

SN 2019vxm: A Shocking Coincidence between Fermi and TESS

Shock breakout and, in some cases, jet-driven high-energy emission are increasingly recognized as key signatures of the earliest phases of core-collapse supernovae, especially in Type IIn systems due to their dense, interaction-dominated circumstellar environments. We present a comprehensive photometric analysis of SN 2019vxm, a long-duration, luminous Type IIn supernova, $M_V^{}=-21.41\pm0.05\;{\rm mag}$, observed from X-ray to near-infrared. SN 2019vxm is the first superluminous supernovae Type IIn to be caught with well-sampled TESS photometric data on the rise and has a convincing coincident X-ray source at the time of first light. The high-cadence TESS light curve captures the early-time rise, which is well described by a broken power law with an index of $n=1.41\pm0.04$, significantly shallower than the canonical $n=2$ behavior. From this, we constrain the time of first light to within 7.2 hours. We identify a spatial and temporal coincidence between SN 2019vxm and the X-ray transient GRB191117A, corresponding to a $3.3σ$ association confidence. Both the short-duration X-ray event and the lightcurve modeling are consistent with shock breakout into a dense, asymmetric circumstellar medium, indicative of a massive, compact progenitor such as a luminous blue variable transitioning to Wolf-Rayet phase embedded in a clumpy, asymmetric environment.

astro-ph.HE↗

arXiv2025

Asteroseismic mass and radius of the naked-eye red giant HD145250

We present the first asteroseismic analysis of the bright, nearby red giant star, HD145250. We calculate the global seismic quantities of the star from single-sector, 2-minute TESS photometry, and determine its mass and radius to be ~1.4 M$_\odot$ and ~16 R$_\odot$ using asteroseismic scaling relations. Our values agree with published non-seismic mass and radius estimates based on comparisons with stellar evolutionary models.

astro-ph.SR↗