arXiv subjects

Clarinda Montilla

Publications and source records attributed to Clarinda Montilla.

3 recordsLinked to original sources

arXiv2026

AT 2020afjz (TSS2020a): The First Fast Extragalactic Transient Discovered by TESS

We report the discovery of AT 2020afjz (TSS2020a): the first hour-scale extragalactic transient discovered in optical wavelengths whose complete evolution -- from explosion onset to decay -- is temporally resolved, and the first such transient discovered by TESS. AT 2020afjz was identified as a $>10σ$ detection in the pilot HiLaTS program run within the TESSELLATE Sky Survey, which blindly searches for transient phenomena in TESS data with the TESSELLATE pipeline. Through cross-matching with legacy imaging, we associate it with DES J042144.37$-$383311.3, a member of an interacting galaxy pair at $z_{\rm phot}=0.67^{+0.07}_{-0.10}$. While AT 2020afjz is similar in duration and brightness to GRB afterglows, it exhibits a slow rise time of $\sim1$ hr and lasts for only 2.4 hr above the half-max brightness; modeling the TESS light curve with VegasAfterglow finds that it is best described as either an on-axis "dirty-fireball" or off-axis orphan afterglow. Each of these rare classifications hinge upon a non-detection at gamma-ray energies, but as Fermi-GBM was Earth-occulted at the time of explosion, AT 2020afjz's gamma-quiet nature cannot be definitively confirmed. Regardless, AT 2020afjz demonstrates TESS's power to discover fast extragalactic transients, and heralds a new population awaiting discovery with TESSELLATE.

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

TESSELLATE: Piecing Together the Variable Sky With TESS

We present TESSELLATE, a dedicated pipeline for performing an untargeted search documenting all variable phenomena captured by the TESS space telescope. Building on the TESSreduce difference imaging pipeline, TESSELLATE extracts calibrated and reduced photometric data for every full frame image in the TESS archive. Using this data, we systematically identify transient, variable and non-sidereal signals across timescales ranging from minutes to weeks. The high cadence and wide field of view of TESS enables us to conduct a comprehensive search of the entire sky to a depth of ~17 $m_i$. Based on the volumetric rates for known fast transients, we expect there to be numerous Fast Blue Optical Transients and Gamma Ray Burst afterglows present in the existing TESS dataset. Beyond transients, TESSELLATE can also identify new variable stars and exoplanet candidates, and recover known asteroids. We classify events using machine learning techniques and the work of citizen scientists via the Zooniverse Cosmic Cataclysms project. Finally, we introduce the TESSELLATE Sky Survey: a complete, open catalog of the variable sky observed by TESS.

astro-ph.IM↗