arXiv subjects

Hrishav Das

Publications and source records attributed to Hrishav Das.

7 recordsLinked to original sources

arXiv2026

Subluminous Type IIP SN 2024abfl as a Result of a Significantly Low-energy Fe-core Collapse

We present extensive, well-sampled multiwavelength photometric and low-resolution optical spectroscopic observations of the low-luminosity Type IIP supernova SN 2024abfl. SN 2024abfl is found to be at the faintest end of Type IIP supernovae with unprecedented flat (0.1 mag/ 100 day) plateau evolution and a mid-plateau absolute magnitude of Mv~-13.8 mag, placing it among one of the faintest Type IIP supernovae discovered to date. SN 2024abfl is adjacent to SN 2018zd in the same host NGC~2146. Using various SN distance measurement probes, we provide independent estimates of the debated distance to the host NGC 2146 (7-9 Mpc). Spectral evolution of SN 2024abfl is found to be similar to other SNe spectra of this subclass but with very narrow line profiles, indicating moderately low expansion velocities of the ejecta. Detailed 1-D hydrodynamical modeling suggests a compact progenitor with an upper limit of 10 Msun, fairly consistent with the directly detected progenitor estimates. It exploded with very low-energy 0.05 foe or less with a very low nickel mass of 0.003 Msun, consistent with the observed parameters. These parameters provide important constraints on the nature of low-energy core-collapse explosions. We discuss possible progenitor scenarios and compare SN 2024abfl with other low-luminosity Type IIP supernovae.

astro-ph.HE↗

arXiv2026

SN 2023dbc in M108: Optical and Near-Infrared Observations of a Highly-Obscured, Moderately Energetic Stripped-Envelope Supernova

We present near-infrared (NIR) and optical observations of the highly reddened and moderately energetic Type Ib supernova (SN) 2023dbc, {\bf covering a period from} 2 to 136 days after the explosion. By comparing its color {\bf evolution}, specifically in $r-JHK_{\mathrm{s}}$ and $i-JHK_{\mathrm{s}}$, with those of broad-lined Type Ic (Ic-BL) and Type IIb SNe, we estimate a significant extinction of $A_{V}=4.1\pm0.1$\,mag toward the SN. The extinction-corrected peak absolute magnitudes are $M_{J} = -16.8\pm0.2$\,mag, $M_{H} = -16.8\pm0.2$\,mag, and $M_{K_{\mathrm{s}}} = -17.0\pm0.2$\,mag. The SN {\bf exhibited} an $r$-band rise time of 14.9 days. The spectra {\bf display} broad features {\bf indicative of} high expansion velocities; the He~{\sc i} line velocity was measured at $16,000\,\mathrm{km\,s^{-1}}$ at $t=-4$\,d. Its spectral profile is broader than {\bf those} of typical moderately energetic Type Ib SNe, {\bf yet narrower than those of Type Ic-BL SNe, placing it in an intermediate category}. Based on the light-curve timescale and velocity, we estimate {\bf a} kinetic energy of $E_k = (4.1\pm0.7) \times 10^{51}$\,erg, {\bf an} ejecta mass of $M_{\mathrm{ej}} = 2.3\pm0.7\,M_{\odot}$, and a radioactive $^{56}\mathrm{Ni}$ mass of $(3.8\pm0.1) \times 10^{-2}\,M_{\odot}$. {\bf An} analysis using a two-component model suggests a steep density profile in the outer layer {\bf contrasted with} a dense inner core, {\bf which implies} ejecta asphericity. The low $^{56}\mathrm{Ni}$ mass is consistent with a partial fallback scenario. We conclude that SN 2023dbc originated from an aspherical explosion with partial core fallback, {\bf arising} from a progenitor ($M_{\mathrm{ini}} \simeq 15\,M_{\odot}$) that had retained {\bf its} helium envelope {\bf within} a binary system.

astro-ph.HE↗

arXiv2026

Input Matrix Optimization for Desired Reachable Set Warping of Linear Systems

Shaping the reachable set of a dynamical system is a fundamental challenge in control design, with direct implications for both performance and safety. This paper considers the problem of selecting the optimal input matrix for a linear system that maximizes warping of the reachable set along a direction of interest. The main result establishes that under certain assumptions on the dynamics, the problem reduces to a finite number of linear optimization problems. When these assumptions are relaxed, we show heuristically that the same approach yields good results. The results are validated on two systems: a linearized ADMIRE fighter jet model and a damped oscillator with complex eigenvalues. The paper concludes with a discussion of future directions for reachable set warping research.

eess.SY↗

arXiv2025

Unveiling SN 2022eyw: A Bright Member of the Type Iax Supernova Subclass

We present comprehensive photometric and spectroscopic observations of Supernova (SN) 2022eyw, a luminous member of the Type Iax SN subclass. SN 2022eyw reached a peak absolute magnitude of $M_g = -17.80\pm0.15$ mag and exhibited a rise time of $\sim$15 days, placing it among the brighter Iax events. The bolometric light curve indicates a synthesized $^{56}$Ni mass of $0.11\pm0.01~\text{M}_{\odot}$, with an estimated ejecta mass of $0.79\pm0.09~\text{M}_{\odot}$ and kinetic energy of $0.19\times10^{51}$ erg. The spectral evolution from -8 to +110 days past maximum reveals features characteristic of bright Type Iax Supernovae, including a transition from Fe III to Fe II dominance, moderate expansion velocities, and a lack of strong C III absorption. TARDIS spectral modelling of the early-phase spectra indicates a well-mixed ejecta dominated by Fe-group elements. In addition, traces of unburnt carbon are detected, pointing to incomplete burning as expected in pure deflagration models. Late-time spectral evolution shows a blend of permitted and forbidden lines. Comparison with deflagration models suggests that SN 2022eyw originated from a partial deflagration of a Chandrasekhar-mass white dwarf, with explosion properties intermediate between the N3-def and N5-def models. These observations support pure deflagration of a CO white dwarf as a viable explosion mechanism for its luminous members.

astro-ph.HE↗

arXiv2025

SN 2024aecx: A double-peaked rapidly evolving Type IIb supernova at 11 Mpc

We present the results of low-resolution spectroscopic and densely sampled multi-band photometric follow-up of supernova (SN) 2024aecx. The SN was discovered in the spiral galaxy NGC 3521 (distance $\sim$11 Mpc) within a day after the explosion. The early spectra of SN 2024aecx show a weak signature of hydrogen lines, which disappeared in $\sim$30 days after the explosion. Light curves in all bands show a distinct feature of two peaks, and the first peak is likely due to the shock cooling emission. The early phase light curve evolution of SN 2024aecx has similarity with the typical Type IIb events, but the decay rate in different bands (e.g., $\rm \Delta m_{15}$ = 1.60 $\pm$ 0.05 mag, $g$-band) is significantly faster in the post-peak phase. It attained the secondary maximum in $\sim$19 days ($g$-band) with a peak absolute magnitude of M$_{g}$ = -17.94 $\pm$ 0.10 mag. SN 2024aecx colors trend redder in early epochs ($<$8 days), followed by a duration in which it grows bluer, then later gets redder again $>$20 days after explosion. The analytical model fitting to the light curves reveals an envelope mass and progenitor radii in the range of $\sim$0.03 - 0.24 $M_\odot$ and $\sim$169 - 200 $R_\odot$, respectively. Modeling of the pseudo-bolometric light curve suggests that synthesized $^{56}$Ni in the explosion was $\sim$0.15 M$_{\odot}$ with ejecta mass and kinetic energy of $\sim$0.7 M$_{\odot}$ and $\sim$0.16 $\times$ 10$^{51}$ erg, respectively. The observational properties and modeling indicate that the SN~2024aecx progenitor belongs to the extended progenitor category.

astro-ph.HE↗

arXiv2025

A Corrector-aided Look-ahead Distance-based Guidance for Online Reference Path Following with an Efficient Mid-course Guidance Strategy

Efficient path-following is crucial in most of the applications of autonomous vehicles (UxV). Among various guidance strategies presented in literature, the look-ahead distance ($L_1$)-based nonlinear guidance has received significant attention due to its ease in implementation and ability to maintain a low cross-track error while following simpler reference paths and generating bounded lateral acceleration commands. However, the constant value of $L_1$ becomes problematic when the UxV is far away from the reference path and also produces higher cross-track error while following complex reference paths having high variation in radius of curvature. To address these challenges, the notion of look-ahead distance is leveraged in a novel way to develop a two-phase guidance strategy. Initially, when the UxV is far from the reference path, an optimized $L_1$ selection strategy is developed to guide the UxV towards the vicinity of the start point of the reference path, while maintaining minimal lateral acceleration command. Once the vehicle reaches a close neighborhood of the reference path, a novel notion of corrector point is incorporated in the constant $L_1$-based guidance scheme to generate the guidance command that effectively reduces the root mean square of the cross-track error and lateral acceleration requirement thereafter. Simulation results validate satisfactory performance of this proposed corrector point and look-ahead point pair-based guidance strategy, along with the developed mid-course guidance scheme. Also, its superiority over the conventional constant $L_1$ guidance scheme is established by simulation studies over different initial condition scenarios.

cs.RO↗

arXiv2024

Quantifying Maximum Actuator Degradation for a Given $H_2/H_{\infty}$ Performance with Full-State Feedback Control

In this paper, we address the issue of quantifying maximum actuator degradation in linear time-invariant dynamical systems. We present a new unified framework for computing the state-feedback controller gain that meets a user-defined closed-loop performance criterion while also maximizing actuator degradation. This degradation is modeled as a first-order filter with additive noise. Our approach involves two novel convex optimization formulations that concurrently determine the controller gain, maximize actuator degradation, and maintain the desired closed-loop performance in both the $H_2$ and $H_{\infty}$ system norms. The results are limited to open-loop stable systems. We demonstrate the application of our results through the design of a full-state feedback controller for a model representing the longitudinal motion of the F-16 aircraft.

eess.SY↗