arXiv subjects

Danielle Dickinson

Publications and source records attributed to Danielle Dickinson.

5 recordsLinked to original sources

arXiv2026

JWST Detects a Dusty AGB-like Source Before the Type Ia-CSM Supernova 2026sqf

Supernova (SN) 2026sqf recently appeared in the nearby face-on spiral galaxy NGC 3310 and has shown signs of strong interaction with a circumstellar medium (CSM). Such intense interaction, rare among nearby SNe, offers a valuable opportunity to reveal details on the origin and nature of its progenitor system. We analyzed the early-phase spectra and light curves (LCs) of SN 2026sqf. The general shapes of the observed spectra, the strengths of the emission lines, and the LC evolution all suggest that SN 2026sqf belongs to the rare SN Ia-CSM subclass. If confirmed, this would be the closest known member of this class, at D~19 Mpc. We also report the first candidate progenitor system for a thermonuclear supernova identified in JWST pre-explosion imaging, and the first evidence for a (probable) carbon-rich AGB donor to the exploding white dwarf (WD). Our results are consistent with the expectation that SNe Ia-CSM emerge from a system consisting of a WD and an AGB star undergoing a common-envelope phase. The CSM mass and dust content are consistent with expectations for an AGB environment, but the narrow-line width exceeds superwind expansion velocities, favoring an episodic ejection. Binary interaction shortly before the explosion is a natural explanation, though the channel and timescale remain uncertain. Late-time follow-up, especially with JWST, will test the identification and the conclusions of our early-phase analysis.

astro-ph.SR↗

arXiv2024

The Immediate, Exemplary, and Fleeting echelle spectroscopy of SN 2023ixf: Monitoring acceleration of slow progenitor circumstellar material, driven by shock interaction

We present high resolution WIYN/NEID echelle spectroscopy (R $\approx70$,000) of the supernova (SN) 2023ixf in M101, obtained 1.51 to 18.51 days after explosion over nine epochs. Daily monitoring for the first four days after explosion shows narrow emission features ($\leq200$ km s$^{-1}$), exhibiting predominantly blueshifted velocities, that rapidly weaken, broaden, and vanish in a manner consistent with radiative acceleration and the SN shock eventually overrunning or enveloping the full extent of dense circumstellar medium (CSM). The most rapid evolution is in the He I emission, which is visible on day 1.51 but disappears by day 2.62. We measure the maximum pre-SN speed of He I to be 25 $^{+0}_{-5} \pm2$ km s$^{-1}$, where the error is attributable to the uncertainty in how much the He I had already been radiatively accelerated, and to measurement of the emission line profile. The radiative acceleration of material is likely driven by the shock-CSM interaction, and the CSM is accelerated to $\geq200$ km s$^{-1}$ before being completely swept up by the SN shock to $\sim 2000$ km s$^{-1}$. We compare the observed spectra with spherically-symmetric r16wb HERACLES/CMFGEN model spectra and find the line evolution to generally be consistent with radiative acceleration and optical depth effects. The progenitor of SN2023ixf underwent an enhanced mass loss phase $\gtrsim 4$ year prior to core-collapse, creating a dense, asymmetric CSM region extending out to approximately $r_{CSM} = 3.7 \times 10^{14}$ ($v_\textrm{shock}$/9500 km s$^{-1}$) cm.

astro-ph.HE↗

arXiv2024

The Green Monster hiding in front of Cas A: JWST reveals a dense and dusty circumstellar structure pockmarked by ejecta interactions

JWST observations of the young Galactic supernova remnant Cassiopeia A revealed an unexpected structure seen as a green emission feature in colored composite MIRI F1130W and F1280W images - hence dubbed the Green Monster - that stretches across the central parts of the remnant in projection. Combining the kinematic information from NIRSpec and MIRI MRS with the multi-wavelength imaging from NIRCam and MIRI, we associate the Green Monster with circumstellar material that was lost during an asymmetric mass-loss phase. MIRI images are dominated by dust emission but its spectra show emission lines from Ne, H and Fe with low radial velocities indicative of a CSM nature. An X-ray analysis of this feature in a companion paper (Vink et al. 2024) supports its CSM nature and detects significant blue shifting, thereby placing the Green Monster on the near side, in front of the Cas A SN remnant. The most striking features of the Green Monster are dozens of almost perfectly circular 1" - 3" sized holes, most likely created by interaction between high-velocity SN ejecta material and the CSM. Further investigation is needed to understand whether these holes were formed by small 8000-10500 km/s N-rich ejecta knots that penetrated and advanced out ahead of the remnant's 5000 - 6000 km/s outer blastwave, or by narrow ejecta fingers that protrude into the forward-shocked CSM. The detection of the Green Monster provides further evidence of the highly asymmetric mass-loss that Cas A's progenitor star underwent prior to explosion.

astro-ph.HE↗

arXiv2024

A JWST Survey of the Supernova Remnant Cassiopeia A

We present initial results from a JWST survey of the youngest Galactic core-collapse supernova remnant Cassiopeia A (Cas A), made up of NIRCam and MIRI imaging mosaics that map emission from the main shell, interior, and surrounding circumstellar/interstellar material (CSM/ISM). We also present four exploratory positions of MIRI/MRS IFU spectroscopy that sample ejecta, CSM, and associated dust from representative shocked and unshocked regions. Surprising discoveries include: 1) a web-like network of unshocked ejecta filaments resolved to 0.01 pc scales exhibiting an overall morphology consistent with turbulent mixing of cool, low-entropy matter from the progenitor's oxygen layer with hot, high-entropy matter heated by neutrino interactions and radioactivity, 2) a thick sheet of dust-dominated emission from shocked CSM seen in projection toward the remnant's interior pockmarked with small (approximately one arcsecond) round holes formed by knots of high-velocity ejecta that have pierced through the CSM and driven expanding tangential shocks, 3) dozens of light echoes with angular sizes between 0.1 arcsecond to 1 arcminute reflecting previously unseen fine-scale structure in the ISM. NIRCam observations place new upper limits on infrared emission from the neutron star in Cas A's center and tightly constrain scenarios involving a possible fallback disk. These JWST survey data and initial findings help address unresolved questions about massive star explosions that have broad implications for the formation and evolution of stellar populations, the metal and dust enrichment of galaxies, and the origin of compact remnant objects.

astro-ph.HE↗

arXiv2023

The Superluminous Type IIn Supernova ASASSN-15ua: Part of a continuum in extreme precursor mass loss

We present a series of ground-based photometry and spectroscopy of the superluminous Type IIn supernova (SN) ASASSN-15ua, which shows evidence for strong interaction with pre-existing dense circumstellar material (CSM). Our observations constrain the speed, mass-loss rate, and extent of the progenitor wind shortly before explosion. A narrow P Cygni absorption component reveals a progenitor wind speed of $\sim$100 km s$^{-1}$. As observed in previous SNe IIn, the intermediate-width H$α$ emission became more asymmetric and blueshifted over time, suggesting either asymmetric CSM, an asymmetric explosion, or increasing selective extinction from dust within the post-shock shell or SN ejecta. Based on the CSM radius and speed, we find that the progenitor suffered extreme eruptive mass loss with a rate of 0.1-1 M$_\odot$ yr$^{-1}$ during the $\sim$12 years immediately before the death of the star that imparted $\sim$ 10$^{48}$ erg of kinetic energy to the CSM. Integrating its $V$-band light curve over the first 170 days after discovery, we find that ASASSN-15ua radiated at least 3$\times$10$^{50}$ erg in visual light alone, giving a lower limit to the total radiated energy that may have approached 10$^{51}$ erg. ASASSN-15ua exhibits many similarities to two well-studied superluminous SNe IIn: SN 2006tf and SN 2010jl. Based on a detailed comparison of these three, we find that ASASSN-15ua falls in between these two events in a wide variety of observed properties and derived physical parameters, illustrating a continuum of behavior across superluminous SNe IIn.

astro-ph.SR↗