We present high-cadence photometric and spectroscopic observations of SN~2023axu, a classical Type II supernova with an absolute $V$-band peak magnitude of $-16.5 \pm 0.1$ mag. SN~2023axu was discovered by the Distance Less Than 40 Mpc (DLT40) survey within 1 day of the last non-detection in the nearby galaxy NGC 2283 at 13.7 Mpc. We modeled the early light curve using a recently updated shock cooling model that includes the effects of line blanketing and found the explosion epoch to be MJD 59971.48 $\pm$ 0.03 and the probable progenitor to be a red supergiant with a radius of 417 $\pm$ 28 $R_\odot$. The shock cooling model cannot match the rise of observed data in the $r$ and $i$ bands and underpredicts the overall UV data which points to possible interaction with circumstellar material. This interpretation is further supported by spectral behavior. We see a ledge feature around 4600 \AA\ in the very early spectra (+1.1 and +1.5 days after the explosion) which can be a sign of circumstellar interaction. The signs of circumstellar material are further bolstered by the presence of absorption features blueward of H$\alpha$ and H$\beta$ at day $>$40 which is also generally attributed to circumstellar interaction. Our analysis shows the need for high-cadence early photometric and spectroscopic data to decipher the mass-loss history of the progenitor.

Blanketing

Circumstellar envelope

Extinction (optical mineralogy)

10.48550/arxiv.2310.00162

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Submitted Galaxy Scores to the Gravitational Wave Treasure Map for event MS230322s Preliminary

Zenodo (CERN European Organization for Nuclear Research) (2023)

S. Wyatt

Attached in a .json file is the ranked galaxy information within the contour region of the EM counterpart search associated with the gravitational wave event MS230322s Preliminary. A reference to these calculations can be found here: https://ui.adsabs.harvard.edu/abs/2020arXivNicePaper

Treasure

10.5281/zenodo.7826577

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SN 2016dsg: A Thermonuclear Explosion Involving a Thick Helium Shell

The Astrophysical Journal (2022)

Yize Dong S. Valenti Abigail Polin Aoife Boyle Andreas Flörs

Abstract A thermonuclear explosion triggered by a He-shell detonation on a carbon–oxygen white-dwarf core has been predicted to have strong UV line blanketing at early times due to the iron-group elements produced during He-shell burning. We present the photometric and spectroscopic observations of SN 2016dsg, a subluminous peculiar Type I supernova consistent with a thermonuclear explosion involving a thick He shell. With a redshift of 0.04, the i -band peak absolute magnitude is derived to be around −17.5. The object is located far away from its host, an early-type galaxy, suggesting it originated from an old stellar population. The spectra collected after the peak are unusually red, show strong UV line blanketing and weak O i λ 7773 absorption lines, and do not evolve significantly over 30 days. An absorption line around 9700–10500 Å is detected in the near-infrared spectrum and is likely from the unburnt He in the ejecta. The spectroscopic evolution is consistent with the thermonuclear explosion models for a sub-Chandrasekhar-mass white dwarf with a thick He shell, while the photometric evolution is not well described by existing models.

Blanketing

Thermonuclear Fusion

Red giant

10.3847/1538-4357/ac75eb

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Submitted Galaxy Scores to the Gravitational Wave Treasure Map for event TEST_EVENT Preliminary

Zenodo (CERN European Organization for Nuclear Research) (2023)

S. Wyatt

Attached in a .json file is the ranked galaxy information within the contour region of the EM counterpart search associated with the gravitational wave event TEST_EVENT Preliminary. A reference to these calculations can be found here: https://ui.adsabs.harvard.edu/abs/2020arXivNicePaper

Treasure

10.5281/zenodo.7786955

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An Overview of the D<40 Mpc One Day Cadence Supernova Search, DLT40

AAS (2018)

David J. Sand S. Valenti L. Tartaglia S. Yang S. Wyatt

Cadence

Source

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Announcing the GW Treasure Map