Insights Into Stellar Explosions From Infrared Light

Massive stars are the workhorse of the Universe. While accounting for a minute fraction of baryonic mass, their influence on the cosmos is profound. Their lives and deaths lead to nucleosynthesis of all elements heavier than helium, including those essential to life. They produce some of the most energetic eruptions and explosions, core-collapse (CC) supernovae (SNe) at the end of their life. These explosions are common, about once per century per galaxy, and are one of the primary drivers of the gas dynamics of their host galaxies. Despite their importance, many facets of the massive stars' evolution and their eventual death in CCSNe are still uncertain. In this thesis, I use a variety of observations in the infrared (IR) part of the electromagnetic spectrum to probe aspects of these stellar explosions elusive to visible light. IR observations of SNe remain sparse compared to the optical, even for the most nearby events. I present the first systematic study of CCSNe light curves from the Spitzer Space Telescope showing trends in IR properties of CCSNe and identifying outliers that exhibit signs of interactions between the SN shock and the circumstellar medium (CSM) ejected from the star. I also present in-depth explorations of nearby SN 2017eaw, a typical and common hydrogen-rich explosion; and SN 2014C, a hydrogen-poor explosion whose shock wave crashes into the CSM containing material lost from the star. IR observations provide insights into the chemical evolution and circumstellar environment in these SNe. In the second part of this thesis, I present the development and commissioning of a near-IR spectropolarimeter WIRC+Pol at Palomar Observatory. WIRC+Pol utilizes a novel, highly efficient polarization grating as its polarimetric beam splitter and spectral disperser. The resulting high sensitivity allows WIRC+Pol to observe sources as faint as J = 14.5 to 0.1% polarimetric accuracy in 2 hours. I also present the first scientific results from the instrument: the spectropolarimetric measurements of four nearby SNe, which are the first such observations in the IR. We detected polarization from SN 2018hna, which allowed us to constrain that its explosion geometry looks similar to the very well-studied SN 1987A observed from a different angle, suggesting the same underlying geometry.</p

Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultra-Narrowband Photometry

Infrared observations of metastable 2$^3$S helium absorption with ground- and space-based spectroscopy are rapidly maturing, as this species is a unique probe of exoplanet atmospheres. Specifically, the transit depth in the triplet feature (with vacuum wavelengths near 1083.3 nm) can be used to constrain the temperature and mass loss rate of an exoplanet's upper atmosphere. Here, we present a new photometric technique to measure metastable 2$^3$S helium absorption using an ultra-narrowband filter (full-width at half-maximum of 0.635 nm) coupled to a beam-shaping diffuser installed in the Wide-field Infrared Camera (WIRC) on the 200-inch Hale Telescope at Palomar Observatory. We use telluric OH lines and a helium arc lamp to characterize refractive effects through the filter and to confirm our understanding of the filter transmission profile. We benchmark our new technique by observing a transit of WASP-69b and detect an excess absorption of $0.498\pm0.045$% (11.1$\sigma$), consistent with previous measurements after considering our bandpass. Then, we use this method to study the inflated gas giant WASP-52b and place a 95th-percentile upper limit on excess absorption in our helium bandpass of 0.47%. Using an atmospheric escape model, we constrain the mass loss rate for WASP-69b to be $5.25^{+0.65}_{-0.46}\times10^{-4}~M_\mathrm{J}/\mathrm{Gyr}$ ($3.32^{+0.67}_{-0.56}\times10^{-3}~M_\mathrm{J}/\mathrm{Gyr}$) at 7,000 K (12,000 K). Additionally, we set an upper limit on the mass loss rate of WASP-52b at these temperatures of $2.1\times10^{-4}~M_\mathrm{J}/\mathrm{Gyr}$ ($2.1\times10^{-3}~M_\mathrm{J}/\mathrm{Gyr}$). These results show that ultra-narrowband photometry can reliably quantify absorption in the metastable helium feature.Comment: 17 pages, 8 figures (figures 1 and 2 are rasterized for arXiv file size compliance), accepted to A

Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultranarrowband Photometry

Infrared observations of metastable 2³S helium absorption with ground- and space-based spectroscopy are rapidly maturing, as this species is a unique probe of exoplanet atmospheres. Specifically, the transit depth in the triplet feature (with vacuum wavelengths near 1083.3 nm) can be used to constrain the temperature and mass-loss rate of an exoplanet's upper atmosphere. Here, we present a new photometric technique to measure metastable 23S helium absorption using an ultranarrowband filter (FWHM 0.635 nm) coupled to a beam-shaping diffuser installed in the Wide-field Infrared Camera on the 200 inch Hale Telescope at Palomar Observatory. We use telluric OH lines and a helium arc lamp to characterize refractive effects through the filter and to confirm our understanding of the filter transmission profile. We benchmark our new technique by observing a transit of WASP-69b and detect an excess absorption of 0.498% ± 0.045% (11.1σ), consistent with previous measurements after considering our bandpass. We then use this method to study the inflated gas giant WASP-52b and place a 95th percentile upper limit on excess absorption in our helium bandpass of 0.47%. Using an atmospheric escape model, we constrain the mass-loss rate for WASP-69b to be 5.25^(+0.65)_(−0.46) × 10⁻⁴ M_J/Gyr⁻¹ (3.32^(+0.67)_(−0.56) × 10⁻³ M_J/Gyr⁻¹) at 7000 K (12,000 K). Additionally, we set an upper limit on the mass-loss rate of WASP-52b at these temperatures of 2.1 × 10⁻⁴ M_J/Gyr⁻¹ (2.1×10⁻³ M_J/Gyr⁻¹) . These results show that ultranarrowband photometry can reliably quantify absorption in the metastable helium feature

Infrared spectropolarimetric detection of intrinsic polarization from a core-collapse supernova

Massive stars die an explosive death as a core-collapse supernova (CCSN). The exact physical processes that cause the collapsing star to rebound into an explosion are not well understood1–3, and the key to resolving this issue may lie in the measurement of the shape of CCSNe ejecta. Spectropolarimetry is the only way to perform this measurement for CCSNe outside the Milky Way and Magellanic Clouds. We present the infrared spectropolarimetric detection of a CCSN enabled by the new highly sensitive WIRC+Pol instrument at Palomar Observatory, which can observe CCSNe (magnitude M = −17 mag) out to 20 Mpc at ~0.1% polarimetric precision. Infrared spectropolarimetry is less affected than optical spectropolarimetry by dust scattering in the circumstellar and interstellar media, thereby providing a less biased probe of the intrinsic geometry of the supernova ejecta. SN 2018hna, a SN 1987A-like explosion, shows 2.0 ± 0.3% continuum polarization in the J band oriented at ~160° on sky 182 days after the explosion. Assuming a prolate geometry as in SN 1987A, we infer an ejecta axis ratio of &lt;0.48 with the axis of symmetry pointing at a 70° position angle. The axis ratio is similar to that of SN 1987A, suggesting that the two CCSNe may share intrinsic geometry and inclination angles. Our data do not rule out oblate ejecta. We also observe one other CCSN and two thermonuclear supernovae in the J band. Supernova 2020oi, a stripped-envelope type Ic SN in Messier 100 has broadband p = 0.37 ± 0.09% at peak light, indicative of either a 10% asymmetry or host interstellar polarization. The type Ia SNe 2019ein and 2020ue have &lt;0.33% and &lt;1.08% polarization near peak light, indicative of asymmetries of less than 10% and 20%, respectively