Special Talk

• Special Talks

  Speaker: Elena Manjavacas (ESA for STScI)
  Title: Stable Rotational Modulation Across Seven Years Baseline for the Planetary-mass Companion Ross 458C
  Abstract: Spectroscopic variability is detected in brown dwarfs across all spectral types, suggesting the existence of weather patterns in brown dwarf atmospheres. We present the spectral variability of the T8.0 planetary-mass companion Ross 458C, measured using time-resolved JWST/NIRSpec spectroscopy. We compared the spectral variability and light curve obtained with these data with that obtained by Manjavacas et al. (2019) more than 7.5 yr before with HST/WFC3. We concluded that the light curve of Ross 458C is remarkably similar in the two epochs in terms of shape and variability amplitude potentially created by stable weather patterns. We measured a rotational period of 11.38+/-0.52 hr, demonstrating that the previously reported HST/WFC3 period of 6.75+/-1.58 hr is most likely a harmonic produced by an unresolved double-peaked rotational modulation, due to the higher uncertainties of the HST/WFC3 light curve. We measured a variability amplitude in the white light curve of 1.47+/-0.18 %, and the overall spectral variability which is consistent with that measured by Manjavacas et al. (2019).

  Speaker: David Coulter (JHU/STScI)
  Title: Spectroscopic Confirmation of a Gravitationally Lensed Supernova 1 Billion Years After the Big Bang
  Abstract: I will present the JWST discovery of "SN Eos": a multiply-imaged, strongly lensed SN with a combined magnification of ~60 (i.e., 30x for each of two near-identical images). SN Eos occurred at a spectroscopic redshift of z=5.13, in a Lyman-α Emitter (LAE) host galaxy. Using this large magnification, we have obtained a spectacular, high signal-to-noise spectrum that shows strong H-alpha emission (rest-frame 6565 Å), and indicates that the progenitor to SN Eos had a massive hydrogen envelope consistent with that of local-Universe Type IIP SNe (SNe IIP). Archival HST imaging in the rest-frame far ultraviolet (1800 Å) places a strong constraint on the time of explosion, and allows us to place the phase of our spectrophotometric observations at ~90 days post-explosion. SN Eos is now the most distant SN ever spectroscopically classified, and our observations give an unprecedented view into the local conditions of an LAE host galaxy at the EoR. Elemental signatures in the spectrum of SN Eos confirm that it exploded in a particularly low-metallicity environment, consistent with expectations for a small, star-forming galaxy at z~5. SN Eos also shows a remarkable similarity in luminosity, chemical abundance, and explosion properties to local, metal-poor SNe, and confirms that these are excellent analogs to the high-redshift Universe. This result demonstrate show transient searches that leverage the magnification afforded by gravitational lensing surveys have opened a new frontier in precision, high-redshift transient science.

  Speaker: Greg Sloan (STScI)
  Title: Proto-PAHS: The Steps to the Formation of Polycyclic Aromatic Hydrocarbons
  Abstract: Polycyclic aromatic hydrocarbons (PAHs) are an important component of the interstellar medium. They can dominate the infrared emission from entire galaxies that are actively forming stars. And yet, how they form remains a mystery. The JWST Proto-PAH Project observed seven carbon-rich objects developing into planetary nebulae using NIRSpec and the MIRI/MRS. The data reveal a wealth of spectroscopic features as the circumstellar gas and dust evolves into PAHs. The solid-state component shows a mixture of aliphatic and aromatic hydrocarbons, including the rare phenomenon of absorption from PAH-like material. The molecular component shows emission and absorption from simpler hydrocarbons like methane, acetylene, methylene, and benzene, just to name a few. Relating the spectra from the sources in our sample to their overall properties is helping us to reveal stages of the chemical pathways that lead to PAHs.