Please join us for the CCAPP seminar next Tuesday, November 17th at 11:30 am. We will have two talks given by Curtis McCully (LCO & UCSB) and Vedran Brdar (Fermilab & Northwestern U.).
Speaker: Curtis McCully (LCO & UCSB) Host: Marshall Johnson
Title: Type Iax Supernovae: Not All White-Dwarf Supernovae are Good for Cosmology
Abstract: White-dwarf supernovae (SNe) play a key role in cosmology and led to the discovery of the accelerating universe driven by dark energy. As our sample sizes have increased, we have found that not all white-dwarf explosions produce normal SNe Ia that can be used for cosmology. Type Iax supernovae represent the largest class of white-dwarf supernovae. I will present observations of the full life cycle of SNe Iax starting from detection of the progenitor system in pre-explosion images (the first for any white-dwarf supernova) to nearly 1500 days past peak brightness for one of the brightest objects, SN~2012Z. I will discuss possible physical mechanisms including a bound remnant, shock-heated companion star, and radioactive decay to explain our observations. As we begin to better understand white-dwarf explosions in general, we will use the discoveries about SNe Iax to inform our understanding of our cosmological standard(izable) candles, normal SNe Ia.
Speaker: Vedran Brdar (Fermilab & Northwestern U.) Host: Ivan Esteban
Title: Beyond the Standard Model interpretation of recent NANOGrav result
Abstract: The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has recently reported strong evidence for a stochastic common-spectrum process affecting the pulsar timing residuals in its 12.5-year data set. In this talk, we demonstrate that this process admits an interpretation in terms of a stochastic gravitational-wave background emitted by a cosmic-string network in the early Universe. We also show that the entire viable parameter space of cosmic-string tension and loop size will be probed by an array of future experiments.
