FLASH Talk: The All-sky Survey Estimate of the Galactic Nova Rate (Adam Kawash) & Examining a Lobster and Some Speckles for Unresolved Third Components in Low-mass Wide Binaries (Zachary Hartman)

Friday, 12 November 2021 noon — 1 p.m. MST

Adam Kawash (MSU) & Zachary Hartman (NOIRLab)
Adam Kawash, Michigan State University
The All-sky Survey Estimate of the Galactic Nova Rate
The discrepancy between the predicted global rate of nova production in the Milky Way of ~50 per year and the discovery rate of ~10 per year has long been poorly understood. However, the emergence of all-sky surveys in recent years provide an unprecedented opportunity to better constrain the nova rate of the Galaxy. We have built a mock galaxy containing novae and interstellar dust to explore what fraction of the population should be observable with current surveys. By using three dimensional dust maps to model the dust, we find that about half of novae are too highly extinguished to be detectable with most optical observations. We have injected these model novae into the data of the only two transient reporting surveys observing the entire sky: The All-Sky Automated Search for Supernovae (ASAS-SN) and Gaia. Preliminary analysis of this work predicts a nova rate between 20--30 per year, lower than previous estimates.
Zachary Hartman, NOIRLab
Examining a Lobster and Some Speckles for Unresolved Third Components in Low-mass Wide Binaries
Wide stellar binaries with separations more than 10,000 au hold a unique role in astronomy.  As they are believed to be coeval in nature, they have been thought of as essentially two single stars with the same age and chemical composition.  However, over the past two decades, numerous studies have shown that, for the widest solar-type binaries, this is not the case.  Instead, the higher order multiplicity fraction, i.e. how many binaries are triples, quadruples, etc., increases as a function of physical separation.  Several possible formation channels have been proposed to explain this, each predicting a large higher order multiplicity fraction.  However, much of the data that we have comes from studies of solar-type stars.  In this talk, we examine low-mass wide binaries to look for clues on whether they follow the same trend seen in solar-type wide binaries.  By examining the K-dwarf region of the Gaia H-R diagram and identifying overluminous stars that are most likely unresolved binaries, we are able to estimate a lower limit on the higher order multiplicity of K+K wide binaries.  Examining this as a function of physical separation, we do not find the same trend seen in solar-type stars.  To examine this more, we report the findings of several speckle imaging campaigns of low-mass wide binaries which show a lack of detected third components in these systems compared with predictions from solar-type wide binaries.
You can see the full schedule of FLASH talks here: https://noirlab.edu/science/events/flash-talks
Additionally, if you or a collaborator are interested in presenting at FLASH please get in touch. All FLASH talks are virtual for the foreseeable future, so feel free to suggest speakers from outside of Tucson!


FLASH Talks are scientific talks for the staff at NOIRLab and the University of Arizona's Steward Observatory.