2 research outputs found
Double Mode Cepheids from the Zwicky Transient Facility Survey
Multi-mode Cepheids pulsate simultaneously in more than one mode of
oscillation. They provide an independent means to test stellar models and
pulsation theories. They can also be used to derive metallicities. In recent
years, the number of known multi-mode Cepheids has increased dramatically with
the discovery of a large number of Galactic double-mode Cepheids. To date, 209
double-mode Cepheids have been detected in the Galactic bulge and disk, mostly
based on the Optical Gravitational Lensing Experiment's (OGLE) catalog. In this
paper, we conduct a comprehensive search for double-mode Cepheids in the
northern sky based on Zwicky Transient Facility Data Release 5. We found 72
such objects in the Milky Way. The periods of the 30 sample objects already
included in the OGLE catalog show excellent agreement with the OGLE periods.
The period ratios of our new Cepheids are consistent with those of known
double-mode Cepheids, as evidenced by their loci in the so-called `Petersen
diagram'. Compared with OGLE, the completeness of our double-mode Cepheid
sample is around 71\%. The much improved temporal sampling of the Zwicky
Transient Facility offers significant scope to find more double-mode Cepheids,
especially at the distribution's short-period end.Comment: 11 pages, 3 figures, 3 tables; accepted for publication in ApJ
CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources
We present the discovery of 25 new repeating fast radio burst (FRB) sources
found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1.
The sources were found using a new clustering algorithm that looks for multiple
events co-located on the sky having similar dispersion measures (DMs). The new
repeaters have DMs ranging from 220 pc cm to 1700 pc
cm, and include sources having exhibited as few as two bursts to as many
as twelve. We report a statistically significant difference in both the DM and
extragalactic DM (eDM) distributions between repeating and apparently
nonrepeating sources, with repeaters having lower mean DM and eDM, and we
discuss the implications. We find no clear bimodality between the repetition
rates of repeaters and upper limits on repetition from apparently nonrepeating
sources after correcting for sensitivity and exposure effects, although some
active repeating sources stand out as anomalous. We measure the repeater
fraction and find that it tends to an equilibrium of % over
our exposure thus far. We also report on 14 more sources which are promising
repeating FRB candidates and which merit follow-up observations for
confirmation.Comment: Submitted to ApJ. Comments are welcome and follow-up observations are
encouraged