151 research outputs found
Discovery of an intermediate-luminosity red transient in M51 and its likely dust-obscured, infrared-variable progenitor
We present the discovery of an optical transient (OT) in Messier 51,
designated M51 OT2019-1 (also ZTF19aadyppr, AT 2019abn, ATLAS19bzl), by the
Zwicky Transient Facility (ZTF). The OT rose over 15 days to an observed
luminosity of (), in the
luminosity gap between novae and typical supernovae (SNe). Spectra during the
outburst show a red continuum, Balmer emission with a velocity width of
km s, Ca II and [Ca II] emission, and absorption features
characteristic of an F-type supergiant. The spectra and multiband light curves
are similar to the so-called "SN impostors" and intermediate-luminosity red
transients (ILRTs). We directly identify the likely progenitor in archival
Spitzer Space Telescope imaging with a m luminosity of
and a color redder than 0.74 mag, similar
to those of the prototype ILRTs SN 2008S and NGC 300 OT2008-1. Intensive
monitoring of M51 with Spitzer further reveals evidence for variability of the
progenitor candidate at [4.5] in the years before the OT. The progenitor is not
detected in pre-outburst Hubble Space Telescope optical and near-IR images. The
optical colors during outburst combined with spectroscopic temperature
constraints imply a higher reddening of mag and higher
intrinsic luminosity of
() near peak than seen in previous ILRT
candidates. Moreover, the extinction estimate is higher on the rise than on the
plateau, suggestive of an extended phase of circumstellar dust destruction.
These results, enabled by the early discovery of M51 OT2019-1 and extensive
pre-outburst archival coverage, offer new clues about the debated origins of
ILRTs and may challenge the hypothesis that they arise from the
electron-capture induced collapse of extreme asymptotic giant branch stars.Comment: 21 pages, 5 figures, published in ApJ
An 8.8 minute orbital period eclipsing detached double white dwarf binary
We report the discovery of ZTF J2243+5242, an eclipsing double white dwarf
binary with an orbital period of just minutes, the second known eclipsing
binary with an orbital period less than ten minutes. The system likely consists
of two low-mass white dwarfs, and will merge in approximately 400,000 years to
form either an isolated hot subdwarf or an R Coronae Borealis star. Like its
counterpart, ZTF J1539+5027, ZTF J2243+5242 will be among the
strongest gravitational wave sources detectable by the space-based
gravitational-wave detector The Laser Space Interferometer Antenna (LISA)
because its gravitational-wave frequency falls near the peak of LISA's
sensitivity. Based on its estimated distance of ,
LISA should detect the source within its first few months of operation, and
should achieve a signal-to-noise ratio of after four years. We find
component masses of and
, radii of
and , and effective temperatures of
and . We
determined all of these properties, and the distance to this system, using only
photometric measurements, demonstrating a feasible way to estimate parameters
for the large population of optically faint ()
gravitational-wave sources which the Vera Rubin Observatory (VRO) and LISA
should identify.Comment: 12 pages, 7 figures, 3 tables, submitte
ZChecker: Finding Cometary Outbursts with the Zwicky Transient Facility
ZChecker is new, automated software for finding, measuring, and visualizing known comets in the Zwicky Transient Facility time-domain survey. ZChecker uses on-line ephemeris generation and survey metadata to identify images of targets of interest in the archive. Photometry of each target is measured, and the images processed with temporal filtering to highlight morphological variations in time. Example outputs show outbursts of comets 29P/Schwassmann-Wachmann 1 and 64P/Swift-Gehrels, and an asymmetric coma at C/2017 M4 (ATLAS)
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