148 research outputs found
Multimessenger Universe with Gravitational Waves from Binaries
Future GW detector networks and EM observatories will provide a unique
opportunity to observe the most luminous events in the Universe involving
matter in extreme environs. They will address some of the key questions in
physics and astronomy: formation and evolution of compact binaries, sites of
formation of heavy elements and the physics of jets.Comment: 11 pages, two tables, White Paper submitted to the Astro-2020 (2020
Astronomy and Astrophysics Decadal Survey) by GWIC-3G Science Case Team
(GWIC: Gravitational-Wave International Committee
Unsupervised machine learning for transient discovery in deeper, wider, faster light curves
Identification of anomalous light curves within time-domain surveys is often challenging. In addition, with the growing number of wide-field surveys and the volume of data produced exceeding astronomers’ ability for manual evaluation, outlier and anomaly detection is becoming vital for transient science. We present an unsupervised method for transient discovery using a clustering technique and the ASTRONOMALY package. As proof of concept, we evaluate 85 553 min-cadenced light curves collected over two ∼1.5 h periods as part of the Deeper, Wider, Faster program, using two different telescope dithering strategies. By combining the clustering technique HDBSCAN with the isolation forest anomaly detection algorithm via the visual interface of ASTRONOMALY, we are able to rapidly isolate anomalous sources for further analysis. We successfully recover the known variable sources, across a range of catalogues from within the fields, and find a further seven uncatalogued variables and two stellar flare events, including a rarely observed ultrafast flare (∼5 min) from a likely M-dwarf
Presto-Color: A Photometric Survey Cadence for Explosive Physics and Fast Transients
We identify minimal observing cadence requirements that enable photometric astronomical surveys to detect and recognize fast and explosive transients and fast transient features. Observations in two different filters within a short time window (e.g., g-and-i, or r-and-z, within 1.5 hr) are desirable for this purpose. Such an observing strategy delivers both the color and light curve evolution of transients on the same night. This allows the identification and initial characterization of fast transient—or fast features of longer timescale transients—such as rapidly declining supernovae, kilonovae, and the signatures of SN ejecta interacting with binary companion stars or circumstellar material. Some of these extragalactic transients are intrinsically rare and generally all hard to find, thus upcoming surveys like the Large Synoptic Survey Telescope (LSST) could dramatically improve our understanding of their origin and properties. We colloquially refer to such a strategy implementation for the LSST as the Presto-Color strategy (rapid-color). This cadence's minimal requirements allow for overall optimization of a survey for other science goals
Zwicky Transient Facility constraints on the optical emission from the nearby repeating FRB 180916.J0158+65
The discovery rate of fast radio bursts (FRBs) is increasing dramatically
thanks to new radio facilities. Meanwhile, wide-field instruments such as the
47 deg Zwicky Transient Facility (ZTF) survey the optical sky to study
transient and variable sources. We present serendipitous ZTF observations of
the CHIME repeating source FRB 180916.J0158+65, that was localized to a spiral
galaxy 149 Mpc away and is the first FRB suggesting periodic modulation in its
activity. While 147 ZTF exposures corresponded to expected high-activity
periods of this FRB, no single ZTF exposure was at the same time as a CHIME
detection. No optical source was found at the FRB location in 683
ZTF exposures, totalling 5.69 hours of integration time. We combined ZTF upper
limits and expected repetitions from FRB 180916.J0158+65 in a statistical
framework using a Weibull distribution, agnostic of periodic modulation priors.
The analysis yielded a constraint on the ratio between the optical and radio
fluences of , corresponding to an optical energy erg for a fiducial 10 Jy ms FRB (90%
confidence). A deeper (but less statistically robust) constraint of can be placed assuming a rate of Jy ms)= hr and
FRB occurring during exposures taken in high-activity windows. The
constraint can be improved with shorter per-image exposures and longer
integration time, or observing FRBs at higher Galactic latitudes. This work
demonstrated how current surveys can statistically constrain multi-wavelength
counterparts to FRBs even without deliberately scheduled simultaneous radio
observation.Comment: Accepted for publication in ApJL, 9 pages, 4 figures, 1 tabl
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