AstroNote 2019-101

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DRAFT
2019-10-10 03:01:40
Type: Object/s-Discovery/Classification
Possible Rapidly Evolving Superluminous Blue Transient AT 2019rwd
Authors: Dheeraj Pasham (MIT), Iair Arcavi (Tel Aviv University), Jamison Burke (Las Cumbres / UCSB)
Abstract:
We report optical, UV and X-ray data of this rapidly evolving event. The nature of the event can not yet be determined, additional immediate followup is encouraged.

AT 2019rwd is a rapidly evolving transient in the ZTF public alert stream (ZTF19acctwpz). It rose by 1.5-2 magnitudes between a non detection on 2019-10-04 UTC and detection on 2019-10-05 UTC, and is now already fading (e.g. https://lasair.roe.ac.uk/object/ZTF19acctwpz/).

We observed AT 2019rwd with the Las Cumbres Observatory network as part of the Global Supernova Project (PI: Howell). We obtained photometry with the SInistro camera on one of the network's 1-meter telescopes at the Cerro Tololo Interamerican Observatory in Chile and a spectrum with the Floyds spectrograph on the 2-meter telescope at Haleakala Observatory in Hawaii. We detect the transient at a magnitude of ~18.6 in the bluer bands, and only marginally detect it in the redder bands. The spectrum displays a blue continuum with no obvious broad features, but with a possible narrow Halpha emission line at z~0.286. If this line identification is correct it implies the transient is superluminous. Our spectrum is publicly available on the TNS.

Swift also observed AT 2019rwd on three occasions (PI: Schulze). The transient is detected in all UVOT ultraviolet bands and is declining rapidly (~0.5-1 mag in 2 days). The transient is marginally detected in the XRT by combining the three XRT observations taken so far (yielding a total X-ray exposure of 3.2 ks). Running the sosta tool of HEASARC’s ximage suggests a source with a signal to noise of just 1.8-sigma. The measure count rate in 0.3-8 keV band is 2e-3 counts/sec. Using WebPIMMS and assuming that the X-ray spectrum can be fit with a power law index of 1.7 modified by a Galactic column density of 4e20 cm^2 suggests an X-ray flux of 8e-14 erg/s/cm^2. Further X-ray observations are necessary to confirm the X-ray emission from this region.

Show current TNS values
CatalogNameReported RAReported DECReported Obj-TypeReported RedshiftHost NameHost RedshiftRemarksTNS RATNS DECTNS Obj-TypeTNS Redshift
TNS2019rwd [ZTF19acctwpz]00:10:45.888+21:08:20.7500:10:45.903+21:08:20.75