Please find attached our submission of a Cycle 28 mid-cycle proposal for observations of GRB 191019A. Please let us know if there are any issues that need to be addressed.
Best Wishes,
Andrew1475950571Assigned ID: 1240
----- Attempting Submission 1 (Wed Sep 30 21:40:55 GMT 2020) -----FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser
FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browserPlease find attached our first submission of GO 16458 for UV observations of the host galaxy of GRB 191019A. If it is possible we would like to obtain these observations in the current visbility window that runs to 1 Jan.
Best Wishes,
Andrew-2144185002----- Attempting Submission 1 (Mon Nov 09 19:55:30 GMT 2020) -----I believe these errors refer to the FLASH level in the observations which has been set to bring the background to 20 electrons following the latest advice from the WFC3 team.A long gamma-ray burst from the nucleus of an ancient galaxyLong-duration gamma-ray bursts are associated with the collapse of massive stars, occurring ubiquitously in star-forming environments. These insights are based on studies of the more than 1000 bursts localised over the past 20 years. However, last year one burst, GRB 191019A, was discovered which appeared to challenge this rule. GRB 191019A is a regular long GRB coincident with the nucleus of an apparently passive galaxy at z=0.248. The probability of chance alignment within 0.1" of the galaxy nucleus is minimal (~10^-6), and so the association appears secure. There is no sign of any underlying supernova (SN) to limits >10 times fainter than typically in GRB supernovae. There is also no indication of nuclear SMBH activity in the galaxy (no X-ray detection to deep limits, or emission lines in the optical spectrum), and the source vanishes within a few hours, too quick for the expected evolution of tidal disruption events. This event may therefore represent a genuinely new route to the creation of a long GRB. Here we request deep UV observations to search for any underlying star formation to limits of <0.01 Msol/yr. The detection of even weak star formation would favour the origin in a massive star, in keeping with other GRBs. In this case, it is likely to provide evidence for the direct collapse of a massive star to a black hole. Alternatively, the absence of star formation may suggest a dynamical channel in the dense nuclear regions of the host galaxy. These HST observations are hence crucial in determining the origin of this new, and possibly so-far unidentified signal of stellar death.We will obtain two orbits of observations of the host galaxy of GRB 191019A with WFC3 UVIS. One orbit will be on obtain in F225W and one in F275W. A standard 4 point dither pattern will be used. The source will be placed close to the corner of the chip to avoid mitigate for CTE, and the chip will be flashed to ~20 electrons. In practice, since the source is extended the CTE is less of a concern.We have extensive experience of using HST to study GRBs and associated transient phenomena. The PI is the PI of 42 previous HST programmes. This includes the DDT proposal that obtained the first observations of GRB 191019A. We have an excellent track record in publishing our output and have contributed significantly to the field through this over the years. Our highlights include seminal work on the host galaxies of GRBs (e.g. Fruchter et al. 2006, Svensson et al. 2010, Tanvir et al. 2012), the identification of new popualtions of gamma-ray burst (Levan et al. 2011, Levan et al. 2014) and the first HST observations of gravitational wave counterparts (Levan et al. 2017, Tanvir et al. 2017). We continue to have the skills and resources necessary to undertake these observations from inception to publicaiton.Stellar Physics and Stellar TypesSupermassive Black Holes and Active Galaxies3falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYELLIPTICALNUCLEUSJ2000J2000WFC3/UVISImagingNoNoF225WWFC3/UVISImagingNoNoF275WPOS-TARGDITHER0.173LINE0.112falsefalse81.785423.884WFC3-UVIS-DITHER-BOX1false/private/var/folders/9d/znlr3gj56k5gg7kstwq1rs1w0000gn/T/OPVisit9881370306327898998.xmlThe scheduling data was generated by CASM 28.2.CASM was run in Phase II mode.(Tic-Visit
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