0Assigned ID: 6535
----- Attempting Submission 1 (Thu Apr 10 17:09:58 GMT 2025) -----
HST Phase I Proposal 6535 successfully submitted.
Receipt: # 6535-1
----- Attempting Submission 2 (Thu Apr 10 17:12:50 GMT 2025) -----
HST Phase I Proposal 6535 successfully submitted.
Receipt: # 6535-2This proposal aims to get deep F435W, F814W and F160W images of a GRB host galaxy and any possible lensing objects. The ORIENTs have now been removed 2025/11/26-1639946378----- Attempting Submission 1 (Wed Aug 13 12:41:39 GMT 2025) -----
HST Phase II Proposal 18013 successfully submitted.
Receipt: # 18013-1
----- Attempting Submission 2 (Wed Nov 26 15:15:44 GMT 2025) -----Searching for Strong Lensing Signatures in a Possible Lensed GRB.Gamma-ray bursts (GRBs) are among the most energetic phenomena in the universe, capable of being detected at high redshifts with sub-second timing precision. This makes them compelling candidates for probing cosmological parameters through gravitational lensing. However, despite nearly 20 years of observations, no strong lensing candidate has been conclusively identified, largely due to uncertainties in the prompt emission and localisation of GRBs.
Recently, we have identified a potential lensed GRB pair. We now aim to leverage the excellent depth and resolution capabilities of the HST to search for a potential host galaxy, determine image multiplicity, and identify any intervening lensing object(s) along the line of sight. A confirmed detection of gravitational lensing in a GRB would be a historic first and return an immediate, high-impact scientific result.Images will be taken with ACS/WFC F435W, F814W and WFC/IR F160W. With this data, we will be able to 1) confirm the presence or absence of any host galaxy and enable a sensitive search for lensing systems in the foreground, i.e. z <0.824. 2) determine if lensing signatures are present, in particular, multiply imaged host galaxy candidates and 3) derive a photometric redshift for possible lenses and host galaxies. HST /ACS high resolution capabilities and multi-band colour information are essential in determining the existence of multiply imaged galaxies. Using this data it will be possible to construct a lensing model. We assume the the maximum possible redshift of the lens as z=1.6. The majority of past LGRB hosts can be recovered with a limiting magnitude of r <26 AB mag with all hosts being recovered with r <27 mag. ([5] figure 9). Therefore we require imaging to recover at minimum a r =27 AB mag Sc-galaxy-like host at z=1.6 as 1" extended source with S/N>5 in any of the filters. For ACS observations, we will use 4 dithered images to allow for the removal of artifacts and cosmic rays. Each set of 4 images will require 4 + 3 x 2.5 minutes with an additional 6.5 minutes for guide star acquisition and 1.5 minutes to allow for maneuvering for dithering.
This results in a total overhead of 19.5 minutes per orbit. This leaves ~1950s in the orbit to carry out the exposures. For a 26 and 27 AB mag target this would result in a S/N in F435W ~15.1 and 6.1, S/N F814W ~6.5 and 2.6 respectively. For WFC3/IR observations, we will also use a set of 4 dithered images. Total overheads from guide star acquisition, dither maneuvering and 4x1 min for each exposure results in a total overhead of 12 minutes. The remaining 1800s integration time split across the 4 exposures returns a S/NF 160W ~16 for a r =27 AB mag galaxy. These observations will allow for the unambiguous confirmation on the presence or absence of the host galaxy, whether it has been multiply imaged as well as the existence of nearby possible lensing objects.
To avoid diffraction spikes from a nearby star, constraints on orientation are required.
To mitigate the effects of CTE, the target will be placed in the corner of the B amplifier in ACS/WFC observations.Dr. David O'Neill has expertise in extra-galactic transients, their progenitors and GRB discovery and analysis.
Dr. B. Gompertz has expertise in GRB analysis, modelling and multi-messenger astronomy
Prof. G Smith has expertise in high-redshift galaxies, gravitatioinal lensing and multi-messenger astronomy.
Dr. Dimple has expertise in detailed GRB analysis and machine learning.Galaxies6falsefalsefalsefalsefalsefalseSUPPORTEDGALAXYGRAVITATIONAL LENSJ2000J2000ACS/WFCImagingNoNoF475WWFC3/IRImagingNoNoF160WACS/WFCImagingNoNoF814WPOS-TARGDITHER0.2637LINE0.1856falsefalse69.02441.859ACS-WFC-DITHER-BOX1falsePOS-TARGDITHER0.2637LINE0.1856falsefalse69.02420.7ACS-WFC-DITHER-BOX2falsePOS-TARGDITHERDITHER45.183WFC3-IR-DITHER-BOX-MINfalse74.653true0.3650.572441.859POS-TARGWFC3-IR-DITHER-BLOB18.5283false/Users/david/Documents/OP-cache/GRB240205B-v01.xmlThe scheduling data was generated by CASM 33.1.CASM was run in Phase II mode.(Tic-Visit
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