15613( 12) - 06-Dec-2018 14:16:01 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15613 Version: 12 Check-in Time: 06-Dec-2018 14:16:01 STScI Edit Number: 3 Title The Astrophysics of the Most Energetic Gamma-Ray Bursts ------------------------------------------------------------------------------------ Type Cycle GO 26 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Andrew S. Fruchter Space Telescope Science Institute Y CoI: Tuomas Kangas Space Telescope Science Institute N CoI: Dr. Benjamin Paul Gompertz The University of Warwick N CoI: Dr. Antonino Cucchiara University of the Virgin Islands N CoI: Dr. Daniel Perley Liverpool John Moores University N CoI: Dr. Kuntal Misra Aryabhatta Research Institute of N Observational Sci CoI: Dr. John F. Graham Peking University N CoI: Dr. Asaf Peer University College Cork N CoI: Prof. Nial Rahil Tanvir University of Leicester N CoI: Prof. Andrew James Levan The University of Warwick N CoI: Dr. Stephen Bradley Cenko NASA Goddard Space Flight Center N CoI: Judith Racusin NASA Goddard Space Flight Center N ------------------------------------------------------------------------------------ Abstract The Fermi Large Area Telescope (LAT) has found a sample of highly relativistic gamma-ray bursts (GRBs), which may be among the most energetic bursts ever discovered. Here we propose to use Chandra and HST to follow the late time X-ray and optical light curves of a LAT detected burst that also has excellent early multiwavelength coverage. Our observations, in conjunction with the Fermi data, will allow us to measure the energy, bulk Lorentz factor, and in some cases probe the jet physics of the explosion. Recent work by us and others on some of the most powerful GRBs has begun to substantially constrain physical models of the progenitors. Our observations may greatly strengthen these constraints as well as provide new insight into the relativistic physics of the bursts. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to observe a LAT-detected burst with {\it Chandra}. We will select a burst that has $\Eiso > 5 \times10^{53}\, $ erg (bolometric), as well as {\it Swift} XRT and ground-based optical detections of the afterglow. As a luminosity distance is require to estimate $\Eiso$, the requirement on $\Eiso$ means that we will only observe a burst with a measured redshift. There is one exception to these requirements. In the rare instance that an ULGRB fulfills all of these conditions except for a LAT detection, we will ask the Director for permission to trigger. We estimate that ULGRBs meeting our large $\Eiso$ requirement are on average detected only once per 5 -- 10 years. 15613( 12) - 06-Dec-2018 14:16:01 - [ 2] Based on the history of LAT bursts since the launch of {\it Fermi}, there is a $\sim 75\%$ chance that a burst will meet our criteria during the next Cycle of {\it Chandra}. We will take the first burst during the Cycle meeting our criteria which has good ongoing ground-based optical and {\it Swift} XRT observations. Our default strategy is to have two or three visits with {\it Chandra}, depending on the behavior of the burst. We will use the {\it Swift} data to estimate when the burst is likely to reach a flux of $4 \times 10^{-14} \erg \cm^{-2} {\rm s}^{-1}$, which is the effective limit of {\it Swift}, and will plan a first visit by {\it Chandra} at a time 50\% later after the burst, assuming that the burst will fall with a constant slope as the bursts in Figure 2. This visit should occur between twenty-four and thirty days after burst. We will therefore be asking for a trigger with a lead time of about two weeks. If {\it Swift} and ground-based optical data show an unambiguous break, {\it Chandra} and {\it HST} observations would likely prove superfluous and we will not trigger. If the break is marginal, we will trigger, as {\it Chandra} could clearly determine a break and measure its size -- which is important for understanding the relativistic physics of the outflow. The {\it Swift} XRT band is nearly identical to that of {\it Chandra} ACIS. We estimate that at the first visit {\it Chandra} will detect approximately $2.5\times 10^{-3}\, $ cps, assuming the burst continues to fall approximately as $t^{-1.2}$. So in 25ks we will reach a SNR of about eight. Should the burst break to $t^{-2}$ we will obtain a SNR of about four -- though this depends greatly on the luminosity of the burst and the depth to which {\it Swift} followed the burst. If the first visit indicates a strong break has already occurred we will use the remaining time for a single deep observation between 1.5 and 2 times later than the first observation. However, it is unlikely we will get a strong signal of a break in the first visit without an earlier indication from the ground. Therefore, we will more likely re-observe at about 1.5 times later than the first {\it Swift} observation using about 40 ks of time, reserving 55 ks for a final deep third epoch, for a total of 120 ks. {\it We note that the point-source sensitivity required by our late-time observations can only be achieved by Chandra.} Several co-Is of this proposal have direct access to optical/near-infrared follow-up facilities, which will enable rapid afterglow identification and redshift determination. However after about two weeks, it is likely that the observations from the ground will become insufficiently deep to follow the optical transient, even using the time on eight to ten meter class telescopes. {\it HST} will allow us to continue to follow the optical 15613( 12) - 06-Dec-2018 14:16:01 - [ 3] transient for several more weeks. We therefore ask for an {\it HST} ToO. As prior Cycles show, the three-week notification for HST works for this project, as the ground-based observations should typically get us reliable data points out to two weeks, and we can typically accept a gap of two weeks after that before the {\it HST} observations. We plan four visits with {\it HST}: the first an orbit long, a second two orbits long, a third four orbits long and a fourth final visit also four orbits long. Where possible the {\HST} observations will roughly coincide with the corresponding {\it Chandra} epochs. The exact times will be scaled according to the decay seen from the ground and earlier {\it HST} observations. The first three visits will be used to measure the decay slope of the light curve. The fourth visit will be taken at least six months after the burst to allow an accurate host galaxy subtraction. We will use the UVIS camera on WFC3 because of its point source sensitivity and low noise, and will choose the filter at the time of the ToO to match one of the best observed bands from the ground (most likely a red band). If, however, the burst has a redshift $z < 1.25$, we will want to observe in a bluer band to avoid possible supernova contamination. Our team's past success in obtaining Gemini and VLT time makes it likely we (as well as others) will be able to acquire the early ground-based observations necessary for us to trigger on a burst. As the spectral energy distribution of the afterglow is also important for modelling the burst, if we do not have a good SED from the ground, we will use part of our time to image the transient in the IR, again using WFC3. In this proposal, we also are asking for JVLA time to follow up to two bursts that meet our trigger criteria. The JVLA observations will start shortly after the burst, and it is possible (but not at all probable) that a burst that meets our trigger criteria could clearly break while it is still visible to {\it Swift}. If this happens we will not trigger {\it Chandra} or {\it HST}, but instead will wait for the next burst meeting our criteria. We will require three hours for each of the two bursts to allow this early follow up to determine if the burst is visible in the radio. We will break these early observations into 30 minute observations in C (4--8 GHz) and Ku (18--26 GHz) bands. While the Ku band is less sensitive, the GRB is expected to be brighter and interstellar scintillation less of an issue at higher frequencies, so using both bands can be valuable. If a radio afterglow is well-detected ($f_{\nu} > 100$\, $\mu$Jy), we will carry out more detailed observations. We will want to follow the evolution of the light curve sufficiently long to 15613( 12) - 06-Dec-2018 14:16:01 - [ 4] measure the jet break and to see the source fade as the synchrotron peak moves through the radio band. Experience shows that this will typically require another dozen epochs $\sim$1--100 days after the burst. Each epoch can be 30 min in duration. Our total request of JVLA time for the two bursts is therefore 18 hours. If an afterglow is still visible after $\sim$150 days it may be possible to use late-time JVLA observations to estimate the total energy of the burst (SB11) using the Sedov-Taylor approximation. If this method works to the accuracy hoped for, it could provide an independent check on the energies determined from the break observations, and thus on our understanding of the physics of the relativistic jet. In cases where this approach looks promising, we will submit a separate proposal to NRAO to follow any such events to very late times (years -- though in the case of GRB 130427A, which is a powerful burst in a tenuous medium, it may be more like a decade! ------------------------------------------------------------------------------------ 15613( 12) - 06-Dec-2018 14:16:01 - [ 5] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB-180720B EXT-STAR, GAMMA RAY RA=00H02M7.0729S, J2000 V = 26 BURSTER DEC=-02D56'5.68" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15613( 12) - 06-Dec-2018 14:16:01 - [ 6] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15613( 12) - 06-Dec-2018 14:16:01 - [ 7] Visit: 01 Visit Requirements: ORIENT 65D TO 65 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB-180720B WFC3/UVI ACCUM UVIS1 F438W FLASH=7 1 550 S GS ACQ SCENARIO SINGLE; S (2200 S) PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 GRB-180720B WFC3/UVI ACCUM UVIS1 F606W 1 550 S S (2200 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 1 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 2 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 3 none none none 2 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 4 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 3 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 4 none none none 2 N/A S 15613( 12) - 06-Dec-2018 14:16:01 - [ 8] Visit: T1 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB-180720B WFC3/UVI ACCUM UVIS1 F438W FLASH=7 1 550 S POS TARG S (2200 S) -61.62995788269611, -3.9737750538771808; GS ACQ SCENARIO BASE1B3; PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 GRB-180720B WFC3/UVI ACCUM UVIS1 F606W 1 550 S POS TARG S (2200 S) -61.62995788269611, -3.9737750538771808 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 1 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 2 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 3 none none none 2 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 4 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 3 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 4 none none none 2 N/A S 15613( 12) - 06-Dec-2018 14:16:01 - [ 9] Visit: T2 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB-180720B WFC3/UVI ACCUM UVIS1 F438W FLASH=7 1 550 S POS TARG S (2200 S) -54.84304796804822, 20.994436025262832; GS ACQ SCENARIO BASE1B3; PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 GRB-180720B WFC3/UVI ACCUM UVIS1 F606W 1 550 S POS TARG S (2200 S) -54.84304796804822, 20.994436025262832 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 1 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 2 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 3 none none none 2 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 4 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 3 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 4 none none none 2 N/A S 15613( 12) - 06-Dec-2018 14:16:01 - [ 10] Visit: T3 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB-180720B WFC3/UVI ACCUM UVIS1 F438W FLASH=7 1 550 S POS TARG S (2200 S) 54.84304796804822, 20.994436025262832; GS ACQ SCENARIO BASE1B3; PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 GRB-180720B WFC3/UVI ACCUM UVIS1 F606W 1 550 S POS TARG S (2200 S) 54.84304796804822, 20.994436025262832 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 1 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 2 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 3 none none none 2 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS1 F438W 4 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 1 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 2 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 3 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS1 F606W 4 none none none 2 N/A S 15613( 12) - 06-Dec-2018 14:16:01 - [ 11] Visit: T5 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB-180720B WFC3/UVI ACCUM UVIS2 F438W FLASH=7 1 550 S GS ACQ SCENARIO BASE1B3; S (2200 S) PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ 2 GRB-180720B WFC3/UVI ACCUM UVIS2 F606W 1 550 S S (2200 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GRB-180720B 1 WFC3/UVI ACCUM UVIS2 F438W 1 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS2 F438W 2 none none none 1 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS2 F438W 3 none none none 2 N/A S GRB-180720B 1 WFC3/UVI ACCUM UVIS2 F438W 4 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS2 F606W 1 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS2 F606W 2 none none none 1 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS2 F606W 3 none none none 2 N/A S GRB-180720B 2 WFC3/UVI ACCUM UVIS2 F606W 4 none none none 2 N/A S 15613( 12) - 06-Dec-2018 14:16:01 - [ 12] Summary Form for Proposal 15613 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, UVIS2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=7 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO BASE1B3, GS ACQ SCENARIO SINGLE, ORIENT 65D TO 65 D, PATTERN 1 1-2, POS TARG -54.84304796804822, 20.994436025262832, POS TARG -61.62995788269611, -3.9737750538771808, POS TARG 54.84304796804822, 20.994436025262832 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F438W, F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GRB-180720B ------------------------------------------------------------------------------------------------------------------------------------