16167( 3) - 19-Oct-2020 19:24:33 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16167 Version: 3 Check-in Time: 19-Oct-2020 19:24:33 STScI Edit Number: 0 Title Confirming the binarity of Kuiper Belt Object 2015 RR245: a test of the streaming instability ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Wesley C Fraser Dominion Astrophysical Observatory Y CoI: Dr. Michael Marsset Massachusetts Institute of Technology N CoI: Dr. J. J. Kavelaars National Research Council of Canada N CoI: Dr. Susan D. Benecchi Planetary Science Institute N CoI: James Robinson The Queen's University of Belfast N CoI: Richard Smith The Queen's University of Belfast N ------------------------------------------------------------------------------------ Abstract Binary systems are prevalent throughout the Kuiper Belt, with roughly 110 systems known to date. The question of how these binary systems formed is of great interest, as each proposed mechanism has its own implications for the conditions in the early Solar System during planetesimal growth. The favoured mechanism - streaming instability in a gaseous dusty disc followed by gravitational collapse of a pebble cloud (SI-GC) - naturally produces many of the observed features of Kuiper Belt binaries. This mechanism also predicts the presence of a class of relatively massive systems with nearly equal sized primary and secondary components. Such systems are virtually absent from the observed sample, with the exception of the Varda-Ilume system. Here we propose observations of the KBO 2015 RR245, the ground-based observations of which hint at a barely resolved binary. The inferred brightnesses and locations of the primary and secondary are consistent from image to image, and imply a system with mass and mass ratio very similar to the Varda system. If binarity is confirmed, RR245 and Varda together would reveal the presence of a class of binary that has simply gone unnoticed, and would solve one of the current tensions between observations and formation simulation of SI-GC. We propose a simple two orbit WFC3 program, with an aim to confirm the binarity of RR245. Observations will be tuned to avoid non-detection in the case of overlapping binary components, and will enable measure of both component's colors and relative sizes, properties that are necessary to confirm consistency with formation via SI-GC. ------------------------------------------------------------------------------------ Observations Description ------------------------ To time our pair of observations to minimize the chances that the secondary and primary are unresolvable during both sequences, we request observations separated by roughly 15 days, or ~1/4 of our estimated orbital period. We require no special timing for the first sequence though we would like to check the proposed scheduling timing timing windows to make sure that we avoid bright star and foreground sources that would otherwise compromise the data. Once scheduling windows are determined, Benecchi will do this field check. Both visits to RR245 are identical. We make use of the WFC3's fast filter change capabilities, to gather three UVIS exposures each in the F606w and F814w 16167( 3) - 19-Oct-2020 19:24:33 - [ 2] filters, with 3" dithers between three different positions. This affords us some protection against cosmic ray strikes and hot pixels. Observations are to be acquired in FGS fine lock mode, slewing at the very-well known rate of motion (at most 3"/hr) of the target during each visit to preserve maximum spatial resolution. The 3-sigma ephemeris uncertainty is sub-arcsecond. We will use 358-s and 358-s exposure times for the F606w and F814w filters, respectively and have placed them in a non-interruptable sequence to avoid any rotation curve complications on the object. These exposure times have been chosen to provide high SNR while minimizing the time wasted to buffer downlinks and optimized to fit the orbit. The WFC3 UVIS imaging ETC provides an estimated SNR>100 in each filter, or ~90 and ~50 for the primary and secondary, respectively. Images will be acquired in the UVIS2-C512C-SUB sub-aperture to prevent any time lost due to mid-orbit buffer dumps. We have also put in Flash values such the total background for each filter is about 20 electrons/pixel. ------------------------------------------------------------------------------------ 16167( 3) - 19-Oct-2020 19:24:33 - [ 3] TARGET LIST Solar System Targets ------------------------------------------------------------------------------------------------------------------------------------ TARGET NUMBER: 1 TARGET NAME: 2015RR245 ------------------------------------------------------------------------------------------------------------------------------------ TARGET DESCRIPTION: ASTEROID KBO Binary ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 1 TARGET POSITION LEVEL 2 TYPE=ASTEROID, A=82.03884773628791, E=0.5882820992739525, I=7.551163366915228 , O=211.769513212333, W=260.9179682697775, M=322.1638134145541, EQUINOX=J2000, EPOCH=05-JUL-2014:00:00:00, EpochTimeScale=TDB ------------------------------------------------------------------------------------------------------------------------------------ TARGET POSITION LEVEL 3 WINDOWS ------------------------------------------------------------------------------------------------------------------------------------ DATA COMMENTS V = 21.2 +/- 0.3 Ephemeris Center: EARTH Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 16167( 3) - 19-Oct-2020 19:24:33 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 16167( 3) - 19-Oct-2020 19:24:33 - [ 5] Visit: 01 (2015RR45) 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 2015RR245 WFC3/UVI ACCUM UVIS2-C51 F606W 1 358 S POS TARG 3, null; SEQ S 2C-SUB (1074 S) 1-2 NON-INT; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 2015RR245 WFC3/UVI ACCUM UVIS2-C51 F814W FLASH=5 1 358 S POS TARG 3, null; S 2C-SUB (1074 S) PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2015RR245 1 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2015RR245 1 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 2015RR245 1 WFC3/UVI ACCUM UVIS2-C5 F606W 3 none none none 1 N/A S 12C-SUB 2015RR245 2 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2015RR245 2 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2015RR245 2 WFC3/UVI ACCUM UVIS2-C5 F814W 3 none none none 1 N/A S 12C-SUB 16167( 3) - 19-Oct-2020 19:24:33 - [ 6] Visit: 02 (2015RR45) Visit Requirements: AFTER 01 BY 14 D TO 16 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 2015RR245 WFC3/UVI ACCUM UVIS2-C51 F606W 1 358 S POS TARG 3, null; SEQ S 2C-SUB (1074 S) 1-2 NON-INT; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 2015RR245 WFC3/UVI ACCUM UVIS2-C51 F814W FLASH=5 1 358 S POS TARG 3, null; S 2C-SUB (1074 S) PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2015RR245 1 WFC3/UVI ACCUM UVIS2-C5 F606W 1 none none none 1 N/A S 12C-SUB 2015RR245 1 WFC3/UVI ACCUM UVIS2-C5 F606W 2 none none none 1 N/A S 12C-SUB 2015RR245 1 WFC3/UVI ACCUM UVIS2-C5 F606W 3 none none none 1 N/A S 12C-SUB 2015RR245 2 WFC3/UVI ACCUM UVIS2-C5 F814W 1 none none none 1 N/A S 12C-SUB 2015RR245 2 WFC3/UVI ACCUM UVIS2-C5 F814W 2 none none none 1 N/A S 12C-SUB 2015RR245 2 WFC3/UVI ACCUM UVIS2-C5 F814W 3 none none none 1 N/A S 12C-SUB 16167( 3) - 19-Oct-2020 19:24:33 - [ 7] Summary Form for Proposal 16167 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C512C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=5 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 14 D TO 16 D, PATTERN 1 1, PATTERN 1 2, POS TARG 3, null, SEQ 1-2 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 2015RR245 ------------------------------------------------------------------------------------------------------------------------------------