18067( 2) - 28-Jul-2025 15:08:41 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18067 Version: 2 Check-in Time: 28-Jul-2025 15:08:41 STScI Edit Number: 0 Title Measuring the Accretion Rate for the Least Massive Known Brown Dwarf with a Circumstellar Disk ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Kevin Luhman The Pennsylvania State University Y CoI: Dr. Catherine Espaillat Boston University N CoI: Dr. Catarina Alves de Oliveira ESA, European Space Astronomy Centre N ------------------------------------------------------------------------------------ Abstract A Cycle 3 JWST program has searched for free-floating brown dwarfs down to the mass of Jupiter in the nearby star-forming cluster IC 348 (5 Myr, 300 pc). Those observations have discovered a brown dwarf that has an estimated mass of 2 Jupiter masses and that exhibits excess emission at 3-5 um from a circumstellar disk, making it the least massive known brown dwarf with a disk. We propose to use UV imaging with HST to measure the disk's accretion, which is a vital component of any effort to model the disk and constrain its properties. Using the accretion rate measured with HST, we will develop a model that fits the IR excess emission detected by JWST, which will provide an estimate of the inner radius of the disk. The accretion rate will also facilitate the modeling of any other future observations of the disk, such as JWST spectroscopy at 5-15 um and ALMA millimeter continuum measurements. Ultimately, this system represents a unique opportunity to study disk accretion and planet formation in an extreme, unexplored regime of stellar mass. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will obtain WFC3/UVIS images in the F336W filter of a point source (a brown dwarf) within a cluster of young stars. In each of 10 orbits, we will obtain one 1230 s exposure at each position in a two-point dither pattern. To mitigate CTE losse, a post flash of 13 electrons per pixel will be applied to each exposure, which should raise the background to the desired level of 20 electrons per pixel according to the ETC. The target will be observed at the UVIS2-C512C-CTE aperture, which also should mitigate CTE losses. The 10 orbits are divided among 10 visits. The ORIENT and timing of the visits are unconstrained. ------------------------------------------------------------------------------------ 18067( 2) - 28-Jul-2025 15:08:41 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 IC348-11040 STAR, BROWN DWARF RA=03H45M7.3842S, J2000 V = 30 DEC=+32D15'26.93" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 18067( 2) - 28-Jul-2025 15:08:41 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18067( 2) - 28-Jul-2025 15:08:41 - [ 4] Visit: 01 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 5] Visit: 02 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 6] Visit: 03 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 7] Visit: 04 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 8] Visit: 05 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 9] Visit: 06 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 10] Visit: 07 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 11] Visit: 08 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 12] Visit: 09 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 13] Visit: 10 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 IC348-11040 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=13 1 1230 S PATTERN 1 1 S 2C-CTE (2460 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 | ------------------------------------------------------------------------------------------------------------------------------------ IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 N/A S 12C-CTE IC348-11040 1 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 1 N/A S 12C-CTE 18067( 2) - 28-Jul-2025 15:08:41 - [ 14] Summary Form for Proposal 18067 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C512C-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=13 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W ------------------------------------------------------------------------------------------------------------------------------------ Target Names IC348-11040 ------------------------------------------------------------------------------------------------------------------------------------