18125( 4) - 02-Dec-2025 18:53:01 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18125 Version: 4 Check-in Time: 02-Dec-2025 18:53:01 STScI Edit Number: 1 Title Brown dwarfs or white dwarfs with debris disks? Exploring the faintest stars of 47 Tucanae with HST and JWST ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Antonino Paolo Milone Universita degli Studi di Padova Y CoI: Dr. Emanuele Dondoglio INAF - Istituto Nazionale di Astrofisica N CoI: Dr. Anna Fabiola Marino INAF - Osservatorio Astronomico di Padova N CoI: Dr. Maria Vittoria Legnardi Universita degli Studi di Padova N CoI: Fabrizio Muratore Universita degli Studi di Padova N CoI: Dr. Emanuele Bortolan Universita degli Studi di Padova N CoI: Dr. Marco Tailo Universita di Bologna N CoI: Sofia Lionetto Universita degli Studi di Padova N CoI: Dr. Giacomo Cordoni Australian National University N CoI: Prof. E. P. Lagioia Yunnan University N CoI: Tuila Ziliotto Universita degli Studi di Padova N CoI: Dr. Alessandra Mastrobuono Universita degli Studi di Padova N Battisti ------------------------------------------------------------------------------------ Abstract Recent JWST photometry has identified a sequence of ultracool stars in 47 Tucanae, potentially representing a population of brown dwarfs. If this hypothesis holds, the abundance of brown dwarfs would significantly exceed predictions based on a standard mass function. However, JWST's infrared capability alone is insufficient to distinguish between brown dwarfs and potential white dwarfs with debris disks. To investigate this faint stellar population further, we propose deep UVIS/WFC3 observations in the F606W filter, which is the only dataset that, combined with archival NIRCam data, allows us to examine whether stars in this color-magnitude diagram (CMD) region, traditionally linked to brown dwarfs, may also include white dwarfs with debris disks. By analyzing the distribution of stars in CMDs generated with the new F606W observations alongside archival JWST data in the F115W and F322W2 bands, we aim to test two scenarios: (1) if these stars are exclusively brown dwarfs, they will remain undetected in F606W due to their low luminosity in this band; (2) if a subset comprises white dwarfs with debris disks, these stars will follow the white dwarf cooling sequence, as debris disk flux primarily enhances F322W2 but has minimal impact on F606W and F115W. This study seeks to refine our understanding of low-mass object distributions in globular clusters and may provide new insights into planetary system remnants around white dwarfs. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose deep HST/UVIS observations in the F606W filter to study faint stellar populations specifically white dwarfs and M-dwarfs, in the Galactic globular cluster 47 Tucanae (NGC 104). 18125( 4) - 02-Dec-2025 18:53:01 - [ 2] The observations are dithered and distributed across 13 single-orbit visits to maximize scheduling flexibility within HST's constraints. The field is centered at RA = 00h 20m 58.8s, Dec = -72 -06 -30.6, in the outer regions of 47 Tucanae, and overlaps with JWST/NIRCam data collected as part of Program 2560. ------------------------------------------------------------------------------------ 18125( 4) - 02-Dec-2025 18:53:01 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-104 STELLAR CLUSTER, RA=00H20M58.3800S, J2000 V = 4.09 GLOBULAR CLUSTER DEC=-72D06'30.60" Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 2.32E-4 ------------------------------------------------------------------------------------------------------------------------------------ 18125( 4) - 02-Dec-2025 18:53:01 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 6 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 100 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18125( 4) - 02-Dec-2025 18:53:01 - [ 5] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302.0 S PATTERN 1 1 S ER (2604 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 6] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG -3, 0; PATTERN S ER (2604 S) 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 7] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG 3, 0; PATTERN 1 S ER (2604 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 8] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG 0, -3; PATTERN S ER (2604 S) 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 9] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG 0, 3; PATTERN 1 S ER (2604 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 10] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG 3, 3; PATTERN 1 S ER (2604 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 11] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG -3, -3; PATTERN S ER (2604 S) 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 12] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG -6, 0; PATTERN S ER (2604 S) 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 13] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG 0, 6; PATTERN 1 S ER (2604 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 14] 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG 0, -6; PATTERN S ER (2604 S) 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 15] Visit: 11 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG 6, 0; PATTERN 1 S ER (2604 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 16] Visit: 12 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG 6, 6; PATTERN 1 S ER (2604 S) 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 17] Visit: 13 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 NGC-104 WFC3/UVI ACCUM UVIS-CENT F606W 1 1302 S POS TARG -6, -6; PATTERN S ER (2604 S) 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 1 none none none 1 N/A S TER NGC-104 1 WFC3/UVI ACCUM UVIS-CEN F606W 2 none none none 1 N/A S TER 18125( 4) - 02-Dec-2025 18:53:01 - [ 18] Summary Form for Proposal 18125 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, POS TARG -3, -3, POS TARG -3, 0, POS TARG -6, -6, POS TARG -6, 0, POS TARG 0, -3, POS TARG 0, -6, POS TARG 0, 3, POS TARG 0, 6, POS TARG 3, 0, POS TARG 3, 3, POS TARG 6, 0, POS TARG 6, 6 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC-104 ------------------------------------------------------------------------------------------------------------------------------------