17476( 6) - 13-Jun-2024 21:20:56 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17476 Version: 6 Check-in Time: 13-Jun-2024 21:20:56 STScI Edit Number: 3 Title The most puzzling UV-optical-NIR spectrum of an isolated neutron star: A disk or a magnetosphere? ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. George G. Pavlov The Pennsylvania State University Y CoI: Dr. Bettina Posselt University of Oxford N CoI: Dr. Oleg Y. Kargaltsev George Washington University N ------------------------------------------------------------------------------------ Abstract Unlike the commonly known rotation-powered pulsars, X-ray thermal isolated neutron stars (XTINSs) do not show radio/gamma-ray emission or other signs of magnetospheric activity but emit purely thermal soft X-ray radiation. A few HST observations of these sources have shown very puzzling results, with possible contribution from neutron star magnetospheres or fallback disks, challenging the simplistic model of a purely thermal emitter. However, because most XTINSs only have HST coverage in two spectral bands, the actual spectral shape and the origin of the XTINS UV-optical-IR emission remain unknown. RX J1243.0+0654, the most intriguing XTINS, provides the best opportunity to clarify the origin of the XTINS emission. We propose photometric measurements with high S/N in five spectral bands in the wavelength range of 0.14-1.7 microns. Fits of the five flux density points with different spectral models will help to understand the nature of this and other XTINSs. Using the same observations, we will also check for long-term variability of the target in two bands and measure its (currently unknown) proper motion with an uncertainty not exceeding 2 mas/yr, much lower than expected proper motion values. This will allow us to locate the birth place of this neutron star and estimate its kinematic age. These properties are required to constrain the neutron star cooling models and learn about evolutionary links between the diverse neutron star populations. ------------------------------------------------------------------------------------ Observations Description ------------------------ To infer the shape of the UVOIR spectrum of the target neutron star and confront it with the available models, we will measure its fluxes in 5 bands. The far-UV emission will be observed in the ACS/SBC F140LP filter (two one-orbit visits). We choose two visits to minimize the effect of dark current (thermal glow) and simplify scheduling. In each orbit we will use a two-point dither line for better removal of detector blemishes and improving the PSF sampling. The starting points of the dither lines in the two orbits will be offset by 0.5 arcsec in the X and Y directions with POSTARG for better coverage. 17476( 6) - 13-Jun-2024 21:20:56 - [ 2] The near-UV observation will be carried out with the WFC3/UVIS F300X filter (one two-orbit visit). We chose the UVIS aperture UVIS2-C512C-CTE, which places our faint target near the C readout amplifier to minimize CTE losses but reads out the full detector for better astrometry. We will also mitigate CTE losses using FLASH = 13 electrons. We will use the WFC3-UVIS-DITHER-LINE-3PT in each orbit, which provides optimal 3-step sampling of the PSF and produces spacings of >1 column for removal of hot columns. The observational setup for the two-orbit visit with ACS/WFC F475W repeats that used in the program #11564. The main goals of this observation is measuring the target's proper motion and checking possible flux variabilty. This observation uses ACS-WFC-DITHER BOX in each of the two orbits. The near-IR emission of the target will be observed in two WFC3/IR filters, F110W and F160W, in one two-orbit visit. Since the F110W filter can suffer from unpredictable background variations from the He I airglow in the upper atmosphere (see WFC3/ISR 2013-03), we will sandwich the F110W exposures with F160W exposures at the beginning and end of each of the two orbits. In each orbit we will put the target in two positions, defined with POSTARG values, which provides some sampling of the PSF. We will use the readout mode SAMP-SEQ = 100, NSAMP = 12, 13 or 14 for most part of the visit, and SAMP-SEQ = 50, NSAMP = 14 for two exposures to get an optimal exposure time. We have checked the 2MASS and VLT images of this field and concluded that diffraction spikes from the sparse nearby stars would not be a problem at any ORIENT value. The HEALTH flag raised by BOT for a source at 21 43 1.5894, +06 54 26.74 (~29 arcsec from target) comes from GSC2. GALEX also lists the UV counterpart of this star (Gaia DR3 Teff=5300K) at 21 43 1.5475, +06 54 26.62 (agreement within 0.63 arcsec), but the GALEX Flag is "SAFE". Considering in addition that a similar SBC observation has already been carried out successfully, there is no BOT safety concern for any of our exposures. ------------------------------------------------------------------------------------ 17476( 6) - 13-Jun-2024 21:20:56 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 RXJ2143+0654 STAR, NEUTRON STAR RA=21H43M3.3800S, J2000 V = 27 +/- 1 DEC=+06D54'17.53" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 17476( 6) - 13-Jun-2024 21:20:56 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 5 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.2637 Line_Spacing 0.1856 Coordinate_Frame POS-TARG Pattern_Orient 20.7 Angle_Between_Sides 69.02 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 9 Primary_Pattern Secondary_Pattern Pattern_Type ACS-SBC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.472 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 44.4 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 10 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 ------------------------------------------------------------------------------------------------------------------------------------ 17476( 6) - 13-Jun-2024 21:20:56 - [ 5] Visit: 01 (fuv1) 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 RXJ2143+065 ACS/SBC ACCUM SBC F140LP 1 1305 S PATTERN 9 1 4 (2610 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 | ------------------------------------------------------------------------------------------------------------------------------------ RXJ2143+0654 1 ACS/SBC ACCUM SBC F140LP 1 none none none 1 N/A RXJ2143+0654 1 ACS/SBC ACCUM SBC F140LP 2 none none none 1 N/A 17476( 6) - 13-Jun-2024 21:20:56 - [ 6] Visit: 02 (nuv) 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 RXJ2143+065 WFC3/UVI ACCUM UVIS2-C51 F300X FLASH=13 1 821 S PATTERN 10 1-2 4 S 2C-CTE (2463 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 RXJ2143+065 WFC3/UVI ACCUM UVIS2-C51 F300X FLASH=13 1 821 S 4 S 2C-CTE (2463 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 | ------------------------------------------------------------------------------------------------------------------------------------ RXJ2143+0654 1 WFC3/UVI ACCUM UVIS2-C5 F300X 1 none none none 1 N/A S 12C-CTE RXJ2143+0654 1 WFC3/UVI ACCUM UVIS2-C5 F300X 2 none none none 1 N/A S 12C-CTE RXJ2143+0654 1 WFC3/UVI ACCUM UVIS2-C5 F300X 3 none none none 2 N/A S 12C-CTE RXJ2143+0654 2 WFC3/UVI ACCUM UVIS2-C5 F300X 1 none none none 1 N/A S 12C-CTE RXJ2143+0654 2 WFC3/UVI ACCUM UVIS2-C5 F300X 2 none none none 2 N/A S 12C-CTE RXJ2143+0654 2 WFC3/UVI ACCUM UVIS2-C5 F300X 3 none none none 2 N/A S 12C-CTE 17476( 6) - 13-Jun-2024 21:20:56 - [ 7] Visit: 03 (blue) 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 RXJ2143+065 ACS/WFC ACCUM WFC1 F475W 1 514 S PATTERN 5 1 4 (2056 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 RXJ2143+065 ACS/WFC ACCUM WFC1 F475W 1 532 S POS TARG 0.5, 0.5; 4 (2128 S) PATTERN 5 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 | ------------------------------------------------------------------------------------------------------------------------------------ RXJ2143+0654 1 ACS/WFC ACCUM WFC1 F475W 1 none none none 1 N/A RXJ2143+0654 1 ACS/WFC ACCUM WFC1 F475W 2 none none none 1 N/A RXJ2143+0654 1 ACS/WFC ACCUM WFC1 F475W 3 none none none 1 N/A RXJ2143+0654 1 ACS/WFC ACCUM WFC1 F475W 4 none none none 1 N/A RXJ2143+0654 2 ACS/WFC ACCUM WFC1 F475W 1 none none none 2 N/A RXJ2143+0654 2 ACS/WFC ACCUM WFC1 F475W 2 none none none 2 N/A RXJ2143+0654 2 ACS/WFC ACCUM WFC1 F475W 3 none none none 2 N/A RXJ2143+0654 2 ACS/WFC ACCUM WFC1 F475W 4 none none none 2 N/A 17476( 6) - 13-Jun-2024 21:20:56 - [ 8] Visit: 04 (nir) 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 RXJ2143+065 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP100, NSAMP=13 1 DEF POS TARG 0, 0 4 CUM (699.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 RXJ2143+065 WFC3/IR MULTIAC IR F110W NSAMP=13, SAMP-SEQ=STEP100 1 DEF POS TARG 0, 0 4 CUM (699.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 RXJ2143+065 WFC3/IR MULTIAC IR F110W NSAMP=14, SAMP-SEQ=STEP50 1 DEF POS TARG 0.542, 0.182 4 CUM (449.234 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 RXJ2143+065 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP100, NSAMP=12 1 DEF POS TARG 0.542, 0.182 4 CUM (599.232 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 RXJ2143+065 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP100, NSAMP=14 1 DEF POS TARG 0.339, 0.485 4 CUM (799.233 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 RXJ2143+065 WFC3/IR MULTIAC IR F110W NSAMP=12, SAMP-SEQ=STEP100 1 DEF POS TARG 0.339, 0.485 4 CUM (599.232 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 RXJ2143+065 WFC3/IR MULTIAC IR F110W NSAMP=12, SAMP-SEQ=STEP100 1 DEF POS TARG -0.203, 0.303 4 CUM (599.232 S) ------------------------------------------------------------------------------------------------------------------------------------ 8 RXJ2143+065 WFC3/IR MULTIAC IR F160W SAMP-SEQ=STEP50, NSAMP=13 1 DEF POS TARG -0.203, 0.303 4 CUM (399.233 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 | ------------------------------------------------------------------------------------------------------------------------------------ RXJ2143+0654 1 WFC3/IR MULTIAC IR F160W none none none none 1 N/A CUM RXJ2143+0654 2 WFC3/IR MULTIAC IR F110W none none none none 1 N/A CUM 17476( 6) - 13-Jun-2024 21:20:56 - [ 9] 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 | ------------------------------------------------------------------------------------------------------------------------------------ RXJ2143+0654 3 WFC3/IR MULTIAC IR F110W none none none none 1 N/A CUM RXJ2143+0654 4 WFC3/IR MULTIAC IR F160W none none none none 1 N/A CUM RXJ2143+0654 5 WFC3/IR MULTIAC IR F160W none none none none 2 N/A CUM RXJ2143+0654 6 WFC3/IR MULTIAC IR F110W none none none none 2 N/A CUM RXJ2143+0654 7 WFC3/IR MULTIAC IR F110W none none none none 2 N/A CUM RXJ2143+0654 8 WFC3/IR MULTIAC IR F160W none none none none 2 N/A CUM 17476( 6) - 13-Jun-2024 21:20:56 - [ 10] Visit: 05 (fuv2) 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 RXJ2143+065 ACS/SBC ACCUM SBC F140LP 1 1305 S POS TARG 0.5, 0.5; 4 see below PATTERN 9 1 (2488 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 | ------------------------------------------------------------------------------------------------------------------------------------ RXJ2143+0654 1 ACS/SBC ACCUM SBC F140LP 1 none none none 1 1244.0 S RXJ2143+0654 1 ACS/SBC ACCUM SBC F140LP 2 none none none 1 1244.0 S 17476( 6) - 13-Jun-2024 21:20:56 - [ 11] Summary Form for Proposal 17476 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, SBC, UVIS2-C512C-CTE, WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/SBC, ACS/WFC, WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=13, NSAMP=12, NSAMP=13, NSAMP=14, SAMP-SEQ=STEP100, SAMP-SEQ=STEP50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 10 1-2, PATTERN 5 1, PATTERN 5 2, PATTERN 9 1, POS TARG -0.203, 0.303, POS TARG 0, 0, POS TARG 0.339, 0.485, POS TARG 0.5, 0.5, POS TARG 0.542, 0.182 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W, F140LP, F160W, F300X, F475W ------------------------------------------------------------------------------------------------------------------------------------ Target Names RXJ2143+0654 ------------------------------------------------------------------------------------------------------------------------------------