13642( 2) - 18-Jul-2014 13:58:33 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13642 Version: 2 Check-in Time: 18-Jul-2014 13:58:33 STScI Edit Number: 0 Title The evolutionary link between low-mass X-ray binaries and millisecond radio pulsars ------------------------------------------------------------------------------------ Type Cycle GO 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Nathalie Degenaar University of Michigan Y CoI: Dr. Jon Matthew Miller University of Michigan N CoI: Dr. Rudy Wijnands Universiteit van Amsterdam N CoI: Dr. Diego Altamirano University of Southampton N CoI: Prof. Christian Knigge University of Southampton N CoI: Dr. Adam Hill Southampton University N ------------------------------------------------------------------------------------ Abstract Low-mass X-ray binaries (LMXBs) and millisecond radio pulsars (MSRPs) are two different manifestations of neutron stars in binary systems. They are thought to be evolutionary linked, but many questions about their connection remain. Recent discoveries have opened up a new vista to investigate the LMXB/MSRP link. The neutron star XSS J12270-4859 was recently observed to switch between the two different manifestations. Here, we propose to exploit the unique UV capabilities of the HST to search for the presence of a quiescent accretion disk and to test if the neutron star is hot. This will give insight into its accretion history and the mechanism driving its metamorphosis, which will have direct implications for our understanding of the LMXB/MSRP evolutionary link. ------------------------------------------------------------------------------------ Observations Description ------------------------ Detecting a quiescent accretion disk or a hot neutron star in our target requires observations in the NUV/FUV bands. Observations with the Swift/UVOT (during the current MSRP state) are not sensitive enough to detect the source in the NUV: uvw1 > 19.7 mag (lambda_c~2600 A), uvm2 > 19.7 mag (lambda_c~2246 A), and uvw2 > 20.2 mag (lambda_c~1928 A). This corresponds to NUV fluxes of <5E-17 erg/cm2/s/A, which is well above that expected for a quiescent accretion disk or a hot neutron star (~1-5E-18 erg/cm2/s/A). Our science goals therefore require the unprecedented UV sensitivity of the HST. Given the unknown NUV/FUV magnitude of our target, we propose HST imaging observations. To be able to determine the shape of the UV spectral energy distribution and to measure UV colors, we request observations using different NUV/FUV filters. To achieve the best sensitivity (our target is not in a crowded field), we chose the WFC3/UVIS for the NUV, and the ACS/SBC for the FUV. For the WFC3/UVIS we will use 3 filters: F218W (lambda_c~2224 A), F225W (lambda_c~2359 A), and F275W (lambda_c~2704 A), and for the ACS/SBC we use 1 filter: F150LP (lambda_c~1500 A). We used the online WFC3/UVIS and ACS/SBC exposure time calculators (v. 22.2). The distance to our target is 3.6 kpc, and the reddening is E(B-V)=0.577. 13642( 2) - 18-Jul-2014 13:58:33 - [ 2] Detecting a hot neutron star poses the strongest constraints on the science exposures. We assumed a black body of ~3.5E5 K (corresponding to the lowest neutron star temperatures in LMXBs), which yields a flux of ~1E-18 (NUV) and ~1.5E-18 erg/cm2/s/A (FUV). We aim for a SNR>10 at these fluxes. For a remnant accretion disk we expect a higher flux (a black body with a temperature of ~1E4 K, or a luminosity of ~8E30 erg/s, the coldest detected in quiescent LMXBs, would lead to FUV/NUV fluxes of ~5E-18 erg/cm2/s/A), and hence a higher SNR. We used dither patterns for all science observations and for the WFC2/UVIS exposure time calculation we took into account lamp flashes to ensure that the minimum background for proper CTE is reached. Some of the required UVIS exposures were >3600 s, which we then split into two. We require 2 orbits of ACS/SBC observations, and 4 orbits of WFC3/UVIS observations, together totalling 6 orbits. These are combined into a single visit. ------------------------------------------------------------------------------------ 13642( 2) - 18-Jul-2014 13:58:33 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 XSSJ12270-48 STAR, LMXB, NEUTRON RA=12H27M58.7480S +/- 0.1", J2000 V = 18 59 STAR, PULSAR DEC=-48D53'42.88" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 13642( 2) - 18-Jul-2014 13:58:33 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type ACS-SBC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.472 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 44.4 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 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 ------------------------------------------------------------------------------------------------------------------------------------ 13642( 2) - 18-Jul-2014 13:58:33 - [ 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 XSSJ12270-4 ACS/SBC ACCUM SBC F150LP 2 965 S PATTERN 2 1 859 see below (5838 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 | ------------------------------------------------------------------------------------------------------------------------------------ XSSJ12270-4859 1 ACS/SBC ACCUM SBC F150LP 1 none 1 none 1 948.0 S XSSJ12270-4859 1 ACS/SBC ACCUM SBC F150LP 1 none 2 none 1 948.0 S XSSJ12270-4859 1 ACS/SBC ACCUM SBC F150LP 2 none 1 none 1 948.0 S XSSJ12270-4859 1 ACS/SBC ACCUM SBC F150LP 2 none 2 none 2 998.0 S XSSJ12270-4859 1 ACS/SBC ACCUM SBC F150LP 3 none 1 none 2 998.0 S XSSJ12270-4859 1 ACS/SBC ACCUM SBC F150LP 3 none 2 none 2 998.0 S 13642( 2) - 18-Jul-2014 13:58:33 - [ 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 XSSJ12270-4 WFC3/UVI ACCUM UVIS F218W FLASH=4 2 650 S PATTERN 3 1 859 S see below (6436 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 XSSJ12270-4 WFC3/UVI ACCUM UVIS F225W FLASH=7 1 534.5 S PATTERN 3 2 859 S see below (2342 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 XSSJ12270-4 WFC3/UVI ACCUM UVIS F275W FLASH=8 1 476.5 S PATTERN 3 3 859 S see below (1980 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 | ------------------------------------------------------------------------------------------------------------------------------------ XSSJ12270-4859 1 WFC3/UVI ACCUM UVIS F218W 1 none 1 none 1 655.0 S S XSSJ12270-4859 1 WFC3/UVI ACCUM UVIS F218W 1 none 2 none 1 655.0 S S XSSJ12270-4859 1 WFC3/UVI ACCUM UVIS F218W 2 none 1 none 1 655.0 S S XSSJ12270-4859 1 WFC3/UVI ACCUM UVIS F218W 2 none 2 none 1 655.0 S S XSSJ12270-4859 1 WFC3/UVI ACCUM UVIS F218W 3 none 1 none 2 954.0 S S XSSJ12270-4859 1 WFC3/UVI ACCUM UVIS F218W 3 none 2 none 2 954.0 S S XSSJ12270-4859 1 WFC3/UVI ACCUM UVIS F218W 4 none 1 none 2 954.0 S S XSSJ12270-4859 1 WFC3/UVI ACCUM UVIS F218W 4 none 2 none 3 954.0 S S XSSJ12270-4859 2 WFC3/UVI ACCUM UVIS F225W 1 none none none 3 585.5 S S XSSJ12270-4859 2 WFC3/UVI ACCUM UVIS F225W 2 none none none 3 585.5 S S XSSJ12270-4859 2 WFC3/UVI ACCUM UVIS F225W 3 none none none 3 585.5 S S XSSJ12270-4859 2 WFC3/UVI ACCUM UVIS F225W 4 none none none 4 585.5 S S 13642( 2) - 18-Jul-2014 13:58:33 - [ 7] 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 | ------------------------------------------------------------------------------------------------------------------------------------ XSSJ12270-4859 3 WFC3/UVI ACCUM UVIS F275W 1 none none none 4 495 S S XSSJ12270-4859 3 WFC3/UVI ACCUM UVIS F275W 2 none none none 4 495 S S XSSJ12270-4859 3 WFC3/UVI ACCUM UVIS F275W 3 none none none 4 495 S S XSSJ12270-4859 3 WFC3/UVI ACCUM UVIS F275W 4 none none none 4 495 S S 13642( 2) - 18-Jul-2014 13:58:33 - [ 8] Summary Form for Proposal 13642 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures SBC, UVIS ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/SBC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=4, FLASH=7, FLASH=8 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 2 1, PATTERN 3 1, PATTERN 3 2, PATTERN 3 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F150LP, F218W, F225W, F275W ------------------------------------------------------------------------------------------------------------------------------------ Target Names XSSJ12270-4859 ------------------------------------------------------------------------------------------------------------------------------------