14061( 4) - 05-Apr-2015 09:56:18 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14061 Version: 4 Check-in Time: 05-Apr-2015 09:56:18 STScI Edit Number: 0 Title Exploring the MSP prenatal stage: the optical identification of a NS burster in Terzan 5. ------------------------------------------------------------------------------------ Type Cycle GO/DD 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Francesco R. Ferraro Universita di Bologna Y CoI: Dr. Cristina Pallanca Universita di Bologna N CoI: Mr. Mario Cadelano Universita di Bologna N CoI: Dr. Barbara Lanzoni Universita di Bologna N CoI: Dr. Emanuele Dalessandro Universita di Bologna N CoI: Dr. Alessio Mucciarelli Universita di Bologna N ------------------------------------------------------------------------------------ Abstract Low mass X-ray binaries (LMXBs) and radio Millisecond Pulsars (MSPs) are thought to be the initial and ending points of the evolution of a binary system where a neutron star accretes matter from a companion. Many crucial phases of this scenario still need to be understood. For instance, Papitto et al. (2013, Nature, 501, 517) provided the first evidence of a system currently swinging between the X-ray and the radio emission states, thus showing that an intermediate phase marks the transition from a LMXB to a MSP. The X-ray properties of that object closely resemble those of EXO 1745-248, a transient LMXB located in Terzan 5, which therefore promises to be another system marking the LMXB-MSP transition. On March 13, 2015, SWIFT detected an X-ray burst in Terzan 5 at a location that may be consistent with the coordinates of EXO 1745-248. However, the error circle is still too large (2"-3") to exclude other possibilities. Since the thermonuclear burning runway at the origin of the X-ray burst is expected to produce also a significant enhancement of the optical luminosity, here we propose to invest 2 HST orbits to acquire deep optical images of the region. The comparison between these images (secured during the outburst) and those already available (acquired during quiescence) will immediately pinpoint the source, thus offering a unique opportunity to identify the object, determine precisely its coordinates and possibly confirm its association to EXO 1745-248. The optical emission is expected to fade by ~1mag after 1-2 months from the burst. Hence, the proposed DDT observations represent indeed a unique but temporary opportunity to catch a MSP in its pre-birth phase. ------------------------------------------------------------------------------------ Observations Description ------------------------ The observations are organized in one visit of 2 orbits. In each orbit we require one short exposure (10 sec in F814W and 50 sec in F606W) and 5 long exposures (~372 sec in F814W and ~398 sec in F606W). Dithering is performed by applying small offsets (via POS TARG keyword) to each exposure, adopting a path similar to that used in GO 12933. For each orbit we also planned two parallel WFC3-UVIS exposures (with F814W in the first orbit and F606W in the second orbit). In order to duplicate the field of view of previous observations (Prop 14061( 4) - 05-Apr-2015 09:56:18 - [ 2] GO9799-PI Rich and GO12933-PI Ferraro), we adopted the WFC2 aperture and a proper ORENTATION (ORIENT 271.075287D). Note that, according to the Visit Planner, the required ORIENTATION has little impact on the observations schedulability. We emphasize that, beacuse of the transient nature of the target, the observations need to be performed as soon as possible, nominally before May 31 2015 (see Timing Requirements). However, according to the Visit Planner, one visit of 2 full orbits on the target (Terzan 5) can be executed only between April 10 and April 27, 2015 (independently of the ORIENTATION). ------------------------------------------------------------------------------------ 14061( 4) - 05-Apr-2015 09:56:18 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 TERZAN5-ACS STELLAR CLUSTER, RA=17H48M4.8500S, J2000 V = 13.8 GLOBULAR CLUSTER DEC=-24D46'44.60" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 14061( 4) - 05-Apr-2015 09:56:18 - [ 4] Visit: 01 Visit Requirements: ORIENT 271.075287D TO 271.075287 D; BEFORE 31-MAY-2015:00:00:00 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 TERZAN5-ACS ACS/WFC ACCUM WFC2 F814W FLASH=20 1 10 S (10 POS TARG 0.000, 0.000 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 TERZAN5-ACS ACS/WFC ACCUM WFC2 F814W 1 372 S (372 POS TARG 0.000, 0.000; S) PAR 3 WITH 2 ------------------------------------------------------------------------------------------------------------------------------------ 3 ANY WFC3/UVI ACCUM UVIS1 F814W 1 370 S (370 S S) ------------------------------------------------------------------------------------------------------------------------------------ 4 TERZAN5-ACS ACS/WFC ACCUM WFC2 F814W 1 371 S (371 POS TARG 0.247, 0.094 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 TERZAN5-ACS ACS/WFC ACCUM WFC2 F814W 1 371 S (371 POS TARG 0.124, 0.232 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 TERZAN5-ACS ACS/WFC ACCUM WFC2 F814W 1 371 S (371 POS TARG -0.124, 0.138 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 TERZAN5-ACS ACS/WFC ACCUM WFC2 F814W 1 372 S (372 POS TARG 0.062, 0.116; S) PAR 8 WITH 7 ------------------------------------------------------------------------------------------------------------------------------------ 8 ANY WFC3/UVI ACCUM UVIS1 F814W 1 467 S (467 S S) ------------------------------------------------------------------------------------------------------------------------------------ 9 TERZAN5-ACS ACS/WFC ACCUM WFC2 F606W FLASH=20 1 50 S (50 POS TARG 0.000, 0.000 S) ------------------------------------------------------------------------------------------------------------------------------------ 10 TERZAN5-ACS ACS/WFC ACCUM WFC2 F606W 1 398 S (398 POS TARG 0.000, 0.000; S) PAR 11 WITH 10 ------------------------------------------------------------------------------------------------------------------------------------ 11 ANY WFC3/UVI ACCUM UVIS1 F606W 1 405 S (405 S S) ------------------------------------------------------------------------------------------------------------------------------------ 12 TERZAN5-ACS ACS/WFC ACCUM WFC2 F606W 1 397 S (397 POS TARG 0.247, 0.094 S) ------------------------------------------------------------------------------------------------------------------------------------ 13 TERZAN5-ACS ACS/WFC ACCUM WFC2 F606W 1 397 S (397 POS TARG 0.124, 0.232 S) ------------------------------------------------------------------------------------------------------------------------------------ 14 TERZAN5-ACS ACS/WFC ACCUM WFC2 F606W 1 397 S (397 POS TARG -0.124, 0.138 S) ------------------------------------------------------------------------------------------------------------------------------------ 14061( 4) - 05-Apr-2015 09:56:18 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 15 TERZAN5-ACS ACS/WFC ACCUM WFC2 F606W 1 398 S (398 POS TARG 0.062, 0.116; S) PAR 16 WITH 15 ------------------------------------------------------------------------------------------------------------------------------------ 16 ANY WFC3/UVI ACCUM UVIS1 F606W 1 502 S (502 S 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 | ------------------------------------------------------------------------------------------------------------------------------------ TERZAN5-ACS 1 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A TERZAN5-ACS 2 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A ANY 3 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S TERZAN5-ACS 4 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A TERZAN5-ACS 5 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A TERZAN5-ACS 6 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A TERZAN5-ACS 7 ACS/WFC ACCUM WFC2 F814W none none none none 1 N/A ANY 8 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S TERZAN5-ACS 9 ACS/WFC ACCUM WFC2 F606W none none none none 2 N/A TERZAN5-ACS 10 ACS/WFC ACCUM WFC2 F606W none none none none 2 N/A ANY 11 WFC3/UVI ACCUM UVIS1 F606W none none none none 2 N/A S TERZAN5-ACS 12 ACS/WFC ACCUM WFC2 F606W none none none none 2 N/A TERZAN5-ACS 13 ACS/WFC ACCUM WFC2 F606W none none none none 2 N/A TERZAN5-ACS 14 ACS/WFC ACCUM WFC2 F606W none none none none 2 N/A TERZAN5-ACS 15 ACS/WFC ACCUM WFC2 F606W none none none none 2 N/A ANY 16 WFC3/UVI ACCUM UVIS1 F606W none none none none 2 N/A S 14061( 4) - 05-Apr-2015 09:56:18 - [ 6] Summary Form for Proposal 14061 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, WFC2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=20 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 31-MAY-2015:00:00:00, ORIENT 271.075287D TO 271.075287 D, PAR 11 WITH 10, PAR 16 WITH 15, PAR 3 WITH 2, PAR 8 WITH 7, POS TARG -0.124, 0.138, POS TARG 0.000, 0.000, POS TARG 0.062, 0.116, POS TARG 0.124, 0.232, POS TARG 0.247, 0.094 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ANY, TERZAN5-ACS ------------------------------------------------------------------------------------------------------------------------------------