15403( 2) - 17-Oct-2017 13:22:59 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15403 Version: 2 Check-in Time: 17-Oct-2017 13:22:59 STScI Edit Number: 0 Title Unmask the true identity of MAXI J1749-200 before Halloween ------------------------------------------------------------------------------------ Type Cycle GO/DD 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Cristina Pallanca Universita di Bologna Y CoI: Prof. Francesco R. Ferraro Universita di Bologna N CoI: Dr. Barbara Lanzoni Universita di Bologna N CoI: Mr. Mario Cadelano 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 (NS) accretes matter from a companion. Many crucial phases of this scenario still need to be understood and a new, unexpected tile has been added to the mosaic very recently: a few systems (named "transitional MSPs") are observed to swing between the accretion-powered and the rotation-powered states. The case of the X-ray burster MAXI J1749-200 in the globular cluster NGC 6440 can act the part of the (still unexplored) stage immediately preceding the swinging phase. Swift observations located the source with an uncertainty of 3.5" and suggest a positional coincidence with two previously known x-ray sources, among which SAX J1748.9-2021, an already known X-ray accreting Millisecond pulsar. Since the X-ray bursts are expected to be accompanied by a significant enhancement of the optical luminosity, here we propose to invest only 2 HST orbits to acquire multi-filter images of the region. The comparison between these data (secured during the outburst) and those already available in the archive (acquired during quiescence) will immediately pinpoint the source, allowing to identify the companion to the NS and to characterize the nature of the on-going mass-transfer. The optical emission is expected to fade away in a time-scale of 1-2 months after the X-ray burst. Hence, the proposed DDT observations represent a unique but temporary opportunity to unveil the nature of this possibly new X-ray transient ------------------------------------------------------------------------------------ Observations Description ------------------------ Observations are organized in 1 visit of 2 orbits. In each orbit 2 long exposures in the optical filters F606W and F814W and 2 long exposures in the narrow filter F656N are planned. Dithering is performed by applying small offsets (via POS TARG keyword) to each exposure using a path already tested in the past. The target is located at the aperture UVIS1; with this configuration we are also able to sample the entire cluster core. We also added proper post-flashes when necessary. ------------------------------------------------------------------------------------ 15403( 2) - 17-Oct-2017 13:22:59 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 MAXIJ1749-20 STAR, ACCRETION DISK, RA=17H48M52.3400S, J2000 V = 21 0 INTERACTING BINARY, DEC=-20D21'32.20" NEUTRON STAR, PULSAR, X-RAY TRANSIENT Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 15403( 2) - 17-Oct-2017 13:22:59 - [ 3] 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 MAXIJ1749-2 WFC3/UVI ACCUM UVIS1 F606W 1 382 S (382 00 S S) ------------------------------------------------------------------------------------------------------------------------------------ 2 MAXIJ1749-2 WFC3/UVI ACCUM UVIS1 F656N FLASH=12 1 914 S (914 SAME POS AS 1 00 S S) ------------------------------------------------------------------------------------------------------------------------------------ 3 MAXIJ1749-2 WFC3/UVI ACCUM UVIS1 F656N FLASH=12 1 914 S (914 POS TARG -0.099, -0.165 00 S S) ------------------------------------------------------------------------------------------------------------------------------------ 4 MAXIJ1749-2 WFC3/UVI ACCUM UVIS1 F814W FLASH=6 1 222 S (222 SAME POS AS 3 00 S S) ------------------------------------------------------------------------------------------------------------------------------------ 5 MAXIJ1749-2 WFC3/UVI ACCUM UVIS1 F606W 1 382 S (382 POS TARG 0.059, -0.095 00 S S) ------------------------------------------------------------------------------------------------------------------------------------ 6 MAXIJ1749-2 WFC3/UVI ACCUM UVIS1 F656N FLASH=12 1 969 S (969 SAME POS AS 5 00 S S) ------------------------------------------------------------------------------------------------------------------------------------ 7 MAXIJ1749-2 WFC3/UVI ACCUM UVIS1 F656N FLASH=12 1 969 S (969 POS TARG 0.218, -0.024 00 S S) ------------------------------------------------------------------------------------------------------------------------------------ 8 MAXIJ1749-2 WFC3/UVI ACCUM UVIS1 F814W FLASH=6 1 223 S (223 SAME POS AS 7 00 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 | ------------------------------------------------------------------------------------------------------------------------------------ MAXIJ1749-200 1 WFC3/UVI ACCUM UVIS1 F606W none none none none 1 N/A S MAXIJ1749-200 2 WFC3/UVI ACCUM UVIS1 F656N none none none none 1 N/A S MAXIJ1749-200 3 WFC3/UVI ACCUM UVIS1 F656N none none none none 1 N/A S MAXIJ1749-200 4 WFC3/UVI ACCUM UVIS1 F814W none none none none 1 N/A S MAXIJ1749-200 5 WFC3/UVI ACCUM UVIS1 F606W none none none none 2 N/A S MAXIJ1749-200 6 WFC3/UVI ACCUM UVIS1 F656N none none none none 2 N/A S 15403( 2) - 17-Oct-2017 13:22:59 - [ 4] 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 | ------------------------------------------------------------------------------------------------------------------------------------ MAXIJ1749-200 7 WFC3/UVI ACCUM UVIS1 F656N none none none none 2 N/A S MAXIJ1749-200 8 WFC3/UVI ACCUM UVIS1 F814W none none none none 2 N/A S 15403( 2) - 17-Oct-2017 13:22:59 - [ 5] Summary Form for Proposal 15403 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=12, FLASH=6 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG -0.099, -0.165, POS TARG 0.059, -0.095, POS TARG 0.218, -0.024, SAME POS AS 1, SAME POS AS 3, SAME POS AS 5, SAME POS AS 7 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F656N, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names MAXIJ1749-200 ------------------------------------------------------------------------------------------------------------------------------------