14203( 2) - 23-Jul-2015 09:40:09 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14203 Version: 2 Check-in Time: 23-Jul-2015 09:40:09 STScI Edit Number: 0 Title Confirmation of the First Ultracompact Black Hole X-ray Binary ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. James Miller-Jones Curtin University Y CoI: Prof. Christian Knigge University of Southampton N CoI: Prof. Jay Strader Michigan State University N CoI: Dr. Craig Heinke University of Alberta N CoI: Dr. Maureen van den Berg Harvard University N CoI: Dr. David R. Zurek American Museum of Natural History N CoI: Dr. Slavko Bogdanov Columbia University in the City of New N York CoI: Dr. Thomas J. Maccarone Texas Tech University N CoI: Dr. Gregory R. Sivakoff University of Alberta N CoI: Dr. Laura Chomiuk Michigan State University N ------------------------------------------------------------------------------------ Abstract We have recently detected strong, steady radio emission from the well-known X-ray source X9 in the globular cluster 47 Tuc. The level of radio emission rules out the previous interpretation of the source as a cataclysmic variable, and instead suggests that it hosts a quiescently accreting stellar-mass black hole. An existing far-UV spectrum shows shows a strong C IV 1550 emission line, but no sign of He II 1640 emission. Narrow-band HST photometry exhibits no Halpha excess (down to an equivalent width limit of >~ -10A) and Chandra X-ray observations show an unusual feature that is likely attributable to O VIII emission. All of this evidence, as well as the unusually high X-ray luminosity of the system, points to X9 being an ultracompact binary in which a stellar-mass black hole accretes material from a white dwarf -- which if confirmed would be the first such system ever discovered. Here, we request HST observations to obtain a broad-band optical spectrum of X9 to confirm or reject the ultracompact nature of the system. The resulting data will also be used to evaluate the optimal strategy for determining the system parameters, in particular the orbital period. ------------------------------------------------------------------------------------ Observations Description ------------------------ The main goal of the observations is to search for emission lines (H, He, C, and O) that will help classify the donor star in this candidate ultra-compact black hole binary. A secondary goal is to measure and model the overall SED of the binary. We will first acquire a bright (V~12.4) red giant that is 17" away and then do an offset to the main target, peaking up sing the 52x0.1E1 aperture. The target object has a nominal V~19.8 but is variable, with the faintest recorded mag at V~21.4; we have chosen a peakup exposure time as a compromise in case the object is fainter than expected, but will not saturate the detector even if 14203( 2) - 23-Jul-2015 09:40:09 - [ 2] brighter than expected. All data are taken in a single 4-orbit visit. Two orbits are used on the G430L grating and two with the G750L grating, with 3 CR-SPLITs in all but the first orbit. We have added fringe flats in occultation to the G750L exposures. To improve wavelength calibration, we have added several GO-WAVECALs around the G430L observations. ------------------------------------------------------------------------------------ 14203( 2) - 23-Jul-2015 09:40:09 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 47-TUC-X9 STAR, LMXB RA=00H24M4.2420S +/- 0.1", J2000 V = 19.8 +/- 1.5 DEC=-72D04'58.07" +/- 0.1" Reference Frame: ICRS Extended: NO Comments: Position is from an HST/ACS F606W image calibrated to ICRS using a large sample of 2MASS stars. ------------------------------------------------------------------------------------------------------------------------------------ 2 47-TUC-X9-OF STAR, K III-I RA=00H24M1.2010S +/- 0.06", J2000 V = 12.4 FSET DEC=-72D05'8.28" +/- 0.06" Reference Frame: ICRS Extended: NO Comments: Position is from an HST/ACS F606W image calibrated to ICRS using a large sample of 2MASS stars. ------------------------------------------------------------------------------------------------------------------------------------ 14203( 2) - 23-Jul-2015 09:40:09 - [ 4] 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 47-TUC-X9-O STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 0.3 S (0.3 FFSET S) ------------------------------------------------------------------------------------------------------------------------------------ 2 47-TUC-X9 STIS/CCD ACQ/PEA 52X0.1E1 MIRROR 1 100 S (100 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 47-TUC-X9 STIS/CCD ACCUM 52X0.1E1 G430L 4300 CR-SPLIT=2 1 1322 S (1322 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 WAVE STIS/CCD ACCUM 52X0.1 G430L 4300 1 DEF (0 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 47-TUC-X9 STIS/CCD ACCUM 52X0.1E1 G430L 4300 CR-SPLIT=3 1 3156 S (3156 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 WAVE STIS/CCD ACCUM 52X0.1 G430L 4300 1 DEF (0 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 47-TUC-X9 STIS/CCD ACCUM 52X0.1E1 G750L 7751 CR-SPLIT=3 1 3234 S (3234 S) ------------------------------------------------------------------------------------------------------------------------------------ 8 CCDFLAT STIS/CCD ACCUM 52X0.1 G750L 7751 2 DEF (0 S) ------------------------------------------------------------------------------------------------------------------------------------ 9 47-TUC-X9 STIS/CCD ACCUM 52X0.1E1 G750L 7751 CR-SPLIT=3 1 3153 S (3153 S) ------------------------------------------------------------------------------------------------------------------------------------ 10 CCDFLAT STIS/CCD ACCUM 52X0.1 G750L 7751 2 DEF (0 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 | ------------------------------------------------------------------------------------------------------------------------------------ 47-TUC-X9-OFFSET 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A 47-TUC-X9 2 STIS/CCD ACQ/PEA 52X0.1E1 MIRROR none none none none 1 N/A K 47-TUC-X9 3 STIS/CCD ACCUM 52X0.1E1 G430L 4300 none none none 1 1 N/A 47-TUC-X9 3 STIS/CCD ACCUM 52X0.1E1 G430L 4300 none none none 2 1 N/A WAVE 4 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none none 1 N/A 47-TUC-X9 5 STIS/CCD ACCUM 52X0.1E1 G430L 4300 none none none 1 2 N/A 47-TUC-X9 5 STIS/CCD ACCUM 52X0.1E1 G430L 4300 none none none 2 2 N/A 47-TUC-X9 5 STIS/CCD ACCUM 52X0.1E1 G430L 4300 none none none 3 2 N/A WAVE 6 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none none 2 N/A 14203( 2) - 23-Jul-2015 09:40:09 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ 47-TUC-X9 7 STIS/CCD ACCUM 52X0.1E1 G750L 7751 none none none 1 3 N/A 47-TUC-X9 7 STIS/CCD ACCUM 52X0.1E1 G750L 7751 none none none 2 3 N/A 47-TUC-X9 7 STIS/CCD ACCUM 52X0.1E1 G750L 7751 none none none 3 3 N/A CCDFLAT 8 STIS/CCD ACCUM 52X0.1 G750L 7751 none none 1 none 3 N/A CCDFLAT 8 STIS/CCD ACCUM 52X0.1 G750L 7751 none none 2 none 3 N/A 47-TUC-X9 9 STIS/CCD ACCUM 52X0.1E1 G750L 7751 none none none 1 4 N/A 47-TUC-X9 9 STIS/CCD ACCUM 52X0.1E1 G750L 7751 none none none 2 4 N/A 47-TUC-X9 9 STIS/CCD ACCUM 52X0.1E1 G750L 7751 none none none 3 4 N/A CCDFLAT 10 STIS/CCD ACCUM 52X0.1 G750L 7751 none none 1 none 4 N/A CCDFLAT 10 STIS/CCD ACCUM 52X0.1 G750L 7751 none none 2 none 4 N/A 14203( 2) - 23-Jul-2015 09:40:09 - [ 6] Summary Form for Proposal 14203 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.1, 52X0.1E1, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, CR-SPLIT=2, CR-SPLIT=3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G430L, G750L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names 47-TUC-X9, 47-TUC-X9-OFFSET, CCDFLAT, WAVE ------------------------------------------------------------------------------------------------------------------------------------