13394( 3) - 14-May-2014 11:02:18 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13394 Version: 3 Check-in Time: 14-May-2014 11:02:18 STScI Edit Number: 1 Title Spectroscopic confirmation of the first symbiotic star in a globular cluster ------------------------------------------------------------------------------------ Type Cycle GO 21 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. David R. Zurek American Museum of Natural History Y CoI: Prof. Christian Knigge University of Southampton N CoI: Dr. Thomas J. Maccarone Texas Tech University N CoI: Dr. Michael Shara American Museum of Natural History N CoI: Dr. Andrea Dieball University of Southampton N CoI: Dr. Knox S. Long Space Telescope Science Institute N CoI: Dr. David A. Pooley Eureka Scientific Inc. N ------------------------------------------------------------------------------------ Abstract We have recently discovered an 18-minute period in the ultraviolet of a star in the globular cluster NGC 1851. In the redder optical bands, this star is red and bright, while it shows a clear UV excess relative to other stars at similar positions in the HR diagram. The system is most likely a symbiotic binary, composed of a cool evolved star and a white dwarf, with an 18 minute spin period, accreting the cool star's wind. The binary would be the first such object ever found in a globular cluster, and only the third in the Galaxy where the white dwarf spin period is measured. The only viable alternatives are that the two components are a chance superposition -- something with a nontrivial chance of happening in a globular cluster core. In such a case, the 18 minute period would most likely be the spin period of a magnetic white dwarf in an intermediate polar cataclysmic variable (this would be the first confirmed magnetic CV in a globular cluster), or the orbital period of a double-degenerate AM CVn binary. Each of these three possibilities show unique (and very different) emission line spectra in the blue wavelength range. Two orbits of HST with STIS/G430L will produce a spectrum of sufficient signal-to-noise to distinguish between these 3 scenarios. The result will be an important constraint on N-body models of globular clusters. ------------------------------------------------------------------------------------ Observations Description ------------------------ The cluster center where our target star is located is extremely crowded and would make acquiring and peaking up extremely difficult. In order to alleviate this difficulty we will acquire and peak up on a red giant located to the south and east of our target star out side the most crowded region. We will then move to a second red giant which is closer to our target (about half the distance) and peak up on this second red giant before moving to our target star. Our target star is located right in the cluster core. Once we have moved to our target star we will expose using the grating G430L for the rest of the time. The positions for the two red giants and our target star have been determined using the reference image J9L910010 from proposal 10775 (PI: Sarajedini). Real Time Justification 13394( 3) - 14-May-2014 11:02:18 - [ 2] ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 13394( 3) - 14-May-2014 11:02:18 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1851-OFFS STAR, M V-IV RA=05H14M7.0100S, J2000 V = 13.0 +/- 0.1 ET1 DEC=-40D02'58.70" Reference Frame: ICRS Comments: This is a red giant located to the south and east of our target. This is using the data from proposal 10775 ACS/WFC imaging (J9L910010). ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC1851-OFFS STAR, M V-IV RA=05H14M6.3610S, J2000 V = 13.0 +/- 0.1 ET2 DEC=-40D02'53.67" Reference Frame: ICRS Comments: This is a second red giant star located closer to the target star. It is slightly to the south and west of our target. The position is determined from the proposal 10775 ACS/WFC imaging (J9L910010). ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC1851-FUV1 STAR, ACCRETION DISK, RA=05H14M6.5730S, J2000 V = 16.0 +/- 0.1 COMPOSITE SPECTRAL DEC=-40D02'49.85" TYPE, INTERACTING BINARY, SYMBIOTIC STAR Reference Frame: ICRS Comments: This is our target star. It is located slightly north and west of the red giant. It is located right in the center of the cluster and is thus extremely hard to peak up on. The position is determined from the proposal 10775 ACS/WFC imaging (J9L910010). ------------------------------------------------------------------------------------------------------------------------------------ 13394( 3) - 14-May-2014 11:02:18 - [ 4] Visit: 01 Visit Requirements: PCS MODE FINE 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 NGC1851-OFF STIS/CCD ACQ F25ND3 MIRROR 1 2.6 S (2.6 SET1 S) Comments: This is the first red giant located south and slightly to the east of our target. We will acquire and peak up on this star. It's magnitude is about 13.0 and is one of the brightest red giants in this part of the cluster. The cluster core, where our target is, is too crowded and acquisition is not possible. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC1851-OFF STIS/CCD ACQ/PEA 52X0.1 MIRROR 1 1 S (1 S) SET1 K Comments: This is the first red giant located south and slightly to the east of our target. We will acquire and peak up on this star. It's magnitude is about 13.0 and is one of the brightest red giants in this part of the cluster. The cluster core, where our target is, is too crowded and acquisition is not possible. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC1851-OFF STIS/CCD ACQ/PEA 52X0.1 MIRROR 1 1 S (1 S) SET2 K Comments: This is a second red giant which is closer to our target. It is located to the south and slightly to the west of our target. We will preform a peak up on this red giant and then proceed to our target star. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC1851-FUV STIS/CCD ACCUM 52X0.1 G430L 4300 1 600 S (600 1 S) Comments: We wish to obtain a series of spectra with a signal-to-noise of about 30 in the continuum within each spectrum. This works out to about a 600 seconds. We will continue to take spectra of this length for the rest of the visit. ------------------------------------------------------------------------------------------------------------------------------------ 13394( 3) - 14-May-2014 11:02:18 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC1851-FUV STIS/CCD ACCUM 52X0.1 G430L 4300 1 600 S (600 1 S) Comments: We wish to obtain a series of spectra with a signal-to-noise of about 30 in the continuum within each spectrum. This works out to about a 600 seconds. We will continue to take spectra of this length for the rest of the visit. ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC1851-FUV STIS/CCD ACCUM 52X0.1 G430L 4300 1 550 S (550 1 S) Comments: We wish to obtain a series of spectra with a signal-to-noise of about 30 in the continuum within each spectrum. This works out to about a 600 seconds. We will continue to take spectra of this length for the rest of the visit. Note: this exposure has been adjusted to fill the orbit. ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC1851-FUV STIS/CCD ACCUM 52X0.1 G430L 4300 1 660 S (660 1 S) Comments: We wish to obtain a series of spectra with a signal-to-noise of about 30 in the continuum within each spectrum. This works out to about a 600 seconds. We will continue to take spectra of this length for the rest of the visit. We adjusted the exposure time to 660 seconds to fill the orbit better. ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC1851-FUV STIS/CCD ACCUM 52X0.1 G430L 4300 1 660 S (660 1 S) Comments: We wish to obtain a series of spectra with a signal-to-noise of about 30 in the continuum within each spectrum. This works out to about a 600 seconds. We will continue to take spectra of this length for the rest of the visit. We adjusted the exposure time to 660 seconds to fill the orbit better. ------------------------------------------------------------------------------------------------------------------------------------ 13394( 3) - 14-May-2014 11:02:18 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC1851-FUV STIS/CCD ACCUM 52X0.1 G430L 4300 1 660 S (660 1 S) Comments: We wish to obtain a series of spectra with a signal-to-noise of about 30 in the continuum within each spectrum. This works out to about a 600 seconds. We will continue to take spectra of this length for the rest of the visit. We adjusted the exposure time to 660 seconds to fill the orbit better. ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1851-FUV STIS/CCD ACCUM 52X0.1 G430L 4300 1 660 S (660 1 S) Comments: We wish to obtain a series of spectra with a signal-to-noise of about 30 in the continuum within each spectrum. This works out to about a 600 seconds. We will continue to take spectra of this length for the rest of the visit. We adjusted the exposure time to 660 seconds to fill the orbit better. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC1851-OFFSET1 1 STIS/CCD ACQ F25ND3 MIRROR none none none none 1 N/A NGC1851-OFFSET1 2 STIS/CCD ACQ/PEA 52X0.1 MIRROR none none none none 1 N/A K NGC1851-OFFSET2 3 STIS/CCD ACQ/PEA 52X0.1 MIRROR none none none none 1 N/A K NGC1851-FUV1 4 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 1 1 N/A NGC1851-FUV1 4 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 2 1 N/A NGC1851-FUV1 5 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 1 1 N/A NGC1851-FUV1 5 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 2 1 N/A NGC1851-FUV1 6 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 1 1 N/A NGC1851-FUV1 6 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 2 1 N/A NGC1851-FUV1 7 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 1 2 N/A NGC1851-FUV1 7 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 2 2 N/A NGC1851-FUV1 8 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 1 2 N/A NGC1851-FUV1 8 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 2 2 N/A NGC1851-FUV1 9 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 1 2 N/A NGC1851-FUV1 9 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 2 2 N/A 13394( 3) - 14-May-2014 11:02:18 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC1851-FUV1 10 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 1 2 N/A NGC1851-FUV1 10 STIS/CCD ACCUM 52X0.1 G430L 4300 none none none 2 2 N/A 13394( 3) - 14-May-2014 11:02:18 - [ 8] Summary Form for Proposal 13394 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.1, F25ND3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G430L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1851-FUV1, NGC1851-OFFSET1, NGC1851-OFFSET2 ------------------------------------------------------------------------------------------------------------------------------------