12437( 3) - 18-Jan-2011 20:41:26 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12437 Version: 3 Check-in Time: 18-Jan-2011 20:41:26 STScI Edit Number: 1 Title An Unusual Outburst from the Nucleus of the Quiescent Galaxy NGC 1589 ------------------------------------------------------------------------------------ Type Cycle GO/DD 18 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Alex V. Filippenko University of California - Berkeley CoI: Dr. Stephen Bradley Cenko University of California - Berkeley Y CoI: Dr. Joshua S. Bloom University of California - Berkeley N CoI: Dr. Weidong Li University of California - Berkeley N CoI: Dr. Nathaniel Butler University of California - Berkeley N CoI: Mr. Jeffrey M. Silverman University of California - Berkeley N CoI: Mr. Adam Miller University of California - Berkeley N CoI: Prof. Eliot Quataert University of California - Berkeley N CoI: Ms. Linda Strubbe University of California - Berkeley N ------------------------------------------------------------------------------------ Abstract As part of the Lick Observatory Supernova Search (LOSS), we have recently identified a highly unusual optical outburst from the nucleus (within 0.05", or 10 pc in projection) of the nearby (d ~ 50 Mpc) spiral (S0/a) galaxy NGC 1589. Over a decade of photometric monitoring with LOSS, together with archival spectroscopy from the CfA Redshift Survey, suggest that the galaxy does not harbor an active nucleus. Likewise, the transient, bright observed X-ray emission and broad H-alpha emission-line profile do not appear to closely resemble those of any known Type II supernova. We therefore consider this transient source (dubbed NGC1589-OT) to be the most viable candidate for a tidal disruption flare (TDF) ever discovered in real time. Here we request UV (STIS) spectroscopy with HST to search for "smoking gun" evidence in favor of the TDF interpretation: photoionized stellar debris ejected by the disruption process. DD time is necessary because the outburst will almost certainly not be visible by the time Cycle 19 observations commence. We did not propose for analogous observations during the normal course of a previous GO cycle due to the extraordinarily small number of good, real-time TDF candidates detected in the past. ------------------------------------------------------------------------------------ Observations Description ------------------------ We wish to obtain 3 orbits-worth of STIS FUV spectroscopy (G140L grating) of the tidal disruption flare candidate NGC1589-OT. The target acquisition is probably the trickiest part of the observation. We don't have offsets good to < 0.1" from any nearby point sources, so we have to acquire the target directly. Both our optical and (in particular) laser guide star adaptive optics (K-band) imaging suggest the region surrounding the galaxy nucleus (at least within the central 5" relevant for STIS acquisitions) is dominated by the transient point source. We have inputted our observed LGS K-band image into the STIS Target Acquisition Simulator, and find the point source centroiding algorithm works well, so this is what we have chosen. 12437( 3) - 18-Jan-2011 20:41:26 - [ 2] We used a recent observed spectrum of the transient to calculate the appropriate acquisition exposure time. The exposure time calculator suggests we will reach a SNR of 40 with a 0.1 s exposure. We've increased this to 0.5 s for additional signal. The ETC suggests the source would saturate with an exposure time of ~ 15 s, so our flux estimate would need to be off by a factor of 30 for this to be a problem. We note that because we are using the 0.2" slit, we do not need to conduct a peak-up acquisition. Our remaining STIS FUV exposures are configured to maximize exposure time in the remaining orbits. Real Time Justification ----------------------- Calibration Justification ------------------------- Standard wavelength calibration (performed each orbit) will suffice for our observations. Additional Comments ------------------- ------------------------------------------------------------------------------------ 12437( 3) - 18-Jan-2011 20:41:26 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1589-OT UNIDENTIFIED, NUCLEUS, RA=04H30M45.4500S +/- 0.1", J2000 Z = V = 11.89 +/- 0.06 UNDESIGNATED DEC=+00D51'49.16" +/- 0.1" 0.012652 Reference Frame: ICRS Comments: V-band magnitude above is integrated over the entire galaxy (several arcminutes in extent). The magnitude of the transient (plus nucleus) is several times fainter. ------------------------------------------------------------------------------------------------------------------------------------ 12437( 3) - 18-Jan-2011 20:41:26 - [ 4] Visit: 01 Visit Requirements: BETWEEN 22-JAN-2011:00:00:00 AND 22-FEB-2011:00:00:00 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1589-OT STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 0.5 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC1589-OT STIS/FUV ACCUM 52X0.2 G140L 1425 1 2430.0 S -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC1589-OT STIS/FUV ACCUM 52X0.2 G140L 1425 1 2984.0 S -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC1589-OT STIS/FUV ACCUM 52X0.2 G140L 1425 1 2984.0 S -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC1589-OT 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A NGC1589-OT 2 STIS/FUV ACCUM 52X0.2 G140L 1425 none none none none 1 N/A -MAMA NGC1589-OT 3 STIS/FUV ACCUM 52X0.2 G140L 1425 none none none none 2 N/A -MAMA NGC1589-OT 4 STIS/FUV ACCUM 52X0.2 G140L 1425 none none none none 3 N/A -MAMA 12437( 3) - 18-Jan-2011 20:41:26 - [ 5] Summary Form for Proposal 12437 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 22-JAN-2011:00:00:00 AND 22-FEB-2011:00:00:00 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1589-OT ------------------------------------------------------------------------------------------------------------------------------------