11104( 2) - 05/11/07 14:05 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11104 Version: 2 Check-in Time: 11-May-2007 18:04:29 STScI Edit Number: 0 Title The nature of radio transients ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Avishay Gal-Yam California Institute of Technology CoI: Dr. Eran O. Ofek California Institute of Technology N CoI: Dr. Derek B. Fox The Pennsylvania State University N CoI: Dr. Dale A. Frail Associated Universities, Inc. N ------------------------------------------------------------------------------------ Abstract We have conducted the first ever blind, wide-field survey for radio transients (Levinson et al. 2002; Gal-Yam et al. 2006). We have discovered four radio transients and explored their nature using radio and optical follow-up observations. One is a known pulsar, one is a z~0.1 AGN, and one is most probably an optically obscured radio supernova (SN) in the nearby galaxy NGC 4216 (the first such event to be discovered by a wide field radio survey). The last source appears not to be associated with a bright host galaxy (to a limit of R < 24.5 mag). We request 4 orbits of WFPC2 F606W imaging to check whether we can establish an association between this radio transient and any of three nearby faint resolved galaxies we have detected from the ground. If the source is associated with any of these galaxies it would represent a new type of extra-galactic radio bursts, more luminous than, e.g., radio afterglows of gamma-ray bursts. Alternatively, ruling out an association with these galaxies would disfavor an extra-galactic nature of this object, and suggest instead that this is a radio outburst of a faint Galactic compact object, probably a new type of radio-flaring neutron star. If this is the case, the high luminosity (9 mJy) and relatively high galactic latitude (33 degrees) of this source may indicate it is relatively nearby. This single source represents a large population (comparable in sky density to AGN, pulsars, and radio SNe) and thus merits intensive study. A modest investment of HST time, leveraged by massive ground-based radio and optical efforts, will allow us to identify a new class of radio sources, and complete a census of the variable radio sky down to ~6 mJy, leaving no unidentifed objects. This result can be directly scaled to predict the number and type of transient sources expected to be detected by future surveys with the next generation radio arrays, such as ATA and SKA.Since our science critically requires HST's spatial resolution (rather than sensitivity) it is perfectly suited to be carried out with WFPC2. ------------------------------------------------------------------------------------ 11104( 2) - 05/11/07 14:05 - [ 2] Observations Description ------------------------ We will image the location of the unidentified radio transient RTC9 to look for optical counterparts and examine its association with putative nearby host galaxies. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11104( 2) - 05/11/07 14:05 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 VLA172059.9+ UNIDENTIFIED, RADIO RA=17H20M59.9000S +/- 0.1", J2000 V = 25.0+/-1.0 385227 EMITTER DEC=+38D52'27.00" +/- 0.1" Reference Frame: ICRS 11104( 2) - 05/11/07 14:05 - [ 4] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Single visit in this proposal Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 VLA172059.9 WFPC2 IMAGE WF3 F606W CR-SPLIT=NO 1 1100 S SEQ 1-2 NON-INT +385227 ------------------------------------------------------------------------------------------------------------------------------------ 2 VLA172059.9 WFPC2 IMAGE WF3 F606W CR-SPLIT=NO 1 1100 S POS TARG 1.03, 1.03 +385227 ------------------------------------------------------------------------------------------------------------------------------------ 3 VLA172059.9 WFPC2 IMAGE WF3 F606W CR-SPLIT=NO 1 1100 S POS TARG 0, 1.03; SEQ 3-4 +385227 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 4 VLA172059.9 WFPC2 IMAGE WF3 F606W CR-SPLIT=NO 1 1100 S POS TARG -1.03, 0 +385227 ------------------------------------------------------------------------------------------------------------------------------------ 5 VLA172059.9 WFPC2 IMAGE WF3 F606W CR-SPLIT=NO 1 1100 S POS TARG 1.03, 0; SEQ 5-6 +385227 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 6 VLA172059.9 WFPC2 IMAGE WF3 F606W CR-SPLIT=NO 1 1100 S POS TARG -1.03,-1.03 +385227 ------------------------------------------------------------------------------------------------------------------------------------ 7 VLA172059.9 WFPC2 IMAGE WF3 F606W CR-SPLIT=NO 1 1100 S POS TARG -1.03, 1.03; SEQ +385227 7-8 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 8 VLA172059.9 WFPC2 IMAGE WF3 F606W CR-SPLIT=NO 1 1100 S POS TARG 1.03,-1.03 +385227 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ VLA172059.9+385227 1 WFPC2 IMAGE WF3 F606W none none none none 1 N/A VLA172059.9+385227 2 WFPC2 IMAGE WF3 F606W none none none none 1 N/A VLA172059.9+385227 3 WFPC2 IMAGE WF3 F606W none none none none 2 N/A VLA172059.9+385227 4 WFPC2 IMAGE WF3 F606W none none none none 2 N/A VLA172059.9+385227 5 WFPC2 IMAGE WF3 F606W none none none none 3 N/A VLA172059.9+385227 6 WFPC2 IMAGE WF3 F606W none none none none 3 N/A VLA172059.9+385227 7 WFPC2 IMAGE WF3 F606W none none none none 4 N/A VLA172059.9+385227 8 WFPC2 IMAGE WF3 F606W none none none none 4 N/A 11104( 2) - 05/11/07 14:05 - [ 5] Summary Form for Proposal 11104 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SEQ 1-2 NON-INT; POS TARG 1.03, 1.03; POS TARG 0, 1.03; SEQ 3-4 NON-INT; POS TARG -1.03, 0; POS TARG 1.03, 0; SEQ 5-6 NON-INT; POS TARG -1.03,-1.03; POS TARG -1.03, 1.03; SEQ 7-8 NON-INT; POS TARG 1.03,-1.03; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names VLA172059.9+385227 ------------------------------------------------------------------------------------------------------------------------------------