Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4324c Report Date: 09-May-96:19:32 Version: ********** Check-in Date: ********** 1.Proposal Title: SEARCH FOR THE REAL OPTICAL COUNTERPART OF 4U1543-47 CYC3SUPPLEMENTAL ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category X-RAY BINARIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Sergio A. Ilovaisky OBSERVATOIRE DE HAUTE PROVEN FRANCE ------------------------------------------------------------------------------------ 7. Abstract The identification of the optical counterpart of the 4U1543-47 soft X-ray transient is a puzzle. Ground-based observations made in 1983 during an active state resulted in the identification of a counterpart which displayed a typical low-mass X-ray binary spectrum but had changed in brightness by only 1 magnitude compared to archival Schmidt plates (normally such transients display amplitudes of 6 magnitudes or more). Further ground-based observations in 1989 revealed that during quiescence the visible object is a normal V=16.7 A-type star. Both the active and quiescent images coincide to +/- 0.1 arcsec. While it is unlikely that the A-star is the binary companion to the X-ray source, it appears nevertheless to be at the same distance from us. 4U1543-47 turned on again in April 1992 and we obtained director's discretionary time to make PC images of the field during outburst. They were obtained on 23 July. We propose to obtain PC images during quiescence in 1993 and compare them with those taken in July 1992 to identify the counterpart. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 0.78 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4324c PI: Sergio A. Ilovaisky Proposal Title: SEARCH FOR THE REAL OPTICAL COUNTERPART OF 4U1543-47 CYC3SUPPLEMENTAL ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Sergio A. Ilovaisky OBSERVATOIRE DE HAUTE PROVENCE FRANCE X Claude Chevalier OBSERVATOIRE DE HAUTE PROVENCE FRANCE X Holger Pedersen COPENHAGEN UNIVERSITY DENMARK X OBSERVATORY ------------------------------------------------------------------------------------ 2. Scientific Justification. 4U1543-47 is an X-ray transient which has been observed in outburst in 1971 and 1983. In late April 1992 it went into outburst again (Harmon et al. 1992). From its ultra-soft X-ray spectrum it is considered a black hole candidate, similar to A0620-00 and GS2000+25. During the 1983 outburst EXOSAT observed the source (Blisset 1983, van der Woerd et al. 1989) and it was subsequently identified by Pedersen et al. (1983) with a V=14.6 object displaying the characteristic emission lines of low-mass X-ray binaries. However, comparison with ESO Schmidt plates taken during quiescence showed that the object had brightened by only 1 magnitude. This was surprising for such a type of transient where optical amplitudes of 6 magnitudes or more are common. Optical observations made by us at ESO during quiescence in 1989 (Chevalier 1989) reveal that the V=16.7 star appearing at the location of the outburst image is a normal-looking A-type star. Spectra show interstellar features remarkably similar to those seen in the outburst spectrum, suggesting that both the A-star and the X-ray source are located at 4kpc. Astrometry made by comparing the 1983 and 1989 CCD frames, both taken at the 1.54m Danish telescope, shows that the two stellar images coincide to within 0.2 pixel (0.1 arc-sec). The outburst spectra also show shallow Balmer absorption lines which are obviously due to the A star. What is the counterpart of the X-ray source ? Is the A star an interloper in the line of sight or a third member in the binary system ? If the A star is not in the line of sight to the source, we can detect the true optical counterpart with higher angular resolution (HST) observations. Director's Discretionary time was obtained to get PC images of the field at the end of the 1992 outburst. Comparison of these data, taken in July, with data we propose to take during quiescence should allow the identification of the true optical counterpart of 4U1543-47. If the A-star still appears to be the only viable counterpart, this means that it probably is a third body in a hierarchical triple binary system. This would be a important result as no such systems are known, although their existence has been postulated before, as in the case of 4U2129+47 (Chevalier et al. 1989). Chevalier, C. (1989) ESA SP-296 p.341 Chevalier et al. (1989) Astr.Ap. 217,108 Pedersen, H. et al. (1983) IAUC 3858 van der Woerd et al. (1989) Ap.J. 344,320 Della Valle et al. (1992) IAUC 5512 Harmon et al. (1992) IAUC 5504 Blissett (1983) IAUC 3858 Page 3 ------------------------------------------------------------------------------------ 3. Description of proposed observations. PC images of the 4U1543-47 field were taken in July 1992 through two different filters: F555W to compare with ground-based observations and F336W to maximize the contribution from the X-ray source while minimizing the influence of the A- star and of the bright V=11.7 star a few arc-seconds away. Two exposures of different duration were taken per filter to insure detection of the counterpart in case it had decreased in brightness (Maximum emission was on April 20). We now propose to obtain WF/PC images of the same field during the quiescent state of the source in 1993 through the same filters. Comparison of the images taken during the late stages of the outburst decay with the images to be obtained during quiescence could reveal the true optical counterpart. The counterpart should have decreased in brightness and changed color, as the contribution from the accretion disk decreases. If no such counterpart is detected, the A-star may then be related to the X-ray system. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Existing ground-based observations do not allow us to answer the question of whether the A-star is associated to the X-ray source or not. The images of the source in outburst and in quiescence coincide to within +/- 0.1 arcsec. Only much higher resolving power observations with the WF/PC during the current outburst and in quiescence will allow a direct attack on this problem. We request an approximate repeat of our exposures carried out in July 23. They were taken using two filters (F336W and F555W) to obtain crude spectral information on the objects detected. As the object will now have returned to its quiescent state, 1.8 magnitudes fainter, the new images should have exposure times five times longer in order to reach the same S/N ratio as in July 1992 when the object was brighter. The comparison of these new images with the older ones should reveal whether any change in position of the object has taken place. We also request a deeper exposure in F555W in order to detect any near-by objects which would not have been detected in the shorter exposures. We request exposures of 50sec, 200sec and 800sec with F555W and 2 exposures of 800sec with F336W. The total exposure time and the number of exposures are less than or equal to what was approved in Phase I. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. None. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. None. ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. The PC images of the 4U1543-47 field will be analyzed in order to derive positions and magnitudes for all objects detected. This will make use of the DAOPHOT photometric package, as available in MIDAS. If an object appears to have changed in brightness and/or color, it will be selected for further analysis in Cycle 4. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. None. ------------------------------------------------------------------------------------ 9. Description of previous HST work. Program ID 4165 - GO/DD "Astrometry of the 4U1543-47 X-ray transient optical counterpart" The data have been analyzed and reveal that the transient was still bright in July 1992, consistent with our 1983 ground-based observations made during the last active state. Comparison of the stellar image of the counterpart with PSFs computed using TinyTIM show the object is single. Thus a definitive answer can only come if we compare the active state July 1992 images with images obtained in quiescence. None (complete data set not yet available). Page 4 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Data analysis will make use of the VAX/VMS cluster at Haute-Provence Observatory, which includes a microVAX 3400, a VAXstation 3100 and two VAXstation 4000 VLC. Available astronomical software packages are MIDAS, Iraf and STSDAS. ------------------------------------------------------------------------------------ 11. Address Information Name: SERGIO A. ILOVAISKY Category: PI Institution: Observatoire de Haute Provence Address: 04870 ST.MICHEL L'OBSERVATOIRE City: State: Zip Code: Country: FRANCE Telephone: (33)92706465 Telex (or e-mail): 410690F ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4324c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 4U1543-47 (A;164) RA = 15H 43M 33.72S +/- 1950 COMP 1 V=16.7 0.05S, 2 B=17.5 DEC = -47D 30' 56.6" +/- 3 E(B-V)=0.7 0.5" Comments: BRIGHT STAR (V=11.7) 5"7 WEST AND 2"3 NORTH FROM TARGET ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4324c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 4U1543-47 PC IMAGE P6 F336W PRE-FLASH=YES 4 400S 100 1 1 CYCLE 3 ORIENT 22D +/- 70D / 1.000-4.000 SAME ORIENT FOR 2.000-4.000 AS 1.000 Comments: ORIENT 22D +/- 70D / 1.000- 4.000 ALSO ACCEPTABLE ------------------------------------------------------------------------------------------------------------------------------------ 2 4U1543-47 PC IMAGE P6 F555W PRE-FLASH=YES 1 50S 100 1 1 CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ 3 4U1543-47 PC IMAGE P6 F555W PRE-FLASH=YES 1 200S 100 1 1 CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 4U1543-47 PC IMAGE P6 F555W PRE-FLASH=YES 2 400S 100 1 1 CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4324c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations PC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PRE-FLASH=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 0.78 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category X-RAY BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 3; ORIENT 22D +/- 70D / 1.000-4.000; SAME ORIENT FOR 2.000-4.000 AS 1.000 CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 4U1543-47 ------------------------------------------------------------------------------------------------------------------------------------