Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5317 Report Date: 18-Jul-95:17:08 Version: ********** Check-in Date: ********** 1.Proposal Title: SEARCHING FOR CIRCUMSTELLAR GAS AROUND LOW MASS PRE-MAIN SEQUENCE STARS: CYCLE 4 MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID COOL STARS GO Sub Category EARLY EVOLUTION ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Frederick M. Walter STATE UNIVERSITY OF NEW YORK USA 516-632-8232 ------------------------------------------------------------------------------------ 7. Abstract We seek evidence of the presence of gas disks around low mass pre-main sequence stars. We know that the dust disks disappear rapidly, changing from optically thick to undetectable in less than 1 Myr. Few stars older than 10 Myr retain dust disks. The gas may linger longer, but there is yet no evidence for circumstellar gas around naked (dustless) T Tauri stars. We propose to search for H2 emission from the UV Lyman band, which arises from fluorescently excited molecular hydrogen at 1000- 2000K. Such emission has been seen in T Tauri, and in Herbig-Haro objects. With the GHRS we can detect H2 emission a fraction of a percent of the intensity observed in T Tauri. This UV search is more sensitive than radio and infrared searches for molecular gas. We propose to observe 4 early-mid G stars ranging in age from 1 to 200 Myr. Some have dust disks, most do not. These observations will permit us to discriminate between scenarios where the disk dissipates completely, and one where the dust accumulates into planetesimals while the gaseous disk remains in place. Disk mass estimates based on the H2 will permit estimation of the true timescales for the dissipation of the circumstellar disks; non-detection will indicate that either the gas also dissipates quickly, or that the optically thin circumstellar gas disks do not extend in close to the st This investigation may constrain theories of planetary accumulation. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 19.70 par: 0 10. Num targs pri: 4 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5317 PI: Frederick M. Walter Proposal Title: SEARCHING FOR CIRCUMSTELLAR GAS AROUND LOW MASS PRE-MAIN SEQUENCE STARS: CYCLE 4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Frederick M. Walter 2988 USA Alexander Brown 1764 USA Philip Bennett 1764 USA Jack J. Lissauer 2988 USA Thomas Millar 8046 UK X ------------------------------------------------------------------------------------ 3. Description of proposed observations. The observations are straightforward. In general, acquisitions are handled in sequence NTTS-ACQ. Acquisitions and peakups will use mirror N2, except for target HD115043, where PEAKUP will use the A2 mirror because the star is too bright for the 1.6s step-time used for PEAKUP. We will then switch sides to take 2 exposures with G140L through the LSA. The two exposures, centered at 1300A and 1570A, will cover the 1170-1700A region containing the H2 bands. We will read the spectra out about every 6 minutes (every 12 substep patterns) to negate the effects of GIMP. The sequences NTTS-H2A and NTTS-H2B handle the exposures and associated WAVE exposures. We will also observe target BD+19D706 in the SSA. After the LSA exposures (lines 14.0-14.2), we do an ACQ/PEAKUP into the SSA and repeat the spectral sequence. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The H2 Lyman bands fall in the far-UV, between 1000 and 1700A. IUE is not sufficiently sensitive to detect these emissions, except in the extreme cases of the H-H objects and T Tau (where the H2 emission is likely shocked gas from an H- H object). Limits on the H2 emission from CTTS (including RW Aur, BP Tau, and DG Tau) and NTTS (HD142361, HDE283572) are a factor of 8-10 lower than the flux levels of 5-10x10^-14 erg/cm/cm/s seen in T Tau. We can detect lines with integrated fluxes of 10^(-16) erg/cm/cm/s. This is 2-3 orders of magnitude larger than the expected H2 emission from the starspots, scaling the solar observations to starspot filling factors of 20-30% and the larger stellar radii. For a minimum mass nebula (0.01 solar masses) with a power law surface density of index -7/4, about 10^30 gm of H2 can potentially radiate in the Lyman bands. An efficiency of Lyman alpha fluorescent pumping of 10^(-4) will result in detectable H2 Lyman band fluxes of order 10^(-16) erg/cm/cm/s. This program requires use of side 1 and G140L. The medium resolution modes do not have the wavelength coverage to observe more than a single line in each observation. We require observations of a number of the lines to determine the excitation mechanism. The FOS cannot be used because of its red leak. We are also studying the dust disks, by refining our IRAS upper limits for these stars (Wolk & Walter 1993), and by improving our models of the spectral energy distributions by accounting for starspots. We plan TiO band spectroscopy to determine starspot filling factors directly. One of us (FMW) is also a co-I on an ISO key project which will include deep exposures of selected NTTS. None of these investigations is sensitive to the gas, the majority species in the circumstellar disk. We propose these HST observations to round out the picture. Page 3 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We specify the GROUP special requirement in lines 10.2, 12.1, 13.1, 14.1, and 14.3 to ensure that the two spectra of each target are obtained reasonably close together in time. These stars are variable, and proper interpretation of the H2 line ratios requires that we minimize the possibility of time variability. Interruptions due to earth occultation and SAA passages are expected; we do NOT want the observations of an individual star spread over many days. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. We request standard WAVE exposures accompanying each ACCUM exposure. This provides the best possible offsets for wavelength calibration. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. There is no need for coordinated observations for our primary scientific goal, which is to detect circumstellar gas or place stringent upper limits on it. However, we will attempt to obtain contemporaneous ground based spectra in order to fully utilize the information contained in the chromospheric lines. All of these stars are in the Guide Star Catalog, and hence have accurate coordinates. ------------------------------------------------------------------------------------ 9. Description of previous HST work. 1208 Doppler Imaging of the Chromospheres and Transition Regions of AR Lacertae; F.M. Walter 1209/3949 Non-radiative Heating in Pre-Main Sequence Stars; F.M. Walter 1210/3950 Age Dependence of Non-radiative Heating in Stellar Chromospheres; F.M. Walter 3482 The Nature of the Variable Infalling Material on the Star Beta Pictoris; A. Vidal-Madjar P.I., J. Lissauer U.S. Administrative PI, many co-Is. Data were obtained in December 1992 and are being reduced and analyzed. None of the above proposals are related to this proposal. However, the ancillary data from this proposal on the chromospheric emisssion lines will augment the higher resolution data on 2 T Tauri stars being collected in program 1209/3949. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). We have computing facilities at SUNY and JILA to undertake the data analysis and model computations. We have access to the full range of GHRS-related software written by the GHRS team. We request funding to support a full time graduate student at SUNY, and partial salary support for the US investigators. The PI will contribute up to 5% of his time during the academic year to the program, at no cost to the project. ------------------------------------------------------------------------------------ 11. Address Information Name: Frederick M. Walter Category: PI Institution: 2988 Address: Dept of Earth and Space Sciences Z=2100 State University of New York City: Stony Brook State: NY Zip Code: 117942100 Country: USA Telephone: (516)632-8232 Telex (or e-mail): fwalter@sbast1.ess.sunysb.edu ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5317 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 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 BD+30D743 SU A,156,137,904,906 PLATE-ID=02TR, J2000 1 V = 10.5 +/- 0.8 -AURIGAE RA = 4H 55M 59.26S +/- 0.3", 1 B-V = 0.90 +/- 0.1 GSC977-2387 DEC = 30D 34' 1.9" +/- 0.3" 2 A(V) = 1.0 +/- 0.5 3 F(1400) = 2 +/- 1E-16 4 F-LINE(1335)=34 +/- 3E-15 Comments: F(1400) IS LIMITING FLUX WE EXPECT TO ACHIEVE IF H2 EMISSION IS NOT DETECTED ------------------------------------------------------------------------------------------------------------------------------------ 2 BD+27D657 A,156,137,904 PLATE-ID=0051, J2000 1 V = 9.04 +/- 0.1 V987-TAU RA = 4H 21M 58.88S +/- 1 B-V = 0.83 +/- 0.02 GSC1828-481 0.3", 2 A(V) = 0.4 +/- 0.2 DEC = 28D 18' 6.88" +/- 0.3" 3 F(1400) = 2+/-1E-16 4 F-LINE(1335) = 36 +/- 8 E-15 Comments: F(1400) IS LIMITING FLUX WE EXPECT TO ACHIEVE IF H2 EMISSION IS NOT DETECTED ------------------------------------------------------------------------------------------------------------------------------------ 3 HD142361 CD- A,156,137,904 PLATE-ID=01VY, J2000 1 V = 8.96 +/- 0.01 23D12575 RA = 15H 54M 59.92S +/- 1 B-V = 0.67 +/- 0.02 GSC6779-1372 0.5", 2 E(B-V)=0.07 +/- 0.03 DEC = -23D 47' 18.42" +/- 3 F(1400) = 2+/-1E-16 0.5" 4 F-LINE(1335) = 8 +/- 1 E-14 Comments: F(1400) IS LIMITING FLUX WE EXPECT TO ACHIEVE IF H2 EMISSION IS NOT DETECTED ------------------------------------------------------------------------------------------------------------------------------------ 4 HD115043 A,156,137 RA = 13H 13M 36.92S +/- J2000 1 V = 6.85 +/- 0.01 GSC3846-925 0.2", 2 B-V = 0.61 +/- 0.1 DEC = 56D 42' 29.09" +/- 3 E(B-V)= 0.0 +/- 0.1 0.2" 4 F(1400) = 4+/-1E-16 Comments: F(1400) IS LIMITING FLUX WE EXPECT TO ACHIEVE IF H2 EMISSION IS NOT DETECTED. STANDARD ACTIVE-CHROMOSPHERE STAR. ------------------------------------------------------------------------------------------------------------------------------------ 5 BD+19D706 T- A,156,137,904,906 PLATE-ID=000O, J2000 1 V = 10.3 +/- 0.7 TAURI RA = 4H 21M 59.40S +/- 0.3", 1 B-V = 1.20 +/- 0.2 GSC1272-470 DEC = 19D 32' 7.5" +/- 0.3" 2 A(V) = 1.0 +/- 0.5 3 F(1400) = 8 +/- 1E-16 4 F-LINE(1335)=34 +/- 3E-15 Comments: F(1400) IS LIMITING FLUX WE EXPECT TO ACHIEVE IF H2 EMISSION IS NOT DETECTED. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5317 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 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 DEFINE # HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN 1 9S 1 ONBOARD ACQ FOR NTTS- SEARCH-SIZE=3 1.1 ACQ Comments: STEP-TIME=1.0S ------------------------------------------------------------------------------------------------------------------------------------ 1.1 DEFINE # HRS ACQ/ 2.0 MIRROR-N2 1 163.2S 1 NTTS- PEAKUP ACQ Comments: STEP-TIME=1.6S ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE WAVE HRS ACCUM SC2 G140L 1300 STEP-PATT=2 1 30S 3 CALIB FOR 2.1 NO NTTS- SLEW H2A ------------------------------------------------------------------------------------------------------------------------------------ 2.1 DEFINE # HRS ACCUM # G140L 1300 STEP-PATT=5 # 353.6S 3.0 3 1 NTTS- 4 H2A Comments: S/N IS NOT STRICTLY RELEVANT. THIS IS A SEARCH FOR WEAK EMISSION LINES OR UPPER LIMITS TO THE H2 FLUX. ------------------------------------------------------------------------------------------------------------------------------------ 3 DEFINE WAVE HRS ACCUM SC2 G140L 1570 STEP-PATT=2 1 30S 3 CALIB FOR 3.1 NO NTTS- SLEW H2B ------------------------------------------------------------------------------------------------------------------------------------ 3.1 DEFINE # HRS ACCUM # G140L 1570 STEP-PATT=5 # 353.6S 3.0 2 NTTS- H2B Comments: S/N IS NOT STRICTLY RELEVANT. THIS IS A SEARCH FOR WEAK EMISSION LINES OR UPPER LIMITS TO THE H2 FLUX. ------------------------------------------------------------------------------------------------------------------------------------ 10 HD115043 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN 1 1.8S 1 1 CYCLE 4 / 10.0- SEARCH-SIZE=3 2 10.3 ONBOARD ACQ FOR 10.1-10.3 Comments: STEP-TIME=0.2 ------------------------------------------------------------------------------------------------------------------------------------ 10.1 HD115043 HRS ACQ/ 2.0 MIRROR-A2 1 306.0S 1 1 PEAKUP 2 Comments: STEP-TIME=3.0 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5317 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10.2 USE HD115043 2.0 10 GROUP 10.2-10.3 NO NTTS- GAP H2A Comments: GROUP NO GAP IS REQUESTED BECAUSE THESE STARS ARE VARIABLE. WE WOULD LIKE TO OBTAIN ALL OBSERVATIONS AS CLOSE TOGETHER IN TIME AS POSSIBLE. ------------------------------------------------------------------------------------------------------------------------------------ 10.3 USE HD115043 2.0 11 NTTS- H2B ------------------------------------------------------------------------------------------------------------------------------------ 12 USE BD+27D657 CYCLE 4 / 12.0- NTTS- 12.2 ACQ ONBOARD ACQ FOR 12.1-12.2 ------------------------------------------------------------------------------------------------------------------------------------ 12.1 USE BD+27D657 2.0 21 GROUP 12.1-12.2 NO NTTS- GAP H2A Comments: GROUP NO GAP IS REQUESTED BECAUSE THESE STARS ARE VARIABLE. WE WOULD LIKE TO OBTAIN ALL OBSERVATIONS AS CLOSE TOGETHER IN TIME AS POSSIBLE. ------------------------------------------------------------------------------------------------------------------------------------ 12.2 USE BD+27D657 2.0 22 NTTS- H2B ------------------------------------------------------------------------------------------------------------------------------------ 13 USE HD142361 CYCLE 4 / 13.0- NTTS- 13.2 ACQ ONBOARD ACQ FOR 13.1-13.2 ------------------------------------------------------------------------------------------------------------------------------------ 13.1 USE HD142361 2.0 19 GROUP 13.1-13.2 NO NTTS- GAP H2A Comments: GROUP NO GAP IS REQUESTED BECAUSE THESE STARS ARE VARIABLE. WE WOULD LIKE TO OBTAIN ALL OBSERVATIONS AS CLOSE TOGETHER IN TIME AS POSSIBLE. ------------------------------------------------------------------------------------------------------------------------------------ 13.2 USE HD142361 2.0 20 NTTS- H2B ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5317 [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 14 USE BD+19D706 CYCLE 4 / 14.0- NTTS- 14.5 ACQ ONBOARD ACQ FOR 14.1-14.3 ------------------------------------------------------------------------------------------------------------------------------------ 14.1 USE BD+19D706 2.0 4 GROUP 14.1-14.2 NO NTTS- GAP H2A Comments: GROUP NO GAP IS REQUESTED BECAUSE THESE STARS ARE VARIABLE. WE WOULD LIKE TO OBTAIN ALL OBSERVATIONS AS CLOSE TOGETHER IN TIME AS POSSIBLE. ------------------------------------------------------------------------------------------------------------------------------------ 14.2 USE BD+19D706 2.0 5 NTTS- H2B ------------------------------------------------------------------------------------------------------------------------------------ 14.3 BD+19D706 HRS ACQ/ 0.25 MIRROR-N2 SEARCH-SIZE=5 1 50S 1 ONBOARD ACQ FOR PEAKUP 14.4-14.5 Comments: STEP-TIME=2.0S ------------------------------------------------------------------------------------------------------------------------------------ 14.4 USE BD+19D706 0.25 6 GROUP 14.4-14.5 NO NTTS- GAP H2A Comments: GROUP NO GAP IS REQUESTED BECAUSE THESE STARS ARE VARIABLE. WE WOULD LIKE TO OBTAIN ALL OBSERVATIONS AS CLOSE TOGETHER IN TIME AS POSSIBLE. ------------------------------------------------------------------------------------------------------------------------------------ 14.5 USE BD+19D706 0.25 7 NTTS- H2B ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5317 [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=3 STEP-PATT=2 STEP-PATT=5 SEARCH-SIZE=5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 19.70 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COOL STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category EARLY EVOLUTION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 1.1 CALIB FOR 2.1 NO SLEW CALIB FOR 3.1 NO SLEW CYCLE 4 / 10.0-10.3; ONBOARD ACQ FOR 10.1-10.3 GROUP 10.2-10.3 NO GAP CYCLE 4 / 12.0-12.2; ONBOARD ACQ FOR 12.1-12.2 GROUP 12.1-12.2 NO GAP CYCLE 4 / 13.0-13.2; ONBOARD ACQ FOR 13.1-13.2 GROUP 13.1-13.2 NO GAP CYCLE 4 / 14.0-14.5; ONBOARD ACQ FOR 14.1-14.3 GROUP 14.1-14.2 NO GAP ONBOARD ACQ FOR 14.4-14.5 GROUP 14.4-14.5 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G140L MIRROR-A2 ------------------------------------------------------------------------------------------------------------------------------------ Target Names BD+30D743 SU-AURIGAE GSC977-2387 BD+27D657 V987-TAU GSC1828-481 HD142361 CD-23D12575 GSC6779-1372 HD115043 GSC3846-925 BD+19D706 T-TAURI GSC1272-470 ------------------------------------------------------------------------------------------------------------------------------------