! $Id: 5355,v 4.1 1994/07/27 17:00:52 pepsa Exp $ coverpage: title_1: THE BINARY FREQUENCY AMONG SOLAR-TYPE STARS IN YOUNG title_2: CLUSTERS: CYCLE4 HIGH sci_cat: COOL STARS sci_subcat: EARLY EVOLUTION proposal_for: GO pi_fname: STEPHEN pi_mi: E. pi_lname: STROM pi_inst: 2001 pi_country: USA pi_phone: 413-545-2290 hours_pri: 0.40 num_pri: 7 wf_pc: Y ! end of coverpage abstract: line_1: Recent ground-based observations have led to the unexpected conclusion that line_2: most and possibly all of the youngest, optically-visible solar-type line_3: pre-main sequence stars are members of binary or multiple star systems. line_4: However, this result is based solely on examination of stars located in line_5: sparsely populated, nearby star-forming complexes (e.g. Taurus) line_6: which are not representative of those that line_7: produce most of the stars which populate the Milky Way: giant molecular clouds line_8: (GMCs) which give birth to rich, dense clusters. We propose to take advantage of line_9: the high angular resolution and relatively wide field afforded by WFPC2 on HST line_10: to search for binary stars with angular separations of between 0.1" and 1" among line_11: a sample of about 120 stars located in 2 young (age approximately 1 Myr) line_12: clusters embedded within the nearest GMC: Orion (d = 460 pc). A sample this size line_13: will enable a statistically significant comparison between the binary frequency line_14: in the separation range 46 AU < r < 460 AU found for these young clusters, and line_15: that found for (1) older stars in the solar-neighborhood (expected binaries line_16: about 24/120); and (2) Taurus where most or all stars are binaries (expected line_17: binaries about 65/120). Our observations should thus provide a test of the line_18: hypothesis that all stars are born in binary/multiple systems, not only in line_19: regions like Taurus, but in rich clusters as well. ! ! end of abstract general_form_proposers: lname: STEPHEN fname: STROM mi: E. inst: 2001 country: USA ! lname: EDWARDS fname: SUZAN inst: 2005 country: USA ! lname: DOUGADOS fname: CATHERINE inst: 5428 country: FRANCE esa: Y ! lname: HARTIGAN fname: PATRICK inst: 2001 country: USA ! lname: GHEZ fname: ANDREA inst: 1210 country: USA ! lname: PADGETT fname: DEBORAH mi: L. inst: 1002 country: USA ! lname: KAREN fname: STROM inst: 2001 country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We propose to take advantage of the high angular resolution and line_2: relatively wide field afforded by WFPC2 on HST to search for line_3: binary/multiple stars with angular separations between line_4: 0.1" and 1" among a sample of about 250 stars in 3 line_5: young (age approximately 1 Myr) clusters. line_6: Our plan is to observe 7 fields line_7: through 2 filters: F814W and F547M. These observations line_8: will enable us to derive monochromatic luminosity ratios, colors line_9: and separations for the binary and multiple systems discovered line_10: in our survey. line_12: Because the young clusters which comprise our sample are still partially line_13: embedded within their natal molecular cores, member line_14: stars are expected to suffer extinctions between 1 and 20 mag. line_15: In order to maximize our sample size, we have chosen to line_16: image these clusters at a wavelength (lambda approximately 8500 line_17: angstroms) which both minimizes extinction and measures the line_18: flux at a wavelength near the Planck maximum for line_19: late-type stars; hence our choice of F814W. line_20: Our planned exposures will allow line_21: us to obtain F814W fluxes for stars as faint as I = 25 with line_22: S/N = 10. Because cluster members are expected line_23: to be no older than t aproximately 1 Myr, achieving ! question: 3 section: 2 line_1: this sensitivity will allow us to image primaries and secondaries line_2: with masses as small as the hydrogen-burning limit line_3: provided that extinction is less than 15 mag. line_4: Complementary observations through F547M will provide a line_5: color index, F814W/F547M. In combination with the line_6: flux ratio for each member of the pair measured line_7: through F814W, and a reddening to the system estimated line_8: from ground-based measurements, this index will line_9: enable an initial estimate of the relative masses for line_10: the binary components. line_12: Because the WF camera has a pixel size of 0.1", line_13: the diffraction-limited core will be undersampled line_14: even at wavelength of 8500 angstroms. Hence, in order to line_15: achieve high photometric accuracy at near diffraction-limited line_16: resolution, we plan to take 2 images of all fields, each displaced line_17: by 1/2 pixel. By summing these images, we can more line_18: effectively sample stellar images and recover information close to the line_19: diffraction-limited resolution of HST. line_21: A typical cluster field will include both line_22: bright unreddened stars near the earthward side of the line_23: molecular core, and faint ! question: 3 section: 3 line_1: heavily-reddened stars embedded within the core. line_2: We have thus designed our experiment to line_3: enable measurements of systems line_4: which span a wide range (about 12 mag) in I-band brightness. line_5: To do this, we plan to take two exposures through F814W. The first, line_6: of duration 1 sec, will permit us to observe the line_7: "bright" (I < 20 mag), lightly-reddened members of the line_8: clusters, while the second (of duration 100 s) will enable us to image line_9: stars as faint as I = 25 mag at S/N = 10. line_10: This strategy has the further advantage of enabling discovery line_11: of systems in which the components line_12: might have large mass (and thus, luminosity) ratios. line_13: We anticipate that we should be able to detect systems with line_14: flux ratios = 100 even if they have separations of 0.1". line_15: However, our ability to image faint line_16: companions near bright primaries at separations near the diffraction line_17: limit of HST will depend ultimately on the PSF achieved by line_18: WFPC2 and the details of CCD blooming and "bleeding". line_19: Hence, final assessment of the completeness line_20: of our survey for stars with separations of 0.1", line_21: and of the accuracy with which we can measure large flux ratios must line_22: await both evaluation of WFPC2 performance and subsequent modeling. ! question: 3 section: 4 line_1: We plan to take only one exposure of duration t = 1 sec with F547M. line_2: This decision is driven by observing efficiency considerations: line_3: our desire to complete our imaging of a region within an HST orbit. line_4: The practical consquence will be to limit our color survey line_5: to the brightest (I < 20) members of our sample. ! question: 4 section: 1 line_1: 4a. The Need for HST line_3: The first advantage provided by HST results from line_4: its ability to resolve binary pairs and derive flux ratios line_5: at a wavelength line_6: (about 8500 angstroms) which lies (1) near the Planck maximum line_7: for late-type stars; and (2) near a minimum in the line_8: emission expected from accretion-related phenomena. line_9: By contrast, at 2.2 microns, where speckle techniques are line_10: most sensitive, the fluxes for T-Tauri line_11: stars surrounded by circumstellar accretion disks will line_12: include a large emission component line_13: arising from the disk. Thus, while speckle observations line_14: at 2.2 microns can provide information regarding relative line_15: accretion rates in binary pairs, and identify line_16: optically-invisible, infrared-bright companions, line_17: they cannot provide the accurate corrections for the line_18: contributions of unresolved companions to line_19: stellar luminosities line_20: required for reliable age and mass determinations. line_21: Such corrections must be made at a wavelength (about 1 micron) line_22: where the stellar photosphere dominates the observed flux. ! question: 4 section: 2 line_1: A second advantage derives from the ability of WFPC2 to line_2: image a large number of stars simultaneously. line_3: This is crucial because deciding whether all line_4: cluster stars form in binary systems line_5: requires observation of a large sample. line_6: By contrast, speckle-imaging observations line_7: must be carried out one star at a time, and moreover line_8: require observation of a nearby line_9: star to define a local point spread function. line_10: Speckle imaging of a sample line_11: 120 stars would require many hundred line_12: hours on a large telescope. line_14: The third advantage of HST derives from superior sensitivity. line_15: WF images through F814W will enable flux measurements (S/N = 10) line_16: for stars with masses at the hydrogen-burning limit line_17: even if they are obscured by 15 magnitudes of extinction. line_18: Under the best atmospheric conditions, new-generation line_19: speckle cameras will enable imaging of line_20: binaries with primary stars K < 11.5. line_21: For stars with age approximately 1 Myr located line_22: at d = 460 pc, this corresponds line_23: with mass about 0.2 solar masses. Stars with ! question: 4 section: 3 line_1: M about 0.08 solar masses line_2: will have K = 13.5 mag assuming no foreground extinction, line_3: and K = 15.0 with 15 mag of extinction, respectively line_4: 2 and 3.5 mag below the limit of line_5: speckle camera performance. line_8: We are currently carrying out extensive ground-based optical/infrared line_9: photometric and spectroscopic investigations of line_10: our 3 target clusters. HST observations line_11: will provide essential complementary information line_12: (I-band fluxes and separations for a large number line_13: of unresolved binaries in the separation range 46 AU < r < 460 AU) line_14: which will be crucial to full realization of our line_15: long term goals: (1) characterizing the line_16: IMFs for these clusters and the sequence in which stars line_17: of different masses form, and (2) line_18: understanding the frequency and evolutionary timescales for the line_19: circumstellar accretion disks. line_20: As described in section 2, these observations are prerequisites for line_21: accurate age and mass determinations, and for identifying the factors line_22: which control the evolution of circumstellar disks. ! question: 4 section: 4 line_1: R. Mathieu (private communication) has just initiated a survey line_2: for spectroscopic binaries in some of our target clusters. line_3: His survey will enable detection of binaries in the separation range line_4: (r < 10 AU) provided they are brighter than I = 15 mag. line_5: The Mathieu survey will thus not enable a line_6: comprehensive search for binaries over the full ranges of stellar line_7: masses which we anticipate observing with HST. However, line_8: in the magnitude range where the surveys overlap, line_9: the relative binary frequencies derived line_10: for close (r < 10 AU) and more distant (50 AU < r < 500 AU) pairs line_11: will enable comparison with identical statistics for line_12: older solar neighborhood stars, and thus provide line_13: the basis for evaluating the dynamical evolution of binary systems. ! question: 4 section: 5 line_1: 4b. Justify Exposure Times line_4: A large sample of stars must be observed in order to provide line_5: a robust test of the hypothesis that all solar-type stars form in line_6: binary/multiple systems. From examination of line_7: ground-based I-, J-, H- and K- band images of line_8: our target clusters, line_9: we have selected 7 fields which contain about 120 stars line_10: with I < 25 mag. Our exposure times of 1 sec and 100 sec through line_11: F814W enable us to image stars over the range line_12: 12 < I < 25 mag with S/N > 10 , while our line_13: exposure time of 1 sec through F547M enables line_14: us to image stars with 12 < V < 20 mag. The F814W exposures should line_15: thus permit a complete search for binaries with masses as small as the line_16: hydrogen-burning limit, provided that they are obscured line_17: by extinction of less than 15 mag and have ages t < 1 Myr. Colors, which line_18: enable rough estimates of mass ratios for binary pairs, line_19: can be derived for stars with V < 20 mag. ! question: 5 section: 1 line_1: ! question: 6 section: 1 line_1: ! ! ! question: 8 section: 1 line_1: ! question: 9 section: 1 line_1: The PI and a team of 14 researchers were initially awarded line_2: 20 hours of time during Cycle 1 line_3: to study the "Formation and Evolution of Solar line_4: Nebulae Surrounding Pre-Main Sequence Stars" (proposal line_5: number 2261). Our goal was to image scattered light line_6: from circumstellar disks surrounding line_7: a large sample of classical and line_8: weak-line T Tauri stars, and forbidden line emission line_9: from collimated jets driven by rapidly accreting TTS. line_10: A much scaled-down version of this program was approved line_11: in order to evaluate what fraction of the scientific line_12: goals could be accomplished with the degraded HST line_13: imaging capability. In the end, small but measurable line_14: orbit-to-orbit changes in the PSF, line_15: combined with the power carried in the wings line_16: of the PSF precluded detection of either low surface line_17: brightness disks, extended envelopes or sub-arcsecond jets. line_18: One of our images resolved a close binary (DF Tau; line_19: separation about 0.08") which line_20: had been detected previously via lunar occultation observations. line_21: This pair of stars have a projected separation placing line_22: them both inside the accretion disk inferred for line_23: the primary from observed infrared excesses. ! question: 9 section: 2 line_1: We are currently line_2: analyzing the images to assess whether one line_3: or both components is undergoing inner disk accretion line_4: (based on measuring the [O I] emission flux through the line_5: narrow band F631 N filter). line_7: Although no published results have yet come from our line_8: Cycle 1 data (please note line_9: that our last observations were not taken line_10: until December, 1992 line_11: some of the sophisticated analysis techniques we line_12: had hoped to bring to bear on our Cycle 1 observations line_13: on archived HST images of young stellar objects. line_14: We have just submitted an ApJ Letter line_15: (Kepner et al., 1993) in which we were able to reconstruct line_16: H alpha and [O I] images of the jet associated line_17: with DG Tau. The image line_18: restoration method used is based on the line_19: ``Half-Gaussian'' model and the corresponding ``Half-Quadratic'' line_20: algorithm. This newly developed method is line_21: described fully in Geman and Yang (1993), line_22: and was tailored for use with the HST data by members line_23: of the team we assembled to attempt recovery ! question: 9 section: 3 line_1: of the aberrated Cycle 1 images. line_2: Our reconstructed DG Tau images enable us to line_3: (1) show that collimation takes place within line_4: 30 AU of the stellar surface; line_5: (2) constrain the degree of collimation (the jet is unresolved line_6: in the direction perpendicular to its propagation axis); line_7: and (3) demonstrate that the line_8: jet has discernible knots, separated by 10s of AU, line_9: possibly indicative of episodic mass outflow. line_11: Broadly speaking, both involve study of young stellar objects, but line_12: the current proposal focuses on multiplicity of line_13: solar-type stars and has little or no overlap with line_14: our Cycle 1 proposal. line_16: PUBLICATIONS line_18: "Hubble Space Telescope Images of the Subarcsecond Jet in DG Tau" by line_19: J. Kepner, P. Hartigan, C. Yang, and S.E. Strom 1993, line_20: ApJ Letter, submitted. ! question: 10 section: 1 line_1: ! !end of general form text general_form_address: lname: STROM fname: STEPHEN mi: E. category: PI inst: 2001 addr_1: FIVE COLLEGE ASTRONOMY DEPARTMENT/ addr_2: UNIVERSITY OF MASSACHUSETTS, AMHERST addr_3: 517G LEDERLE GRADUATE RESEARCH TOWER B city: AMHERST state: MA zip: 01003 country: USA phone: 413-525-2290 telex: sstrom@donald.phast.umass.edu ! lname: PADGETT fname: DEBORAH mi: L. category: CON inst: 1002 addr_1: 2939 N. MARENGO AVENUE city: ALTADENA state: CA zip: 91001 country: USA phone: 818-791-4818 telex: dlp@lb6.jpl.nasa.gov ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: NGC2068-POS1 descr_1: C, descr_2: 204 pos_1: RA = 5H 46M 44.749S +/- 0.3S, pos_2: DEC = +0D 5' 21.43" +/- 5" equinox: 2000.0 comment_1: THIS IS A T TAURI STAR CLUSTER, comment_2: WITH AT LEAST 18 STARS FAINTER comment_3: THAN MAGNITUDE 10 IN THE comment_4: FIELD. fluxnum_1: 1 fluxval_1: V = 20 +/- 5 ! targnum: 2 name_1: NGC2068-POS2 descr_1: C, descr_2: 204 pos_1: RA = 5H 46M 37.306S +/- 0.3S, pos_2: DEC = +0D 6' 33.84" +/- 5" equinox: 2000.0 comment_1: THIS IS A T TAURI STAR CLUSTER, comment_2: WITH AT LEAST 18 STARS FAINTER comment_3: THAN MAGNITUDE 10 IN THE comment_4: FIELD. fluxnum_1: 1 fluxval_1: V = 20 +/- 5 ! targnum: 3 name_1: NGC2068-POS3 descr_1: C, descr_2: 204 pos_1: RA = 5H 46M 45.547S +/- 0.3S, pos_2: DEC = +0D 3' 20.65" +/- 5" equinox: 2000.0 comment_1: THIS IS A T TAURI STAR CLUSTER, comment_2: WITH AT LEAST 18 STARS FAINTER comment_3: THAN MAGNITUDE 10 IN THE comment_4: FIELD. fluxnum_1: 1 fluxval_1: V = 20 +/- 5 ! targnum: 4 name_1: NGC2024-POS1 descr_1: C, descr_2: 203 pos_1: RA = 5H 41M 36.4S +/- 0.3S, pos_2: DEC = -1D 53' 54" +/- 5" equinox: 2000.0 comment_1: THIS IS AN OB ASSOCIATION, WITH AT comment_2: LEAST 30 STARS FAINTER THAN comment_3: MAGNITUDE 10 IN THE FIELD. fluxnum_1: 1 fluxval_1: V = 20 +/- 5 ! targnum: 5 name_1: NGC2024-POS2 descr_1: C, descr_2: 203 pos_1: RA = 5H 41M 36.4S +/- 0.3S, pos_2: DEC = -1D 55' 30" +/- 5" equinox: 2000.0 comment_1: THIS IS AN OB ASSOCIATION, WITH AT comment_2: LEAST 30 STARS FAINTER THAN comment_3: MAGNITUDE 10 IN THE FIELD. fluxnum_1: 1 fluxval_1: V = 20 +/- 5 ! targnum: 6 name_1: NGC2024-POS3 descr_1: C, descr_2: 203 pos_1: RA = 5H 41M 43.0S +/- 0.3S, pos_2: DEC = -1D 54' 39" +/- 5" equinox: 2000.0 comment_1: THIS IS AN OB ASSOCIATION, WITH AT comment_2: LEAST 30 STARS FAINTER THAN comment_3: MAGNITUDE 10 IN THE FIELD. fluxnum_1: 1 fluxval_1: V = 20 +/- 5 ! targnum: 7 name_1: NGC2071 descr_1: C, descr_2: 204 pos_1: RA = 5H 47M 04.740S +/- 0.3S, pos_2: DEC = +0D 21' 44.08" +/- 5" equinox: 2000.0 comment_1: THIS IS A T TAURI STAR CLUSTER, comment_2: WITH AT LEAST 15 STARS FAINTER comment_3: THAN MAGNITUDE 10 IN THE comment_4: FIELD. fluxnum_1: 1 fluxval_1: V = 20 +/- 5 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.100 sequence_1: DEFINE sequence_2: BINPIC targname: # config: WFPC2 opmode: IMAGE aperture: WFALL-FIX sp_element: F547M num_exp: 1 time_per_exp: 1S s_to_n: 10 s_to_n_time: 1S fluxnum_1: 1 priority: 1 param_1: CLOCKS=NO, param_2: ATD-GAIN=7 req_1: CYCLE 4; req_2: GROUP 1.1-1.3 NON-INT; req_3: GROUP 1.1-1.6 NO GAP; comment_1: THIS IS A STAR CLUSTER FIELD WITH MANY comment_2: STARS FAINTER THAN MAGNITUDE 10. THE comment_3: BRIGHTEST STARS IN THE FIELD ARE comment_4: EXPECTED TO SATURATE. THE S/N ESTIMATE comment_5: IS FOR LATE-TYPE STARS WITH V = 20. comment_6: POINTING AT DEFAULT TARGET POSITION. ! linenum: 1.200 sequence_1: DEFINE sequence_2: BINPIC targname: # config: WFPC2 opmode: IMAGE aperture: WFALL-FIX sp_element: F814W num_exp: 1 time_per_exp: 1S s_to_n: 10 s_to_n_time: 1S fluxnum_1: 1 priority: 1 param_1: CLOCKS=NO, param_2: ATD-GAIN=7 req_1: CYCLE 4 comment_1: THIS IS A STAR CLUSTER FIELD WITH MANY comment_2: STARS FAINTER THAN MAGNITUDE 10. THE comment_3: BRIGHTEST STARS IN THE FIELD ARE comment_4: EXPECTED TO SATURATE. THE S/N ESTIMATE comment_5: IS FOR LATE-TYPE STARS WITH I = 25. comment_6: POINTING AT DEFAULT TARGET POSITION. ! linenum: 1.300 sequence_1: DEFINE sequence_2: BINPIC targname: # config: WFPC2 opmode: IMAGE aperture: WFALL-FIX sp_element: F814W num_exp: 1 time_per_exp: 100S s_to_n: 10 s_to_n_time: 100S fluxnum_1: 1 priority: 1 param_1: CLOCKS=YES, param_2: ATD-GAIN=7 req_1: CYCLE 4 ! linenum: 1.400 sequence_1: DEFINE sequence_2: BINPIC targname: # config: WFPC2 opmode: IMAGE aperture: WFALL-FIX sp_element: F814W num_exp: 1 time_per_exp: 100S s_to_n: 10 s_to_n_time: 100S fluxnum_1: 1 priority: 1 param_1: CLOCKS=YES, param_2: ATD-GAIN=7 req_1: CYCLE 4; req_2: GROUP 1.4-1.6 NON-INT; req_4: POS TARG +0.05, +0.05 comment_1: THIS IS A STAR CLUSTER FIELD WITH MANY comment_2: STARS FAINTER THAN MAGNITUDE 10. THE comment_3: BRIGHTEST STARS IN THE FIELD ARE comment_4: EXPECTED TO SATURATE. THE S/N ESTIMATE comment_5: IS FOR LATE-TYPE STARS WITH I = 25. comment_6: POINTING IS OFFSET +0.05" IN X AND Y. ! linenum: 1.500 sequence_1: DEFINE sequence_2: BINPIC targname: # config: WFPC2 opmode: IMAGE aperture: WFALL-FIX sp_element: F814W num_exp: 1 time_per_exp: 1S s_to_n: 10 s_to_n_time: 1S fluxnum_1: 1 priority: 1 param_1: CLOCKS=NO, param_2: ATD-GAIN=7 req_1: CYCLE 4; req_4: SAME POS FOR 1.5 AS 1.4 ! linenum: 1.600 sequence_1: DEFINE sequence_2: BINPIC targname: # config: WFPC2 opmode: IMAGE aperture: WFALL-FIX sp_element: F547M num_exp: 1 time_per_exp: 1S s_to_n: 10 s_to_n_time: 1S fluxnum_1: 1 priority: 1 param_1: CLOCKS=NO, param_2: ATD-GAIN=7 req_1: CYCLE 4; req_4: SAME POS FOR 1.6 AS 1.4 comment_1: THIS IS A STAR CLUSTER FIELD WITH MANY comment_2: STARS FAINTER THAN MAGNITUDE 10. THE comment_3: BRIGHTEST STARS IN THE FIELD ARE comment_4: EXPECTED TO SATURATE. THE S/N ESTIMATE comment_5: IS FOR LATE-TYPE STARS WITH I = 25. comment_6: POINTING IS OFFSET +0.05" IN X AND Y. ! linenum: 10.000 sequence_1: USE sequence_2: BINPIC targname: NGC2068-POS1 req_1: PCS MODE F ! linenum: 20.000 sequence_1: USE sequence_2: BINPIC targname: NGC2068-POS2 req_1: PCS MODE F ! linenum: 30.000 sequence_1: USE sequence_2: BINPIC targname: NGC2068-POS3 req_1: PCS MODE F ! linenum: 40.000 sequence_1: USE sequence_2: BINPIC targname: NGC2024-POS1 req_1: PCS MODE F ! linenum: 50.000 sequence_1: USE sequence_2: BINPIC targname: NGC2024-POS2 req_1: PCS MODE F ! linenum: 60.000 sequence_1: USE sequence_2: BINPIC targname: NGC2024-POS3 req_1: PCS MODE F ! linenum: 70.000 sequence_1: USE sequence_2: BINPIC targname: NGC2071 req_1: PCS MODE F ! ! end of exposure logsheet ! No scan data records found