! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 5873,v 13.1 1995/11/21 00:03:43 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Karla Peterson ! Phone: 410 338-4774, E-mail: peterson@stsci.edu ! ! This partially completed template was generated from your Phase I proposal. ! Proposal_Information ! Section 4 Title: UV/X-ray spectroscopy of Cyg X-2 Proposal_Category: GO Scientific_Category: Hot Stars Cycle: 5 Investigators PI_name: Saeqa Vrtilek PI_Institution: University of Maryland CoI_Name: John Raymond CoI_Institution: Smithsonian Astrophysical Observatory Contact: ! Y or N (designate at most one contact) CoI_Name: Francis Primini CoI_Institution: Smithsonian Astrophysical Observatory Contact: ! Y or N (designate at most one contact) CoI_Name: Timothy Kallman CoI_Institution: Goddard Space Flight Center Contact: ! Y or N (designate at most one contact) CoI_Name: Richard McCray CoI_Institution: Joint Institute for Laboratory Astrophysics Contact: ! Y or N (designate at most one contact) CoI_Name: Bram Boroson CoI_Institution: Joint Institute for Laboratory Astrophysics Contact: ! Y or N (designate at most one contact) CoI_Name: Fumiaki Nagase CoI_Institution: ISAS Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to observe simultaneously the UV and X-ray spectral variabilites of Cyg X-2 with HST and ASCA. Previous simultaneous UV/X-ray observations using GINGA and IUE showed a unique relationship between the X-ray spectral states and the UV flux. IUE, however, is not able to measure the short timescales and kinematic velocities of interest in this system. We will use the GHRS G160M with time resolution of 0.5s in the vicinity of the NV and HeII lines. From delays between X-ray and UV line variations, we can analyze the radial structure of velocity in the disk. This will provide an unprecedented probe into the structure and dynamics of the accretion flow, enable us to test models of the UV emission, and constrain properties of the secondary star. We will also use the G140L with a time resolution of 50ms to search for the quasi-periodic oscillations so far seen only in the X-rays. Finding QPOs in the UV would be very important; since the X- ray flux can be easily modulated by geometric effects and emission in the visible can be confused with that of the non- collapsed secondary, the UV observations are most likely to yield direct evidence of the phenomenon related to the accretion disk. Questions ! Free format text (please update) Observing_Description: We will utilize the GHRS G160M in RAPID mode (with readout every 0.5s) to study the NV and HeII lines which are expected to vary on a timescale of minutes. The average flux observed from IUE at the N V line is F_Lambda~eq 2 * 10^-14 erg cm^-2 s^-1 AA^-1, corresponding to a counting rate of .01 counts s^-1 diode^-1. Since we measure the width of the N V emission line to be approximately 12 Angstrom, by summing the diodes over the line we expect a counting rate of approximately 1.6 counts s^-1 in the line. The resolution of G160M at 1240 Angstrom is ~0.08Angstrom corresponding to a velocity resolution of 19 km s^-1. In a 60 minute observation we will get 6.9* 10^3 counts in the line (which spans 167 diodes). This gives 41 counts/s per velocity resolution element. For He II with an average flux from IUE of 8 * 10^-15 erg cm ^-2 s^-1 AA^-1 a 120 minute observation would give 28 counts/s per velocity resolution element. We will utilize the GHRS G140L in RAPID mode with high data rate to allow readout every 50ms in order to search for UV signatures of the QPOs. The average continuum flux observed from IUE at 1300Angstrom is F_Lambda~eq 4 * 10^-15 erg cm^-2 s^-1 AA^-1, corresponding to a counting rate of .07 counts s^-1 diode^-1. If we integrate over the total 140L bandpass of roughly 286 Angstrom, centered at 1400 Angstrom we obtain 35 cts/s. The time estimate for the G140l observation is based on the requirements for time-series analysis. In order to measure the power spectrum at a frequency f (in Hz) we require an observing time given by the formula T = (4n^2f)/(F^2r^4), where n is the number of ``sigmas'' of the detection, F is the count rate, and r is the fractional amplitude of the variability. For a typical case of Cyg X-2 in the normal branch, the X-ray QPO's have Delta f = 5 Hz and r ~ 0.1. Thus we need an observing time of T ~ 1470 s for a 3Sigma and 5,880 s for a 5Sigma measurement. The 20-minute integration limit for high data readout mode will give us a 3 Sigma limit. We understand that it is possible to get a significantly longer high data rate exposure if the on-board tape recorder is bypassed and the data are sent down to the ground in real time. We realize that real time contacts are a limited resource; and only point out that finding UV QPOs simultaneously with X-ray detections could be very important. Cyg X-2 is the only source for which this is currently possible. We request a total time on source of 240 minutes (60-min integration with G160M centered on NV; 120-min integration with G160M centered on HeII; and a 60-min integration with G140L centered at 1400 Angstrom). Assuming a 53-minute viewing window for Cyg X-2, with one guide star acquisition (12 minutes), one target acquisition (11 minutes), 5 target re-acquisitions of 6 minutes each, and 3 instrument read-outs of 4 minutes each, the total number of satellite orbits we require is 6. Real_Time_Justification: The HST observations will be coordinated with simultaneous observations by ASCA. Simultaneous X-ray observations with ASCA add a vital dimension to the proposed program allowing us to analyze the radial structure of velocity in the disk and providing an unprecedented probe into the structure and dynamics of the accretion flow. The HST observations by themselves would allow both the search for QPO's in the UV and tests of the models for UV line emission; however knowing the frequencies of the QPO's from the X-ray observations will substantially lower the threshold for statistically significant detection of QPO's in the UV spectrum; knowing the size of the reprocessing region from cross-correlation of simultaneous X-ray and UV flux measurements will benefit the study of line emission. Cyg X-2 is visible to ASCA for 6 1/2 months of the year starting July 1, 1995 so coordination with HST should not be difficult. We need to utilize real-time contact in order to obtain a high data readout beyond the 20-minute integration limit. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: SIMULTANEOUS OBSERVATIONS WILL BE TAKEN BY THE ASCA X-RAY TELESCOPE. The time intervals when Cyg X-2 is visible to ASCA are: 19-APR-95 to 27-JUL-95; 22-OCT-95 to 24-JAN-95; and 19-APR-96 to 27-JUL-96. We will need at least a one-month lead time on the week in which the observations takes place and a two weeks lead time on the exact time. We need to utilize real-time contact in order to obtain uninterrupted high data readout beyond the 20-minute limit: data gaps would have an adverse affect on our desired scientific goal. Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: 4U2142+380 Alternate_Names: Cygnus X-2, V1341 Cygni Description: STAR, F0-F2, LMXB, Position: RA = 21H 44M 41.10S +/- 0.04S, DEC = 38D 19' 16.4" +/- 0.5", PLATE-ID = 004Z Equinox: J2000 Flux: V = 14.6 +/- 0.1, E(B-V) = 0.45 +/- 0.05, ! B-V = 0.45 +/- 0.05 from Milgrom 1976 TYPE = F2, F-CONT(1300) = 4 +/- 1.0 E-15, F-LINE(1240) = 2.0 +/- 1.0 E-14, W-LINE(1240) = 12.0 +/- 3.0, F-LINE(1640) = 8.0 +/- 1.0 E-15, W-LINE(1640) = 10.0 +/- 3.0, Comments: Coordinates are from a parabolic centroid GASP measurement by Karla Visits Visit_Number: 1 Visit_Requirements: PCS MODE F PERIOD 236.23H AND ZERO-PHASE JD2449746.682 Visit_Comments: SIMULTANEOUS OBSERVATIONS WILL BE TAKEN BY THE ASCA X-RAY TELESCOPE. The time intervals when Cyg X-2 is visible to ASCA are: 19-APR-95 to 27-JUL-95; 22-OCT-95 to 24-JAN-95; and 19-APR-96 to 27-JUL-96. We will need at least a one-month lead time on the week in which the observations takes place and a two weeks lead time on the exact time. Exposure_Number: 1 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: Mirror-N2 Number_of_Iterations: 1 Time_Per_Exposure: 114.75s Special_Requirements: PHASE 0.4 TO 0.7 ONBOARD ACQ FOR 10-80 Comments: Need maximum step-time of 12.75s Exposure_Number: 10 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: RAPID Aperture: 2.0 Sp_Element: G160M Wavelength: 1225-1255 Optional_Parameters: SAMPLE-TIME = 0.5 Number_of_Iterations: 1 Time_Per_Exposure: 865s Exposure_Number: 20 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: RAPID Aperture: 2.0 Sp_Element: G160M Wavelength: 1225-1255 Optional_Parameters: SAMPLE-TIME = 0.5 Number_of_Iterations: 1 Time_Per_Exposure: 2986.0S Exposure_Number: 30 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: RAPID Aperture: 2.0 Sp_Element: G160M Wavelength: 1625-1655 Optional_Parameters: SAMPLE-TIME = 0.5 Number_of_Iterations: 1 Time_Per_Exposure: 2986.0S Exposure_Number: 40 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: RAPID Aperture: 2.0 Sp_Element: G160M Wavelength: 1625-1655 Optional_Parameters: SAMPLE-TIME = 0.5 Number_of_Iterations: 1 Time_Per_Exposure: 2986.0S Exposure_Number: 50 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: RAPID Aperture: 2.0 Sp_Element: G140L Wavelength: 1257-1543 Optional_Parameters: SAMPLE-TIME = 0.05 Number_of_Iterations: 1 Time_Per_Exposure: 870S Special_Requirements: Exposure_Number: 60 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: RAPID Aperture: 2.0 Sp_Element: G140L Wavelength: 1257-1543 Optional_Parameters: SAMPLE-TIME = 0.05 Number_of_Iterations: 1 Time_Per_Exposure: 870S Special_Requirements: Exposure_Number: 70 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: RAPID Aperture: 2.0 Sp_Element: G140L Wavelength: 1257-1543 Optional_Parameters: SAMPLE-TIME = 0.05 Number_of_Iterations: 1 Time_Per_Exposure: 870S Special_Requirements: Exposure_Number: 80 ! Section 6.5 Target_Name: 4U2142+380 Config: HRS Opmode: RAPID Aperture: 2.0 Sp_Element: G140L Wavelength: 1257-1543 Optional_Parameters: SAMPLE-TIME = 0.05 Number_of_Iterations: 1 Time_Per_Exposure: 870S Special_Requirements: Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address Ship_Via: UPS Recipient_Email: