! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6645,v 5.1 1996/02/06 14:12:39 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6645,v 5.1 1996/02/06 14:12:39 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: Landis ! Phone: 410-338-4560 , E-mail: landis@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-0662.pavlov.prop ! Date generated: Fri Dec 22 16:00:34 EST 1995 ! Proposal_Information ! Section 4 Title: UV-OPTICAL SPECTRA OF MIDDLE-AGE PULSARS: THERMAL VS. NONTHERMAL Proposal_Category: GO Scientific_Category: HOT STARS Cycle: 6 Investigators PI_name: George Pavlov PI_Institution: Pennsylvania State University CoI_Name: France Cordova CoI_Institution: NASA HQ and Penn State Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) Deep spectral observations of isolated pulsars are critical for understanding the nature and behavior of neutron stars. In principle, such observations could distinguish between thermal radiation from the neutron star surface and nonthermal radiation from its magnetosphere. We propose to investigate the ultraviolet and optical radiation from the radio/soft-X-ray pulsar PSR B0656+14. We have previously detected B0656+14 with the FOC long-pass filter F130LP. A comparison of these HST data and the ROSAT data with model spectra of neutron star atmospheres shows that the optical-UV flux is mainly provided by nonthermal radiation which exceeds by several orders of magnitude predictions of the theoretical models. To better understand the origin of the nonthermal component, we propose to obtain deep imaging of this object with several filters. Measuring the far-UV flux is essential for the detection of the thermal component and evaluation of the effective temperature of the neutron star atmosphere. Questions ! Free format text (please update) Observing_Description: We propose to obtain deep images in several FOC filters for the radio and soft X-ray pulsar PSR B0656+14. Because of its greater sensitivity, the FOC is essential for the far-UV through B band imaging. PSR B0656+14 was the brightest pulsar in our Cycle 4 observations, which allows its spectral distribution to be studied with greater spectral resolution. In analyzing our Cycle 4 data we have used IRAF photometry routines to measure the count rates in the summed F130LP images, which incorporate the standard pipeline processing. To evaluate the count rates expected for other filters, we fitted our data along with the marginal detection of V~eq 25 mag of Caraveo et al. (1994) using SYNPHOT. We assumed that the nonthermal component of the spectral flux behaves as F_nu\propto Nu^-Alpha, and the thermal component is given by one of the extreme models (`bb' and `atm' in Fig. 1 of Pavlov et al. 1996) obtained by extrapolating the ROSAT spectrum to the UV-optical domain. The best fits correspond to Alpha = 0.45 and Alpha=0.85 for `bb' and `atm' thermal components, respectively. Since attenuation of radiation by interstellar extinction may be potentially important, especially in the far-UV range, we estimated the expected extinction E(B-V) for B0656+14 from optical and IUE observation of nearby stars and from attenuation of the soft X-ray radiation of B0656+14. This estimates show that E(B-V) most likely does not exceed 0.02-0.03; such low extinction can be neglected even in the far-UV band, at least for preliminary estimates of the expected sourse count rates. For the background rate in the FOC, needed to compute exposure times for different filters, we assume R_B=n* 1* 10^-3 s^-1, a typical value obtained in our Cycle 4 observations (n is the number of pixels). Based on these estimates, we propose to observe the pulsar with three FOC filters: F195W, F342W (U) and F430W (B). The expected source count rate in the U filter (3060-3760 Angstrom at half maximum) is R_S=0.20-0.24 s^-1; a S/N=10-12 can be achieved in a 35 min orbit after initial aquisition. The source count rate in the B filter (3520 - 4350 Angstrom ) is less definite, R_S=0.15-0.25; a 40 min (one orbit) exposure would provide sufficiently high S/N=9-12. The filter F195W (the transparency band at half maximum is 1640 - 2580 Angstrom), is the most important for evaluation of the thermal component of the pulsar radiation. Its efficiency is lower than that for U and B although higher than for other far-UV filters. The source count rate estimate for this filter is R_S=0.05- 0.10 s^-1, depending on the (unknown) contribution of the thermal component. This gives S/N =4-7 for one orbit, S/N=6- 10 for two orbits, and S/N=7-12 for three orbits. The latter S/N values would allow us to measure the far UV fluxes with sufficient accuracy. Thus, observation of B0656+14 (one visit) would require a total of 5 FOC orbits. Real_Time_Justification: None. None. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: PSR-B0656+14 Alternate_Names: PSR-J0659+1414 Description: Star,Pulsar,Neutron Star Position: ! Most common specification format is RA=6H 59M 48.13S +/- 0.05S, DEC=+14D 14' 21.2" +/- 0.1", PLATE-ID=02UU Equinox: J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=25 +/- 1 B-V=0.3 +/- 0.3 E(B-V)=0.03 +/- 0.03 ! Include at least V and B-V Comments: ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling ! PCS MODE [Fine | Gyro] ! GUIDing TOLerance ! DROP TO GYRO IF NECESSARY [NO REACQuisition] ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! SCHEDulability ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN