7836( 2) - 11/17/97 09:52 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7836 Version: 2 Check-in Date: 17-Nov-1997 09:51:37 1.Proposal Title: Infrared Radiation from Middle-Aged Pulsars ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: GEORGE PAVLOV PENNSYLVANIA STATE UNIVERSITY CoI: Jules Halpern Columbia University N CoI: Christopher Martin Caltech N ------------------------------------------------------------------------------------ 5. Abstract We have studied several middle-aged pulsars in detail at optical and ultraviolet wavelengths. Their spectral distributions indicate that both surface thermal emission and nonthermal magnetospheric processes are present. These components need to be resolved before reliable tests of theories of neutron-star cooling and nonthermal evolution can be made. The nonthermal component was unexpected theoretically, and it is clear that it will dominate in the near infrared. We propose to measure the IR fluxes of two middle-aged pulsars, 0656+14 and Geminga, with three broad- band filters. This will enable us to determine the slope of the nonthermal components of their radiation, to pin down the intensity of the thermal component, and to understand the origin of certain spectral features which have apparently been observed in their optical spectra and attributed to ion- cyclotron resonances. ------------------------------------------------------------------------------------ 7836( 2) - 11/17/97 09:52 - [ 2] Observations Description ------------------------ The two pulsars chosen for our program are the best- investigated and brightest middle-aged pulsars. Since these are point sources, we do not require the high spatial resolution of Camera 1. We chose Camera 2 as our primary instrument because it has broad-band filters sensitive to longest wavelength, 2.4 Mum. Since our goal is to measure fluxes of these faint objects in broadest possible wavelength range, with reasonably short exposures, we chose three broad- band filters, F110W, F160W and F187W, as a primary filter set. We do not know in advance how large are the pulsar IR fluxes --- it is our goal to measure them. However, reasonable estimates can be made by extrapolating our previous observations. For PSR 0656+14, the best-fit nonthermal flux and the flux corresponding to a lower limit for the power-law index are (Pavlov et al. 1997) F_Nu=1.0 (Nu/2.73* 10^14 Hz)^-1.4 MuJy and F_Nu=0.62 (Nu/2.73* 10^14 Hz)^-0.3 MuJy, respectively (the reference frequency corresponds to Lambda=1.1 Mum). These equations correspond to the following fluxes at the central wavelengths of the Camera 2 filters F110W, F160W and F187W: 0.62--1.0, 0.69--1.7 and 0.73-- 2.2 MuJy, respectively. With the aid of the on-line NICMOS Exposure Time Calculator (ETC), we estimated the following source count rates in the brightest pixel: 0.42-- 0.66, 0.22--0.53 and 0.098--0.29 e^-/s. (The fractions of energy falling in central pixel are 0.29, 0.16 and 0.12). The background count rates for the same filters, given by ETC for an ecliptic latitude of 45 deg, are 0.10, 0.09 and 0.31 e^-/(s pix). Our targets lie at low ecliptic latitudes, so that the first two background values may be greater by a factor of 2--2.5, depending on ecliptic longitude. Since our souces are very faint, we choose the LOW-SKY requirement for the F110W and F160W filters to minimize the zodiacal background. At the relatively low background count rate, and for these very faint objects, the read noise exceeds the background noise, so that we have to choose the ACCUM mode, with NREAD=9, to reduce the read noise. If we choose exposures of 1, 2, and 3 orbits for F110W, F160W and F187W, respectively, and split each orbit into 4 single exposures of 636 sec for rejecting CR events, we obtain resulting S/N ratios of 8--15 for each of the filters. To minimize possible effects of bad pixels, we chose the spiral dithering pattern with four pattern positions. The IR fluxes expected for Geminga are less certain than for PSR 0656+14. From the previous observations a 3 sigma upper limit of 0.065 MuJy was obtained for the 0.77-0.94 Mum. band. Our Keck spectroscopy indicates that the low flux at these wavelengths may be associated with the second ion-cyclotron harmonic, and it would be very important to measure the flux value in order to verify this assumption. A lowest possible limit for the expected flux at Lambda =1.1 Mum (center of the F110W filter) can be estimated as 0.015MuJy, the extrapolation of the thermal spectrum extended to this wavelength. If we take an expected flux of 0.03 MuJy (which we consider as a conservative estimate), then the corresponding F110W source count rate is 0.021 e^-/s in the central pixel, at a background count rate of 0.2 e^-/(s pix). For an exposure of 13.4 ks (5 satellite orbits) we obtain S/N=4--5 for the central pixel which includes 0.29 of the total energy. This estimate is obtained for NREAD=9 and with each orbit split into two exposures. If our hypothesis about the cyclotron nature of the IR flux is correct, we should expect a higher flux in the F160W band, which is expected to lie between two spectral minima. Choosing a four-orbit total exposure for this filter, we obtain S/N=4 and 10 for the flux values of 0.07 and 0.2 MuJy, respectively. We believe that observations at even longer wavelengths would be justified only after the F110W and F160W fluxes are measured. To increase the scientific yield of our program, we also propose to make deep parallel observations of adjacent field with NICMOS Cameras 1 and 3 in filters F110W and F160W. Real Time Justification ----------------------- No special requirements. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7836( 2) - 11/17/97 09:52 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7836( 2) - 11/17/97 09:52 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PSR-B0656+14 Star, Pulsar, Neutron RA=6H 59M 48.12S +/- 0.05S, J2000 V = 24.9+/-0.2 Star DEC=+14D 14' 20.3" +/- 0.9" B-V = 0+/-0.3 E(B-V) = 0.03+/-0.03 2 GEMINGA Star, Pulsar, Neutron RA=6H 33M 54.18S +/- 0.05S, J2000 V = 25.3+/-0.2 Star DEC=+17D 46' 13.2" +/- 1.0" B-V = 0.8+/-0.3 E(B-V) = 0.02+/-0.03 7836( 2) - 11/17/97 09:52 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PSR-B0656+1 NIC2 ACCUM NIC2 F160W NREAD=9,PATTERN=SPIRAL-DITH, 2 636.114 PAR 2,3 WITH 1 LOW-SKY 4 NUM-POS=4,DITH-SIZE=2.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY NIC1 ACCUM NIC1 F110W NREAD=9 2 636.114 Comments: Image C1 field in 110W. Turn off C1 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 3 ANY NIC3 ACCUM NIC3 F110W NREAD=9 2 636.114 Comments: Image C3 field in 110W. Turn off C3 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 4 PSR-B0656+1 NIC2 ACCUM NIC2 F110W NREAD=9,PATTERN=SPIRAL-DITH, 1 636.114 PAR 5,6 WITH 4 LOW-SKY 4 NUM-POS=4,DITH-SIZE=2.0 ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY NIC1 ACCUM NIC1 F110W NREAD=9 1 636.114 Comments: Image C1 field in F110W. Turn off C1 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY NIC3 ACCUM NIC3 F110W NREAD=9 1 636.114 Comments: Image C3 field in F110W. Turn off C3 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 7 PSR-B0656+1 NIC2 ACCUM NIC2 F187W NREAD=9,PATTERN=SPIRAL-DITH, 1 636.114 PAR 8,9 WITH 7 4 NUM-POS=4,DITH-SIZE=2.0 ------------------------------------------------------------------------------------------------------------------------------------ 8 ANY NIC1 ACCUM NIC1 F160W NREAD=9 1 636.114 Comments: Image C1 field in 160W. Turn off C1 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 9 ANY NIC3 ACCUM NIC3 F160W NREAD=9 1 636.114 Comments: Image C3 field in 160W. Turn off C3 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 10 PSR-B0656+1 NIC2 ACCUM NIC2 F187W NREAD=9,PATTERN=SPIRAL-DITH, 1 636.114 PAR 11,12 WITH 10 4 NUM-POS=4,DITH-SIZE=2.0 ------------------------------------------------------------------------------------------------------------------------------------ 11 ANY NIC1 ACCUM NIC1 F160W NREAD=9 1 636.114 Comments: Image C1 field in 160W. Turn off C1 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 12 ANY NIC3 ACCUM NIC3 F160W NREAD=9 1 636.114 Comments: Image C3 field in 160W. Turn off C3 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 7836( 2) - 11/17/97 09:52 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 13 PSR-B0656+1 NIC2 ACCUM NIC2 F187W NREAD=9,PATTERN=SPIRAL-DITH, 1 636.114 PAR 14,15 WITH 13 4 NUM-POS=4,DITH-SIZE=2.0 ------------------------------------------------------------------------------------------------------------------------------------ 14 ANY NIC1 ACCUM NIC1 F160W NREAD=9 1 636.114 Comments: Image C1 field in 160W. Turn off C1 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 15 ANY NIC3 ACCUM NIC3 F160W NREAD=9 1 636.114 Comments: Image C3 field in 160W. Turn off C3 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 7836( 2) - 11/17/97 09:52 - [ 7] Visit: 02 Visit Priority: Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GEMINGA NIC2 ACCUM NIC2 F110W NREAD=9,PATTERN=SPIRAL-DITH, 2 636.114 PAR 2,3 WITH 1 LOW-SKY NUM-POS=10,DITH-SIZE=2.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY NIC1 ACCUM NIC1 F110W NREAD=9 2 636.114 Comments: Image C1 field in F110W. Turn off C1 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 3 ANY NIC3 ACCUM NIC3 F110W NREAD=9 2 636.114 Comments: Image C3 field in F110W. Turn off C3 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 7836( 2) - 11/17/97 09:52 - [ 8] Visit: 03 Visit Priority: Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GEMINGA NIC2 ACCUM NIC2 F160W NREAD=9,PATTERN=SPIRAL-DITH, 2 636.114 PAR 2,3 WITH 1 LOW-SKY NUM-POS=8,DITH-SIZE=2.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY NIC1 ACCUM NIC1 F160W NREAD=9 2 636.114 Comments: Image C1 field in F160W. Turn off C1 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 3 ANY NIC3 ACCUM NIC3 F160W NREAD=9 2 636.114 Comments: Image C3 field in F160W. Turn off C3 Autoflush to eliminate "bars" ------------------------------------------------------------------------------------------------------------------------------------ 7836( 2) - 11/17/97 09:52 - [ 9] Summary Form for Proposal 7836 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations NIC2 NIC1 NIC3 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NREAD=9 PATTERN=SPIRAL-DITH NUM-POS=4 DITH-SIZE=2.0 NUM-POS=10 NUM-POS=8 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F PAR 2,3 WITH 1 LOW-SKY PAR 5,6 WITH 4 LOW-SKY PAR 8,9 WITH 7 PAR 11,12 WITH 10 PAR 14,15 WITH 13 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F160W F110W F187W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PSR-B0656+14 ANY GEMINGA ------------------------------------------------------------------------------------------------------------------------------------