Research Programs

at the Pisgah

Astronomical Research InstituteJ. D. Cline, M. W. Castelaz, C. Osborne (PARI)

D. Moffett (Furman University)

M. Lopez-Morales (UNC-Chapel Hill)

198th Meeting of the American Astronomical Society

4 June 2001. #5.12

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The Pisgah Astronomical Research Institute (PARI) is a not-for-profit public foundation dedicated to providing research and educational access to radio and optical astronomy for a broad cross-section of users. PARI open to astronomers for

on-site radio observations project development instrument development postdoctoral research

Introduction

We present preliminary results related to three ongoing research programs at PARI:

I. A pulsar-timing project using a 340 Mhz receiver on one of PARI’s 26-m radio telescopes;

II. A survey of the galactic plane for binary M-dwarf systems using a dedicated telescope on the PARI optical ridge;

III. A study of Jupiter-Io emission and the Sun at 20 MHz using a pair of 17-30 MHz log periodic yagis.

I. Pulsar Timing Project Precise measurement of pulse arrival

time has several applications.

Deviations of the arrival times from a simple rotation model can both elucidate the nature of the torque acting on neutron stars (causing angular deceleration) and probe their internal structure (starquakes causing temporary angular acceleration or 'glitches').

Dispersion of the arrival time with radio frequency measures the thermal-electron column density toward each star that provides a distance estimate.

Timing observations can also yield information on a pulsar's proper motion, parallax (if close enough) and orbital parameters if the pulsar has companion stars or planets.

PARI 26-W Radio Telescope

The Feed and Detector

Pulsar profiles and timing information (period, spin-down rate and dispersion) are being measured at 340 MHz

PARI 26-m antenna is outfitted with a full wavelength 2 element quad loop antenna as the feed for 340 MHz. A 50 Kelvin low noise amplifier is mounted in close proximity to the feed.

327 - 340 MHz was chosen after a spectrum survey indicated that this was relatively free of any local interference.

Both a 4 MHz wide cavity bandpass filter centered at 340 MHz, and a 400 MHz low pass filter, reside in the feedbox prior to additional gain stages.

A 410 MHz ovenized local oscillator mixes the 340 MHz down to 70 MHz. This signal is filtered in a 4 MHz wide 72 MHz center frequency filter before being amplified and sent to the control room a quarter mile away.

In the control room the 69-73 MHz spectrum is amplified and passed through a waveguide beyond cutoff attenuator and four way power divider.

The spectrum is monitored via: an HP-438 digital power meter, an HP-8559 Spectrum Analyzer, an Icom R8500 receiver, and a baseband downconverter.

The 69-73 MHz spectrum is mixed with a 72 MHz local oscillator and lowpass filtered to obtain 4 MHz of baseband spectrum.

Both downconversions utilize a high side local oscillator, the spectrum is inverted twice, resulting in proper low to high spectral sense at baseband.

Baseband spectrum is fed directly into an RF detector and then into a 20 MHz sampling rate Measurement Computing PCI-DAS4020/12 A/D card.

The RF detection path allows an EG&G Model 113 Instrumentation Amplifier to be used for gain and offset of the resulting < 300 kHz detected baseband. This also enhances the pulse signal to noise ratio.

Since time is critical, PARI has installed a dedicated time server. A description of the time server is given on the following page.

Time & Frequency Standards• Precision Time/Date stamping is available

from a dedicated Time Server at PARI. Up to 8 GPS satellites form the basis of a 20ns precision clock system called the CNS Clock.

• PARI utilizes a variety of frequency references. A Rubidium standard is currently the site master oscillator. A WWVB receiver and ovenized crystal oscillators are also used.

• The CNS Systems Clock and software allow comparison between the Rubidium oscillator and the average of up to 8 Cesium GPS oscillators on orbit. Radio telescope oscillators and other site test equipment can then be calibrated to 1E-12 resolution.

CNS Systems GPS Satellite Receiver

Rubidium Frequency Standard

HP53131A UniversalCounter

1 PPSTAC32 Plus Software

COM2

COM1 with 1 PPS

100Mbps fiber optic LAN and/or

Internet

The output of the A/D card is recorded for 100 seconds.

Measurements were made of PSR 0329+54 and PSR 0950+08 on 19 May and 23 May 2001 UT.

Figures I-1 a) and b) show the power spectra of the 0329+54 and 0950+08, respectively.

The power spectra indicate obvious periodicity of the pulsars. The frequencies in the power spectra are uncorrected for doppler effect.

The monitoring program was recently started. Intend to monitor a dozen pulsars at 340 MHz.

The Measurements

Figure I-1. Power spectra of a) 0329+54 and b) 0950+08 showing harmonics.

Power

Power

The second research program at PARI is an optical sky survey being conducted by Lopez-Morales to detect low-mass detached eclipsing binaries from which masses and radii can be determined.

II. Sky Brightness from Data taken

During the Survey for

Binary M-Dwarfs

The Pisgah Survey Observatory at PARI

• Optical sky brightness and limiting magnitudes at the I filter are derivedfrom the survey data.

• Data taken with 0.2-m telescope and 2048 x 2048 CCD camera binned2x2, 3 minute exposures.

• Field of View = 1.25 degrees and camera scale = 2.25 arcsec/pixel (1 pixel covers 5 square arcsec on the sky).

• 12 images taken from August through November 2000 were selected randomly.

• The images were taken at midnight and the average zenith distance of the fields was 45 degrees.

Surface Brightness

• Sky brightness was measured relative to the known magnitudes of 3 bright (I~8 mag) in each field.

• Table II-1 shows the surface brightness in the I filter bandpass in mag/square arcsec, from August to November 2000.

• The surface brightness varies from 15.3+/-0.7 in August to 16.2+/- 0.5 mag/sq arcsec in November.

Table II-1. Average surface brightness (mag/sq arcsec) in the I filter bandpass. Uncertainties reflect the variation of SB during the month.

Month

(2000)

Surface Brightness

(mag/sq. arcsec)

August 15.3 +/- 0.7

September 15.6 +/- 0.6

October 16.2 +/- 0.5

November 16.2 +/- 0.5

Limiting Magnitude

• Using the same set of 12 images taken from August through November 2000, we measure the limiting magnitude at I.

• We define the limiting magnitude at I as the magnitude with S/N = 10 and exposure time of 180 seconds using the Lopez-Morales sky survey 20-cm optical telescope.

• Table II-2 lists the limiting I magnitudes for each month.

Table II-2. The limiting magnitude at I on the optical ridge at PARI.

Month (2000) Limiting I Magnitude at PARI

August 16.0

September 16.0

October 16.4

November 15.5

• The limiting I magnitude at the KPNO 0.9-m+Mosaic f/7.5 in 3600 seconds is 22.9 with a S/N = 10 from the KPNO CCD Direct Imaging Manual. In 180 seconds, we would then expect a limiting magnitude of 16.4.

• The PARI limiting magnitudes at I are similar to the Kitt Peak values. The uncertainty is +/- 0.5 and is due to the small sample of stars, and interpolation of their I magnitudes

Data from a daily decameter wavelength (17 – 30 MHz) study of Jupiter-Io and Solar radio emissions are being measured.

We are currently searching for frequency-dependent radio emission as the moon Io passes through Jupiter’s magnetic field.

High Solar flare activity also provides opportunities for data recording and analysis using the same equipment.

III. Jupiter/Io and Solar Observations

PARI’s pair of M-Squared 17-30LP7 log periodic yagis for Jupiter/Io and Solar Observations

Jupiter-Io On 28 January 2001 UT, we recorded an

increase in 20 MHz flux from 1:28 UT through 2:28 UT (Figure III-1a), which is attributed to Io passing through Jupiter’s magnetic field.

For comparison, Fig. III-1b shows no increase in 20 MHz flux on 26 Jan 2001 UT

Figure III-1. 20 MHz flux as a function of time.

EDT

F(counts)

F(counts)

(a)

(b)

28 Jan 2001 UT

26 Jan 2001 UT

Solar Activity On 27 March 2001 UT there was a Type

III burst at 14:48 UT and an M2.2 flare 16:39 UT.

These events are marked in Figure III-2.

Note also the decrease in 20 MHz flux on 26 March 2001 UT between 18 and 19h UT and 27 March 2001 UT at 10h UT.

Figure III-2. 20 MHz flux (counts) as a function of UT. Note the dropouts marked by arrows. Two of these are known to correspond to flare events. Saturation of detector occurs at 32,768 counts.

UT

F

On 27 March 2001 UT, a Solar alert from Heliosynoptics (Boulder, Co) reported an expected proton flare over a 72 hour period continuing through 7 April.

A sunspot group was growing near Region 9393A (N20 E25 at 27/0000) and would combine with 9393A to form a very large sunspot complex within 24 hours.

The region is much larger than a July 2000 sunspot group, and accelerated motions signal a Class-X proton flare at least the magnitude of the Bastille-Day 2000 event.

Figure III-3 (a-f) show the sequence of data we recorded at 20 MHz from 1 April through 6 April 2001 UT. The largest dropouts were measured on 4 April 2001 UT during the flare period.

Figure III-3. 20 MHz flux as a function of UT, 1-6 April 2001. Compare to Figure III-1. Note the dramatic decrease in 20 MHZ flux on 4 April 2001 13h-15h UT

(a)

(b)

(c)

1 Apr

2 Apr

3 Apr

UT

UT

UT

(d)

(e)

(f)

4 Apr

5 Apr

6 Apr

Figure III-3. Continued.UT

UT

UT

Workshop

Small Radio Telescopes Small Radio Telescopes in Modern Astronomyin Modern Astronomy

PARI9-11 August 2001

Workshop Topics IncludeThe role of radio telescopes in surveys, long-term monitoring projects, and networks.Using radio telescopes for astronomy and astrophysics education.Remote, robotic, and on-site observing modes, instrumentation development, data collection and web access.

Abstracts Due: 10 June 2001Registration Due: 29 June 2001

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