Detection of a narrowband radio point source in the vicinity of NGC 752
Russell K. Childers
On October 26, 2009, at 03:56 UTC, the Ohio Argus Array detected a
brief (<2 s), narrowband (<10 Hz) radio pulse centered on 1420.8807 MHz.
The Argus Array processor analyzing the narrowband data in real-time
determined the signal source to be at right ascension 01 h 52 m 00s (+/- 11 m),
declination +37d 00m (+/-2.5 d). These coordinates and error bars put
the open cluster NGC 752 (RA 01 h 57 m 55s; dec +37 d 51 m 57 s; 1,300 ly)
within the field of view of the array (HPBW = 5 d, at zenith). The source
makes an excellent match to an ideal beam calculated from the array geometry,
making it highly unlikely that the source is a false alarm caused by local
or receiver noise. Five-minutes-worth of data were archived at the time
of detection, triggered by the ideal-beam-match. Analysis of ephemerides indicate
no known artificial radio sources within the HPBW of the Ohio Argus Array
at the time of detection.
For more information on Argus see:
Argus: An L-Band All-Sky Astronomical Surveillance System
This paper appears in: Antennas and Propagation, IEEE Transactions on
Publication Date: Feb. 2008
Volume: 56, Issue: 2
On page(s): 294-302
ISSN: 0018-926X
INSPEC Accession Number: 9794152
Digital Object Identifier: 10.1109/TAP.2007.915467
Current Version Published: 2008-02-07
![](fxe_20091026_match.png)
Figure 1. Match criterion for narrowband sources, for Oct 26, 2009.
A match of 21.5 elements out of 23 indicates a far-field source.
The source detection occurred at 14160 seconds after 0 h UTC.
![](oct26_3_channels_10_acq.png)
Figure 2. Power in frequency bins over 5-minute data archive period.
Data were from a synthesized beam pointing in the direction of the source.
red = 1420.8707 MHz; blue = 1420.8807 (source); green = 1420.8907 MHz)
![](oct26_NGC752_cropped.png)
Figure 3. Plot of source location with respect to known astronomical objects.
Note the proximity of NGC 752.
![](oct26_skymap.png)
Figure 4. Contour plot of 1/(23-deal_beam_match). This is generated
by doing a least-squares match between the phases of each ideal beam
and the phases of the source frequency bin from each array element.
![](waterfall_oct26_closeup.png)
Figure 5. Closeup of waterfall of beam pointed at source location.
Bottom of image is October 26, 2009 03:54 UTC; top is 03:59 UTC.
Spectra consist of 500 5-Hz channels each. Spectra are aligned to be
centered on source center frequency (1420.8807 MHz). Ignore the time
stamps on the left-hand margin of the Figure.
![](waterfall_oct26_full.png)
Figure 6. Full 60 kHz of waterfall of beam pointed at source location.
Bottom of image is October 26, 2009 03:54 UTC; top is 03:59 UTC.
Spectra consist of 500 channels (max of every 6 channels) each.
The source shows up as a single pixel, 2/3 of the way down the image,
1/4 of the way over from the left-hand side. Ignore the time stamps
on the left-hand margin of the Figure.
![](oct26_filtered_spectra_298acqs.png)
Figure 7. This is a plot of Figure 5, where frequency bin power is
shown across all 298 archived acquisitions.
![](oct26_unfiltered_spectra_10acqs.png)
Figure 8. FFTs of unfiltered synthesized beam spectra, pointed
at source location. Ten spectra are shown: 5 before source event
and 4 after source event (all in red), and the source event itself,
in blue.