Millisecond dips in the RXTE/PCA light curve of Sco X-1 and trans-Neptunian object occultation

Millisecond dips in the RXTE/Proportional Counter Array (PCA) light curve of Sco X-1 were reported recently, which were interpreted as the occultation of X-rays from Sco X-1 caused by trans-Neptunian objects (TNO) of 100-m size. Inconclusive signatures of possible instrumental effects in many of the...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2007-07, Vol.378 (4), p.1287-1297
Main Authors: Chang, Hsiang-Kuang, Liang, Jau-Shian, Liu, Chih-Yuan, King, Sun-Kun
Format: Article
Language:English
Subjects:
Astronomy
Astrophysics
Cosmic rays
Cosmology
Double stars
Earth, ocean, space
Exact sciences and technology
Kuiper Belt
Neutrinos
occultations
Solar system
Solar system: formation
stars: neutron
X-ray astronomy
X-rays: binaries
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Summary:Millisecond dips in the RXTE/Proportional Counter Array (PCA) light curve of Sco X-1 were reported recently, which were interpreted as the occultation of X-rays from Sco X-1 caused by trans-Neptunian objects (TNO) of 100-m size. Inconclusive signatures of possible instrumental effects in many of these dip events related to high-energy cosmic rays were later found and the TNO interpretation became shaky. Here, we report more detailed analysis aiming at distinguishing true occultation events from those related to cosmic rays. Based on some indicative criteria derived from housekeeping data and two-channel spectral information, we suggest that about 10 per cent of the dips are probable events of occultation. The total number of TNOs of size from 60 to 100 m is estimated to be about 1015 accordingly. Limited by the coarser time resolution of standard data modes of RXTE/PCA, however, definite results cannot be obtained. Adequately configured observations with RXTE or other new instruments in the future are very much desired.
ISSN:0035-8711
1365-2966
DOI:10.1111/j.1365-2966.2007.11729.x