J/ApJS/245/19 Thermonuclear burst oscillations (TBOs) with RXTE (Bilous+, 2019)
A uniform search for thermonuclear burst oscillations in the RXTE legacy data
set.
Bilous A.V., Watts A.L.
<Astrophys. J. Suppl. Ser., 245, 19 (2019)>
=2019ApJS..245...19B 2019ApJS..245...19B
ADC_Keywords: Binaries, X-ray; X-ray sources; Stars, neutron
Keywords: X-rays: bursts
Abstract:
We describe a blind uniform search for thermonuclear burst
oscillations (TBOs) in the majority of Type I bursts observed by the
Rossi X-ray Timing Explorer (RXTE) (2118 bursts from 57 neutron
stars). We examined 2-2002Hz power spectra from the Fourier transform
in sliding 0.5-2s windows, using fine-binned light curves in the
2-60keV energy range. The significance of the oscillation candidates
was assessed by simulations which took into account light-curve
variations, dead time, and the sliding time windows. Some of our
sources exhibited multi-frequency variability at ≲15Hz that cannot be
readily removed with light-curve modeling and may have an
astrophysical (non-TBO) nature. Overall, we found that the number and
strength of potential candidates depends strongly on the parameters of
the search. We found candidates from all previously known RXTE TBO
sources, with pulsations that had been detected at similar frequencies
in multiple independent time windows, and discovered TBOs from
SAXJ1810.8-2658. We could not confirm most previously reported
tentative TBO detections or identify any obvious candidates just below
the detection threshold at similar frequencies in multiple bursts. We
computed fractional amplitudes of all TBO candidates and placed upper
limits on non-detections. Finally, for a few sources we noted a small
excess of candidates with powers comparable to fainter TBOs, but
appearing in single independent time windows at random frequencies. At
least some of these candidates may be noise spikes that appear
interesting due to selection effects. The potential presence of such
candidates calls for extra caution if claiming single-window TBO
detections.
Description:
The observations were performed in 1996-2011 with the proportional
counter array (PCA) on board the Rossi X-ray Timing Explorer (RXTE)
telescope. The PCA is sensitive to photons in the energy range between
2 and 60keV.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 62 57 Overview of sources (excerpt from Table 3)
table2.dat 245 2117 Data and upper limit on fractional amplitudes
(FAup) for the bursts
table4.dat 152 434 Fractional amplitudes of candidates per burst
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See also:
J/ApJ/376/161 : X-ray spectra of bursting neutron stars (Madej, 1991)
J/AcA/41/73 : X-ray bursting neutron star atmosphere models (Madej, 1991)
J/ApJS/179/360 : Thermonuclear X-ray bursts observed by RXTE (Galloway+, 2008)
J/A+A/545/A120 : X-ray bursting neutron star atm. models II (Suleimanov+, 2012)
J/ApJ/738/128 : RXTE observations of 4U 1728-34 (Seifina+, 2011)
J/ApJ/747/77 : Thermonuclear X-ray bursts. II. Eddington limit (Guver+, 2012)
J/A+A/581/A83 : Metal enriched X-ray bursting neutron stars. (Nattila+, 2015)
J/A+A/606/A130 : List of 1254 X-ray bursts (in't+, 2017)
http://burst.sci.monash.edu/minbar/ : Multi-INstrument Burst ARchive (MINBAR)
home page
Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- ID X-ray source identifier
19- 21 I3 --- Nb [1/368] Total number of bursts suitable
for TBO search
23- 29 F7.1 s Dur [10/20954] Total burst duration
31- 36 F6.1 --- SNpk [6.4/1406.4] Median SNpeak (1)
38- 39 I2 --- B_FAup1s [2/81] Minimum upper limit on fractional
amplitude in 1s Fourier windows on a burst peak
41- 42 I2 --- FAup1s [2/81] Median upper limit on fractional
amplitude in 1s Fourier windows on a burst peak
44- 48 F5.2 --- Chi2 [0.02/34] χ2 value (2)
50- 54 F5.2 --- Simul [0.02/33] Number of spurious candidates
in simulated data (3)
56- 57 I2 --- Real [0/39] Number of spurious candidates
in real data
59- 62 F4.2 --- p [0/1] Percentile of the real-data number of
noise candidates with respect to a 100-run
simulation sample
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Note (1): Median S/N of the burst peak on the sample of all bursts from
the given source.
Note (2): Number of noise candidates above selected detection threshold
(excluding low-frequency candidates and candidates in the known TBO
frequency range) predicted by Equation (4), treating all time windows
as independent.
Note (3): Mean number per simulation run, averaged over 100 simulation runs.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- ID X-ray source identifier
19- 22 I4 --- BNum [2203/8289] MINBAR database burst entry number
24- 42 A19 "datime" TOA MINBAR database burst time of arrival (UT date)
44- 54 F11.1 s Tpeak [66413835/567575947] Burst peak in Mission
Elapsed Time
56- 60 F5.1 s Rise [-50/0] Size of the rise window
62- 66 F5.1 --- HalfMax [0.5/274.5] Burst half-peak with respect
to Burst Peak
68- 72 F5.1 --- Tail [1.5/814] Burst end with respect to Burst Peak
74- 79 F6.1 --- S/N [2.9/1607.7] Burst peak Signal-to-Noise ratio
81-151 A71 --- Mode Mode of data file(s) analyzed
(semi-colon separated)
153-203 A51 --- Note Additional notes
205-209 F5.1 --- MaxPow [19.7/352.3] Maximum Leahy-normalized power
in the frequency range of 10-2002Hz
211-217 F7.2 Hz Freq [10.5/2001] Frequency of MaxPow
219-221 F3.1 --- Twin [0.5/4] Size of FFT window with maximum power
223-227 F5.1 s FA0.5 [3.2/170.4] Best upper limit on fractional
amplitude in 0.5s FFT window
229-233 F5.1 s FA1.0 [2.4/151] Best upper limit on fractional
amplitude in 1.0s FFT window
235-239 F5.1 s FA2.0 [1.8/128.3] Best upper limit on fractional
amplitude in 2.0s FFT window
241-245 F5.1 s FA4.0 [1.3/101.1] Best upper limit on fractional
amplitude in 4.0s FFT window
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- ID X-ray source identifier
19- 22 I4 --- BNum [2205/8267] MINBAR database burst entry number
24- 42 A19 "datime" TOA MINBAR database burst time of arrival (UT date)
44- 58 A15 Hz Freq Frequency or frequency range
60- 64 A5 --- Where Region of occurrence (R=rise; B=burst or T=tail)
66- 67 I2 --- NAny [1/33] Number of detections in independent
time windows of any size
69 I1 --- N0.5 [0/8] Number of detections in 0.5s independent
time windows
71- 72 I2 --- N1.0 [0/30] Number of detections in 1.0s independent
time windows
74- 75 I2 --- N2.0 [0/26] Number of detections in 2.0s independent
time windows
77- 78 I2 --- N4.0 [0/17] Number of detections in 4.0s independent
time windows
80- 84 F5.1 --- FA0.5 [5.1/680]? Maximum fractional amplitude in 0.5s
time window
86- 91 F6.1 --- e_FA0.5 [0.7/230]? Lower relative uncertainty in FA0.5
93- 98 F6.1 --- E_FA0.5 [0.8/1204]? Upper relative uncertainty in FA0.5
100-104 F5.1 --- FA1.0 [4/318]? Maximum fractional amplitude in 1.0s
time window
106-111 F6.1 --- e_FA1.0 [0.5/178]? Lower relative uncertainty in FA1.0
113-117 F5.1 --- E_FA1.0 [0.5/498]? Upper relative uncertainty in FA1.0
119-123 F5.1 --- FA2.0 [2.4/123]? Maximum fractional amplitude in 2.0s
time window
125-128 F4.1 --- e_FA2.0 [0.3/39]? Lower relative uncertainty in FA2.0
130-134 F5.1 --- E_FA2.0 [0/41]? Upper relative uncertainty in FA2.0
136-139 F4.1 --- FA4.0 [2.3/99]? Maximum fractional amplitude in 4.0s
time window
141-144 F4.1 --- e_FA4.0 [0/28]? Lower relative uncertainty in FA4.0
146-152 F7.2 --- E_FA4.0 [0.3/29]? Upper relative uncertainty in FA4.0
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 25-Mar-2020