J/MNRAS/462/4371 Sample of faint X-ray pulsators (Israel+, 2016)
The Chandra ACIS Timing Survey Project:
glimpsing a sample of faint X-ray pulsators.
Israel G.L., Esposito P., Rodriguez Castillo G.A., Sidoli L.
<Mon. Not. R. Astron. Soc., 462, 4371-4385 (2016)>
=2016MNRAS.462.4371I 2016MNRAS.462.4371I (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, X-ray ; Pulsars
Keywords: methods: data analysis - catalogues - stars: oscillations -
pulsars: general - X-rays: binaries - X-rays: stars
Abstract:
We report on the discovery of 41 new pulsating sources in the data of
the Chandra Advanced CCD Imaging Spectrometer, which is sensitive to
X-ray photons in the 0.3-10 keV band. The archival data of the first
15 yr of Chandra observations were retrieved and analysed by means of
fast Fourier transforms, employing a peak-detection algorithm able to
screen candidate signals in an automatic fashion. We carried out the
search for new X-ray pulsators in light curves with more than 50
photons, for a total of about 190000 light curves out of about 430000
extracted. With these numbers, the ChAndra Timing Survey at Brera And
Roma astronomical observatories (CATS @ BAR) - as we called the
project - represents the largest ever systematic search for coherent
signals in the classic X-ray band. More than 50 per cent of the
signals were confirmed by further Chandra (for those sources with two
or more pointings), XMM-Newton or ROSAT data. The period distribution
of the new X-ray pulsators above ∼2000s resembles that of
cataclysmic variables, while there is a paucity of sources with
shorter period and low fluxes. Since there is not an obvious bias
against these detections, a possible interpretation is in terms of a
magnetic gating mechanism in accreting neutron stars. Finally, we note
that CATS @ BAR is a living project and the detection algorithm will
continue to be routinely applied to the new Chandra data as they
become public. Based on the results obtained so far, we expect to
discover about three new pulsators every year.
Description:
As of 2015 December 31, we extracted about 430000 time series from
sources with more than 10 counts (after background subtraction);
∼190000 of them have more than 50 counts and their PSDs were
searched for significant peaks. At the time of writing, the total
number of searched Fourier frequencies was about 4.3x109. After a
detailed screening, we obtained a final sample of 41 (42) new X-ray
pulsators (signals), which are listed in Table 1.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 168 46 *CATS catalogue
--------------------------------------------------------------------------------
Note on table1.dat: An updated online version of the table is maintained at
http://www.oa-roma.inaf.it/HEAG/catsatbar/.
--------------------------------------------------------------------------------
See also:
IX/45 : The Chandra Source Catalog, Release 1.1 (Evans+ 2012)
http://www.oa-roma.inaf.it/HEAG/catsatbar : CATS catalog Home Page
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- n_Name [*] Note on Name (1)
3- 23 A21 --- Name Name of the source (2)
25- 26 I2 h RAh Right ascension (J2000)
28- 29 I2 min RAm Right ascension (J2000)
31- 34 F4.1 s RAs Right ascension (J2000)
36 A1 --- DE- Declination sign (J2000)
37- 38 I2 deg DEd Declination (J2000)
40- 41 I2 arcmin DEm Declination (J2000)
43- 46 F4.1 arcsec DEs Declination (J2000)
48- 53 F6.2 arcmin GLAT Galactic latitude
55- 65 F11.5 s Per Period of the detected signal
67- 76 F10.5 s e_Per rms uncertainty on Per (90% confidence level)
79- 81 A3 --- Flag [* ] Flags (3)
85- 89 F5.1 10-16W/m2 Flux ? XMM flux (0.5-10keV) or
lower limit of XXM flux interval (4)
90 A1 --- --- [-]
91- 94 F4.1 10-16W/m2 Flux2 ? Upper limit of XXM flux ((0.5-10keV)
interval (4)
97-101 A5 --- NC Number of useful Chandra pointings used to
evaluate the signal/source parameters (5)
102 A1 --- --- [/]
103-106 A4 --- NX Number of useful XMM pointings used to
evaluate the signal/source parameters (5)
108-168 A61 --- Com Comments (6)
--------------------------------------------------------------------------------
Note (1): *: Sources with signals published by other groups while the project
was on-going and/or with rough estimate of the periods
Note (2): The name of the source, where the prefix CXO is used for sources
listed in the Chandra Source Catalog version 1.1 (CSC; Evans et al.,
2010ApJS..189...37E 2010ApJS..189...37E, Cat. IX/45), while CXOU for yet uncatalogued sources.
Note (3): Flag as follows:
*** = Multiple detection of the same signal (either with Chandra or with
other missions)
** = Single high confidence (>10σ) detection
* = Single detection (above 3.5σ). See also Section 4.
Note (4): Observed 0.5-10keV flux in units of 10-13erg/cm2/s for a
power-law fit. A range of values indicates different values measured in the
Chandra observations used for the timing analysis.
Note (5): Number of useful Chandra and XMM-Newton pointings used to evaluate the
signal/source parameters. We counted only those observations where the signal
was detected or those with no detection but 3σ pulsed fraction upper
limits smaller than that of the modulation were inferred. We also counted
observations where the source was not detected at a comparable or lower flux
level with respect to the original detection level or detected at a
significantly different flux level.
Note (6): Comments:
Abbreviations as follows:
E = eclipsing
T = transient: the source was not detected in some observations with
Chandra or other missions
Pst = persistent: the flux did not vary by more than a factor of 5 in the
observations we considered
V = variable: we measured flux variations larger than a factor of 5
O = optical counterpart or association
? = denote tentative identifications or associations
References as follows:
[1] = Esposito et al. (2013MNRAS.433.3464E 2013MNRAS.433.3464E)
[2] = Bartlett et al., (2017MNRAS.466.4659B 2017MNRAS.466.4659B)
[3] = Esposito et al. (2013MNRAS.436.3380E 2013MNRAS.436.3380E)
[4] = Esposito et al. (2015MNRAS.452.1112E 2015MNRAS.452.1112E)
[5] = Nichelli et al. (2011, Swift and the Surprising Sky: The First Seven
Years of Swift 39)
[6] = Farrell et al. (2015, Cat. J/ApJ/813/28)
[7] = Muno et al. (2008ApJ...680..639M 2008ApJ...680..639M)
[8] = Esposito et al. (2013MNRAS.433.2028E 2013MNRAS.433.2028E)
[9] = Lin et al. (2014ApJ...780...39L 2014ApJ...780...39L)
[10] = Sidoli et al. (2016MNRAS.460.3637S 2016MNRAS.460.3637S)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 25-Apr-2018