J/ApJS/244/5 Crosscorrelation function (CCF) studies in GX 17+2 (Sriram+, 2019)
Constraining the coronal heights and readjustment velocities based on the
detection of a few hundred seconds delays in the Z source GX 17+2.
Sriram K., Malu S., Choi C.S.
<Astrophys. J. Suppl. Ser., 244, 5-5 (2019)>
=2019ApJS..244....5S 2019ApJS..244....5S (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, X-ray; X-ray sources
Keywords: accretion, accretion disks; binaries: close
stars: individual: GX 17+2; X-rays: binaries
Abstract:
Neutron star Z-type sources provide a unique platform in order to
understand the structure of accretion disk-corona geometry emitting
close to the Eddington luminosity. Using RXTE and Nuclear
Spectroscopic Telescope Array Mission (NuSTAR) satellite data, we
performed crosscorrelation function (CCF) studies in GX 17+2 in order
to constrain the size of the corona responsible for hard X-rays. From
the RXTE data, we found that during horizontal and normal branches,
the CCFs show anticorrelated hard (16-30keV) and soft (2-5keV) X-ray
delays of the order of a few tens to hundred seconds with a mean
correlation coefficient of 0.42±0.11. Few observations shows
correlated lags and, on one occasion, coincident with radio emission.
We also report an anticorrelated hard X-ray delay of 113±51s using
the NuSTAR data of GX 17+2. Based on RXTE data, we find that soft and
hard X-ray fluxes are varying, indicating the changes in the
disk-corona structure during delays. We bridle the size of the corona
using relativistic precession, transition layer models, and boundary
layer models. Assuming the delays to be a readjustment timescale of
the disk-corona structure, the height of the corona was estimated to
be ∼17-100km. Assuming that the inner region of the truncated disk is
occupied by the corona, we constrain the coronal readjustment
velocities (vcorona=βvdisk, where vdisk is the radial
velocity component of the disk) of the order of β=0.06-0.12. This
study indicates that the observed delays are primarily dependent on
the varying coronal readjustment velocities.
Description:
The public archival data of RXTE satellite was analyzed for GX 17+2.
The satellite consists of three primary instruments: the PCA, the
HEXTE, and the All Sky Monitor (ASM).
The hardness intensity diagram (HID) was generated using the data
collected in the energy domains of 6.2-8.7keV, 8.7-19.7keV, and
2.0-19.7keV with bin sizes of 32s after carefully selecting the
channels using RXTE gain epochs and gain change effects.
The NuSTAR data analysis was performed for both Focal Plane Modules A
and B (i.e., FPMA and FPMB instruments). See Section 2 for further details.
Objects:
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RA (ICRS) DE Designation(s)
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18 16 01.39 -14 02 10.6 GX 17+02 = V* NP Ser
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 130 282 Cross correlation functions of GX 17+2 using
2-5keV (Soft) and 16-30keV (Hard)
background-subtracted 32s bin RXTE PCA light curves
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See also:
B/cb : Cataclysmic Binaries, LMXBs, and related objects (Ritter+, 2004)
V/106 : Catalogue of X-ray binaries (Liu+, 2001)
J/A+A/281/161 : Radio emission from stars at 250GHz (Altenhoff+, 1994)
J/A+A/411/L59 : INTEGRAL reference catalog (Ebisawa+, 2003)
J/A+A/458/21 : INTEGRAL burst observations of 4U 1728-34 (Falanga+, 2006)
J/ApJS/179/360 : Thermonuclear X-ray bursts observed by RXTE (Galloway+, 2008)
J/ApJS/186/1 : The 4th IBIS/ISGRI soft gamma-ray survey catalog (Bird+, 2010)
J/A+A/522/A68 : Variable sources detected by INTEGRAL (Telezhinsky+, 2010)
J/AJ/141/129 : Chandra Transmission Grating Data Cat. (Huenemoerder+, 2011)
J/PAZh/37/651 : Hard X-ray bursts by INTEGRAL in 2003-2009 (Chelovekov+, 2011)
J/AJ/146/60 : X-ray variability in 4U 1735-44 (Lei+, 2013)
J/ApJS/209/14 : The Swift/BAT hard X-ray transient monitor (Krimm+, 2013)
J/BaltA/24/395 : X-ray and radio sources in binaries (Malkov+, 2015)
J/other/NewA/47.81 : Distances of X-ray binaries (Islam+, 2016)
J/ApJS/223/15 : 8yr INTEGRAL/IBIS soft gamma-ray source obs. (Bird+, 2016)
J/A+A/606/A130 : List of 1254 X-ray bursts (in't+, 2017)
J/ApJS/235/4 : The 105-month Swift-BAT all-sky hard X-ray survey (Oh+, 2018)
J/A+A/625/A122 : CIELO-RGS, soft X-ray ionized emission lines cat. (Mao+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- ObsID Observation identifier
16- 20 A5 --- Sec Light curve section identifier
22- 31 A10 "D/M/Y" Start.date Observation Start, UT date
33- 37 A5 "h:m" Start.time Observation Start, UT time
39- 48 A10 "D/M/Y" End.date Observation Stop, UT date
50- 54 A5 "h:m" End.time Observation Stop, UT time
56- 60 I5 s Texp [533/42117] Total exposure time
62- 67 F6.3 --- CC [-0.8/1]? Cross-correlation coefficient
69- 74 F6.3 --- e_CC [0.008/0.3]? Uncertainty in CC
76- 80 F5.3 --- HR1 [0.01/0.06] Hardness Ratio
82- 86 F5.3 --- HR2 [0.01/0.09] Hardness Ratio
88- 98 A11 --- HID Position in the hardness intensity
diagram (HID)
100-111 F12.7 s Lag [-692/1507]? Lag
113-120 F8.3 s B_Lag [-766/1364]? Upper bound on Lag
122-130 F9.3 s b_Lag [-636/1638]? Lower bound on Lag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Feb-2020