J/ApJ/901/57 MAVERIC survey: Chandra X-ray sources in 38 GCs (Bahramian+, 2020)
The MAVERIC survey: Chandra/ACIS catalog of faint X-ray sources in 38
Galactic globular clusters.
Bahramian A., Strader J., Miller-Jones J.C.A., Chomiuk L., Heinke C.O.,
Maccarone T.J., Pooley D., Shishkovsky L., Tudor V., Zhao Y., Li K.L.,
Sivakoff G.R., Tremou E., Buchner J.
<Astrophys. J., 901, 57 (2020)>
=2020ApJ...901...57B 2020ApJ...901...57B
ADC_Keywords: Clusters, globular; X-ray sources; Surveys
Keywords: Globular star clusters ; Low-mass x-ray binary stars ; Neutron
stars ; Astrophysical black holes ; Stellar accretion disks ;
Celestial objects catalogs
Abstract:
Globular clusters host a variety of lower-luminosity
(LX<1035erg/s) X-ray sources, including accreting neutron stars
(NSs) and black holes (BHs), millisecond pulsars (MSPs), cataclysmic
variables, and chromospherically active binaries. In this paper, we
provide a comprehensive catalog of more than 1100 X-ray sources in 38
Galactic globular clusters (GCs) observed by the Chandra X-ray
Observatory's Chandra/ACIS detector. The targets are selected to
complement the MAVERIC survey's deep radio continuum maps of Galactic
GCs. We perform photometry and spectral analysis for each source,
determine a best-fit model, and assess the possibility of it being a
foreground or background source based on its spectral properties and
location in the cluster. We also provide basic assessments of
variability. We discuss the distribution of X-ray binaries in GCs and
their X-ray luminosity function, and we carefully analyze systems with
LX>1033erg/s. Among these moderately bright systems, we discover a
new source in NGC 6539 that may be a candidate accreting stellar-mass
BH or a transitional MSP. We show that quiescent NS low-mass X-ray
binaries in GCs may spend ∼2% of their lifetimes as transitional MSPs
in their active (LX>1033erg/s) state. Finally, we identify a
substantial underabundance of bright (LX>1033erg/s) intermediate
polars in GCs compared to the Galactic field, in contrast with the
literature of the past two decades.
Description:
In our selected sample of 38 Galactic globular clusters (GCs), 10 have
new data taken as part of the Milky Way ATCA VLA Exploration of Radio
Sources in Clusters (MAVERIC; Shishkovsky+ 2020, J/ApJ/903/73):
six (Djorg 2, M10, M19, NGC 4372, NGC 4833, and M107) have single
Chandra/ACIS observations obtained specifically for MAVERIC follow-up,
while four others (M22, M62, Terzan 1, and Terzan 5) have both
previous data and newer MAVERIC follow-up data.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 33 89 List of all Galactic globular clusters (GCs)
and their Chandra/ACIS observations reduced
and analyzed in this work
tablea1.dat 954 1667 *Final X-ray source catalog
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Note on tablea1.dat: We extracted data products and performed the analysis
using ACIS-Extract (hereafter AE; Broos+ 2010ApJ...714.1582B 2010ApJ...714.1582B) and the
Bayesian X-ray analysis package BXA (Buchner+ 2014, J/A+A/564/A125).
See text for further explanations.
--------------------------------------------------------------------------------
See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/A+AS/146/407 : Symbiotic stars catalogue (Belczynski+, 2000)
J/other/Sci/292.2290 : Chandra compact binaries in 47 Tuc (Grindlay+, 2001)
J/ApJ/578/405 : Neutron stars in NGC 5139 (Rutledge+, 2002)
J/ApJ/625/796 : X-ray sources in 47 Tuc (Heinke+, 2005)
J/ApJ/651/1098 : Faint X-ray sources in Terzan 5 (Heinke+, 2006)
J/ApJ/662/525 : LMXBs in globular clusters of 5 galaxies (Kundu+, 2007)
J/ApJ/657/286 : Chandra X-ray sources in M30 (NGC 7099) (Lugger+, 2007)
J/AJ/133/1658 : ACS survey of galactic GCs (Sarajedini+, 2007)
J/ApJS/179/360 : Thermonuclear X-ray bursts with RXTE (Galloway+, 2008)
J/A+A/480/397 : XMM observations of NGC2808 & NGC4372 (Servillat+, 2008)
J/A+A/490/641 : X-ray sources toward NGC 2808 (Servillat+, 2008)
J/ApJ/697/224 : Chandra X-ray sources in ω Cen (Haggard+, 2009)
J/ApJ/709/241 : X-rays sources in NGC 6397 (Bogdanov+, 2010)
J/ApJ/766/136 : Stellar encounter rates in Gal. GCs (Bahramian+, 2013)
J/ApJS/207/19 : Hard X-ray survey from Swift-BAT 6yrs (Baumgartner+, 2013)
J/MNRAS/428/2500 : GX 339-4 radio/X-ray flux correlation (Corbel+, 2013)
J/A+A/564/A125 : AGN Torus model comparison of AGN in CDFS (Buchner+, 2014)
J/AJ/152/1 : Spectroscopy of EG And over roughly 14 years (Kenyon+, 2016)
J/ApJS/222/15 : WATCHDOG: all-sky database of Gal. BHXBs (Tetarenko+, 2016)
J/MNRAS/472/3706 : Globular cluster 47 Tuc with Chandra (Bhattacharya+, 2017)
J/MNRAS/478/1520 : Milky Way globular clusters data (Baumgardt+, 2018)
J/MNRAS/479/2834 : 233 X-ray sources in omega Centauri (Henleywillis+, 2018)
J/ApJ/883/90 : X-ray sources in GCs. II. (Cheng+, 2019)
J/ApJ/876/59 : Chandra X-ray sources in 47 Tuc (Cheng+, 2019)
J/A+A/632/A3 : MUSE binaries in NGC 3201 (Giesers+, 2019)
J/ApJ/903/73 : MAVERIC survey: deep VLA imaging of GCs (Shishkovsky+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- GCl Globular cluster name
9- 13 I5 --- ObsID [79/20796] Chandra observation ID
15 A1 --- f_ObsID Flag on ObsID (1)
17- 27 A11 "Y/M/D" Date Observation date (UT)
29- 33 F5.1 ks Exp [2.5/147.7] Exposure time
--------------------------------------------------------------------------------
Note (1): Flag as follows:
a = Indicates that the observation was taken with the target on ACIS-I
(as opposed to ACIS-S).
b = Indicates the observation was taken in subarray mode.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- CXOU Chandra identifier
(HHMMSS.ss+DDMMSS.s; J2000;
<[BSM2020b] CXOU JHHMMSS.ss+DDMMSS.s>
in Simbad)
20 I1 --- Det [0/2] Detection quality flag
(0=confident detection) (1)
22 I1 --- Sp [0/2] Spectrum quality flag (0=relatively
reliable to 2=not reliable) (2)
24- 28 A5 --- Pile Pile up flag (if TRUE=photometry and
spectroscopy are likely inaccurate) (3)
30- 34 A5 --- Frgd Foreground flag (4)
36- 40 F5.3 --- Pagn [0/1]? Probability source is a
background AGN (5)
42- 46 A5 --- Astrom Absolute astrometry flag (6)
48- 57 F10.6 deg RAdeg [137.99/325.12] Centroiding right Ascension
(J2000) (7)
59- 68 F10.6 deg DEdeg [-73/43.2] Centroiding declination
(J2000) (7)
70- 75 F6.4 arcsec errc [0.003/1.7] Centroiding uncertainty radius
77- 86 F10.6 deg RARdeg [137.99/325.12]? Right Ascension (J2000)
estimated via image reconstruction
88- 97 F10.6 deg DERdeg [-72.73/43.16]? Declination (J2000)
estimated via image reconstruction
99- 108 F10.6 deg RACdeg [137.99/325.12]? Right Ascension (J2000)
via correlating image and PSF
110- 119 F10.6 deg DECdeg [-72.73/43.16]? Declination (J2000)
via correlating image and PSF
121- 122 I2 --- Ntot [1/18] Total number of source observations
124- 125 I2 --- Nmrg [1/18] Number of merged observation to
enhance validity
127- 139 F13.6 s Exp [8410.2/745615] Total source exposure
time in merged observations
141 I1 --- CCD [0/7] Chandra/ACIS CCD containing
most/all observations
143- 146 F4.2 arcmin theta [0.01/6.6] Average off-axis angle
148- 151 F4.2 arcmin b_theta [0.01/6.4] Minimum of-axis angle
153- 156 F4.2 arcmin B_theta [0.01/6.7] Maximum of-axis angle
158- 161 F4.2 --- PSF [0.38/0.96] Average PSF fraction
163- 167 I5 ct TCt0.5-8 [1/15409] Total source counts in
0.5-8keV band
169- 173 I5 ct TCt0.5-2 [0/12140] Total source counts in
0.5-2keV band
175- 178 I4 ct TCt2-8 [0/6873] Total source counts in 2-8keV band
180- 184 I5 ct TCt0.5-10 [1/15454] Total source counts in
0.5-10keV band
186- 190 I5 ct TCt1-10 [0/12786] Total source counts in 1-10keV
band
192- 195 I4 ct Bkg0.5-8 [4/2195] Total background counts in
0.5-8keV band
197- 200 I4 ct Bkg0.5-2 [3/1159] Total background counts in
0.5-2keV band
202- 205 I4 ct Bkg2-8 [1/1145] Total background counts in
2-8keV band
207- 210 I4 ct Bkg0.5-10 [8/3569] Total background counts in
0.5-10keV band
212- 215 I4 ct Bkg1-10 [8/3004] Total background counts in
1-10keV band
217- 224 F8.3 --- BScl0.5-8 [1.29/1644] Background scaling factor in
0.5-8keV band
226- 233 F8.3 --- BScl0.5-2 [1.27/1644] Background scaling factor in
0.5-2keV band
235- 242 F8.3 --- BScl2-8 [1.29/1644] Background scaling factor in
2-8keV band
244- 251 F8.3 --- BScl0.5-10 [1.29/1644] Background scaling factor in
0.5-10keV band
253- 260 F8.3 --- BScl1-10 [1.29/1644] Background scaling factor in
1-10keV band
262- 270 F9.3 ct NCt0.5-8 [-8.8/15376] Net source counts in
0.5-8keV band
272- 280 F9.3 ct NCt0.5-2 [-4.6/12104] Net source counts in
0.5-2keV band
282- 289 F8.3 ct NCt2-8 [-5.9/6855] Net source counts in 2-8keV
band
291- 299 F9.3 ct NCt0.5-10 [-10/15420] Net source counts in
0.5-10keV band
301- 309 F9.3 ct NCt1-10 [-9.2/12759] Net source counts in
1-10keV band
311- 317 F7.3 ct E_NCt0.5-8 [2.3/126] The 1σ upper-limit on
NCt0.5-8
319- 325 F7.3 ct E_NCt0.5-2 [1.8/112]? The 1σ upper-limit on
NCt0.5-2
327- 332 F6.3 ct E_NCt2-8 [1.8/84]? The 1σ upper-limit on
NCt2-8
334- 340 F7.3 ct E_NCt0.5-10 [2.3/126] The 1σ upper-limit on
NCt0.5-10
342- 348 F7.3 ct E_NCt1-10 [1.8/115] The 1σ upper-limit on
NCt1-10
350- 356 F7.3 ct e_NCt0.5-8 [0.8/125] The 1σ lower-limit on
NCt0.5-8
358- 364 F7.3 ct e_NCt0.5-2 [0.8/111]? The 1σ lower-limit on
NCt0.5-2
366- 371 F6.3 ct e_NCt2-8 [0.8/83]? The 1σ lower-limit on
NCt2-8
373- 379 F7.3 ct e_NCt0.5-10 [0.8/125] The 1σ lower-limit on
NCt0.5-10
381- 387 F7.3 ct e_NCt1-10 [0.8/114]? The 1σ lower-limit on
NCt1-10
389- 395 F7.3 --- Sig0.5-8 [-2.2/123] Photometric SNR in 0.5-8keV band
397- 403 F7.3 --- Sig0.5-2 [-1.7/109] Photometric SNR in 0.5-2keV band
405- 410 F6.3 --- Sig2-8 [-1.7/82] Photometric SNR in 2-8keV band
412- 418 F7.3 --- Sig0.5-10 [-1.6/123] Photometric SNR in 0.5-10keV
band
420- 426 F7.3 --- Sig1-10 [-1.5/112] Photometric SNR in 1-10keV band
428- 432 F5.3 --- NoSrc0.5-8 [0/1] P-value for no-source hypothesis
in 0.5-8keV band
434- 438 F5.3 --- NoSrc0.5-2 [0/1] P-value for no-source hypothesis
in 0.5-2keV band
440- 444 F5.3 --- NoSrc2-8 [0/1] P-value for no-source hypothesis
in 2-8keV band
446- 450 F5.3 --- NoSrc0.5-10 [0/0.96] P-value for no-source
hypothesis in 0.5-10keV band
452- 456 F5.3 --- NoSrc1-10 [0/1] P-value for no-source hypothesis
in 1-10keV band
458- 462 F5.3 --- MinKS [0/1]? Minimum p-value for KS
variability test (8)
464- 468 F5.3 --- AllKS [0/1]? P-value for KS variability test
for all observations (9)
470- 477 E8.2 mW/m2 AEaFl0.5-2 [1.5e-27/1.6e-13]? Power-law fit in AE
0.5-2keV absorbed flux; erg/s/cm2
479- 486 E8.2 mW/m2 AEaFl2-8 [6.3e-23/5.7e-13]? Power-law fit in AE
2-8keV absorbed flux; erg/s/cm2
488- 495 E8.2 mW/m2 AEaFl0.5-8 [6.3e-23/5.8e-13]? Power-law fit in AE
0.5-8keV absorbed flux; erg/s/cm2
497- 504 E8.2 mW/m2 AEaFl0.5-10 [7.6e-23/9e-13]? Power-law fit in AE
0.5-10keV absorbed flux; erg/s/cm2
506- 513 E8.2 mW/m2 AEaFl1-10 [7.6e-23/9e-13]? Power-law fit in AE
1-10keV absorbed flux; erg/s/cm2
515- 522 E8.2 mW/m2 AEuFl0.5-2 [2e-21/4.4e-13]? Power-law fit in AE
0.5-2keV unabsorbed flux; erg/s/cm2
524- 531 E8.2 mW/m2 AEuFl2-8 [3.7e-22/6.1e-13]? Power-law fit in AE
2-8keV unabsorbed flux; erg/s/cm2
533- 540 E8.2 mW/m2 AEuFl0.5-8 [2.6e-21/6.5e-13]? Power-law fit in AE
0.5-8keV unabsorbed flux; erg/s/cm2
542- 549 E8.2 mW/m2 AEuFl0.5-10 [2.6e-21/9.8e-13]? Power-law fit in AE
0.5-10keV unabsorbed flux; erg/s/cm2
551- 558 E8.2 mW/m2 AEuFl1-10 [1e-21/9.7e-13]? Power-law fit in AE
1-10keV unabsorbed flux; erg/s/cm2
560- 567 E8.2 cm-2 plNH [5e+19/3.7e+23] BXA power-law fit NH
569- 576 E8.2 cm-2 e_plNH [3.6e+19/3.7e+23] Lower uncertainty in plNH
578- 585 E8.2 cm-2 E_plNH [6.2e+19/7.7e+23] Upper uncertainty in plNH
587- 591 F5.2 --- plGamma [-0.98/4] BXA power-law fit photon index
593- 596 F4.2 --- e_plGamma [0.01/2.8] Lower uncertainty in plGamma
598- 601 F4.2 --- E_plGamma [0/2.9] Upper uncertainty in plGamma
603- 610 E8.2 mW/m2 plFlux [3.6e-17/1.5e-12] BXA power-law fit
unabsorbed 0.5-10keV flux; erg/s/cm2
612- 619 E8.2 mW/m2 e_plFlux [2.3e-17/9.7e-14] Lower uncertainty in
plFlux
621- 628 E8.2 mW/m2 E_plFlux [1e-16/3.6e-13] Upper uncertainty in plFlux
630- 637 E8.2 10-7W plLum [2.3e+28/1.7e+34] BXA power-law fit
0.5-10keV luminosity; erg/s
639- 646 E8.2 10-7W e_plLum [1.5e+28/1.5e+33] Lower uncertainty in
plLum
648- 655 E8.2 10-7W E_plLum [6.6e+28/2.3e+33] Upper uncertainty in
plLum
657- 664 F8.4 [-] plProb [-52/0] BXA power-law fit log goodness
probability (10)
666- 673 E8.2 cm-2 apecNH [1.2e+19/4.5e+23] BXA APEC fit NH
675- 682 E8.2 cm-2 e_apecNH [2.2e+18/4.2e+23] Lower uncertainty in
apecNH
684- 691 E8.2 cm-2 E_apecNH [6e+18/7.7e+23] Upper uncertainty in apecNH
693- 698 F6.3 keV apeckT [0.05/29.6] BXA APEC temperature
700- 705 F6.3 keV e_apeckT [0.007/10.3] Lower uncertainty in apeckT
707- 712 F6.3 keV E_apeckT [0.008/19] Upper uncertainty in apeckT
714- 721 E8.2 mW/m2 apecFlux [5.5e-17/1.1e-11] BXA APEC fit
unabsorbed 0.5-10keV flux; erg/s/cm2
723- 730 E8.2 mW/m2 e_apecFlux [3.7e-17/1.1e-11] Lower uncertainty in
apecFlux
732- 739 E8.2 mW/m2 E_apecFlux [1.8e-16/3e-9] Upper uncertainty in
apecFlux
741- 748 E8.2 10-7W apecLum [3.4e+28/2e+34] BXA APEC fit 0.5-10keV
luminosity; erg/s
750- 757 E8.2 10-7W e_apecLum [2.3e+28/2e+34] Lower uncertainty in
apecLum
759- 766 E8.2 10-7W E_apecLum [1.3e+29/1.7e+37] Upper uncertainty in
apecLum
768- 776 F9.4 [-] apecProb [-561/0] BXA APEC fit log goodness
probability (10)
778- 785 E8.2 cm-2 bbNH [1.1e+19/2.8e+23] BXA blackbody fit NH
787- 794 E8.2 cm-2 e_bbNH [1.5e+18/2.8e+23] Lower uncertainty in bbNH
796- 803 E8.2 cm-2 E_bbNH [3.9e+18/7.2e+23] Upper uncertainty in bbNH
805- 809 F5.3 keV bbkT [0.04/9.7] BXA blackbody fit temperature
811- 815 F5.3 keV e_bbkT [0.003/4.5] Lower uncertainty in bbkT
817- 821 F5.3 keV E_bbkT [0.003/6.8] Upper uncertainty in bbkT
823- 830 E8.2 mW/m2 bbFlux [5.9e-17/1.9e-11] BXA blackbody fit
unabsorbed 0.5-10keV flux; erg/s/cm2
832- 839 E8.2 mW/m2 e_bbFlux [4.4e-17/1.9e-11] Lower uncertainty in
bbFlux
841- 848 E8.2 mW/m2 E_bbFlux [1e-16/3e-9] Upper uncertainty in bbFlux
850- 857 E8.2 10-7W bbLum [3.7e+28/6.6e+34] BXA blackbody fit
0.5-10keV luminosity; erg/s
859- 866 E8.2 10-7W e_bbLum [2.8e+28/6.6e+34] Lower uncertainty in
bbLum
868- 875 E8.2 10-7W E_bbLum [7e+28/1.1e+37] Upper uncertainty in bbLum
877- 885 F9.4 [-] bbProb [-323.4/0] BXA blackbody fit log
goodness probability (10)
887- 894 A8 --- Best Model with highest probability
896- 902 F7.1 --- bgAGNSoft [0/35799.1]? Number of expect background
AGN with 0.5-2keV flux > source (11)
904- 908 F5.1 --- bgAGNHard [0/269.5]? Number of expect background
AGN with 2-10keV flux > source (11)
910- 913 F4.2 arcmin Dist [0.01/5.2] Source distance from cluster
center
915- 921 A7 --- GCl Host GC name
923- 926 F4.1 kpc GCDist [2.2/26.5] GC distance
928- 935 E8.2 cm-2 GCNH [1.7e+20/2.1e+22] Host cluster NH (12)
937- 944 E8.2 cm-2 e_GCNH [8.7e+19/2.4e+21] Uncertainty in GCNH (13)
946- 949 F4.2 arcmin GCRad [0.03/1.8] Host cluster core radius
951- 954 F4.2 arcmin GCHL [0.5/4.33] Host cluster half-light radius
-------------------------------------------------------------------------------
Note (1): If a source has a minimum false probability value of ≥1%, we
classify it as a poor detection (with a detection quality flag
value of 2). If a source has a minimum false probability value
of <1% and a net source count <5 (in the 0.5-10keV band), we
classify it as a marginal detection (detection quality flag
value =1). Finally, if a source has a minimum false probability
value of <1% and a net source count ≥5, we classify it as a
confident detection (detection quality flag value =0). For more
details see Section 4.2 and Figure 3.
Note (2): Indicating spectrum quality based on total number of source counts:
if a source has ~>100 counts, it would have relatively reliable
spectral analysis (and we assign a flag value of 0). If the total
number of counts is somewhere between ~<100 and ~>20, the estimates
are less reliable and should be taken with caution (flag value of 1).
Lastly, if a source has ~<20 counts, spectral analysis is merely
suggestive, and model comparison is not to be taken with confidence
(flag value of 2).
Note (3): If True, photometry and spectroscopy presented in this catalog are
likely inaccurate. Only 15 sources are identified as potentially
piled in our catalog.
Note (4): This is determined based on comparing the upper limit on the source
NH (from the best-fit model) compared to the host cluster NH
(estimated based on E(B-V)). False doesn't necessarily reject that
source is a foreground object. Just that the source NH is not
inconsistent with the host cluster. Refer to Section 4.7 and 5.1 for
details on this assessment and its caveats.
Note (5): Estimated based on source flux, population of sources in the cluster
and the location of the source in the cluster. If the source is
located outside the GC half-light radius, this probability is not
estimated. See Section 4.7 for details.
Note (6): If the coordinates are corrected for absolute astrometry. This is
currently only done for Terzan 5. For the rest of the catalog, one
should consider an additional 0.8" uncertainty to consider Chandra's
astrometry accuracy.
Note (7): Coordinates used for most analyses in this paper.
Note (8): Within each observation. These values should be considered with
caution. See Section 4.5 and 5.1 for further details.
Note (9): These values should be considered with caution. See Section 4.5
and 5.1 for further details.
Note (10): Normalized relative to the best model, which will have a
probability of 1.
Note (11): Within the half-light radius of the GC based on
Mateos et al. (2008A&A...492...51M 2008A&A...492...51M).
Note (12): As estimated based on cluster E(B-V). This value is not used in
spectral analyses in this work and is provided for comparison.
Note (13): Considering the reported uncertainties on E(B-V) in the Harris
catalog, the reported uncertainty on the correlation slope by
Bahramian et al. (2015MNRAS.452.3475B 2015MNRAS.452.3475B), and assuming an
uncertainty of 0.1 on RV.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Jan-2022