J/ApJ/961/168 Five-epoch survey of 55 bright X-ray sources in M33 (Kyer+, 2024)
Monitoring the X-ray variability of bright X-ray sources in M33.
Kyer R., Albrecht S., Williams B.F., Hinton K., Binder B., Lazzarini M.,
Garofali K., Lehmer B., Eracleous M., Plucinsky P.P., Antoniou V.
<Astrophys. J., 961, 168 (2024)>
=2024ApJ...961..168K 2024ApJ...961..168K
ADC_Keywords: Binaries, X-ray; Transient; Galaxies, nearby
Keywords: X-ray point sources ; X-ray binary stars ; Triangulum Galaxy ;
X-ray transient sources
Abstract:
We present a new five-epoch Chandra X-ray Observatory monitoring
survey of the nearby spiral galaxy M33 which probes X-ray variability
with time sampling between two weeks and four months. We characterize
the X-ray variability of 55 bright point sources outside of the
nucleus, many of which are expected to be high-mass X-ray binaries
(HMXBs). We detect eight new candidate transients not detected in
previous X-ray catalogs of M33 and discuss their possible nature. The
final catalog includes 26 known HMXB candidates identified in the
literature. We extend the baseline of the X-ray light curves up to
21yr by including archival X-ray observations of these sources. We
compare the detection and nondetection epochs of the sources to suites
of simulated source duty cycles and infer that most of our detected
sources have duty cycles >30%. We find only four sources whose
detection patterns are consistent with having duty cycles below 30%.
This large fraction of sources with high duty cycles is unexpected for
a population of HMXBs; thus more frequent X-ray monitoring will likely
reveal many more low duty cycle HMXBs in M33.
Description:
We obtained ten 5ks observations of M33 with Chandra's ACIS-I
detector. Five pointings were centered on the Northern half of M33 and
five pointings were centered on the Southern half. These 10 exposures
(ObsIDs 23603-23612) cover ∼66% of the B-band D25 isophote of M33 with
observations taken between 2020 November and 2021 June. The
observations were designed to probe variability on multiple
timescales. The five epochs in each pointing are separated by two
weeks, four weeks, two months, and four months consecutively.
Objects:
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RA (ICRS) DE Designation(s)
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01 33 50.89 +30 39 36.6 M33 = NAME Triangulum Galaxy
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 74 56 Final source catalog
table4.dat 147 616 Final catalog source likelihood and count rates
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See also:
J/ApJS/89/85 : Blue and red supergiants in M33 (Ivanov+ 1993)
J/ApJ/609/735 : M31 Chandra X-ray sources (Williams+, 2004)
J/ApJS/161/271 : The X-ray binary population in M33. I (Grimm+, 2005)
J/A+A/451/835 : X-ray sources in M31/M33 (Hatzidimitriou+, 2006)
J/A+A/448/1247 : XMM-Newton survey of M33 (Misanovic+, 2006)
J/ApJ/643/356 : Transient X-ray sources in M31 (Williams+, 2006)
J/A+A/469/807 : Catalogue of Galactic low-mass X-ray binaries (Liu+, 2007)
J/AJ/134/2474 : Ha emission-line stars in 7 dwarfs galaxies (Massey+, 2007)
J/ApJS/174/366 : Chandra ACIS survey of M33 (ChaSeM33) (Plucinsky+, 2008)
J/ApJS/187/495 : SNRs in M33 from optical and X-ray (Long+, 2010)
J/ApJS/192/6 : A GALEX UV imaging survey of nearby galaxies (Lee+, 2011)
J/ApJ/733/123 : The Wolf-Rayet content of M33 (NGC 598) (Neugent+, 2011)
J/ApJS/193/31 : M33 Chandra ACIS survey: final catalog (Tullmann+, 2011)
J/MNRAS/419/2095 : HMXBs in nearby galaxies (Mineo+, 2012)
J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)
J/ApJ/764/41 : X-ray binary evolution across cosmic time (Fragos+, 2013)
J/ApJ/776/L31 : Energy feedback from XRB from z=0 to z=19.92 (Fragos+, 2013)
J/ApJ/774/136 : X-ray observations of SINGS galaxies (Tzanavaris+, 2013)
J/AJ/150/94 : Chandra Local Volume Survey. I. (Binder+, 2015)
J/MNRAS/449/4048 : The Hα rotation curve of M33 (Kam+, 2015)
J/ApJS/218/9 : Deep XMM-Newton survey of M33 (Williams+, 2015)
J/A+A/586/A81 : High-mass X-ray binaries in the SMC (Haberl+, 2016)
J/ApJS/222/15 : WATCHDOG: all-sky database of Gal. BHXBs (Tetarenko+, 2016)
J/ApJ/836/50 : Chandra observations of IC 10 (Laycock+, 2017)
J/MNRAS/473/4937 : AllWISE ctp to ROSAT/2RXS & XMMSLEW2 cat. (Salvato+, 2018)
J/ApJ/887/20 : Deep Chandra survey of the SMC. III. HMXBs (Antoniou+, 2019)
J/ApJS/243/3 : Chandra observations of SINGS galaxies (Lehmer+, 2019)
J/MNRAS/501/2790 : The Swift Bulge Survey. 1st X-ray results (Bahramian+, 2021)
J/ApJ/906/120 : X-Ray binary population in M31 (Lazzarini+, 2021)
J/ApJ/907/17 : HMXB-dominant galaxy sample and properties (Lehmer+, 2021)
J/ApJS/253/53 : PHATTER. I. HST obs. of stars in M33 (Williams+, 2021)
J/ApJ/938/81 : PHATTER. IV. Star cluster catalog (Johnson+, 2022)
J/MNRAS/517/2990 : ∼1000 RC sources in M33 with the VLA (Tabatabaei+, 2022)
J/A+A/677/A186 : UltraCompCAT catalog (Armas Padilla+, 2023)
J/ApJ/952/114 : HMXBs in M33 with Chandra & HST obs. (Lazzarini+, 2023)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Source J2000 position-based name
21- 29 F9.6 deg RAdeg [23.29/23.72] Right Ascension (J2000)
31- 39 F9.6 deg DEdeg [30.45/30.93] Declination (J2000)
41- 44 F4.2 arcsec PosErr [0.5/2.71] Positional error (1)
46- 49 F4.1 arcmin Theta [2.2/13.8] Average off-axis angle of source on
detector
51- 52 I2 --- Nobs [1/10] Number of observations
54- 66 A13 --- Match Archival Matches (2)
68- 70 A3 --- T11 Tullmann+ 2011, J/ApJS/193/31 Final Catalog
designations (3)
72- 74 F3.1 --- Det [0.5/1]? Source detected in single pixel size
wavdetect (4)
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Note (1): Positional uncertainties reported by AE as less than 0.5 arcsec
were set to 0.5 arcsec to match the minimum astrometric
uncertainty of the T11 which we used for alignment.
Note (2): Archival matches include as follows:
M06 = Misanovic+ 2006, J/A+A/448/1247 (<[MPH2006] NNN> in Simbad)
T11 = Tullmann+ 2011, J/ApJS/193/31
W15 = Williams+ 2015, J/ApJS/218/9
Note (3): T11 Source Numbers refer to the T11 (Tullmann+ 2011, J/ApJS/193/31;
<ChASeM33 JHHMMSS.ss+DDMMSS.s> in Simbad) Final Catalog designations,
not to be confused with the Plucinsky+ 2008, J/ApJS/174/366 first look
catalog source numbers.
Note (4): Source detected in the 0.5" or 1.0" pixel size wavdetect run
only (see Section 2.1).
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Source J2000 position-based name
21- 26 A6 --- ObsID Chandra Observation identifier (1)
28- 34 F7.1 s Exp [4808/49748]? Exposure or Total exposure time
(1)
36- 42 E7.1 --- PNS1 [0/1]? Catalog source likelihood, 0.35-8.0keV
44- 50 E7.1 --- PNS2 [0/1]? Catalog source likelihood, 0.35-1.1keV
52- 58 E7.1 --- PNS3 [0/1]? Catalog source likelihood, 1.1-2.6keV
60- 66 E7.1 --- PNS4 [0/1]? Catalog source likelihood, 2.6-8.0keV
68 A1 --- l_CR1 Limit flag on CR1 (2)
70- 78 F9.5 10-3ct/s CR1 [-0.4/696]? Count rate, 0.35-8.0keV
80- 84 E5 10-3ct/s e_CR1 [0.05/10]? Lower uncertainty on CR1
86- 90 E5 10-3ct/s E_CR1 [0.08/10]? Upper uncertainty on CR1
92 A1 --- l_CR2 Limit flag on CR2 (2)
94- 98 F5.2 10-3ct/s CR2 [0.02/36]? Count rate, 0.35-1.1keV
100- 103 F4.2 10-3ct/s e_CR2 [0.03/3]? Lower uncertainty on CR2
105- 108 F4.2 10-3ct/s E_CR2 [0.05/3]? Upper uncertainty on CR2
110 A1 --- l_CR3 Limit flag on CR3 (2)
112- 117 F6.2 10-3ct/s CR3 [0.04/408]? Count rate, 1.1-2.6keV
119- 122 F4.2 10-3ct/s e_CR3 [0.03/9]? Lower uncertainty on CR3
124- 127 F4.2 10-3ct/s E_CR3 [0.07/9]? Upper uncertainty on CR3
129 A1 --- l_CR4 Limit flag on CR4 (2)
131- 136 F6.2 10-3ct/s CR4 [0.04/268]? Count rate, 2.6-8.0keV
138- 141 F4.2 10-3ct/s e_CR4 [0.03/7]? Lower uncertainty on CR4
143- 147 F5.2 10-3ct/s E_CR4 [0.07/8]? Upper uncertainty on CR4
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Note (1): The ObsID contains the Chandra observation identifier or the
term, "Merged" corresponding to the values for the multi-ObsID
extraction. All of the ObsIDs in this work are listed for all sources. All
of the ExpTime, PNS and CR values are set to blanks when a source
was not within the field of an ObsID.
Note (2): 1σ upper limits are given when a source's position was
on the detector for an ObsID but was not detected.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 08-Apr-2026