J/ApJS/250/23 AstroSat/UVIT and Chandra X-ray sources in M31 (Leahy+, 2020)
AstroSat UVIT detections of Chandra X-ray sources in M31.
Leahy D.A., Chen Y.
<Astrophys. J. Suppl. Ser., 250, 23-23 (2020)>
=2020ApJS..250...23L 2020ApJS..250...23L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby; X-ray sources; Photometry, ultraviolet;
Extinction; Clusters, globular; Binaries, X-ray
Keywords: Andromeda Galaxy; Ultraviolet sources; X-ray sources
Low-mass x-ray binary stars; Globular star clusters
Abstract:
An ultraviolet (UV) survey of M31 has been carried out during 2017-19
with the Ultra-Violet Imaging Telescope (UVIT) instrument on board the
AstroSat Observatory. Here we match the M31 UVIT source catalog with
the Chandra source catalog. We find 67 UVIT/Chandra sources detected
in a varying number of UV and X-ray bands. The UV and X-ray photometry
is analyzed using power-law and blackbody models. The X-ray types
include 15 low-mass X-ray binaries (LMXBs) and five active galactic
nuclei. Crossmatches with catalogs of stars, clusters, and other
source types yield the following: 20 of the UVIT/Chandra sources match
with M31 globular clusters, and nine with foreground stars. Three more
globular clusters and two more foreground stars are consistent with
the UVIT source positions although outside the Chandra match radius of
1". The UV emission of the UVIT/Chandra sources associated with
globular clusters is consistent with emission from blue horizontal
branch stars rather than from the X-ray source. The LMXBs in globular
clusters are among the most luminous globular clusters in M31.
Comparison with stellar evolutionary tracks shows that the
UVIT/Chandra sources with high UV blackbody temperatures are
consistent with massive (10-30M☉) stars in M31.
Description:
The AstroSat Ultra-Violet Imaging Telescope (UVIT) is comprised of two
38cm telescopes, one for FUV (130-180nm) wavelengths and one for NUV
(200-300nm) and visible (VIS) (320-550nm) wavelengths.
The following filters were used for the M31 UVIT survey:
CaF2 (123-173nm), BaF2 (135-173nm), Sapphire (146-175nm),
Silica (165-178nm), NUVB15 (206-233nm), and NUVN2 (275-284nm).
This paper presents an analysis of sources in M31 detected in both UV
and X-rays. It utilizes the M31 UVIT catalog (Leahy+ 2020, J/ApJS/247/47)
and M31 Chandra catalog (Vulic+ 2016, J/MNRAS/461/3443).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 165 67 AstroSat/UVIT sources matched with Chandra
sources and power law indices
table2.dat 182 49 Blackbody (BB) and power-law (PL) fits to
UVIT photometry
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
J/ApJ/663/320 : IR-through-UV extinction curve (Fitzpatrick+, 2007)
J/A+A/534/A55 : Deep XMM-Newton Survey of M31 (Stiele+, 2011)
J/ApJ/802/127 : PHAT stellar cluster survey. II. AP catalog (Johnson+, 2015)
J/other/RAA/15.1438 : LAMOST new QSOs in M31 and M33 vicinity (Huo+, 2015)
J/ApJ/824/42 : Star clusters in M31. VII. GCs velocities (Caldwell+, 2016)
J/ApJ/829/116 : H-band spectroscopy of 25 bright M31 GCs (Sakari+, 2016)
J/MNRAS/461/3443 : M31 deepest Chandra catalog of point sources (Vulic+, 2016)
J/A+A/620/A28 : XMM northern disc of M31 sources (Sasaki+, 2018)
J/ApJS/239/13 : Chandra PHAT X-ray catalog of the M31 disk (Williams+, 2018)
J/ApJS/247/47 : Ultraviolet survey of M31 with UVIT on AstroSat (Leahy+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/67] Source running number
4- 21 A18 --- CXOU CXOU name (HHMMSS.ss+DDMMSS.s; J2000;
in Simbad)
23- 29 F7.4 deg RAdeg [9.59/11.58] Right Ascension (J2000)
31- 37 F7.4 deg DEdeg [40.21/41.72] Declination (J2000)
39- 43 F5.2 mag F148Wmag [19.3/24.3]?=99.99 Astrosat/UVIT F148W filter
AB magnitude
45- 48 F4.2 mag e_F148Wmag [0.05/0.4]?=9.99 1σ uncertainty
in F148Wmag
49 A1 --- n_F148Wmag [e] Flag on F148Wmag (5)
51- 55 F5.2 mag F169Mmag [21.1/22.2]?=99.99 Astrosat/UVIT F169M filter
AB magnitude
57- 60 F4.2 mag e_F169Mmag [0.09/0.2]?=9.99 The 1σ uncertainty
in F169Mmag
62- 66 F5.2 mag F172Mmag [18.8/22.7]?=99.99 Astrosat/UVIT F172M filter
AB magnitude
68- 71 F4.2 mag e_F172Mmag [0.07/0.4]?=9.99 The 1σ uncertainty
in F172Mmag
73- 77 F5.2 mag N219Mmag [16.6/22.5]?=99.99 Astrosat/UVIT N219M filter
AB magnitude
79- 82 F4.2 mag e_N219Mmag [0.04/0.3]?=9.99 The 1σ uncertainty
in N219Mmag
83 A1 --- n_N219Mmag [e] Flag on N219Mmag (5)
85- 89 F5.2 mag N279Nmag [15.18/22]?=99.99 Astrosat/UVIT N279N filter
AB magnitude
91- 94 F4.2 mag e_N279Nmag [0.03/0.4]?=9.99 The 1σ uncertainty
in N279Nmag
95 A1 --- n_N279Nmag [e] Flag on N279Nmag (5)
97-106 A10 --- Filter Filters with match separation between 1-2" (1)
108-112 F5.2 --- XInd [-1.5/5.4]?=-9.99 X-ray spectral index (2)
114-118 F5.2 --- E_XInd [0.01/6.7]?=-9.99 Upper 90% uncertainty in XInd
120-124 F5.2 --- e_XInd [0.01/2.7]?=-9.99 Lower 90% uncertainty in XInd
126-129 F4.2 --- U-XInd [0.7/2.6]?=-9.99 UV-to-X-ray spectral index (3)
131-134 F4.2 --- E_U-XInd [0.01/0.6]?=-9.99 Upper uncertainty in U-XInd
136-139 F4.2 --- e_U-XInd [0.01/0.2]?=-9.99 Lower uncertainty in U-XInd
141-153 A13 --- Class X-ray class (4)
155-165 A11 --- Opt Optical counterpart (5)
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Note (1): Filters in which the UVIT source is separated from the Chandra source
by >1" and <2". These have a larger probability of being accidental
matches. Code as follows:
F1 = F148W;
F2 = F169M;
F3 = F172M;
F4 = N219M;
F5 = N279N.
Note (2): The X-ray index is calculated two X-ray bands, assuming a power-law
spectrum. The X-ray fluxes are corrected for a fixed extinction of
NH=6.66x1020cm-2, so the index is the source intrinsic index.
Note (3): The UV to X-ray index is calculated from the shortest available
wavelength UV flux and the longest available wavelength X-ray band,
assuming a power-law spectrum between UV and X-ray. Both UV and X-ray
fluxes are corrected for a fixed extinction of NH=6.66x1020cm-2,
so the index is the source intrinsic index.
Note (4): For column X-ray Class, the class type from
Vulic+ (2016, J/MNRAS/461/3443) is given as LMXB, AGN, or otherwise
blank; the Class from Sasaki+ (2018, J/A+A/620/A28) is given
as XRB, fgStar, and v is attached if the source is variable.
Note (5): Counterpart type as follows:
C = Star cluster from Johnson+ (2015, J/ApJ/802/127)
n = none counterpart type from Williams+ (2018, J/ApJS/239/13)
f = foreground from Williams+ (2018, J/ApJS/239/13)
s = SNR from Williams+ (2018, J/ApJS/239/13)
c = cluster from Williams+ (2018, J/ApJS/239/13)
GD = Gaia DR2 (I/345) parallax and distance measurement in
Bailer-Jones+ 2018, I/349)
GDfg = Gaia plx and dist consistent with foreground stars
GC = globular cluster from Caldwell & Romanowsky (2016, J/ApJ/824/42) or
Sakari+ (2016, J/ApJ/829/116).
* = Matches to Gaia DR2 distance sources (GD), globular clusters (GC) and
other sources with separation 1-2".
e = UVIT-Chandra matches that have separation 1-2" with a larger
probability of being accidental matches.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [2/60] Source number
4- 6 A3 --- fg Identified as foreground star (1)
8- 25 A18 --- CXOU CXOU name (HHMMSS.ss+DDMMSS.s; J2000)
27- 40 A14 --- Filter UVIT filters with a detected
magnitude (2)
42- 45 F4.2 mag BBAv [0/1.83] Foreground extinction
from BB fit (3)
47- 51 F5.2 mag E_BBAv [0.01/0.2]?=-9.99 90% upper error
in BBAv
53- 57 F5.2 mag e_BBAv [0.02/0.2]?=-9.99 90% lower error
in BBAv
59- 67 F9.5 Rsun BBRad [0.0069/466] Radius from BB fit (4)
69- 76 F8.5 Rsun E_BBRad [0.0001/31] 90% upper error in BBRad
78- 85 F8.5 Rsun e_BBRad [8e-5/28] 90% lower error in BBRad
87- 90 F4.1 10+3K BBTeff [5.4/26.3] Effective temperature
from BB fit
92- 95 F4.2 10+3K E_BBTeff [0.03/1.5] 90% upper error in BBTeff
97-100 F4.2 10+3K e_BBTeff [0.03/1.3] 90% lower error in BBTeff
102-106 F5.2 --- BBChi2 [0/95] Chi-square of BB fit
108-112 F5.2 --- BBrChi2 [0/10]?=-9.99 Reduced χ2 of
BB fit (5)
114-117 F4.2 mag PLAv [0/1.31] Foreground extinction
from PL fit (3)
119-123 F5.2 mag E_PLAv [0.01/0.2]?=-9.99 90% upper error in PLAv
125-129 F5.2 mag e_PLAv [0.01/0.2]?=-9.99 90% lower error in PLAv
131-135 F5.2 10-28mW/m2/Hz PLNorm [0.38/76.6] Norm from PL fit
137-140 F4.2 10-28mW/m2/Hz E_PLNorm [0.1/6] 90% upper error in PLNorm
142-145 F4.2 10-28mW/m2/Hz e_PLNorm [0.08/5.5] 90% lower error in PLNorm
147-150 F4.2 --- PLInd [0.2/9.1] Spectral index from PL fit
152-155 F4.2 --- E_PLInd [0.2/1.3] 90% upper error in PLInd
157-160 F4.2 --- e_PLInd [0.2/1.3] 90% lower error in PLInd
162-167 F6.2 --- PLChi2 [0/340] Chi-square from PL fit
169-174 F6.2 --- PLrChi2 [0.02/111]?=-9.99 Reduced chi-square
from PL fit (5)
176-178 A3 --- BBbest Identify BB as the best-fit model
180-182 A3 --- PLbest Identify PL as the best-fit model
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Note (1): Source is identified in Table 1 as foreground star with a
distance measurement (GD).
Note (2): Filter code as follows:
F1 = F148W;
F2 = F169M;
F3 = F172M;
F4 = N219M;
F5 = N279N.
Note (3): For sources detected in only two UVIT filters, the AV value is
fixed at 0.30, and the errors are undefined.
Note (4): If the source is marked as a foreground star in column fgStar, the
radius is calculated using Gaia distance instead of distance to M31.
Note (5): Reduced chi-square given as chi-square divided by the degrees of
freedom, where the degrees of freedom is taken as
the number of UVIT filters -3.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Nov-2020