J/AJ/161/215 Far-ultraviolet variable sources in M31 (Leahy+, 2021)
Far-ultraviolet variable sources in M31.
Leahy D., Buick M., Postma J., Morgan C.
<Astron. J., 161, 215 (2021)>
=2021AJ....161..215L 2021AJ....161..215L
ADC_Keywords: Galaxies; Photometry, ultraviolet;
Keywords: Ultraviolet astronomy ; Ultraviolet transient sources ; Local Group ;
Andromeda galaxy ; Disk galaxies ; Stellar populations
Abstract:
The Ultraviolet Imaging Telescope (UVIT) on board the AstroSat
observatory has imaged the Andromeda galaxy (M31) from 2017 to 2019 in
the far- and near-UV (FUV and NUV) with the high spatial resolution of
∼1". The survey covered the large sky area of M31 with a set of
observations (Fields), each 28' in diameter. Field 1 was observed in
two epochs with the F148W filter, separated by ∼1133days (∼3.10yr).
The 6.4kpc diameter Field 1 (at the distance of M31) includes a
substantial part of the inner spiral arms of the galaxy. We identify
UVIT sources in both epochs of Field 1 and obtain catalogs of sources
that are variable in FUV at >3σ and >5σ confidence level.
The fraction of FUV-variable sources is higher for brighter sources,
and the fraction is higher in the two main spiral arms compared to
other areas. This is evidence that a significant fraction of the FUV
variables are associated with hot young stars. Source counterparts are
found for 42 of the 86 >5σ FUV variables using existing
catalogs. The counterparts include 10 star clusters, 6 HII regions, 5
regular or semiregular variables, 6 other variables, and 6 nova or
nova candidates. The UVIT FUV-NUV and FUV-FUV color-magnitude diagrams
confirm the association of most of the FUV variables with hot young
stars. A catalog of UVIT photometry for the variable sources is
presented.
Description:
M31 was observed in Far Ultra Violet (FUV) and Near Ultra Violet (NUV)
at ∼1" spatial resolution by Ultraviolet Imaging Telescope (UVIT). It
was covered in nineteen 28' diameter fields. UVIT Field 1 was observed
in the F148W, F172M, N219M, and N279N filters near the beginning of
the observing project and in a new observation that has not been
reported previously. The first observation is referred to as
Observation A, the second as Observation B. Observation B was made in
filters F148W, F169M, and F172M. The F172M filter is narrow with
δλ=12.5nm versus 50nm for F148W, thus has a lower
signal-to-noise ratio (S/N) than images in F148W.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 93 555 Photometry for >3σ variable FUV sources
measured in UVIT Field 1
table4.dat 115 43 Multiwavelength counterparts of the UVIT
FUV>5σ variables
refs.dat 58 25 References used for table4
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+AS/92/625 : Ionized nebulae in M31 (Walterbos+ 1992)
J/MNRAS/351/1071 : POINT-AGAPE Survey. M31 variables (An+, 2004)
J/A+A/445/423 : WeCAPP Survey. M31 variables (Fliri+, 2006)
J/MNRAS/351/1071 : POINT-AGAPE Survey. M31 variables (An+, 2004)
J/MNRAS/369/97 : M31 planetary nebulae velocities (Halliday+, 2006)
J/MNRAS/402/803 : M31 globular cluster system (Peacock+, 2010)
J/AJ/142/139 : A new catalog of HII regions in M31 (Azimlu+, 2011)
J/ApJ/759/11 : Wolf-Rayet content of M31 (Neugent+, 2012)
J/ApJS/215/9 : PHAT X. UV-IR photometry of M31 stars (Williams+, 2014)
J/ApJ/802/127 : PHAT stellar cluster survey. II. AP catalog (Johnson+, 2015)
J/ApJ/836/64 : Luminous variable stars in M31 & M33. IV. (Humphreys+, 2017)
J/ApJ/844/40 : Variable stars in M31 and M33.V. HR diagram (Humphreys+, 2017)
J/AJ/156/241 : First catalog variable stars measured by ATLAS (Heinze+, 2018)
J/A+A/630/A92 : The Hubble Catalog of Variables (Bonanos+, 2019)
J/ApJS/247/47 : Ultraviolet survey of M31 with UVIT on AstroSat (Leahy+, 2020)
J/ApJS/250/23 : AstroSat/UVIT and Chandra X-ray sources in M31 (Leahy+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 F9.6 deg RAdeg [10.4/11.1] Right Ascension, UVIT (J2000)
11- 19 F9.6 deg DEdeg [41/41.5] Declination, UVIT (J2000)
21- 25 F5.2 mag F148W-A [17.86/26.71]? F148W band AB magnitude,
Observation A
27- 31 F5.2 mag e_F148W-A [0.07/0.84]? Uncertainty in F148W-A
33- 37 F5.2 mag F148W-B [17.69/28.77]? F148W band AB magnitude,
Observation B
39- 43 F5.2 mag e_F148W-B [0.07/1.5]? Uncertainty in F148W-B
45- 49 F5.2 --- F148W-S/N [3/20.8] Signal-to-noise, F148W
51- 55 F5.2 mag N279N-A [17.02/25.65]? N279N band AB magnitude,
Observation A
57- 60 F4.2 mag e_N279N-A [0.04/1.6]? Uncertainty in N279N-A
62- 66 F5.2 mag N219M-A [17.41/26.6]? N219M band AB magnitude,
Observation A
68- 71 F4.2 mag e_N219M-A [0.04/1.6]? Uncertainty in N219M-A
73- 77 F5.2 mag F172M-B [17.51/25.58]? F172M band AB magnitude,
Observation B
79- 82 F4.2 mag e_F172M-B [0.04/0.79]? Uncertainty in F172M-B
84- 88 F5.2 mag F169M-B [17.81/28.95]? F169M band AB magnitude,
Observation B
90- 93 F4.2 mag e_F169M-B [0.03/2.9]? Uncertainty in F169M-B
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Source [1/42] Source number identifier
4- 10 F7.4 deg RAdeg [10.48/11] Right Ascension, UVIT (J2000)
12- 18 F7.4 deg DEdeg [41.14/41.46] Declination, UVIT (J2000)
20- 50 A31 --- Cat1 First catalog match (1)
52- 53 I2 --- r_Cat1 [1/25] Reference for Cat1
55- 59 F5.3 arcsec Sep [0.03/1.89] Separation between the UVIT source
and the identified match from VizieR
61- 64 F4.2 arcsec Rad [0.41/2.56]? radius of cluster from literature
for sources that match with a cluster
66-103 A38 --- Cat23 Second and third catalog match
105-109 A5 --- r_Cat23 References used for Cat23
111-115 F5.3 arcsec Dist [0.02/1.53]? Distance
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Note (1): The first, second, and third catalog matches refer to the
identified typing of the object in catalogs in VizieR.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref [1/25] Reference number
4- 21 A18 --- Author Main author of the reference
23- 41 A19 --- BIB BIBcode
43- 58 A16 --- Cat Catalog in VizieR
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History:
From electronic version of the journal
(End) Prepared by [AAS], Fix Coralie [CDS], 05-Jul-2021