J/AJ/161/204 Astrometry and photometry for 156 ZNG UV-bright stars (Bond+, 2021)
Astrometric membership tests for the Zinn-Newell-Gibson UV-bright stars in
Galactic globular clusters.
Bond H.E.
<Astron. J., 161, 204-204 (2021)>
=2021AJ....161..204B 2021AJ....161..204B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular; Stars, giant; Positional data;
Parallaxes, trigonometric; Photometry, G band
Keywords: Globular star clusters; Late stellar evolution
Post-asymptotic giant branch stars; Horizontal branch stars
Space astrometry
Abstract:
In 1972, Zinn, Newell, & Gibson (ZNG) published a list of 156
candidate UV-bright stars they had found in 27 Galactic globular
clusters (GCs), based on photographs in the U and V bands. UV-bright
stars lie above the horizontal branch (HB) and blueward of the
asymptotic giant branch (AGB) and red giant branch in the clusters'
color-magnitude diagrams. They are in rapid evolutionary phases-if
they are members and not unrelated bright foreground stars. The ZNG
list has inspired numerous follow-up studies, aimed at understanding
late stages of stellar evolution. However, the ZNG candidates were
presented only in finding charts, and celestial coordinates were not
given. Using my own collection of CCD frames in u and V, I have
identified all of the ZNG objects, and have assembled their
coordinates, parallaxes, and proper motions from the recent Gaia Early
Data Release 3 (EDR3). Based on the Gaia astrometry, I have determined
which objects are probable cluster members (45% of the sample). For
the members, using photometry from EDR3, I have assigned the stars to
various evolutionary stages, including luminous post-AGB stars, and
stars above the HB. I point out several ZNG stars of special interest
that have still, to my knowledge, never been studied in detail. This
study is an adjunct to a forthcoming survey of the Galactic GCs in the
uBVI photometric system, designed for detection of low-gravity stars
with large Balmer discontinuities.
Description:
I first identified each Zinn, Newell, & Gibson (ZNG) star in my uBVI
CCD GC survey CCD images. These frames had been obtained with 0.9,
1.5, and 4m telescopes at Kitt Peak National Observatory and Cerro
Tololo Inter-American Observatory.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 108 156 The ZNG UV-bright candidates and Gaia
astrometry and photometry
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/AJ/140/1119 : Radial velocities of NGC 5466 members (Shetrone+, 2010)
J/AJ/142/22 : Heavy-element dispersion in M92 (Roederer+, 2011)
J/AJ/143/121 : UV properties Galactic globulars with GALEX. (Schiavon+, 2012)
J/AJ/149/204 : Spectroscopy of 25 stars in M68 (Schaeuble+, 2015)
J/AJ/151/40 : Differential BV photometry of 5 variables in M79 (Bond+, 2016)
J/ApJ/824/5 : Chemical abundances in NGC 5024 (M53) (Boberg+, 2016)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/AJ/155/116 : Globular cluster M14.II. Variable stars (Contreras Pena+, 2018)
J/A+A/621/A38 : Gaia catalogue of hot subluminous stars (Geier+, 2019)
J/A+A/622/A60 : Gaia DR2 misclassified RR Lyrae list (Clementini+, 2019)
J/A+A/627/A34 : GC hot UV-bright stars model spectra (Moehler+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster NGC/M identifier(s)
10- 11 I2 --- ZNG [1/18] ZNG number
13- 14 I2 h RAh [7/21] Hour of Right Ascension (J2000)
16- 17 I2 min RAm Minute of Right Ascension (J2000)
19- 24 F6.3 s RAs Second of Right Ascension (J2000)
26- 26 A1 --- DE- [-/+] Sign of the Declination (J2000)
27- 28 I2 deg DEd Degree of Declination (J2000)
30- 31 I2 arcmin DEm Arcminute of Declination (J2000)
33- 37 F5.2 arcsec DEs Arcsecond of Declination (J2000)
39- 45 F7.4 mas plx [-0.55/5.27]? Gaia EDR3 parallax
47- 52 F6.4 mas e_plx [0.01/0.45]? Uncertainty in plx
54- 60 F7.3 mas/yr pmRA [-78.1/19.2]? Gaia EDR3 Proper motion along RA
62- 66 F5.3 mas/yr e_pmRA [0.01/0.51]? Uncertainty in pmRA
68- 74 F7.3 mas/yr pmDE [-89.5/17.2]? Gaia EDR3 proper motion along DE
76- 80 F5.3 mas/yr e_pmDE [0.01/0.47]? Uncertainty in pmDE
82- 87 F6.3 mag Gmag [9.73/17.5] Gaia EDR3 G band magnitude
89- 94 F6.3 mag BP-RP [-0.45/2.45] Gaia EDR3 (Blue-Red) color
96- 99 A4 --- Memb? Cluster Member? (1)
101-105 A5 --- Class Classification (2)
107-108 I2 --- Note [1/53]? Additional remarks (3)
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Note (1): Indication of cluster membership, based on parallax and proper motion.
A few uncertain cases are labeled with question marks.
Note (2): Class as follows:
AGB = asymptotic-giant branch (12 occurrences)
AHB = above horizontal branch (27 occurrences)
CV? = candidate cataclysmic variable (1 occurrence)
HB = horizontal branch (14 occurrences)
RGB = red-giant branch ( 5 occurrences)
bPAGB = blue post-AGB stars (5 occurrences)
rPAGB = red post-AGB stars (2 occurrences)
vPAGB = violet post-AGB stars (3 occurrences)
yPAGB = yellow post-AGB stars (1 occurrence)
Note (3): Note as follows:
1 = 4147 ZNG 2: HST images show object to be blend of 5 cluster members
of similar brightness; brightest one listed.
2 = 4590 ZNG 2: At tip of AGB/RGB; see Schaeuble+, 2015AJ....143..121S 2015AJ....143..121S
and references therein.
3 = 5024 ZNG 3: considered a non-member by Boberg+, 2016, J/ApJ/824/5.
4 = 5024 ZNG 7: Close nearly equal pair, separation 0".9. Astrometry has
large uncertainties, but both components consistent with membership.
Brighter component listed. Non-member according to
Boberg+, 2016, J/ApJ/824/5.
5 = 5024 ZNG 8: Astrometry has large uncertainties. Member according to
Boberg+, 2016, J/ApJ/824/5.
6 = 5024 ZNG 9: Member according to Boberg+, 2016, J/ApJ/824/5. Blended with
a fainter AGB star 2.0" away.
7 = 5024 ZNG 14: Identification uncertain. Astrometry has large
uncertainties, but membership unlikely.
8 = 5272 ZNG 1: M3 von Zeipel 1128.
9 = 5272 ZNG 3: RR Lyr variable V10.
10 = 5272 ZNG 4: Blend of 3 stars; bluest one listed. RR Lyr variable V165.
11 = 5272 ZNG 5: RR Lyr variable V90.
12 = 5466 ZNG 5: Extreme HB star; see Geier+, 2019A&A...621A..38. 2019A&A...621A..38.
13 = 5466 ZNG 6: AGB star; see Shetrone+, 2010 J/AJ/140/1119.
14 = 5897 ZNG 2: Luminous red post-AGB star. Gaia RV consistent
with membership.
15 = 5904 ZNG 1: Proper motion consistent with membership,
parallax discordant; AGB or RGB star if member.
16 = 5904 ZNG 2: Proper motion consistent with membership,
parallax discordant; AGB or RGB tip star if member.
17 = 5904 ZNG 6: RR Lyr variable V41.
18 = 5904 ZNG 7: RR Lyr variable V25.
19 = 6093 ZNG 1: Proper motion consistent with membership,
parallax discordant; RGB star if member.
20 = 6093 ZNG 3: EDR3 does not give a parallax or proper motion for this
source; there is a bright blue object at this position in HST images,
but the Gaia BP-RP color is red. Position is close to that of the
X-ray source CX3 (Heinke+, 2003ApJ...598..516H 2003ApJ...598..516H).
21 = 6121 ZNG 2: RR Lyr variable V19.
22 = 6121 ZNG 4: RR Lyr variable V10.
23 = 6121 ZNG 5: This object is a blend of two RR Lyr variables, separated
by 1.6" (Clementini+, 2019, J/A+A/622/A60).
Brighter component is listed in table.
24 = 6121 ZNG 6: Candidate RR Lyr, V58, but non-variable according to
Safonova+, 2016AJ....151...27S 2016AJ....151...27S.
25 = 6121 ZNG 7: Very bright star at tip of RGB. Gaia RV consistent
with membership.
26 = 6121 ZNG 9: RR Lyr variable V28.
27 = 6205 ZNG 1: Barnard 29 (see M+19).
28 = 6205 ZNG 2: Proper motion consistent with membership, but large
uncertainties and discordant parallax; suspected low-amplitude
variable (Deras+, 2019, 2019MNRAS.486.2791D 2019MNRAS.486.2791D.
29 = 6205 ZNG 3: Variable star V51, uncertain type
(Servillat+, 2011ApJ...733..106S 2011ApJ...733..106S).
30 = 6205 ZNG 4: Spectroscopic analysis by Ambika+, 2004A&A...417..293A 2004A&A...417..293A.
31 = 6218 ZNG 7: Gaia RV consistent with membership.
32 = 6218 ZNG 8: Gaia RV consistent with membership.
33 = 6254 ZNG 1: Blue PAGB star (see M+19).
34 = 6273 ZNG 2: Blue PAGB star (see B+21).
35 = 6273 ZNG 3: Type II Cepheid, V1
(Clement & Sawyer Hogg, 1978AJ.....83..167C 1978AJ.....83..167C);
proper motion consistent with membership, parallax discordant.
36 = 6273 ZNG 4: Yellow PAGB star (see B+21).
37 = 6333 ZNG 1: Proper motion consistent with membership; parallax
slightly discrepant. On boundary between yellow and blue PAGB stars.
38 = 6333 ZNG 4: Astrometry consistent with membership, but
uncertainties are large.
39 = 6341 ZNG 4: Proper motion consistent with membership, but parallax
is discordant. Considered a member by Zinn, 1974ApJ...193..593Z 1974ApJ...193..593Z,
but not by Roederer+, 2011, 2011AJ....142...22R 2011AJ....142...22R.
40 = 6356 ZNG 2: Proper motion marginally consistent with membership.
41 = 6402 ZNG 1: Blue PAGB star
(star 33 in Schiavon+, 2012, J/AJ/143/121)
42 = 6402 ZNG 5: Above HB (star 202 in Schiavon+, 2012, J/AJ/143/121)
43 = 6402 ZNG 14: Type II Cepheid, V167 (Contreras+, 2018, J/AJ/155/116).
44 = 6626 ZNG 5: RV Tauri variable V2342 Sgr V17.
45 = 6656 ZNG 14: Gaia RV consistent with membership.
46 = 6712 ZNG 1: Blue PAGB star (see M+19).
47 = 6712 ZNG 4: Luminous star at AGB tip; Mira variable AP Sct = V2.
48 = 6779 ZNG 2: Violet PAGB star (see M+19).
49 = 7078 ZNG 1: Hot post-HB or violet PAGB star (see M+19).
50 = 7078 ZNG 4: Identification difficult and uncertain. Listed star
is brighter of close 1.4" pair.
51 = 7078 ZNG 5: Identification difficult and uncertain. Listed star
is brighter of close 1.4" pair.
52 = 7078 ZNG 6: Proper motion consistent with membership, but parallax
is discordant. If it is a member, it is a bright star near the AGB tip.
53 = 7078 ZNG 7: Astrometry has large uncertainties;
Gebhardt+, 1997, J/AJ/113/1026 give a radial velocity
consistent with membership.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 02-Jul-2021