J/AJ/152/170 RRLs in globulars. IV. UBVRI photometry in Omega Cen (Braga+, 2016)
On the RR Lyrae stars in globulars. IV. ω Centauri optical UBVRI
photometry.
Braga V.F., Stetson P.B., Bono G., Dall'Ora M., Ferraro I., Fiorentino G.,
Freyhammer L.M., Iannicola G., Marengo M., Neeley J., Valenti E.,
Buonanno R., Calamida A., Castellani M., da Silva R., Degl'Innocenti S.,
Di Cecco A., Fabrizio M., Freedman W.L., Giuffrida G., Lub J., Madore B.F.,
Marconi M., Marinoni S., Matsunaga N., Monelli M., Persson S.E.,
Piersimoni A.M., Pietrinferni A., Prada-Moroni P., Pulone L.,
Stellingwerf R., Tognelli E., Walker A.R.
<Astron. J., 152, 170-170 (2016)>
=2016AJ....152..170B 2016AJ....152..170B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular; Stars, variable ; Photometry, UBVRI ;
Abundances, [Fe/H]
Keywords: globular clusters: individual: omega Cen - stars: distances -
stars: horizontal-branch - stars: variables: RR Lyrae
Abstract:
New accurate and homogeneous optical UBVRI photometry has been
obtained for variable stars in the Galactic globular cluster ω
Cen (NGC 5139). We secured 8202 CCD images covering a time interval of
24 years and a sky area of 84x48arcmin. The current data were
complemented with data available in the literature and provided new,
homogeneous pulsation parameters (mean magnitudes, luminosity
amplitudes, periods) for 187 candidate ω Cen RR Lyrae (RRLs).
Among them we have 101 RRc (first overtone) and 85 RRab (fundamental)
variables, and a single candidate RRd (double-mode) variable.
Candidate Blazhko RRLs show periods and colors that are intermediate
between the RRc and RRab variables, suggesting that they are
transitional objects. A comparison of the period distribution and the
Bailey diagram indicates that RRLs in ω Cen show a long-period
tail not present in typical Oosterhoff II (OoII) globulars. The RRLs
in dwarf spheroidals and in ultra-faint dwarfs have properties between
Oosterhoff intermediate and OoII clusters. Metallicity plays a key
role in shaping the above evidence. These findings do not support the
hypothesis that ω Cen is the core remnant of a spoiled dwarf
galaxy. Using optical period-Wesenheit relations that are
reddening-free and minimally dependent on metallicity we find a mean
distance to ω Cen of 13.71±0.08±0.01mag (semi-empirical and
theoretical calibrations). Finally, we invert the I-band
period-luminosity-metallicity relation to estimate individual RRLs'
metal abundances. The metallicity distribution agrees quite well with
spectroscopic and photometric metallicity estimates available in the
literature.
Description:
We provide new, accurate, and homogeneous calibrated multi-band UBVRI
photometry for the candidate RR Lyrae (RRLs) in ω Cen.
We acquired 8202 optical CCD images of ω Cen that cover a time
interval of 24 years (1988 Feb-2012 Feb) and a sky area of 84*48arcmin
across the cluster center. The bulk of these images were collected
with the Danish 1.5m telescope at ESO La Silla as time-series data in
three main long runs (more than 4500 images). The others were
collected with several telescopes available at Cerro Tololo
Inter-American Observatory (CTIO): 0.9m, 1.5m, Blanco 4m, at European
Southern Observatory (ESO): 0.9m, MPI/ESO 2.2m, New Technology
Telescope (NTT), Very Large Telescope (VLT), and at South African
Astronomical Observatory (SAAO; 1m).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 77 199 Positions and periods for ω Cen RR Lyrae (RRLs)
table3.dat 124 183 Optical-UBVRI-mean magnitudes and amplitudes
for ω Cen RR Lyrae (RRLs)
table10.dat 55 174 Metallicity estimates ([Fe/H]) of candidate ω
Cen RR Lyrae (RRLs) based on spectroscopy (Sollima
et al. 2006, Cat. J/ApJ/640/L43) and on photometric
indices (Rey et al. 2000, Cat. J/AJ/119/1824, ours)
notes.dat 399 100 Notes
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See also:
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/A+A/576/A30 : Light-curve templates for classical Cepheids (Inno+, 2015)
J/A+A/583/A76 : Om. Cen candidates RAVE-selected (Fernandez-Trincado+, 2015)
J/A+A/574/A15 : RR Lyrae in omega Cen (Fernandez-Trincado+, 2015)
J/ApJS/219/25 : Light curves of RR Lyrae stars in M3 (Jurcsik+, 2015)
J/PASP/126/521 : UBVRIJHK photometry of RR Lyrae in M4 (Stetson+, 2014)
J/MNRAS/419/2173 : Long-term photometry of M3 RR Lyrae (Jursik+, 2012)
J/A+A/547/A109 : Parameters of HB stars in ω Cen (Moni Bidin+, 2012)
J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010)
J/A+A/505/117 : Abundances of red giants in 15 globulars (Carretta+, 2009)
J/A+A/493/959 : UBV(RI)cHalpha photometry in omega Cen (Bellini+, 2009)
J/ApJ/706/1277 : Stromgren photometry in ω Cen (Calamida+, 2009)
J/ApJ/698/2048 : Abundances of red giants in ω Cen (Johnson+, 2009)
J/AJ/136/506 : Radial velocities of ω Cen members (Da Costa+, 2008)
J/AJ/133/1447 : Light curves of variables in ω Cen (Weldrake+, 2007)
J/ApJ/663/1021 : Log of ω Cen scientific images (Castellani+, 2007)
J/ApJ/640/L43 : Metallicities of RRL stars in Omega Cen (Sollima+, 2006)
J/A+A/424/1101 : Variable Stars in the field of ω Cen (Kaluzny+, 2004)
J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)
J/A+A/360/472 : Proper motions in omega Centauri (van Leeuwen+, 2000)
J/AJ/119/1824 : Caby photometry of ω Centauri (Rey+, 2000)
J/A+AS/125/343 : RR Lyr stars in omega Cen (Kaluzny+ 1997)
J/ApJ/462/241 : Ca abundance for Omega Cen red giants (Norris+ 1996)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Name Name of the ω Cen RR Lyrae
7- 9 A3 --- f_Name Flag on Name (e, f, or h) (1)
11- 12 I2 h RAh Hour of Right Ascension (J2000) (2)
14- 15 I2 min RAm Minute of Right Ascension (J2000) (2)
17- 21 F5.2 s RAs Second of Right Ascension (J2000) (2)
23 A1 --- DE- Sign of the Declination (J2000) (2)
24- 25 I2 deg DEd Degree of Declination (J2000) (2)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000) (2)
30- 33 F4.1 arcsec DEs Arcsecond of Declination (J2000) (2)
35- 41 F7.5 d Per1 [0.25/1.1]? Pulsation period based on a
compilation of literature values (Clement et al.
2001AJ....122.2587C 2001AJ....122.2587C) (3)
43- 50 F8.6 d Per2 [0.25/1.1]? Pulsation period based on the current
estimate using the Lomb-Scargle (LS) method
(Scargle 1982ApJ...263..835S 1982ApJ...263..835S)
52 A1 --- Band1 [BVRI] Band used for the epoch of light maximum
(T0(max)) (B, V, R, or I)
54- 63 F10.4 d HJD1 [49113.5/54273.5]? Epoch of light maximum
(T0(max)) in Heliocentric Julian Date
(HJD-2400000) (4)
65 A1 --- Band2 [BVRI] Band used for the epoch of mean magnitude
on the rising branch (T0(rising)) (B, V, R, or
I)
67- 77 F11.4 d HJD2 [49082.5/451270]? Epoch of mean magnitude on
the rising branch (T0(rising)) in Heliocentric
Julian Date (HJD-2400000) (4)
--------------------------------------------------------------------------------
Note (1): Flag codes are defined as follows:
e = Coordinates from Clement's catalog (2001AJ....122.2587C 2001AJ....122.2587C);
f = Candidate field RR Lyrae (RRL);
g = Coordinates from Fernandez-Trincado et al. 2015 (Cat. J/A+A/574/A15);
h = Coordinates from Navarrete et al. 2015A&A...577A..99N 2015A&A...577A..99N.
Note (2): The mean epoch associated to these coordinates is 2004 May.
Note (3): V80, V172 and V173 from Navarrete et al. 2015A&A...577A..99N 2015A&A...577A..99N, V175
from Fernandez-Trincado et al. 2015 (Cat. J/A+A/574/A15), others from
Clement et al. 2001AJ....122.2587C 2001AJ....122.2587C.
Note (4): Epoch of light maximum and of mean magnitude on the rising branch
(HJD-2400000) estimated using the spline fit to optical light curves.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Name Name of the ω Cen RR Lyrae
7- 12 F6.3 mag <Umag> [14.67/15.81]? Mean U-band magnitude (1)
14- 18 F5.3 mag e_<Umag> [0.009/0.43]? Error in Umag (2)
20- 25 F6.3 mag <Bmag> [14.59/15.5]? Mean B-band magnitude (1)
27- 31 F5.3 mag e_<Bmag> [0.003/0.21]? Error in Bmag (2)
33- 38 F6.3 mag <Vmag> [14/18.2]? Mean V-band magnitude (1)
40- 44 F5.3 mag e_<Vmag> [0.003/0.14]? Error in Vmag (2)
46- 51 F6.3 mag <Rmag> [12.36/15.43]? Mean R-band magnitude (1)
53- 57 F5.3 mag e_<Rmag> [0.008/0.28]? Error in Rmag (2)
59- 64 F6.3 mag <Imag> [13.3/14.6]? Mean I-mag magnitude (1)
66- 70 F5.3 mag e_<Imag> [0.007/0.18]? Error in Imag (2)
72- 76 F5.3 mag AU [0.2/1.6]? Luminosity amplitude in U (3)
78- 82 F5.3 mag AB0 [0.039/1.54]? Luminosity amplitude in B
(or lower range) (3)
83 A1 --- --- [-]
84- 88 F5.3 mag AB1 [0.27/1.7]? Upper range of luminosity
amplitude in B (3)
90- 94 F5.3 mag AV0 [0.04/1.4]? Luminosity amplitude in V (or
lower range) (3)
95 A1 --- --- [-]
96-100 F5.3 mag AV1 [0.13/1.3]? Upper range of luminosity
amplitude in V (3)
102-106 F5.3 mag AR [0.024/1.12]? Luminosity amplitude in R (3)
108-112 F5.3 mag AI [0.04/0.91]? Luminosity amplitude in I (3)
114 I1 --- qU [0/2]? Photometric quality index of the U-band
light curve (qU) (4)
115 I1 --- qB [0/3]? Photometric quality index of the B-band
light curve (qB) (4)
116 I1 --- qV [0/3]? Photometric quality index of the V-band
light curve (qV) (4)
117 I1 --- qR [0/3]? Photometric quality index of the R-band
light curve (qR) (4)
118 I1 --- qI [0/3]? Photometric quality index of the I-band
light curve (qI) (4)
120-123 A4 --- Mode Pulsation mode identification (RRab, RRc, or
RRd) (5)
124 A1 --- f_Mode [*] An asterisk flag on Mode indicates that
the variable is candidate Blazhko RR Lyrae
--------------------------------------------------------------------------------
Note (1): The means were computed as intensity averages and then transformed
into magnitudes.
Note (2): The errors of the mean magnitudes have been determined as the weighted
standard deviation between the spline fit and the individual phase points.
Note (3): The amplitudes were estimated as the difference between the minimum
and the maximum of the spline fit. The U-band amplitude is only available
for a few variables (see the Appendix). The minimum and maximum amplitudes
of candidate Blazhko RRLs and of the candidate mixed-mode variable were
estimated as the amplitudes of the lower and upper envelope of the observed
data points.
Note (4): Taking account of the phase coverage, uncertainties on individual
measurements, and photometric scatter. The ranking is as follows:
0 = no phase coverage;
1 = poor phase coverage;
2 = decent coverage;
3 = good coverage.
Note (5): The types of RR Lyrae are defined as follows:
RRab = Fundamental;
RRc = First overtone;
RRd = Mixed-mode.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table10.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Name Name of the candidate ω Cen RR Lyrae
7- 11 F5.2 [Sun] S06 [-2.2/-1.11]? Spectroscopic iron abundance
provided by Sollima et al. 2006
(Cat. J/ApJ/640/L43)
13- 16 F4.2 [Sun] e_S06 [0/1]? Error in S06
18- 22 F5.2 [Sun] Rey [-2.21/-0.9]? Metallicity estimate provided
by Rey et al. 2000 (Cat. J/AJ/119/1824) (1)
24- 27 F4.2 [Sun] e_Rey [0.01/0.55]? Error in Rey
29- 33 F5.2 [Sun] S06+Rey [-2.33/-1.02]? Mean iron abundance based on
Sollima et al. 2006 (Cat. J/ApJ/640/L43)
and Rey et al. 2000 (Cat. J/AJ/119/1824)
abundances (2)
35- 38 F4.2 [Sun] e_S06+Rey [0/1]? Error in S06+Rey
40- 44 F5.2 [Sun] PLI [-3/-0.52]? Iron abundance based on the
inversion of the I-band PLZ relations for
RRab and RRc variables (3)
46- 50 F5.2 [Sun] S06+Rey+PLI [-3/-1.16] Mean iron abundance based on
Sollima et al. 2006 (Cat. J/ApJ/640/L43),
Rey et al. 2000 (Cat. J/AJ/119/1824) and on
the current estimates (4)
52- 55 F4.2 [Sun] e_S06+Rey+PLI [0/0.8] Error in S06+Rey+PLI
--------------------------------------------------------------------------------
Note (1): Using the hk photometric index.
Note (2): The original iron abundances provided by Sollima et al. 2006
(Cat. J/ApJ/640/L43) and Rey et al. 2000 (Cat. J/AJ/119/1824) were rescaled
to the homogeneous cluster metallicity scale provided by Carretta et al.
2009 (Cat. J/A+A/505/117). The abundances from Rey et al. 2000
(Cat. J/AJ/119/1824) were transformed into this metallicity scale using the
linear relation (Zinn and West 1984ApJS...55...45Z 1984ApJS...55...45Z to UVES) given in
Section 5 of Carretta et al. 2009 (Cat. J/A+A/505/117). The abundances from
Sollima et al. 2006 (Cat. J/ApJ/640/L43) were transformed into the the same
scale by accounting for the difference in solar iron abundance in number
logεFe=7.52 versus 7.54 (Gratton et al. 2003, Cat. J/A+A/404/187;
Carretta et al. 2009, Cat. J/A+A/505/117).
Note (3): For more details see Section 8. The solar iron abundance
logεFe was rescaled from 7.50 (pulsation and evolutionary
models) to 7.54 of the Carretta's metallicity scale. The typical relative
error on the abundance of RRLs based on the PLZ relations ranges from 0.2
to 0.3dex. The error budget accounts for uncertainties in the I-band mean
magnitude, in the differential reddening and in the standard deviation of
the PLZ relations. The mean weighted metallicities listed in the last
column, were estimated by adopting for the current estimates a mean error
of 0.25dex.
Note (4): The iron abundances listed in this column were shifted by 0.09dex, to
take account of the difference in the metallicity distributions plotted in
Figure 16.
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Name Name of the ω Cen RR Lyrae
7-399 A393 --- Note Notes about the star
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History:
From electronic version of the journal
References:
Braga et al., Paper I 2015ApJ...799..165B 2015ApJ...799..165B
Neeley et al., Paper II 2015ApJ...808...11N 2015ApJ...808...11N, Cat. J/ApJ/808/11
Stetson et al., Paper III 2014PASP..126..521S 2014PASP..126..521S, Cat. J/PASP/126/521
Braga et al., Paper V 2018AJ....155..137B 2018AJ....155..137B
(End) Sylvain Guehenneux [CDS] 16-May-2017