J/ApJ/765/71 VI light curves of RRL stars in M31 (Contreras Ramos+, 2013)
Does the Oosterhoff dichotomy exist in the Andromeda galaxy?
I. The case of G11.
Contreras Ramos R., Clementini G., Federici L., Fiorentino G., Cacciari C.,
Catelan M., Smith H.A., Fusi Pecci F., Marconi M., Pritzl B.J.,
Kinemuchi K.
<Astrophys. J., 765, 71 (2013)>
=2013ApJ...765...71C 2013ApJ...765...71C
ADC_Keywords: Photometry, HST ; Clusters, globular ; Stars, variable
Keywords: galaxies: individual: M31; globular clusters: individual: G11;
stars: distances; stars: variables: RR Lyrae; techniques: photometric
Abstract:
We present the first evidence that Oosterhoff type II globular
clusters exist in the Andromeda galaxy (M31). On the basis of
time-series photometry of the moderately metal-poor ([Fe/H]~-1.6dex)
M31 globular cluster G11, obtained with the Wide Field Planetary
Camera 2 on board the Hubble Space Telescope, we detected and derived
periods for 14 RR Lyrae stars, of which five are found to lie inside
the cluster tidal radius. They include three fundamental-mode (RRab)
and two first-overtone (RRc) pulsators, with average periods
<Pab≥0.70 days, and <Pc≥0.40 days, respectively. These mean
periods and the position of the cluster variable stars in the
period-amplitude and period-metallicity diagrams all suggest that G11
is likely to be an Oosterhoff type II globular cluster. This appears
to be in agreement with the general behavior of Milky Way globular
clusters with similar metallicity and horizontal branch morphology.
Description:
HST/WFPC2 time-series observations of G11 were obtained on 2007 July,
as part of the Cycle 15, HST GO program 11081 (PI: G. Clementini).
They consist of 11 F606W (broad V) and 11 F814W (I) exposures each of
1100s in length, taken by alternating the two filters. Our proprietary
data were complemented by WFPC2/HST archive observations of G11
obtained in 2000 as part of the GO program 6671 (PI: Rich). They
consist of four F555W (V) and four F814W (I) frames.
Objects:
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RA (ICRS) DE Designation(s)
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00 36 20.86 +40 53 37.1 G11 = SKHB 11
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 107 14 Identification and properties of the RRL stars
identified in the FOV of the G11 observations
table4.dat 36 359 F606W, F814W photometry for the RRL stars
detected in this FOV of the G11 observation
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/AJ/148/4 : JHK photometry of 913 globular clusters in M31 (Wang+, 2014)
J/ApJ/745/156 : M31 Cepheids with HST/WFC3 (Riess+, 2012)
J/A+A/544/A155 : HST photometry of M31 globular clusters (Federici+, 2012)
J/A+A/539/A138 : RR Lyr variable stars in M32 (Fiorentino+, 2012)
J/MNRAS/425/1459 : RR Lyrae in M32 (Sarajedini+, 2012)
J/AJ/141/171 : RRL stars in six ultra-deep fields of M31 (Jeffery+, 2011)
J/MNRAS/402/803 : M31 globular cluster system (Peacock+, 2010)
J/ApJ/725/200 : An updated cat. of M31 globular-like clusters (Fan+, 2010)
J/ApJ/708/817 : RR Lyrae variables in M32 and M31 (Fiorentino+, 2010)
J/A+A/508/1285 : Metallicities of M31 globular clusters (Galleti+, 2009)
J/AJ/138/184 : RRL variables in 2 M31 spheroid fields (Sarajedini+, 2009)
J/A+A/471/127 : New globular clusters in M31 (Galleti+, 2007)
J/PASP/119/7 : HST WFPC2 star clusters in M31 (Krienke+, 2007)
J/AJ/129/2232 : Variable stars in And I and And III (Pritzl+, 2005)
J/AJ/129/267 : RR Lyrae variables in NGC 5272 (Cacciari+, 2005)
J/A+A/416/917 : Revised Bologna Cat. of M31 GCs (Galleti+, 2004)
J/AJ/127/2738 : ACS VI photometry of M31 halo RR Lyrea (Brown+, 2004)
J/AJ/127/318 : BV photometry of Andromeda II variables (Pritzl+, 2004)
J/AJ/124/1464 : Variable stars in Andromeda VI (Pritzl+, 2002)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1 A1 --- n_ID [bw] Location of star (1)
3- 5 A3 --- ID Star identifier
7- 9 A3 --- f_ID [abc, ] Flag(s) on star (2)
11- 13 A3 --- Cam Camera of the WFPC2 where the star is located
15- 20 F6.2 pix Xpos [84/763] Star's coordinate along X axis (3)
22- 27 F6.2 pix Ypos [97/709] Star's coordinate along Y axis (3)
29- 33 F5.2 arcsec Dist [2.7/99] Estimated distance from the cluster
center
35- 38 A4 --- Type RR Lyrae type (RRab or RRc)
40- 47 F8.6 d Per [0.3/0.8] Period
49- 57 F9.4 d Epoch Heliocentric Julian date of maximum light;
JD-2450000
59- 63 F5.2 mag <F606W> Intensity-averaged mean HST F606W magnitude
64 A1 --- u_<F606W> <F606W> uncertainty flag
66- 70 F5.2 mag <F814W> [24.4/25.1] Intensity-averaged mean HST F814W
magnitude
72- 73 A2 --- l_F606amp [≥ ] Limit flag on F606amp
74- 77 F4.2 mag F606amp F606W amplitude (AF606W)
79- 82 F4.2 mag F814amp [0.2/0.9] F814W amplitude (AF814W)
84- 88 F5.2 mag <Vmag> Intensity-averaged mean V-band magnitude
89 A1 --- u_<Vmag> <Vmag> uncertainty flag
91- 95 F5.2 mag <Imag> [24.4/25.1] Intensity-averaged mean I-band
magnitude
97- 98 A2 --- l_Vamp [≥ ] Limit flag on Vamp
99-102 F4.2 mag Vamp V-band amplitude (AV)
104-107 F4.2 mag Iamp [0.2/0.9] I-band amplitude (AI)
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Note (1): Note as follows:
w = Variable stars within the cluster tidal radius
b = Variable stars beyond the cluster tidal radius
Note (2): Flag as follows:
a = Stars with a counterpart in the archival WFPC2/HST data.
b = Stars showing blue amplitudes (AF606W or AV) smaller than the red
amplitudes (AF814W or AI), possibly due to contamination by companions.
c = Candidate RRL star in Clementini et al. (2001ApJ...559L.109C 2001ApJ...559L.109C) that has
been confirmed in the present study.
Note (3): Star's coordinates in pixels, as measured on the reference image
(see Section 3).
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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- 3 A3 --- ID Star identifier
5- 8 A4 --- Type RR Lyrae type (RRab or RRc)
10- 14 A5 --- Filt HST/WFPC2 filter (F555W, F606W or F814W)
16- 29 F14.6 d HJD Heliocentric Julian Date
31- 36 F6.3 mag mag [23.9/26] Observed magnitude in Filt
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 31-Oct-2014