J/MNRAS/405/1711 VRIg'i' photometry of 7 M15 giants (McDonald+, 2010)
Discovery of long-period variable stars in the very metal-poor
globular cluster M15.
McDonald I., van Loon J.T., Dupree A.K., Boyer M.L.
<Mon. Not. R. Astron. Soc., 405, 1711-1722 (2010)>
=2010MNRAS.405.1711M 2010MNRAS.405.1711M
ADC_Keywords: Clusters, globular ; Stars, giant ; Photometry, VRI ;
Photometry, SDSS
Keywords: stars: AGB and post-AGB - stars: late-type - stars: Population II -
stars: variables: general - stars: winds, outflows -
globular clusters: individual: M15
Abstract:
We present a search for long-period variable (LPV) stars among giant
branch stars in M15 which, at [Fe/H]~-2.3, is one of the most
metal-poor Galactic globular clusters. We use multicolour optical
photometry from the 0.6-m Keele Thornton and 2-m Liverpool Telescopes.
Variability of δV∼0.15mag is detected in K757 and K825 over
unusually long time-scales of nearly a year, making them the most
metal-poor LPVs found in a Galactic globular cluster. K825 is placed
on the long secondary period sequence, identified for metal-rich LPVs,
though no primary period is detectable. We discuss this variability in
the context of dust production and stellar evolution at low
metallicity, using additional spectra from the 6.5-m Magellan (Las
Campanas) telescope. A lack of dust production, despite the presence
of gaseous mass loss raises questions about the production of dust
and the intracluster medium of this cluster.
Description:
The first data set for this work comes from the 2-m Liverpool
Telescope, situated on La Palma. A total of 38 observation blocks were
taken, spanning 462d, from 2007 April 23 to 2008 July 27. A gap is
present between 2007 December 04 and 2008 April 23 when the cluster
was viewed in too close proximity to the Sun.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 80 7 Candidate variable giant stars in M15 from
Mosley & White (1975BAAS....7..535M 1975BAAS....7..535M) with
tablea1.dat 55 169 Difference photometry of comparison stars with
variable stars in data from Keele Thornton
Telescope (VRI observations)
tablea2.dat 49 71 Difference photometry of comparison stars with
variable stars in data from Liverpool Telescope
(g'i' observations)
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Name Name (from Mosley & White 1975BAAS....7..535M 1975BAAS....7..535M)
6- 11 A6 --- Arp Arp designation (1955AJ.....60..317A 1955AJ.....60..317A,
Cl* NGC 7078 ARP A-NNN)
13- 15 I3 --- Buo ? Buonanno et al, 1983A&AS...51...83B 1983A&AS...51...83B number
(Cl* NGC 7078 BBFP NNN)
17- 18 A2 --- San Sandage, 1970ApJ...162..841S 1970ApJ...162..841S designation
(Cl* NGC 7078 SANDA SN)
20- 21 I2 h RAh Right ascension (J2000)
23- 24 I2 min RAm Right ascension (J2000)
26- 30 F5.2 s RAs Right ascension (J2000)
32 A1 --- DE- Declination sign (J2000)
33- 34 I2 deg DEd Declination (J2000)
36- 37 I2 arcmin DEm Declination (J2000)
39- 42 F4.1 arcsec DEs Declination (J2000)
44 A1 --- l_Mm [~] Limit flag on Mm
45- 46 I2 % Mm Membership probability
48- 54 F7.2 km/s HRV ? Heliocentric radial velocities
56- 60 F5.2 mag Vmag V magnitude
62- 65 F4.2 mag B-V B-V colour index
67- 71 A5 --- Var? Variability found ?
73 A1 --- l_Per [~] Limit flag on Per
74- 76 I3 d Per ? Period
78- 79 I2 d e_Per ? rms uncertainty on Per
80 A1 --- u_Per [?] Uncertainty flag on Per
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Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Band [VRI g'i'] Observed band
4- 13 F10.2 d JD Julian date
15- 19 F5.3 mag K169mag Apparent magnitude in Band for K169
21- 25 F5.3 mag K825mag Apparent magnitude in Band for K825
27- 31 F5.3 mag K134mag Apparent magnitude in Band for K134
33- 37 F5.3 mag K147mag ?=- Apparent magnitude in Band for K147
39- 43 F5.3 mag K757mag Apparent magnitude in Band for K757
45- 49 F5.3 mag K288mag ?=- Apparent magnitude in Band for K288
51- 55 F5.3 mag K709mag ? Apparent magnitude in Band for K709 (1)
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Note (1): No i' g' data for K709.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 10-Dec-2010