J/MNRAS/439/2618 VISTA variables in Sagittarius dSph (McDonald+, 2014)
VISTA variables in the Sagittarius dwarf spheroidal galaxy:
pulsation-versus dust-driven winds on the giant branches.
McDonald I., Zijlstra A.A., Sloan G.C., Kerins E., Lagadec E., Minniti D.
<Mon. Not. R. Astron. Soc., 439, 2618-2637 (2014)>
=2014MNRAS.439.2618M 2014MNRAS.439.2618M
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Photometry
Keywords: stars: AGB and post-AGB - stars: atmospheres - stars: oscillations -
stars: variables: RR Lyrae - galaxies: individual: Sgr dSph
Abstract:
Variability is examined in over 2.6 million stars covering 11 square
degrees of the core of the Sagittarius dwarf spheroidal galaxy (Sgr
dSph) from Visible and Infrared Survey Telescope for Astronomy Z-band
observations. Generally, pulsation on the Sgr dSph giant branches
appears to be excited by the internal κ mechanism. Pulsation
amplitudes appear identical between red and asymptotic (red giant
branch/asymptotic giant branch) giant stars, and between unreddened
carbon and oxygen-rich stars at the same luminosity. The lack of
correlation between infrared excess and variability among oxygen-rich
stars indicates that pulsations do not contribute significantly to
wind driving in oxygen-rich stars in the Sgr dSph, though the low
amplitudes of these stars mean this may not apply elsewhere. The
dust-enshrouded carbon stars have the highest amplitudes of the stars
we observe. Only in these stars does an external
κ-mechanism-driven pulsation seem likely, caused by variations
in their more opaque carbon-rich molecules or dust. This may allow
pulsation driving of winds to be effective in carbon stars.
Variability can be simplified to a power law (A∝L/T2), as in
other systems. In total, we identify 3026 variable stars (with rms
variability of δZ≳0.015mag), of which 176 are long-period
variables associable with the upper giant branches of the Sgr dSph. We
also identify 324 candidate RR Lyrae variables in the Sgr dSph and 340
in the outer Galactic bulge.
Description:
Details of the VISTA photometric observations can be found in Paper
II (McDonald et al., 2013MNRAS.436..413M 2013MNRAS.436..413M, Cat. J/MNRAS/436/413).
Briefly summarized, the observations cover seven tiles, each of which
is 1.5x1.0 square degrees, placed on the known overdensities of Sgr
dSph stars, in an irregular polygon around M54. Each tile was observed
in Z over either 12 or 13 epochs taken between 2012 April 06 and 2012
August 01 ut. Through tile overlaps, a small subset of objects are
covered in up to 48 epochs. Tile-by-tile data catalogues were
automatically reduced with the VISTA version 1.2 pipeline at the
Cambridge Astronomy Survey Unit.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 3056 List of candidate short-period variables in our data
table2.dat 91 176 List of bright LPVs in our data
table3.dat 90 189 List of candidate faint LPVs in our data
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See also:
J/MNRAS/427/2647 : Sgr dSph stars spectral classification (McDonald+, 2012)
J/MNRAS/436/413 : Sgr dSph ZJKs photometry (McDonald+, 2013)
Byte-by-byte Description of file: table1.dat table2.dat table3.dat
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Bytes Format Units Label Explanations
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1- 22 A22 --- Name Star designation (1)
24- 34 F11.7 deg RAdeg Right ascension (J2000)
36- 46 F11.7 deg DEdeg Declination (J2000)
48- 54 F7.4 mag Zmag VISTA Z magnitude
56- 64 F9.7 mag e_Zmag Standard deviation of Zmag (rms variability
in the light-curve)
66- 73 F8.5 mag <Zmag> Total observed range
75- 82 F8.5 mag Jmag VISTA J magnitude
84- 91 F8.5 mag Ksmag VISTA Ks magnitude
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Note (1): Names are:
SPVSgrHHMMSSss+DDMMSSs in table1 and LPVSgrHHMMSSss+DDMMSSs in table 2 and 3.
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History:
From electronic version of the journal
References:
McDonald et al., Paper I 2012MNRAS.427.2647M 2012MNRAS.427.2647M, Cat. J/MNRAS/427/2647
McDonald et al., Paper II 2013MNRAS.436..413M 2013MNRAS.436..413M, Cat. J/MNRAS/436/413
(End) Patricia Vannier [CDS] 19-Dec-2014