J/MNRAS/430/2932 WASP-44 griz light curves (Mancini+, 2013)
Physical properties of the WASP-44 planetary system from simultaneous
multi-colour photometry.
Mancini L., Nikolov N., Southworth J., Chen G., Fortney J.J.,
Tregloan-Reed J., Ciceri S., Van Boekel R., Henning T.
<Mon. Not. R. Astron. Soc., 430, 2932-2942 (2013)>
=2013MNRAS.430.2932M 2013MNRAS.430.2932M
ADC_Keywords: Stars, double and multiple ; Planets ; Photometry, SDSS
Keywords: stars: planetary systems - methods: data analysis -
methods: observational - techniques: photometric
Abstract:
We present ground-based broad-band photometry of two transits in the
WASP-44 planetary system obtained simultaneously through four optical
(Sloan g', r', i', z') and three near-infrared (NIR; J, H, K) filters.
We achieved low scatters of 1-2mmag per observation in the optical
bands with a cadence of roughly 48s, but the NIR-band light curves
present much greater scatter. We also observed another transit of
WASP-44 b by using a Gunn r filter and telescope defocussing, with a
scatter of 0.37 mmag per point and an observing cadence around 135 s.
We used these data to improve measurements of the time of mid- transit
and the physical properties of the system. In particular, we improved
the radius measurements of the star and planet by factors of 3 and 4,
respectively. We find that the radius of WASP-44 b is
1.002±0.033±0.018RJup (statistical and systematic errors,
respectively), which is slightly smaller than previously thought and
differs from that expected for a core-free planet. In addition, with
the help of a synthetic spectrum, we investigated the theoretically
predicted variation of the planetary radius as a function of
wavelength, covering the range 370-2440nm. We can rule out extreme
variations at optical wavelengths, but unfortunately our data are not
precise enough (especially in the NIR bands) to differentiate between
the theoretical spectrum and a radius which does not change with
wavelength.
The resulting measurements of transit mid-points were fitted with a
straight line to obtain a new orbital ephemeris:
T0=BJD(TDB)2455434.37642(37)+2.4238133(23)xE,
where E is the number of orbital cycles after the reference epoch [the
mid-point of the first transit observed by Anderson et al. (2012, Cat.
J/MNRAS/422/1988)] and quantities in parentheses denote the
uncertainty in the final digit of the preceding number.
Description:
Nine light curves of three transits of the extrasolar planetary system
WASP-44 are presented.
Eight of the datasets were obtained using the MPG/ESO 2.2m telescope,
GROND camera and filters similar to Sloan-g', Sloan-r', Sloan-i',
Sloan-z', at the ESO Observatory in La Silla (Chile) in 2011.
Another dataset was obtained using the 2.5m INT telescope, WFC camera
and Gunn-r filter at La Palma (Spain) in 2011, 2011 and 2012.
Objects:
-------------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------------
00 15 36.770 -11 56 17.30 WASP-44 = GSC 05264-00740
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 99 15 Log of the observations presented in this work
phot/* . 9 Individual light curves
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See also:
J/MNRAS/408/1680 : Transiting planetary system WASP-2 (Southworth+, 2010)
J/MNRAS/396/1023 : Transiting planetary system WASP-5 (Southworth+, 2009)
J/MNRAS/399/287 : Transiting planetary system WASP-4 (Southworth+, 2009)
J/A+A/527/A8 : Transiting planetary system WASP-7 (Southworth+, 2011)
J/ApJ/707/167 : Transiting planetary system WASP-18 (Southworth+, 2009)
J/MNRAS/426/1338 : Transiting planetary system WASP-17 (Southworth+, 2012)
J/A+A/551/A11 : Transiting planetary system HAT-P-8 (Mancini+, 2013)
J/MNRAS/422/3099 : Transiting planetary system HAT-P-5 (Southworth+, 2012)
J/MNRAS/420/2580 : Transiting planetary system HAT-P-13 (Southworth+, 2012)
J/A+A/549/A10 : Transiting planetary system GJ1214 (Harpsoe+, 2013)
J/MNRAS/422/1988 : Transiting exoplanets WASP-44b, 45b & 46b (Anderson+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Tr [1/3] Transit number (1)
3- 12 A10 "YYYY-MM-DD" Obs.date Observation date (start)
14- 18 A5 "h:m" Obs.time Observation time (UT)
19 A1 --- --- [-]
20- 24 A5 "h:m" End End of observation time (UT)
26- 28 I3 --- Nobs [156/631] Number of observations
30- 32 I3 s ExpTime Exposure time
34- 41 A8 --- Filt Filter name (J, H, K, Gunn r,
Sloan g', r', i', z')
43- 46 F4.2 --- AirM1 Airmass at start
47- 48 A2 --- --- [->]
49- 52 F4.2 --- AirM2 Airmass at mid-observation or end
53- 54 A2 --- --- [->]
55- 58 F4.2 --- AirM3 ? Airmass at end
60- 61 I2 % Moon [31/80] Fractional illumination of the Moon
at the mid-point of the transit
63- 66 F4.1 pix Ap* Radius of the software aperture for
the star
68- 71 F4.1 pix ApI Radius of the software aperture for
the inner sky
73- 76 F4.1 pix ApO Radius of the software aperture for
the outer sky
78- 81 F4.2 mmag Scat Magnitude scatter
83- 86 F4.2 --- beta β factor used to inflate the error
bars, in order to assess red noise
(see section 3)
88- 99 A12 --- FileName Name of the light curve file in
subdirectory phot
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Note (1): Transit 1 was observed using the 2.5 m INT in La Palma, whereas
transits 2 and 3 using the MPG/ESO 2.2m telescope in La Silla.
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Byte-by-byte Description of file: phot/*
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 F13.7 d BJD Barycentric JD-2400000 for the midpoint of
observation, BJD(TDB)
16- 25 F10.7 mag mag Differential magnitude of WASP-44
29- 37 F9.7 mag e_mag Measurement error of the magnitude
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Acknowledgements:
Luigi Mancini, mancini(at)mpia.de
Max Planck Institute for Astronomy, Germany
(End) Luigi Mancini [Max Planck Inst.], Patricia Vannier [CDS] 17-Jun-2013