J/AJ/153/93 MOST photometry of Proxima (Kipping+, 2017)
No conclusive evidence for transits of Proxima b in MOST photometry.
Kipping D.M., Cameron C., Hartman J.D., Davenport J.R.A., Matthews J.M.,
Sasselov D., Rowe J., Siverd R.J., Chen J., Sandford E., Bakos G.A.,
Jordan A., Bayliss D., Henning T., Mancini L., Penev K., Csubry Z.,
Bhatti W., Da Silva Bento J., Guenther D.B., Kuschnig R., Moffat A.F.J.,
Rucinski S.M., Weiss W.W.
<Astron. J., 153, 93-93 (2017)>
=2017AJ....153...93K 2017AJ....153...93K (SIMBAD/NED BibCode)
ADC_Keywords: Planets ; Stars, double and multiple ; Photometry
Keywords: planetary systems - stars: individual: Proxima Cen -
techniques: photometric
Abstract:
The analysis of Proxima Centauri's radial velocities recently led
Anglada-Escude et al. to claim the presence of a low-mass planet
orbiting the Sun's nearest star once every 11.2 days. Although the a
priori probability that Proxima b transits its parent star is just
1.5%, the potential impact of such a discovery would be considerable.
Independent of recent radial velocity efforts, we observed Proxima
Centauri for 12.5 days in 2014 and 31 days in 2015 with the Microwave
and Oscillations of Stars space telescope. We report here that we
cannot make a compelling case that Proxima b transits in our precise
photometric time series. Imposing an informative prior on the period
and phase, we do detect a candidate signal with the expected depth.
However, perturbing the phase prior across 100 evenly spaced intervals
reveals one strong false positive and one weaker instance. We estimate
a false-positive rate of at least a few percent and a much higher
false-negative rate of 20%-40%, likely caused by the very high flare
rate of Proxima Centauri. Comparing our candidate signal to HATSouth
ground-based photometry reveals that the signal is somewhat, but not
conclusively, disfavored (1σ-2σ), leading us to argue that
the signal is most likely spurious. We expect that infrared
photometric follow-up could more conclusively test the existence of
this candidate signal, owing to the suppression of flare activity and
the impressive infrared brightness of the parent star.
Description:
Microwave and Oscillations of STars (MOST) telescope is a 53kg
satellite in low Earth orbit with a 15cm aperture visible band camera
(35-750nm).
MOST observed Proxima Centauri in 2014 May (beginning on HJD(2000)
2456793.18) for about 12.5 days. MOST again observed Proxima Centauri
in 2015 May (starting on HJD(2000) 2457148.54), this time for a total
of 31 days.
Independent of the MOST observations, Proxima Cen was also monitored
by the HATSouth ground-based telescope network. The network consists
of six wide-field photometric instruments located at three
observatories in the Southern Hemisphere (Las Campanas Observatory
[LCO] in Chile, the High Energy Stereoscopic System [HESS] site in
Namibia, and Siding Spring Observatory [SSO] in Australia), with two
instruments per site. Each instrument consists of four 18cm diameter
astrographs and associated 4K*4K backside-illuminated CCD cameras and
Sloan r-band filters, placed on a common robotic mount. The four
astrographs and cameras together cover a 8.2°*8.2° mosaic
field of view at a pixel scale of 3.7''/pixel.
Observations of a field containing Proxima Cen were collected as part
of the general HATSouth transit survey, with a total of 11071 (this
number does not count observations that were rejected as not useful
for high-precision photometry, or those that produced large-amplitude
outliers in the Proxima Cen light curve) composite 3*80s exposures
gathered between 2012 June 14 and 2014 September 20. These include
3430 observations made with the HS-2 unit at LCO, 4630 observations
made with the HS-4 unit at the HESS site, and 3011 observations made
with the HS-6 unit at the SSO site. Due to weather and other factors,
the cadence was nonuniform. The median time difference between
consecutive observations in the full time series is 368s.
Objects:
------------------------------------------------------------
RA (ICRS) DE Designation(s)
------------------------------------------------------------
14 29 42.95 -62 40 46.2 Proxima = V* V645 Cen
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 41 13934 Reduced Microwave and Oscillations of STars (MOST)
photometry used in this work, excluding times
afflicted by large flares
table5.dat 28 11071 *Reduced HATSouth photometry used in this work
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Note on table5.dat: After correction for systematic trends by Trend Filtering
Algorithm (TFA).
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See also:
J/AJ/145/5 : Follow-up photometry of HATS-1 (Penev+, 2013)
J/ApJ/772/L2 : Keck/HIRES radial velocities for HD 97658 (Dragomir+, 2013)
J/A+A/534/A133 : Proxima Cen chromospheric emission lines (Fuhrmeister+, 2011)
J/ApJ/710/1724 : Follow-up photometry for HAT-P-11 (Bakos+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 20 F20.15 d HJD [5248.1/5634.5] Heliocentric Julian Date of
observation with correction for UTC (HJD-2451545)
22- 31 F10.7 mag Dmag [-0.039/0.042] Differential MOST magnitude
33- 41 F9.7 mag e_Dmag [0.005/0.015] uncertainty in Dmag
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 12 F12.7 d HJD [4547.6/5376.5] Heliocentric Julian Date of
observation with correction for UTC (HJD-2451545)
14- 20 F7.5 mag mag [7.12/7.32] Trend Filtering Algorithm (TFA)
corrected HATSouth magnitude (1)
22- 28 F7.5 mag e_mag [0.00125/0.005] Uncertainty in mag
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Note (1): The data were reduced to trend-filtered light curves using the
aperture photometry pipeline described by Penev et al. 2013
(Cat. J/AJ/145/5) and making use of the External Parameter Decorrelation
(EPD) procedure described by Bakos et al. 2010 (Cat. J/ApJ/710/1724) and
the Trend Filtering Algorithm (TFA) from Kovacs et al. 2005MNRAS.356..557K 2005MNRAS.356..557K.
See Section 6.1 for more details.
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 27-Jun-2017