J/AJ/149/166 Photometry and spectroscopy of HATS-6 (Hartman+, 2015)
HATS-6b: a warm Saturn transiting an early M dwarf star, and a set of empirical
relations for characterizing K and M dwarf planet hosts.
Hartman J.D., Bayliss D., Brahm R., Bakos G.A., Mancini L., Jordan A.,
Penev K., Rabus M., Zhou G., Butler R.P., Espinoza N., de Val-Borro M.,
Bhatti W., Csubry Z., Ciceri S., Henning T., Schmidt B., Arriagada P.,
Shectman S., Crane J., Thompson I., Suc V., Csak B., Tan T.G., Noyes R.W.,
Lazar J., Papp I., Sari P.
<Astron. J., 149, 166 (2015)>
=2015AJ....149..166H 2015AJ....149..166H
ADC_Keywords: Planets ; Stars, double and multiple ; Photometry ;
Stars, dwarfs ; Stars, M-type ; Radial velocities
Keywords: planetary systems - stars: individual (HATS-6) -
techniques: photometric - techniques: spectroscopic
Abstract:
We report the discovery by the HATSouth survey of HATS-6b, an
extrasolar planet transiting a V=15.2mag, i=13.7mag M1V star with a
mass of 0.57M☉ and a radius of 0.57R☉ . HATS-6b has a
period of P=3.3253d, mass of Mp=0.32MJ, radius of Rp=1.00RJ,
and zero-albedo equilibrium temperature of Teq=712.8±5.1K. HATS-6
is one of the lowest mass stars known to host a close-in gas giant
planet, and its transits are among the deepest of any known transiting
planet system. We discuss the follow-up opportunities afforded by this
system, noting that despite the faintness of the host star, it is
expected to have the highest K-band S/N transmission spectrum among
known gas giant planets with Teq<750K. In order to characterize the
star we present a new set of empirical relations between the density,
radius, mass, bolometric magnitude, and V-, J-, H- and K-band
bolometric corrections for main sequence stars with M<0.80M☉, or
spectral types later than K5. These relations are calibrated using
eclipsing binary components as well as members of resolved binary
systems. We account for intrinsic scatter in the relations in a
self-consistent manner. We show that from the transit-based stellar
density alone it is possible to measure the mass and radius of a
∼0.6M☉ star to ∼7 and ∼2% precision, respectively. Incorporating
additional information, such as the V-K color, or an absolute
magnitude, allows the precision to be improved by up to a factor of
two.
Description:
Observations of a field containing HATS-6 were carried out with the
HS-2, HS-4, and HS-6 units of the HATSouth network (located at Las
Campanas Observatory in Chile, the High Energy Spectroscopic Survey
gamma-ray telescope site in Namibia, and Siding Spring Observatory in
Australia, respectively; see Bakos et al. 2013PASP..125..154B 2013PASP..125..154B for a
detailed description of the HATSouth network) between UT 2009
September 17 and UT 2010 September 10. Observations were made through
a Sloan r filter.
We carried out follow-up photometric observations of HATS-6 using the
0.3m Perth Exoplanet Survey Telescope (PEST; 2013 Feb 17, 2013 Feb 27,
and 2013 Mar 29, with a RC filter), the CTIO 0.9m (2012 Sep 03 with
a Gunn z' filter, and 2013 Oct 27 with a Kron-Cousins RC filter),
telescopes in the Las Cumbres Observatory Global Telescope (LCOGT) 1m
network (2013 Nov 23 with a Pan-STARSS zS filter, and 2013 Dec 07
with a Sloan i' filter), and Gamma-Ray Burst Optical and Near-Infrared
Detector (GROND) on the MPG 2.2m (2014 Mar 06 with griz filters).
Initial reconnaissance spectroscopic observations of HATS-6 were
carried out using the Wide Field Spectrograph (WiFeS) on the
Australian National University (ANU) 2.3m telescope at Siding Spring
Observatory (SSO) together with the Echelle spectrograph on the du
Pont 2.5m telescope at Las Campanas Observatory (LCO). A single WiFeS
spectrum was obtained with a resolution of
R=λ/Δλ=3000 (on 2012 May 13), while four
observations were obtained at a resolution of R=7000 (on 2012 Aug
6-Oct 24). The two du Pont spectra (2012 Oct 25-26) each had a
resolution of R=40000 covering a wavelength range of 3700-7000Å.
In order to confirm HATS-6 as a transiting planet system through a
detection of the radial velocity orbital variation we obtained
high-resolution spectra with three facilities. These are the Fiber-fed
Extended Range Optical Spectrograph (FEROS) on the MPG 2.2m telescope
at La Silla Observatory (LSO), the Planet Finder Spectrograph (PFS) on
the Magellan Clay 6.5m telescope at Las Campanas Observatory (LCO),
and the High Accuracy Radial Velocity Planet Searcher (HARPS)
spectrograph on the ESO 3.6m telescope at LSO. Table 4 lists the
individual measurements. A total of 8 R=48000 spectra were obtained
with FEROS between 2013 March 24 and May 13. The PFS observations
consisted of an I2-free template spectrum obtained on the night of
UT 2013 Nov 8, and seven observations taken through an I2 cell
obtained between 2013 Nov 7 and 16 (R=100000). Observations were
carried out with a 0.5''*2.5'' slit. The HARPS observations consisted
of three exposures taken on the nights of UT 2013 December 7-9. The
spectra have a resolution of R=115000 covering a range of 378-691nm.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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05 52 35.23 -19 01 54.0 HATS-6 = 2MASS J05523523-1901539 (P=3.325272)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 49 12172 Differential photometry of HATS-6
table4.dat 50 16 Relative radial velocities and bisector span
measurements of HATS-6
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See also:
J/AJ/149/149 : Photometry and spectroscopy of HAT-P-54 (Bakos+, 2015)
J/A+A/562/A126 : Light curves of WASP-80 transit events (Mancini+, 2014)
J/AJ/148/29 : Spectroscopy and photometry of HATS-4 (Jordan+, 2014)
J/A+A/558/A55 : HATS-2b griz light curves (Mohler-Fischer+, 2013)
J/AJ/146/113 : Differential griz photometry of HATS-3 (Bayliss+, 2013)
J/AJ/145/5 : Follow-up photometry of HATS-1 (Penev+, 2013)
J/AJ/144/139 : HAT-P-39, HAT-P-40, and HAT-P-41 follow-up (Hartman+, 2012)
J/AJ/144/19 : Follow-up photometry for HAT-P-34--HAT-P-37 (Bakos+, 2012)
J/AJ/141/166 : HATNet variability survey of K and M dwarfs (Hartman+, 2011)
J/ApJ/710/1724 : Follow-up photometry for HAT-P-11 (Bakos+, 2010)
J/ApJ/701/764 : Light curves for five M-dwarf stars (Fernandez+, 2009)
http://www.hatsouth.org/ : HATSouth website
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 F12.5 d BJD UTC Barycentric Julian date (BJD-2400000) (1)
14- 21 F8.5 mag Dmag Differential observed magnitude in Filter (2)
23- 29 F7.5 mag e_Dmag Uncertainty in Dmag
31- 38 F8.5 mag omag ? Raw, observed magnitude (3)
40- 41 A2 --- Flt Filter (Rc, g, r, i, z, zs) (4)
43- 49 A7 --- Inst Instrument (HS, PEST, LCOGT1m, CTIO09m, GROND) (5)
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Note (1): Barycentric Julian Date calculated directly from UTC without
correction for leap seconds.
Note (2): The out-of-transit level has been subtracted. For the HATSouth light
curve (rows with "HS" in the Instrument column), these magnitudes have been
detrended using the External Parameter Decorrelation (EPD; Bakos et al.
2010, cat. J/ApJ/710/1724) and Trend Filtering Algorithm (TFA; Kovacs et
al., 2005MNRAS.356..557K 2005MNRAS.356..557K) procedures prior to fitting a transit model to
the light curve. Primarily as a result of this detrending, but also due to
blending from neighbors, the apparent HATSouth transit depth is somewhat
shallower than that of the true depth in the Sloan r filter (the apparent
depth is 90% that of the true depth). For the follow-up light curves (rows
with an Instrument other than "HS") these magnitudes have been detrended
with the EPD procedure, carried out simultaneously with the transit fit
(the transit shape is preserved in this process).
Note (3): Raw magnitude values without application of the EPD procedure. This is
only reported for the follow-up light curves.
Note (4): The filters used in the observation are defined as below:
Rc = Kron-Cousins RC (for PEST and CTIO09m);
g = Sloan g filter for GROND;
r = Sloan r filter (for HS and GROND);
i = Sloan i filter (for GROND and LCOGT1m);
z = Gunn z' filter for CTI09m, or Sloan z filter for GROND;
zs = Pan-STARSS zS for LCOGT1m.
Note (5): The instruments used in the observation are defined as below:
HS = HS-2, HS-4, and HS-6 units of the HATSouth network (located at Las
Campanas Observatory in Chile, the High Energy Spectroscopic Survey
gamma-ray telescope site in Namibia, and Siding Spring Observatory in
Australia);
PEST = 0.3m Perth Exoplanet Survey Telescope;
LCOGT1m = 1m Las Cumbres Observatory Global Telescope Network;
CTIO09m = 0.9m telescope at Cerro Tololo Inter-American Observatory;
GROND = Gamma-Ray Burst Optical/Near-Infrared Detector on MPG/ESO 2.2m.
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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- 9 F9.5 d BJD Barycentric Julian Date (BJD-2456000)
11 A1 --- f_BJD Observational flag (1)
13- 19 F7.2 m/s RV [-177/82]? Radial velocity (2)
21- 25 F5.2 m/s e_RV ? The 1σ uncertainty in RV (3)
27- 32 F6.1 m/s BS [-466/708.1]? Bissector span measurement (4)
34- 38 F5.1 m/s e_BS ? The 1σ uncertainty in BS
40- 44 F5.3 --- Phase [0/1] Phase
46- 50 A5 --- Inst Instrument (FEROS, PFS, HARPS) (5)
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Note (1): Flag defined as follows:
d = The cross-correlation function (CCF) peak height was too low in the orders
where we computed the bissector span to be able to extract a bissector span
measurement for this observation;
e = This Planet Finder Spectrograph (PFS) observation was taken without the
iodine cell to be used as a template. The radial velocity is not measured
for this observations, but bissector span value is measured;
f = These PFS observations have high sky contamination relative to the other
PFS observations which were obtained with the moon below the horizon. The
values for these two exposures are large as a result.
Note (2): The zero-point of these velocities is arbitrary. An overall offset
γrel fitted separately to the PFS, HARPS, and FEROS velocities in
Section 3 has been subtracted.
Note (3): Internal errors excluding the component of astrophysical/instrumental
jitter considered in Section 3.
Note (4): The median BS value has been subtracted for each instrument.
Note (5): The instruments used in observation are described as follows:
FEROS = Fiber-fed Extended Range Optical Spectrograph (on the MPG 2.2m
telescope at La Silla Observatory, LSO);
PFS = Planet Finder Spectrograph (on the Magellan Clay 6.5m telescope at
Las Campanas Observatory, LCO);
HARPS = High Accuracy Radial Velocity Planet Searcher spectrograph on the
ESO 3.6m telescope at LSO.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 28-May-2015