J/ApJ/726/52 HAT-P-18 and HAT-P-19 follow-up (Hartman+, 2011)
HAT-P-18b and HAT-P-19b: two low-density Saturn-mass planets transiting
metal-rich K stars.
Hartman J.D., Bakos G.A., Sato B., Torres G., Noyes R.W., Latham D.W.,
Kovacs G., Fischer D.A., Howard A.W., Johnson J.A., Marcy G.W.,
Buchhave L.A., Furesz G., Perumpilly G., Beky B., Stefanik R.P.,
Sasselov D.D., Esquerdo G.A., Everett M., Csubry Z., Lazar J., Papp I.,
Sari P.
<Astrophys. J., 726, 52 (2011)>
=2011ApJ...726...52H 2011ApJ...726...52H
ADC_Keywords: Photometry, SDSS ; Radial velocities ; Planets ; Stars, K-type ;
Stars, double and multiple
Keywords: planetary systems - stars: individual (HAT-P-18, GSC 2594-00646,
HAT-P-19, GSC 2283-00589) - techniques: photometric -
techniques: spectroscopic
Abstract:
We report the discovery of two new transiting extrasolar planets.
HAT-P-18b orbits the V=12.759 K2 dwarf star GSC 2594-00646, with a
period P=5.508023±0.000006 days, transit epoch
Tc=2454715.02174±0.00020(BJD), and transit duration
0.1131±0.0009 days. The host star has a mass of 0.77±0.03M☉,
radius of 0.75±0.04R☉, effective temperature 4803±80K, and
metallicity [Fe/H]=+0.10±0.08. The planetary companion has a mass of
0.197±0.013MJ and radius of 0.995±0.052RJ, yielding a mean
density of 0.25±0.04g/cm3. HAT-P-19b orbits the V=12.901 K1 dwarf
star GSC 2283-00589, with a period P=4.008778±0.000006 days,
transit epoch Tc=2455091.53417±0.00034(BJD), and transit duration
0.1182±0.0014 days. The host star has a mass of 0.84±0.04M☉,
radius of 0.82±0.05R☉, effective temperature 4990±130K, and
metallicity [Fe/H]=+0.23±0.08. The planetary companion has a mass of
0.292±0.018MJ and radius of 1.132±0.072RJ, yielding a mean
density of 0.25±0.04g/cm3. The radial velocity residuals for
HAT-P-19 exhibit a linear trend in time, which indicates the presence
of a third body in the system. Comparing these observations with
theoretical models, we find that HAT-P-18b and HAT-P-19b are each
consistent with a hydrogen-helium-dominated gas giant planet with
negligible core mass. HAT-P-18b and HAT-P-19b join HAT-P-12b and
WASP-21b in an emerging group of low-density Saturn-mass planets, with
negligible inferred core masses. However, unlike HAT-P-12b and
WASP-21b, both HAT-P-18b and HAT-P-19b orbit stars with super-solar
metallicity.
Description:
HAT-P-18 was observed, as part of HATNet project, during 2007 Mar-Jun
(I filter) and with KeplerCam on 2008 Apr 25 (Sloan i filter) and 2009
May 10 (Sloan g filter). HAT-P-19 was observed, as part of HATNet
project, during 2007 Sep-2008 Feb (R filter) and with KeplerCam (Sloan
i filter) in 2009 Oct 6, 30, 2009 Nov 27 and 2009 Dec 1.
We made use of three different facilities to conduct spectroscopic
observations, including the Harvard-Smithsonian Center for
Astrophysics (CfA) Digital Speedometer (DS; 2007 Sep-2008 Mar for
HAT-P-18 and 2008 Dec-2009 Jan for HAT-P-19), and, for HAT-P-19, the
Tillinghast Reflector Echelle Spectrograph (TRES; 2009 Sep 4), both on
the 1.5m Tillinghast Reflector at the Whipple Observatory on Mount
Hopkins, Arizona, and the FIbre-fed Echelle Spectrograph (FIES; 2009
Jan-2009 Oct) on the 2.5m Nordic Optical Telescope (NOT) at La Palma,
Spain.
High-resolution spectra were obtained for HAT-P-18 with Keck/HIRES
during 2007 Oct-2010 Mar and for HAT-P-19, during 2009 Oct-2010 Feb.
HAT-P-19 was also observed with Subaru/HDS on 2009 Aug 8 and 10.
Objects:
-----------------------------------------------------------------
RA (2000) DE Designation(s) (Period)
-----------------------------------------------------------------
17 05 23.28 +33 00 45.0 HAT-P-18 = GSC 02594-00646 (P=5.5080)
00 38 04.02 +34 42 41.7 HAT-P-19 = GSC 02283-00589 (P=4.0088)
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File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 56 31 Relative radial velocities, bisector spans, and
activity index measurements of HAT-P-18
table5.dat 58 47 Relative radial velocities, bisector spans, and
activity index measurements of HAT-P-19
table6.dat 40 398 High-precision differential photometry of HAT-P-18
table7.dat 40 397 High-precision differential photometry of HAT-P-19
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See also:
J/MNRAS/422/2024 : Exoplanet evaporation (Jackson+, 2012)
J/MNRAS/411/L46 : Exoplanet magnetic fields (Vidotto+, 2011)
Byte-by-byte Description of file: table[45].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.5 d BJD Barycentric Julian Date (BJD-2454000) (1)
11 A1 --- f_BJD [e] e: outlier RV measurements excluded from
the analysis
13- 18 F6.2 m/s RV ? Relative radial velocity (2)
20- 23 F4.2 m/s e_RV ? RV uncertainty (3)
25- 31 F7.2 m/s BS Bisector span
33- 37 F5.2 m/s e_BS BS uncertainty
39- 44 F6.4 --- S Activity index (4)
46- 51 F6.4 --- e_S S uncertainty
53- 58 A6 --- Inst Instrument (Subaru or Keck)
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Note (1): Barycentric Julian dates throughout the paper are calculated from
Coordinated Universal Time (UTC).
Note (2): The zero point of these velocities is arbitrary. An overall offset
γrel fitted to these velocities in Section 3.3 has not been
subtracted.
Note that for the iodine-free template exposures we do not measure the
RV, but do measure the BS and S index. Such template exposures can be
distinguished by the missing RV value.
Note (3): Internal errors excluding the component of the velocity jitter
considered in Section 3.3.
Note (4): Relative chromospheric activity index, not calibrated to the scale of
Vaughan et al. (1978PASP...90..267V 1978PASP...90..267V).
Note that the values for the Keck and Subaru observations have
independently been scaled to have a mean of 1.0.
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Byte-by-byte Description of file: table[67].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
2- 12 F11.5 d BJD Baryocentric Julian Date (BJD-2400000)
14- 21 F8.5 mag mag Processed magnitude in Filter (1)
23- 29 F7.5 mag e_mag The 1σ error in mag
31- 38 F8.5 mag Rmag Raw magnitude in Filter (2)
40 A1 --- Filt [gi] KeplerCam filter used in the observation
(only i for HAT-P-19)
--------------------------------------------------------------------------------
Note (1): The out-of-transit level has been subtracted. These magnitudes have
been subjected to the EPD and TFA procedures, carried out
simultaneously with the transit fit.
Note (2): Raw magnitude values without application of the EPD and TFA
procedures.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 16-Aug-2012