HAT-P-18b and HAT-P-19b: Two low-density Saturn-mass planets transiting metal-rich K stars

J. D. Hartman, G. Á Bakos, B. Sato, G. Torres, R. W. Noyes, D. W. Latham, G. Kovács, D. A. Fischer, A. W. Howard, J. A. Johnson, G. W. Marcy, L. A. Buchhave, G. Füresz, G. Perumpilly, B. Béky, R. P. Stefanik, D. D. Sasselov, G. A. Esquerdo, M. Everett, Z. CsubryJ. Lázár, I. Papp, P. Sári

Research output: Contribution to journalArticle

10 Citations (Scopus)

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 ±0.03 M, radius of 0.75 ± 0.04 R, effective temperature 4803 ± 80 K, and metallicity [Fe/H] = +0.10 ± 0.08. The planetary companion has amass of 0.197 ±0.013 MJ and radius of 0.995 ±0.052 R J, yielding a mean density of 0.25 ±0.04 gcm-3. 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 ±0.04 M, radius of 0.82 ±0.05 R, effective temperature 4990 ± 130 K, and metallicity [Fe/H] = +0.23 ±0.08. The planetary companion has amass of 0.292 ±0.018 MJ and radius of 1.132 ± 0.072 R J, yielding a mean density of 0.25 ±0.04 gcm-3. 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-heliumdominated 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. This calls into question the heretofore suggestive correlation between the inferred core mass and host star metallicity for Saturn-mass planets.

Original languageEnglish
JournalAstrophysical Journal
Volume726
Issue number1
DOIs
Publication statusPublished - Jan 1 2011

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K stars
Saturn
planets
planet
transit
metal
metallicity
metals
dwarf stars
stars
radii
orbits
time measurement
gas giant planets
extrasolar planets
radial velocity
emerging
temperature
hydrogen
trends

Keywords

  • GSC 2283-00589)
  • Planetary systems
  • Stars: individual (HAT-P-18, GSC 2594-00646, HAT-P-19
  • Techniques: photometric
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics
  • Nuclear and High Energy Physics

Cite this

HAT-P-18b and HAT-P-19b : Two low-density Saturn-mass planets transiting metal-rich K stars. / Hartman, J. D.; Bakos, G. Á; Sato, B.; Torres, G.; Noyes, R. W.; Latham, D. W.; Kovács, G.; Fischer, D. A.; Howard, A. W.; Johnson, J. A.; Marcy, G. W.; Buchhave, L. A.; Füresz, G.; Perumpilly, G.; Béky, B.; Stefanik, R. P.; Sasselov, D. D.; Esquerdo, G. A.; Everett, M.; Csubry, Z.; Lázár, J.; Papp, I.; Sári, P.

In: Astrophysical Journal, Vol. 726, No. 1, 01.01.2011.

Research output: Contribution to journalArticle

Hartman, JD, Bakos, GÁ, Sato, B, Torres, G, Noyes, RW, Latham, DW, Kovács, G, Fischer, DA, Howard, AW, Johnson, JA, Marcy, GW, Buchhave, LA, Füresz, G, Perumpilly, G, Béky, B, Stefanik, RP, Sasselov, DD, Esquerdo, GA, Everett, M, Csubry, Z, Lázár, J, Papp, I & Sári, P 2011, 'HAT-P-18b and HAT-P-19b: Two low-density Saturn-mass planets transiting metal-rich K stars', Astrophysical Journal, vol. 726, no. 1. https://doi.org/10.1088/0004-637X/726/1/52
Hartman, J. D. ; Bakos, G. Á ; Sato, B. ; Torres, G. ; Noyes, R. W. ; Latham, D. W. ; Kovács, G. ; Fischer, D. A. ; Howard, A. W. ; Johnson, J. A. ; Marcy, G. W. ; Buchhave, L. A. ; Füresz, G. ; Perumpilly, G. ; Béky, B. ; Stefanik, R. P. ; Sasselov, D. D. ; Esquerdo, G. A. ; Everett, M. ; Csubry, Z. ; Lázár, J. ; Papp, I. ; Sári, P. / HAT-P-18b and HAT-P-19b : Two low-density Saturn-mass planets transiting metal-rich K stars. In: Astrophysical Journal. 2011 ; Vol. 726, No. 1.
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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 ±0.03 M⊙, radius of 0.75 ± 0.04 R⊙, effective temperature 4803 ± 80 K, and metallicity [Fe/H] = +0.10 ± 0.08. The planetary companion has amass of 0.197 ±0.013 MJ and radius of 0.995 ±0.052 R J, yielding a mean density of 0.25 ±0.04 gcm-3. 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 ±0.04 M⊙, radius of 0.82 ±0.05 R⊙, effective temperature 4990 ± 130 K, and metallicity [Fe/H] = +0.23 ±0.08. The planetary companion has amass of 0.292 ±0.018 MJ and radius of 1.132 ± 0.072 R J, yielding a mean density of 0.25 ±0.04 gcm-3. 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-heliumdominated 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. This calls into question the heretofore suggestive correlation between the inferred core mass and host star metallicity for Saturn-mass planets.",
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T2 - Two low-density Saturn-mass planets transiting metal-rich K stars

AU - Hartman, J. D.

AU - Bakos, G. Á

AU - Sato, B.

AU - Torres, G.

AU - Noyes, R. W.

AU - Latham, D. W.

AU - Kovács, G.

AU - Fischer, D. A.

AU - Howard, A. W.

AU - Johnson, J. A.

AU - Marcy, G. W.

AU - Buchhave, L. A.

AU - Füresz, G.

AU - Perumpilly, G.

AU - Béky, B.

AU - Stefanik, R. P.

AU - Sasselov, D. D.

AU - Esquerdo, G. A.

AU - Everett, M.

AU - Csubry, Z.

AU - Lázár, J.

AU - Papp, I.

AU - Sári, P.

PY - 2011/1/1

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N2 - 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 ±0.03 M⊙, radius of 0.75 ± 0.04 R⊙, effective temperature 4803 ± 80 K, and metallicity [Fe/H] = +0.10 ± 0.08. The planetary companion has amass of 0.197 ±0.013 MJ and radius of 0.995 ±0.052 R J, yielding a mean density of 0.25 ±0.04 gcm-3. 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 ±0.04 M⊙, radius of 0.82 ±0.05 R⊙, effective temperature 4990 ± 130 K, and metallicity [Fe/H] = +0.23 ±0.08. The planetary companion has amass of 0.292 ±0.018 MJ and radius of 1.132 ± 0.072 R J, yielding a mean density of 0.25 ±0.04 gcm-3. 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-heliumdominated 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. This calls into question the heretofore suggestive correlation between the inferred core mass and host star metallicity for Saturn-mass planets.

AB - 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 ±0.03 M⊙, radius of 0.75 ± 0.04 R⊙, effective temperature 4803 ± 80 K, and metallicity [Fe/H] = +0.10 ± 0.08. The planetary companion has amass of 0.197 ±0.013 MJ and radius of 0.995 ±0.052 R J, yielding a mean density of 0.25 ±0.04 gcm-3. 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 ±0.04 M⊙, radius of 0.82 ±0.05 R⊙, effective temperature 4990 ± 130 K, and metallicity [Fe/H] = +0.23 ±0.08. The planetary companion has amass of 0.292 ±0.018 MJ and radius of 1.132 ± 0.072 R J, yielding a mean density of 0.25 ±0.04 gcm-3. 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-heliumdominated 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. This calls into question the heretofore suggestive correlation between the inferred core mass and host star metallicity for Saturn-mass planets.

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