WASP-South hot Jupiters: WASP-178b, WASP-184b, WASP-185b & WASP-192b
C. Hellier, D.R. Anderson, K. Barkaoui, Z. Benkhaldoun, F. Bouchy, A., Burdanov, A. Collier Cameron, L. Delrez, M. Gillon, E. Jehin, L.D. Nielsen,, P.F.L. Maxted, F. Pepe, D. Pollacco, F.J. Pozuelos, D. Queloz, D. Segransan,, B. Smalley, A.H.M.J. Triaud, O.D. Turner, S. Udry

TL;DR
This paper reports the discovery of four new hot Jupiters by the WASP-South survey, highlighting their unique characteristics such as host star temperature, planetary inflation, and orbital properties, contributing to exoplanet diversity understanding.
Contribution
The paper presents four newly discovered hot Jupiters with detailed characterization, including the second-hottest host star and ultra-hot Jupiter candidate, expanding knowledge of planetary and stellar properties.
Findings
WASP-178b is one of the hottest transiting exoplanets known.
WASP-185b has an eccentric orbit and a relatively long period.
WASP-178b's large radius makes it ideal for studying ultra-hot Jupiters.
Abstract
We report on four new transiting hot Jupiters discovered by the WASP-South survey. WASP-178b transits a V = 9.9, A1V star with Teff = 9350 +/- 150 K, the second-hottest transit host known. It has a highly bloated radius of 1.81 +/- 0.09 Rjup, in line with the known correlation between high irradiation and large size. With an estimated temperature of 2470 +/- 60 K, the planet is one of the best targets for studying ultra-hot Jupiters that is visible from the Southern hemisphere. The three host stars WASP-184, WASP-185 and WASP-192 are all post-main-sequence G0 stars of ages 4-8 Gyr. The larger stellar radii (1.3-1.7 Msun) mean that the transits are relatively shallow (0.7-0.9%) even though the planets have moderately inflated radii of 1.2-1.3 Rjup. WASP-185b has an eccentric orbit (e = 0.24) and a relatively long orbital period of 9.4 d. A star that is 4.6 arcsec from WASP-185 and 4.4ā¦
| Facility | Date | Notes |
| WASP-178: | ||
| WASP-South | 2006 Mayā2014 Aug | 101ā600 points |
| CORALIE | 2017 Aprā2018 Jul | 23 RVs |
| EulerCAM | 2018 Mar 26 | I filter |
| WASP-184: | ||
| WASP-South | 2007 Febā2012 Jul | 24ā300 points |
| CORALIE | 2015 Junā2018 Jul | 19 RVs |
| TRAPPIST-South | 2016 Mar 05 | blue-block |
| EulerCAM | 2018 Apr 11 02 | filter |
| WASP-185: | ||
| WASP-South | 2006 Mayā2012 Jun | 34ā000 points |
| CORALIE | 2015 Junā2018 Aug | 24 RVs |
| TRAPPIST-South | 2014 Apr 09 | band |
| TRAPPIST-North | 2019 Jun 09 | band |
| WASP-192: | ||
| WASP-South | 2006 Mayā2012 Jul | 42ā200 points |
| CORALIE | 2016 Junā2019 Apr | 12 RVs |
| TRAPPIST-South | 2016 Apr 17 | blue-block |
| TRAPPIST-South | 2019 Jun 06 | band |
| Star | [Gyr] | [] | [Gyr] | [] | |||||
|---|---|---|---|---|---|---|---|---|---|
| WASP-184 | 4.0 | 1.29 | +0.168 | ||||||
| WASP-185 | 7.2 | 1.09 | +0.066 | ||||||
| WASP-192 | 5.1 | 1.16 | +0.215 |
| 1SWASPāJ150904.89-424217.7 | |
|---|---|
| HDā134004; 2MASSā15090488ā4242178 | |
| GAIA RAā=ā15h09m04.89s, Decā=āā42ā4217.8 (J2000) | |
| mag = 9.95; GAIA = 9.91; = 9.77 | |
| Rotational modulation: 1.5 mmag | |
| GAIA DR2 pm (RA) ā10.01āā0.12 (Dec) ā5.65āā 0.10 mas/yr | |
| GAIA DR2 parallax: 2.3119 0.0600 mas | |
| Distance = 418 16 pc | |
| Stellar parameters from spectroscopic analysis. | |
| Spectral type | A1 IVāV |
| (K) | 9350 150 |
| 4.35 0.15 | |
| (kmās-1) | 8.2 0.6 |
| Microturbulence (kmās-1) | 2.9 0.2 |
| [Fe/H] | +0.21 0.16 |
| [Ca/H] | ā0.06 0.14 |
| [Sc/H] | ā0.35 0.08 |
| [Cr/H] | +0.43 0.10 |
| [Y/H] | +0.35 0.10 |
| [Ba/H] | +0.96 0.15 |
| [Ni/H] | +0.32 0.12 |
| Parameters from MCMC analysis. | |
| (d) | 3.3448285 0.0000012 |
| (HJD)ā(UTC) | 245ā6927.06839 0.00047 |
| (d) | 0.1446 0.0016 |
| (d) | 0.0197 0.0016 |
| /R | 0.01243 0.00028 |
| 0.54 0.05 | |
| (ā) | 85.7 0.6 |
| (km s-1) | 0.139 0.009 |
| (km s-1) | 23.908 0.007 |
| 0 (adopted) (ā0.08 at 2) | |
| 7.17 0.21 | |
| (Mā) | 2.07 0.11 |
| (Rā) | 1.67 0.07 |
| (cgs) | 4.31 0.04 |
| () | 0.44 0.05 |
| (K) | 9360 150 |
| (MJup) | 1.66 0.12 |
| (RJup) | 1.81 0.09 |
| (cgs) | 3.07 0.05 |
| () | 0.28 0.05 |
| (AU) | 0.0558 0.0010 |
| (K) | 2470 60 |
| Priors were and | |
| Errors are 1; Limb-darkening coefficients were: | |
| band: a1 = 0.669, a2 = ā0.223, a3 = 0.280, a4 = ā0.125 | |
| band: a1 = 0.724, a2 = ā0.616, a3 = 0.644, a4 = ā0.245 | |
| 1SWASPāJ135804.10ā302053.0 | |
|---|---|
| 2MASSā13580408ā3020532 | |
| GAIA RAā=ā13h58m04.09s, Decā=āā30ā2053.3 (J2000) | |
| mag = 12.9; GAIA = 12.57; = 11.6 | |
| Rotational modulation: 2 mmag | |
| GAIA DR2 pm (RA) ā4.36āā0.06 (Dec) ā5.09āā 0.06 mas/yr | |
| GAIA DR2 parallax: 1.480 0.037 mas | |
| Distance = 640 28 pc | |
| Stellar parameters from spectroscopic analysis. | |
| Spectral type | G0 |
| (K) | 6000 100 |
| 4.0 0.2 | |
| (kmās-1) | 4.5 1.1 |
| [Fe/H] | +0.12 0.08 |
| log A(Li) | 2.04 0.08 |
| Parameters from MCMC analysis. | |
| (d) | 5.18170 0.00001 |
| (HJD)ā(UTC) | 245ā7630.008 0.001 |
| (d) | 0.1990 0.0027 |
| (d) | 0.0187 0.0024 |
| /R | 0.0069 0.0003 |
| 0.44 0.14 | |
| (ā) | 86.9 1.1 |
| (km s-1) | 0.058 0.010 |
| (km s-1) | 8.366 0.008 |
| 0 (adopted) (ā0.25 at 2) | |
| 8.19 0.42 | |
| (Mā) | 1.23 0.07 |
| (Rā) | 1.65 0.09 |
| (cgs) | 4.09 0.05 |
| () | 0.27 0.05 |
| (K) | 6000 100 |
| (MJup) | 0.57 0.10 |
| (RJup) | 1.33 0.09 |
| (cgs) | 2.87 0.10 |
| () | 0.24 0.07 |
| (AU) | 0.0627 0.0012 |
| (K) | 1480 50 |
| Priors were and | |
| Errors are 1; Limb-darkening coefficients were: | |
| band: a1 = 0.578, a2 = 0.022, a3 = 0.359, a4 = ā0.230 | |
| 1SWASPāJ141614.30ā193232.1 | |
|---|---|
| 2MASSā14161431ā1932321 | |
| GAIA RAā=ā14h16m14.31s, Decā=āā19ā3232.2 (J2000) | |
| mag = 11.1; GAIA = 10.89; = 9.87 | |
| Rotational modulation: 1 mmag | |
| GAIA DR2 pm (RA) ā13.40āā0.08 (Dec) ā6.06āā 0.07 mas/yr | |
| GAIA DR2 parallax: 3.552 0.043 mas | |
| Distance = 275 6 pc | |
| Stellar parameters from spectroscopic analysis. | |
| Spectral type | G0 |
| (K) | 5900 100 |
| 4.0 0.2 | |
| (kmās-1) | 2.8 0.9 |
| [Fe/H] | ā0.02 0.06 |
| log A(Li) | 2.37 0.09 |
| Parameters from MCMC analysis. | |
| (d) | 9.38755 0.00002 |
| (HJD)ā(UTC) | 245ā6935.982 0.002 |
| (d) | 0.192 0.006 |
| (d) | 0.040 0.006 |
| /R | 0.0073 0.0005 |
| 0.81 0.03 | |
| (ā) | 86.8 0.3 |
| (km s-1) | 0.088 0.004 |
| (km s-1) | 23.874 0.003 |
| 0.24 0.04 | |
| (deg) | ā42 7 |
| 12.9 0.7 | |
| (Mā) | 1.12 0.06 |
| (Rā) | 1.50 0.08 |
| (cgs) | 4.13 0.05 |
| () | 0.33 0.06 |
| (K) | 5900 100 |
| (MJup) | 0.98 0.06 |
| (RJup) | 1.25 0.08 |
| (cgs) | 3.15 0.07 |
| () | 0.50 0.12 |
| (AU) | 0.0904 0.0017 |
| (K) | 1160 35 |
| Priors were and | |
| Errors are 1; Limb-darkening coefficients were: | |
| band: a1 = 0.568, a2 = ā0.009, a3 = 0.443, a4 = ā0.271 | |
| band: a1 = 0.651, a2 = ā0.334, a3 = 0.621, a4 = ā0.320 | |
| 1SWASPāJ145438.06ā384439.6 | |
|---|---|
| 2MASSā14543809ā3844403 | |
| GAIA RAā=ā14h54m38.09s, Decā=āā38ā4440.3 (J2000) | |
| mag = 12.3; GAIA = 12.53; = 11.5 | |
| Rotational modulation: 2 mmag | |
| GAIA DR2 pm (RA) 0.72āā0.07 (Dec) ā1.53āā 0.06 mas/yr | |
| GAIA DR2 parallax: 1.939 0.062 mas | |
| Distance = 495 22 pc | |
| Stellar parameters from spectroscopic analysis. | |
| Spectral type | G0 |
| (K) | 5900 150 |
| 4.5 0.2 | |
| (kmās-1) | 3.1 1.1 |
| [Fe/H] | +0.14 0.08 |
| log A(Li) | 2.11 0.13 |
| Parameters from MCMC analysis. | |
| (d) | 2.8786765 0.0000028 |
| (HJD)ā(UTC) | 245ā7271.3331 0.0017 |
| (d) | 0.0964 0.0040 |
| (d) | 0.026 0.004 |
| /R | 0.00926 0.00061 |
| 0.84 0.03 | |
| (ā) | 82.7 0.6 |
| (km s-1) | 0.307 0.017 |
| (km s-1) | 15.896 0.013 |
| 0 (adopted) (ā0.25 at 2) | |
| 6.65 0.34 | |
| (Mā) | 1.09 0.06 |
| (Rā) | 1.32 0.07 |
| (cgs) | 4.236 0.051 |
| () | 0.476 0.080 |
| (K) | 5910 145 |
| (MJup) | 2.30 0.16 |
| (RJup) | 1.23 0.08 |
| (cgs) | 3.54 0.07 |
| () | 1.22 0.31 |
| (AU) | 0.0408 0.0008 |
| (K) | 1620 60 |
| Priors were and | |
| Errors are 1; Limb-darkening coefficients were: | |
| band: a1 = 0.621, a2 = ā0.179, a3 = 0.655, a4 = ā0.356 | |
| band: a1 = 0.697, a2 = ā0.435, a3 = 0.801, a4 = ā0.394 | |
| Name | Eq.Ā Temp | Host | Host | Period | Radius | Mass | Discovery |
|---|---|---|---|---|---|---|---|
| (K) | Ā Ā | (d) | (Jup) | (Jup) | |||
| KELT-9b | 4050 | A0 | 7.6 | 1.48 | 1.89 | 2.9 | Gaudi etĀ al. (2017) |
| WASP-33b | 2780 | A5 | 8.3 | 1.22 | 1.60 | 2.1 | Collier Cameron etĀ al. (2010) |
| Kepler-13b | 2750 | A2 | 10.0 | 1.76 | 1.41 | 9 | Shporer etĀ al. (2011) |
| WASP-189b | 2640 | A6 | 6.6 | 2.72 | 1.40 | 1.9 | Anderson etĀ al. (2018) |
| WASP-12b | 2590 | G0 | 11.7 | 1.09 | 1.90 | 1.5 | Hebb etĀ al. (2009) |
| MASCARA-1b | 2570 | A8 | 8.3 | 2.15 | 1.50 | 3.7 | Talens etĀ al. (2017) |
| HAT-P-70b | 2560 | 9.5 | 2.74 | 1.87 | Zhou etĀ al. (2019) | ||
| WASP-103b | 2510 | F8 | 12.0 | 0.92 | 1.53 | 1.5 | Gillon etĀ al. (2014) |
| WASP-178b | 2470 | A1 | 9.9 | 3.34 | 1.81 | 1.7 | This work |
| WASP-78b | 2470 | F8 | 12.0 | 2.17 | 2.06 | 0.9 | Smalley etĀ al. (2012) |
| KELT-16b | 2450 | F7 | 11.9 | 0.97 | 1.42 | 2.7 | Oberst etĀ al. (2017) |
| WASP-18b | 2410 | F9 | 9.3 | 0.94 | 1.20 | 10.5 | Hellier etĀ al. (2009) |
| WASP-121b | 2360 | F6 | 10.4 | 1.27 | 1.87 | 1.2 | Delrez etĀ al. (2016) |
| WASP-167b/KELT-13b | 2330 | F1 | 10.5 | 2.02 | 1.51 | Temple etĀ al. (2017) | |
| WASP-87Ab | 2320 | F5 | 10.7 | 1.68 | 1.39 | 2.2 | Anderson etĀ al. (2014) |
| BJDāāā2400ā000 | RV | Bisector | |
| (UTC) | (km s-1) | (km s-1) | (km s-1) |
| WASP-178: | |||
| 57850.91018 | 24.0725 | 0.0192 | 0.3486 |
| 57893.80235 | 23.8966 | 0.0426 | 0.2225 |
| 57894.56659 | 24.0744 | 0.0285 | 0.4313 |
| 57904.73294 | 24.0182 | 0.0364 | 0.2893 |
| 57934.67540 | 23.9881 | 0.0360 | 0.4670 |
| 57949.66427 | 23.7647 | 0.0545 | 0.3473 |
| 57951.58735 | 24.0164 | 0.0675 | 0.1183 |
| 57952.64066 | 23.8640 | 0.0377 | 0.3355 |
| 57954.60536 | 24.0314 | 0.0319 | 0.3859 |
| 57955.60534 | 23.8620 | 0.0957 | 0.1964 |
| 57958.65602 | 23.9400 | 0.0843 | 0.2004 |
| 57959.60533 | 23.7802 | 0.0220 | 0.3087 |
| 57974.59726 | 23.9948 | 0.0316 | 0.1979 |
| 58002.52881 | 23.8935 | 0.0367 | 0.4032 |
| 58018.48523 | 24.0258 | 0.0345 | 0.3217 |
| 58020.49026 | 23.8387 | 0.0359 | 0.2958 |
| 58030.48938 | 23.8311 | 0.0320 | 0.3998 |
| 58203.89388 | 23.7806 | 0.0299 | 0.3586 |
| 58207.82049 | 23.8350 | 0.0322 | 0.4199 |
| 58247.69603 | 23.8210 | 0.0366 | 0.2646 |
| 58276.47209 | 24.0082 | 0.0590 | 0.4419 |
| 58277.49486 | 23.6794 | 0.0367 | 0.4725 |
| 58320.57235 | 23.7790 | 0.0367 | 0.3855 |
| WASP-184: | |||
| 57190.68828 | 8.3083 | 0.0564 | 0.0095 |
| 57618.50533 | 8.4188 | 0.0306 | 0.0288 |
| 57817.78113 | 8.2765 | 0.0317 | 0.0066 |
| 57905.73109 | 8.3261 | 0.0273 | 0.0545 |
| 57924.47781 | 8.4413 | 0.0312 | 0.0950 |
| 57933.67645 | 8.4528 | 0.0730 | 0.0404 |
| 57954.53219 | 8.4176 | 0.0317 | 0.0363 |
| 57959.56409 | 8.4350 | 0.0347 | 0.0586 |
| 58170.79185 | 8.3245 | 0.0323 | 0.0012 |
| 58171.73350 | 8.3443 | 0.0372 | 0.1005 |
| 58172.74625 | 8.3889 | 0.0350 | 0.1351 |
| 58173.88416 | 8.3900 | 0.0292 | 0.0547 |
| 58174.70319 | 8.3157 | 0.0400 | 0.0645 |
| 58175.72199 | 8.3224 | 0.0337 | 0.0258 |
| 58247.77332 | 8.3381 | 0.0419 | 0.0371 |
| 58277.47072 | 8.3834 | 0.0384 | 0.0459 |
| 58307.53963 | 8.4145 | 0.0284 | 0.0570 |
| 58308.56619 | 8.3448 | 0.0482 | 0.2351 |
| 58309.57037 | 8.3142 | 0.0291 | 0.0041 |
| 58593.66628 | 8.0600 | 0.0625 | 0.0982 |
| Bisector errors are twice RV errors | |||
| BJDāāā2400ā000 | RV | Bisector | |
| (UTC) | (km s-1) | (km s-1) | (km s-1) |
| WASP-185: | |||
| 57191.68952 | 23.7717 | 0.0243 | 0.0183 |
| 57193.69299 | 23.7864 | 0.0248 | 0.0048 |
| 57194.58975 | 23.8364 | 0.0150 | 0.0324 |
| 57218.60712 | 23.8076 | 0.0267 | 0.0193 |
| 57221.56637 | 23.7937 | 0.0160 | 0.0179 |
| 57412.87431 | 23.9926 | 0.0187 | 0.0396 |
| 57487.74786 | 23.9708 | 0.0106 | 0.0601 |
| 57488.68674 | 23.9470 | 0.0089 | 0.0051 |
| 57591.52359 | 23.9950 | 0.0116 | 0.0061 |
| 57599.55951 | 23.9768 | 0.0102 | 0.0201 |
| 57809.83999 | 23.8754 | 0.0105 | 0.0063 |
| 57815.86446 | 23.9621 | 0.0099 | 0.0093 |
| 57820.70709 | 23.8470 | 0.0114 | 0.0043 |
| 57901.58066 | 23.9342 | 0.0143 | 0.0072 |
| 57905.75841 | 23.8140 | 0.0123 | 0.0364 |
| 57918.49287 | 23.9202 | 0.0122 | 0.0222 |
| 57933.62653 | 23.7907 | 0.0239 | 0.0183 |
| 57951.54401 | 23.8020 | 0.0213 | 0.0090 |
| 57952.60960 | 23.7811 | 0.0148 | 0.0286 |
| 57990.48949 | 23.7948 | 0.0196 | 0.0256 |
| 58311.55039 | 23.8551 | 0.0147 | 0.0610 |
| 58312.57675 | 23.8646 | 0.0148 | 0.0097 |
| 58324.57747 | 23.8505 | 0.0198 | 0.0167 |
| 58357.50144 | 23.8219 | 0.0153 | 0.0224 |
| WASP-192: | |||
| 57568.61900 | 15.5839 | 0.0340 | 0.0655 |
| 58312.63770 | 16.2129 | 0.0304 | 0.0336 |
| 58329.60684 | 16.0837 | 0.0331 | 0.0253 |
| 58541.83740 | 15.6896 | 0.0533 | 0.1255 |
| 58542.87037 | 16.2018 | 0.0453 | 0.0570 |
| 58543.80761 | 15.8034 | 0.0445 | 0.0852 |
| 58544.74536 | 15.6832 | 0.0514 | 0.0766 |
| 58544.88449 | 15.7419 | 0.0518 | 0.1486 |
| 58545.72117 | 16.1702 | 0.1396 | 0.2143 |
| 58576.82272 | 15.9405 | 0.0537 | 0.0655 |
| 58576.88842 | 15.9702 | 0.0671 | 0.0397 |
| 58578.83595 | 15.5516 | 0.0611 | 0.0154 |
| Bisector errors are twice RV errors | |||
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WASP-South hot Jupiters: WASP-178b, WASP-184b, WASP-185b &Ā WASP-192b
Coel Hellier1, D.R. Anderson1,2, K. Barkaoui3,4, Z. Benkhaldoun3, F. Bouchy5,A. Burdanov6, A. Collier Cameron7, L. Delrez6,8, M. Gillon6, E. Jehin6, L.D. Nielsen5, P.F.L. Maxted1, F. Pepe5, D. Pollacco2, F.J. Pozuelos4,6, D. Queloz8, D. SƩgransan5, B. Smalley1, A.H.M.J. Triaud9, O.D. Turner1,5, S. Udry5, and R.G. West2
1Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
2Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
3Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco
4Astrobiology Research Unit, Université de Liège, Liége, Belgium
5Observatoire astronomique de lāUniversitĆ© de GenĆØve 51 ch. des Maillettes, 1290 Sauverny, Switzerland
6Space sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, Liège 1, Belgium
7SUPA, School of Physics and Astronomy, University of St.Ā Andrews, North Haugh, Fife, KY16 9SS, UK
8Cavendish Laboratory, J J Thomson Avenue, Cambridge, CB3 0HE, UK
9School of Physics &Ā Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
(date)
Abstract
We report on four new transiting hot Jupiters discovered by the WASP-South survey. WASP-178b transits a = 9.9, A1V star with = 9350 150 K, the second-hottest transit host known. It has a highly bloated radius of 1.81 0.09 RJup, in line with the known correlation between high irradiation and large size. With an estimated temperature of 2470 60 K, the planet is one of the best targets for studying ultra-hot Jupiters that is visible from the Southern hemisphere. The three host stars WASP-184, WASP-185 and WASP-192 are all post-main-sequence G0 stars of ages 4ā8 Gyr. The larger stellar radii (1.3ā1.7 M*ā*) mean that the transits are relatively shallow (0.7ā0.9%) even though the planets have moderately inflated radii of 1.2ā1.3 RJup. WASP-185b has an eccentric orbit ( = 0.24) and a relatively long orbital period of 9.4 d. A star that is 4.6 arcsec from WASP-185 and 4.4 mag fainter might be physically associated.
keywords:
Planetary Systems ā stars: individual (WASP-178, WASP-184, WASP-185, WASP-192)
ā ā pagerange: range
1 Introduction
Since its start in May 2006 the WASP-South survey for transiting exoplanets operated until mid 2016, obtaining data on over 2500 nights and recording 400 billion photometric data points on 10 million stars. From 2006 to mid-2012 WASP-South used 200-mm, f/1.8 lenses, searching for transits of stars of = 9ā13, and obtaining typically 20ā000 data points on each star. Coverage adds up to the whole sky between declination +8*ā* and ā70*ā*, other than the crowded galactic plane, with each field being observed in typically 3 or 4 different years. In mid-2012 WASP-South switched to 85-mm, f/1.2 lenses, changing the useful magnitude range to = 6.5ā11.5, with the aim of finding the very brightest hot-Jupiter hosts such as WASP-189 (Anderson etĀ al., 2018).
WASP-South transit candidates proved well matched to follow-up with the 1.2-m Euler telescope and CORALIE spectrograph, teamed with the TRAPPIST-South photometric telescope and (more recently) TRAPPIST-North, which together observed 1600 planet candidates. So far WASP-South has led to the announcement of 154 transiting exoplanets (34 of them jointly with data from WASP-Southās northern counterpart, SuperWASP).111See https://wasp-planets.net
Follow-up of WASP-South candidates is now nearing completion, and in any case such surveys are rapidly being superseded by the space-based TESS survey (Ricker etĀ al., 2016). We report here four new transiting hot Jupiters. While WASP-184b and WASP-192b are routine hot Jupiters transiting fainter, = 12, stars, WASP-178b transits a bright A1V star that is the hottest of the WASP planet hosts, while WASP-185b has an eccentric, 9.4-d orbit.
2 Observations
The WASP-South photometry was accumulated into multi-year lightcurves for every catalogued star, which were then searched for transits using automated routines (Pollacco etĀ al., 2006; Collier Cameron etĀ al., 2007b), followed by human vetting of the search outputs. Planet candidates were then listed for followup observations by the TRAPPIST-South 0.6-m robotic photometer (e.g.Ā Gillon etĀ al. 2013) and the Euler/CORALIE spectrograph (e.g.Ā Triaud etĀ al. 2013). Transit photometry for the stars reported here was also obtained with the EulerCAM photometer (e.g.Ā Lendl etĀ al. 2012) and with TRAPPIST-North (Barkaoui etĀ al., 2019). Our observations are listed in TableĀ 1.
For three of our stars (WASP-184, WASP-185 and WASP-192) the CORALIE spectra were reduced to radial-velocity measurements using a standard G2 mask (Pepe etĀ al., 2002), while for the hotter star WASP-178 we used an A0 mask. The resulting values are listed in TableĀ A1.
As we routinely do for WASP-South planet discoveries, we used the WASP photometry, typically spanning 6 months of observation in a year and several years of coverage, to look for rotational modulations of the planet-host stars. Our methods are detailed in Maxted etĀ al. (2011). For the four stars reported here we found no significant modulations with upper limits of 1ā2 mmags (as reported in the Tables for each star).
3 Spectral analyses
We combined the CORALIE spectra for each object in order to make a spectral analysis. For three of the stars discussed here (WASP-184, WASP-185 and WASP-192) we adopt the same methods used in recent WASP-South papers (e.g.Ā Hellier etĀ al. 2019a), as described by Doyle etĀ al. (2013). Thus we estimated the effective temperature, , from the H line, and the surface gravity, , from NaĀ i D and MgĀ i b lines. We also translate the value to give an indicative spectral type. To estimate the metallicity, [Fe/H], we make equivalent-width measurements of unblended FeĀ i lines, quoting errors that take account of the uncertainties in and . We use the same FeĀ i lines to measure values, taking into account the CORALIE instrumental resolution ( = 55ā000) and adopting macroturbulence values from Doyle etĀ al. (2014). The spectral analysis values are reported in the Tables for each star.
WASP-178 is much hotter than the above stars, with K. For this star we measured over 100 clean, unblended, FeĀ i and FeĀ ii lines in the spectral range 500ā600 nm. The stellar parameters of , and microturbulence were obtained by iteratively adjusting them, using non-linear least squares, in order to find the values which minimized the scatter in the abundance obtained from the Fe lines. This procedure simultaneously attempts to remove any trends in abundance with excitation potential (temperature diagnostic) and equivalent width (microturbulence diagnostic), as well as any differences between the FeĀ i and FeĀ ii lines (surface gravity diagnostic). The parameter uncertainties were obtained from the residual scatter in the optimal solution (see Niemczura etĀ al. 2014 for further discussion on stellar parameter determination).
4 System parameters
Our process for parametrising the systems combines all our data, photometry and radial-velocity measurements, in one Markov-chain Monte-Carlo (MCMC) analysis, using a code developed in several iterations from that originally described by Collier Cameron etĀ al. (2007a).
Our standard procedure (see, e.g., Hellier etĀ al. 2019a) places a Gaussian āpriorā on the stellar mass. We derive this using the stellar effective temperature and metallicity, from the spectral analysis, and an estimate of the stellar density, from initial analysis of the transit. These are used as inputs to the bagemass code (Maxted etĀ al., 2015), based on the garstec stellar evolution code (Weiss & Schlattl, 2008), which then outputs estimates for the stellar mass and age. WASP-178 is too hot for the bagemass code to be reliable, so we instead adopted a mass prior of 2.04 0.12 M*ā*, from expectations of a main-sequence star of its temperature (e.g.Ā Boyajian etĀ al. 2013), followed by checking that this models the transit to give a self-consistent set of parameters.
In more recent WASP-South papers, following the availability of GAIA DR2 parallaxes (Gaia Collaboration etĀ al., 2016, 2018), we also place a prior on the stellar radius. We apply the Stassun & Torres (2018) correction to the parallax to produce a distance estimate, and then use the Infra-Red Flux Method (Blackwell & Shallis, 1977) to arrive at the stellar radius. Before the GAIA DR2, getting the stellar radius wrong was one of the commonest sources of systematic error in transit analyses, and thus a prior on the radius improves the reliability of the solution and can make up for limitations in the transit photometry (see, e.g., Hellier etĀ al. 2019b).
In modelling the RVs we first allowed an eccentric orbit (which is required for WASP-185) but where it was not required (the other three systems) we enforced a circular orbit (as discussed in Anderson etĀ al. 2012, this makes use of the expectation that the time for tidal circularisation of a hot-Jupiter orbit is often shorter than the time in its current orbit). To fit the transit photometry we adopted limb-darkening coefficients by interpolating from the 4-parameter, non-linear law of Claret (2000), as appropriate for the starās temperature and metallicity. The WASP passband and the TRAPPIST āblue blockā filter are wide, non-standard pass bands, for which we approximate by using -band coefficients, which is sufficient for the quality of our photometry. The MCMC code includes a step where the error bars are inflated such that the fit to each dataset has a of 1. This allows for red noise not accounted for in the input errors, thus balancing the different datasets and increasing the output error ranges. An account of the effects of red noise in typical WASP-planet discovery datasets is given in Smith etĀ al. (2012).
The parameters resulting from the MCMC analysis are listed in the tables for each system. is the mid-transit epoch, is the orbital period, is the transit depth that would be observed in the absence of limb-darkening, is the duration from first to fourth contact, the impact parameter, and the stellar reflex velocity. For WASP-184, WASP-185 and WASP-192 the bagemass outputs are tabulated in TableĀ 2 while the best-fit stellar evolution tracks and isochrones are shown in Fig.Ā 1 (WASP-178 is too hot for the bagemass code to be reliable).
5 WASP-178
WASP-178 (= HD 134004) is a bright, = 9.95, star for which the spectral analysis suggests = 9350 150 K and an A1 IVāV classification (TableĀ 3; Fig.Ā 2). It appears to be a mild hot Am star, slightly enhanced in Fe ([Fe/H] = +0.21 0.16) and slightly depleted in Ca and Sc ([Ca/H] = ā0.06 0.14; [Sc/H] = ā0.35 0.08). Y and Ba are also enhanced by +0.35 0.10 and +0.96 0.15, respectively. Interstellar Na D lines lead to an estimate of (ā) = 0.06 0.01, which then implies (through the Infra Red Flux Method) a of 9390 190 K, consistent with that from the spectral analysis. The projected rotation speed is relatively low at Ā = 8.2 0.6 kmās*-1*Ā (measured assuming zero macroturbulence). We report (TableĀ 3) a stellar mass of 2.07 0.11 M*ā* and a stellar radius of 1.67 0.07 R*ā*, which are compatible with a main-sequence, non-evolved status.
WASP-178 appears to be relatively isolated on the sky, with no nearby stars within 17 arcsec listed in GAIA DR2, and all stars within 30 arcsecs being 7 magnitudes fainter. However, WASP-178 is noted in GAIA DR2 as having significant excess noise in the astrometry, amounting to 0.18 mas in 254 astrometric observations. This could indicate an unresolved and unseen binary companion.
With a temperature of 9350 150 K, WASP-178 is the second hottest known host of a hot Jupiter, behind the A0 star KELT-9 (Gaudi etĀ al., 2017) at 10ā170 K and ahead of the A2 star MASCARA-2/KELT-20 (Lund etĀ al., 2017; Talens etĀ al., 2018) at 8980 K.
Despite the high stellar temperature, CORALIE RVs are able to detect the orbital motion. The planet is in a 3.3-day orbit with a mass of 1.66 0.12 MJup and a bloated radius of 1.81 0.09 RJup. The estimated equilibrium temperature is 2470 60 K, the hottest of any planet with an orbital period of ā3 d. Fig.Ā 2 shows the transit photometry and radial-velocity orbit. We also plot the bisector spans against phase, where the absence of a correlation is a check against transit mimics (e.g. Queloz etĀ al. 2001).
6 WASP-184
WASP-184 is a = 12.9, G0 star with a metallicity of [Fe/H] = +0.12 0.08 and a distance of 640 28 pc (TableĀ 4; Fig.Ā 3). WASP-184 is relatively isolated with no stars recorded in GAIA DR2 within 10 arcsecs, and only 2 stars (6 magnitudes fainter) within 30 arcsecs. There is no excess astrometric noise recorded in DR2. The mass and radius of WASP-184 (1.23 0.07 M*ā; 1.65 0.09 Rā*) imply that it is evolving off the main sequence. Using the bagemass code we compute an age of 4.7 1.1 Gyr. Lithium depletion to the measured value of log A(Li)= 2.04 0.08 could take ā5 Gyr according to TableĀ 3 of Sestito & Randich (2005), which is consistent with the bagemass age.
The system is reasonably well parametrised by a partial transit from TRAPPIST-South, a nearly-full transit from EulerCAM, and 19 RVs from CORALIE. The planet is in a 5.18-d orbit and is a moderately bloated, lower-mass hot Jupiter (0.57 0.07 MJup; 1.33 0.09 RJup).
7 WASP-185
WASP-185 is a = 11.1, G0 star with a solar metallicity ([Fe/H] = ā0.02 0.06) at a distance of 275 6 pc (TableĀ 5; Fig.Ā 4). It has an apparent companion star 4.6 arcsecs away and 4.4 mag fainter in GAIA (too faint for GAIA to report its proper motion, so we donāt know whether the two are physically associated; at the distance of WASP-185 the separation would correspond to 1200 AU). Otherwise WASP-185 is relatively isolated (with 3 other stars, 9 magnitudes fainter, between 20 and 30 arcsecs away). There is no DR2 excess astrometric noise reported for WASP-185. The companion star is sufficiently distant that it will not affect the CORALIE RVs, however it is included in the extraction aperture for the TRAPPIST photometry. We therefore applied a correction of 1.8%Ā to the transit photometry, though in practice this amount is much less than the uncertainties.
The mass and radius of WASP-185 (1.12 0.06 M*ā; 1.50 0.08 Rā*) indicate an evolved star, and the bagemass code suggests an age of 6.6 1.6 Gyr. Lithium depletion to the measured value of log A(Li) = 2.37 0.09 could take ā2 Gyr, but this abundance of lithium is found in NGC 188 which is ā8 Gyr old according to TableĀ 3 of Sestito & Randich (2005). Thus the lithium is consistent with the bagemass age.
We have only limited photometry of the transit, one ingress and one egress, both obtained in deteriorating observing conditions, and so the transit parameterisation depends substantially on the stellar radius deduced from the GAIA DR2 distance. Our 24 CORALIE RVs trace out an eccentric orbit, though there is clearly additional scatter of unknown origin. This could be magnetic activity of the host star, though no rotational modulation is seen in the WASP data to a limit of 1 mmag (WASP-166 is an example of a system showing RV variation owing to magnetic activity, but no rotational modulation; Hellier etĀ al. 2019b).
The planetās orbit has a relatively long period for a hot Jupiter, at 9.39 d, and has an eccentricity of = 0.24 0.04. The impact factor is relatively high at = 0.81 0.03. The planetās mass and radius (0.98 0.06 MJup; 1.25 0.08 RJup) are typical for hot Jupiters.
8 WASP-192
WASP-192 is a = 12.3, G0 star with metallicity [Fe/H] = +0.14 0.08 at a distance of 495 22 pc (TableĀ 6; Fig.Ā 5). It is isolated in the sky, with no stars, less than 6 magnitudes fainter, within 30 arcsecs according to GAIA DR2. There is no excess astrometric noise reported in DR2. The mass and radius (1.09 0.06 M*ā; 1.32 0.07 Rā*) indicate a moderately evolved star, and the bagemass code produces an age of 5.7 1.9 Gyr. Lithium depletion to the measured log A(Li) = 2.11 0.13 could take ā5 Gyr according to TableĀ 3 of Sestito & Randich (2005), which is consistent with the bagemass age.
The planet WASP-192b has a typical hot-Jupiter orbit of = 2.88 d with a relatively high impact parameter of = 0.84 0.03. We have TRAPPIST photometry of one partial transit and one full transit, though that was in poorer observing conditions. The planet is more massive than average for a hot Jupiter at 2.30 0.16 MJup, such that 12 CORALIE RVs show a well-defined orbital motion. The radius of 1.23 0.08 RJup is typical of hot Jupiters that have masses in the range 2ā3 MJup.
9 Discussion
Recent papers have outlined a class of āultra-hot Jupitersā, defined by Parmentier etĀ al. (2018) as Jupiters with day-side temperatures greater than 2200 K. Atmospheric characterisation of UHJs such as WASP-18b, WASP-103b and WASP-121b (e.g.Ā Kreidberg etĀ al. 2018a; Arcangeli etĀ al. 2019) has revealed systematically different behaviour from cooler planets. Whereas cooler planets can show strong water features (e.g.Ā WASP-107b; Kreidberg etĀ al. 2018b) water is thought to disassociate on the day-sides of UHJs, such that no water features are seen. The disassociated ions then drift to the night side, where they recombine. The molecule CO, however, has a stronger molecular bond, and is still present on the day sides of UHJs, where it can produce an emission feature (e.g.Ā Parmentier etĀ al. 2018).
In TableĀ 7 we list the hottest of all the known UHJs, those with a calculated equilibrium temperature above 2300 K (the UHJ definition of day-side temperature ā2200 K includes many more objects than we list). We use equilibrium temperature, taking the data from TEPcat222https://www.astro.keele.ac.uk/jkt/tepcat/ (Southworth, 2011), since it can be calculated uniformly for all the known systems. WASP-178b now joins this group. Transiting a = 9.95 star, it is among the best UHJ targets visible from the Southern Hemisphere, along with WASP-18b, WASP-103b, WASP-121b and WASP-189b.
A correlation between high irradiation of hot Jupiters and bloated radii is now well established (e.g.Ā Hartman etĀ al. 2016; Bhatti etĀ al. 2016; Sestovic etĀ al. 2018). WASP-178b is at the upper end of such a relationship, as illustrated for known planets in Fig.Ā 6. Also apparent in TableĀ 7 is a tendency for the hottest HJs to be more massive than typical. The median mass of a transiting hot Jupiter is ā0.9 MJup, whereas the median of those in TableĀ 7 is 2.2 MJup. This presumably reflects the destruction of irradiated gas giants by photo-evaporation (e.g.Ā Owen & Lai 2018), such that lower-mass UHJs would have short lifetimes. Indeed, lower-mass UHJs such as WASP-12b (1.5 MJup) are seen to be losing mass (e.g.Ā Fossati etĀ al. 2013). With a moderate mass of 1.7 MJup, WASP-178b is thus also a candidate for photo-evaporation.
We turn now to WASP-185b, which is notable for its eccentric orbit of . The tidal circularisation timescale increases markedly with orbital period, and so eccentric orbits are more likely for longer periods such as WASP-185bās 9.39 d (see Fig.Ā 7). Using eqn 3 of Adams & Laughlin (2006) we can estimate the circularisation timescale of WASP-185b as ā2 Gyr, though this depends on assuming āā105, which is uncertain. There is a tendency, however, for hot Jupiters with eccentric orbits to be either more massive (e.g.Ā WASP-8b at 2.2 MJup; Queloz etĀ al. 2010, WASP-162b at 5.2 MJup; Hellier etĀ al. 2019a, and HAT-P-34b at 3.3 MJup; Bakos etĀ al. 2012) or to have indications of additional bodies in the system that might be perturbing the hot Jupiter (e.g.Ā HAT-P-31b,c; Kipping etĀ al. 2011 and HAT-P-17b,c; Howard etĀ al. 2012). Given that WASP-185b is only 1 MJup, and so should circularise more rapidly, and given the relatively long 6.6 1.6 Gyr age of the host star, it may be that WASP-185b has arrived in its current orbit more recently, or that it is being perturbed by an outer companion (e.g.Ā Petrovich & Tremaine 2016), possibly the putative companion at 1200 AU. It would thus be worthwhile to obtain RossiterāMcLaughlin observations of WASP-185b to discern whether the planetās orbit is aligned or mis-aligned with the stellar rotation.
Acknowledgements
WASP-South was hosted by the South African Astronomical Observatory and we are grateful for their support and assistance. Funding for WASP came from consortium universities and from the UKās Science and Technology Facilities Council. The Euler Swiss telescope is supported by the Swiss National Science Foundation. The research leading to these results has received funding from the ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation. TRAPPIST-South is funded by the Belgian Fund for Scientific Research (Fond National de la Recherche Scientifique, FNRS) under the grant FRFC 2.5.594.09.F, with the participation of the Swiss National Science Fundation (SNF). MG and EJ are F.R.S.-FNRS Senior Research Associates.
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