We announce the discovery of KELT-23Ab, a hot Jupiter transiting the relatively bright (\(V=10.3\)) star BD+66 911 (TYC 4187-996-1), and characterize the system using follow-up photometry and ...spectroscopy. A global fit to the system yields host-star properties of \(T_{eff}=5900\pm49 K\), \(M_*=0.945^{+0.060}_{-0.054} M_{\odot}\), \(R_*=0.995\pm0.015 R_{\odot}\), \(L_*=1.082^{+0.051}_{-0.048} L_{\odot}\), log\(g_{*}=4.418^{+0.026}_{-0.025}\) (cgs), and \(\left{\rm Fe}/{\rm H}\right=-0.105\pm0.077\). KELT-23Ab is a hot Jupiter with mass \(M_P=0.938^{+0.045}_{-0.042} M_{\rm J}\), radius \(R_P=1.322\pm0.025 R_{\rm J}\), and density \(\rho_P=0.504^{+0.038}_{-0.035}\) g cm\(^{-3}\). Intense insolation flux from the star has likely caused KELT-23Ab to become inflated. The time of inferior conjunction is \(T_0=2458149.40776\pm0.00091~\rm {BJD_{TDB}}\) and the orbital period is \(P=2.255353^{+0.000031}_{-0.000030}\) days. There is strong evidence that KELT-23A is a member of a long-period binary star system with a less luminous companion, and due to tidal interactions, the planet is likely to spiral into its host within roughly a Gyr. This system has one of the highest positive ecliptic latitudes of all transiting planet hosts known to date, placing it near the Transiting Planet Survey Satellite and James Webb Space Telescope continuous viewing zones. Thus we expect it to be an excellent candidate for long-term monitoring and follow-up with these facilities.
We present the discovery of KELT-24 b, a massive hot Jupiter orbiting a bright (V=8.3 mag, K=7.2 mag) young F-star with a period of 5.6 days. The host star, KELT-24 (HD 93148), has a \(T_{\rm eff}\) ...=\(6509^{+50}_{-49}\) K, a mass of \(M_{*}\) = \(1.460^{+0.055}_{-0.059}\) \(M_{\odot}\), radius of \(R_{*}\) = \(1.506\pm0.022\) \(R_{\odot}\), and an age of \(0.78^{+0.61}_{-0.42}\) Gyr. Its planetary companion (KELT-24 b) has a radius of \(R_{\rm P}\) = \(1.272\pm0.021\) \(R_{\rm J}\), a mass of \(M_{\rm P}\) = \(5.18^{+0.21}_{-0.22}\) \(M_{\rm J}\), and from Doppler tomographic observations, we find that the planet's orbit is well-aligned to its host star's projected spin axis (\(\lambda\) = \(2.6^{+5.1}_{-3.6}\)). The young age estimated for KELT-24 suggests that it only recently started to evolve from the zero-age main sequence. KELT-24 is the brightest star known to host a transiting giant planet with a period between 5 and 10 days. Although the circularization timescale is much longer than the age of the system, we do not detect a large eccentricity or significant misalignment that is expected from dynamical migration. The brightness of its host star and its moderate surface gravity make KELT-24b an intriguing target for detailed atmospheric characterization through spectroscopic emission measurements since it would bridge the current literature results that have primarily focused on lower mass hot Jupiters and a few brown dwarfs.
We present the discovery of KELT-22Ab, a hot Jupiter from the KELT-South survey. KELT-22Ab transits the moderately bright (\(V\sim 11.1\)) Sun-like G2V star TYC 7518-468-1. The planet has an orbital ...period of \(P = 1.3866529 \pm 0.0000027 \) days, a radius of \(R_{P} = 1.285_{-0.071}^{+0.12}~R_{J}\), and a relatively large mass of \(M_{P} = 3.47_{-0.14}^{+0.15}~ M_{J}\). The star has \(R_{\star} = 1.099_{-0.046}^{+0.079}~ R_{\odot}\), \(M_{\star} = 1.092_{-0.041}^{+0.045}~ M_{\odot}\), \({T_{\rm eff}\,} = 5767_{-49}^{+50}~\) K, \({\log{g_\star}} = 4.393_{-0.060}^{+0.039}~\) (cgs), and m/H = \(+0.259_{-0.083}^{+0.085}~\), and thus, other than its slightly super-solar metallicity, appears to be a near solar twin. Surprisingly, KELT-22A exhibits kinematics and a Galactic orbit that are somewhat atypical for thin disk stars. Nevertheless, the star is rotating quite rapidly for its estimated age, shows evidence of chromospheric activity, and is somewhat metal rich. Imaging reveals a slightly fainter companion to KELT-22A that is likely bound, with a projected separation of 6\arcsec (\(\sim\)1400 AU). In addition to the orbital motion caused by the transiting planet, we detect a possible linear trend in the radial velocity of KELT-22A suggesting the presence of another relatively nearby body that is perhaps non-stellar. KELT-22Ab is highly irradiated (as a consequence of the small semi-major axis of \(a/R_{\star} = 4.97\)), and is mildly inflated. At such small separations, tidal forces become significant. The configuration of this system is optimal for measuring the rate of tidal dissipation within the host star. Our models predict that, due to tidal forces, the semi-major axis of KELT-22Ab is decreasing rapidly, and is thus predicted to spiral into the star within the next Gyr.
We announce the discovery of KELT-16b, a highly irradiated, ultra-short period hot Jupiter transiting the relatively bright (\(V = 11.7\)) star TYC 2688-1839-1. A global analysis of the system shows ...KELT-16 to be an F7V star with \(T_\textrm{eff} = 6236\pm54\) K, \(\log{g_\star} = 4.253_{-0.036}^{+0.031}\), Fe/H = -0.002\(_{-0.085}^{+0.086}\), \(M_\star = 1.211_{-0.046}^{+0.043} M_\odot\), and \(R_\star = 1.360_{-0.053}^{+0.064} R_\odot\). The planet is a relatively high mass inflated gas giant with \(M_\textrm{P} = 2.75_{-0.15}^{+0.16} M_\textrm{J}\), \(R_\textrm{P} = 1.415_{-0.067}^{+0.084} R_\textrm{J}\), density \(\rho_\textrm{P} = 1.20\pm0.18\) g cm\(^{-3}\), surface gravity \(\log{g_\textrm{P}} = 3.530_{-0.049}^{+0.042}\), and \(T_\textrm{eq} = 2453_{-47}^{+55}\) K. The best-fitting linear ephemeris is \(T_\textrm{C} = 2457247.24791\pm0.00019\) BJD\(_{tdb}\) and \(P = 0.9689951 \pm 0.0000024\) d. KELT-16b joins WASP-18b, -19b, -43b, -103b, and HATS-18b as the only giant transiting planets with \(P < 1\) day. Its ultra-short period and high irradiation make it a benchmark target for atmospheric studies by HST, Spitzer, and eventually JWST. For example, as a hotter, higher mass analog of WASP-43b, KELT-16b may feature an atmospheric temperature-pressure inversion and day-to-night temperature swing extreme enough for TiO to rain out at the terminator. KELT-16b could also join WASP-43b in extending tests of the observed mass-metallicity relation of the Solar System gas giants to higher masses. KELT-16b currently orbits at a mere \(\sim\) 1.7 Roche radii from its host star, and could be tidally disrupted in as little as a few \(\times 10^{5}\) years (for a stellar tidal quality factor of \(Q_*' = 10^5\)). Finally, the likely existence of a widely separated bound stellar companion in the KELT-16 system makes it possible that Kozai-Lidov oscillations played a role in driving KELT-16b inward to its current precarious orbit.
The amount of ultraviolet irradiation and ablation experienced by a planet depends strongly on the temperature of its host star. Of the thousands of extra-solar planets now known, only four giant ...planets have been found that transit hot, A-type stars (temperatures of 7300-10,000K), and none are known to transit even hotter B-type stars. WASP-33 is an A-type star with a temperature of ~7430K, which hosts the hottest known transiting planet; the planet is itself as hot as a red dwarf star of type M. The planet displays a large heat differential between its day-side and night-side, and is highly inflated, traits that have been linked to high insolation. However, even at the temperature of WASP-33b's day-side, its atmosphere likely resembles the molecule-dominated atmospheres of other planets, and at the level of ultraviolet irradiation it experiences, its atmosphere is unlikely to be significantly ablated over the lifetime of its star. Here we report observations of the bright star HD 195689, which reveal a close-in (orbital period ~1.48 days) transiting giant planet, KELT-9b. At ~10,170K, the host star is at the dividing line between stars of type A and B, and we measure the KELT-9b's day-side temperature to be ~4600K. This is as hot as stars of stellar type K4. The molecules in K stars are entirely dissociated, and thus the primary sources of opacity in the day-side atmosphere of KELT-9b are likely atomic metals. Furthermore, KELT-9b receives ~700 times more extreme ultraviolet radiation (wavelengths shorter than 91.2 nanometers) than WASP-33b, leading to a predicted range of mass-loss rates that could leave the planet largely stripped of its envelope during the main-sequence lifetime of the host star.
We report the discovery of KELT-18b, a transiting hot Jupiter in a 2.87d orbit around the bright (V=10.1), hot, F4V star BD+60 1538 (TYC 3865-1173-1). We present follow-up photometry, spectroscopy, ...and adaptive optics imaging that allow a detailed characterization of the system. Our preferred model fits yield a host stellar temperature of 6670+/-120 K and a mass of 1.524+/-0.069 Msun, situating it as one of only a handful of known transiting planets with hosts that are as hot, massive, and bright. The planet has a mass of 1.18+/-0.11 Mjup, a radius of 1.57+/-0.04 Rjup, and a density of 0.377+/-0.040 g/cm^3, making it one of the most inflated planets known around a hot star. We argue that KELT-18b's high temperature and low surface gravity, which yield an estimated ~600 km atmospheric scale height, combined with its hot, bright host make it an excellent candidate for observations aimed at atmospheric characterization. We also present evidence for a bound stellar companion at a projected separation of ~1100 AU, and speculate that it may have contributed to the strong misalignment we suspect between KELT-18's spin axis and its planet's orbital axis. The inferior conjunction time is 2457542.524998 +/-0.000416 (BJD_TDB) and the orbital period is 2.8717510 +/- 0.0000029 days. We encourage Rossiter-McLaughlin measurements in the near future to confirm the suspected spin-orbit misalignment of this system.
We present the discovery of a hot-Jupiter transiting the V=9.23 mag main-sequence A-star KELT-17 (BD+14 1881). KELT-17b is a 1.31 -0.29/+0.28 Mj, 1.525 -0.060/+0.065 Rj hot-Jupiter in a 3.08 day ...period orbit misaligned at -115.9 +/- 4.1 deg to the rotation axis of the star. The planet is confirmed via both the detection of the radial velocity orbit, and the Doppler tomographic detection of the shadow of the planet over two transits. The nature of the spin-orbit misaligned transit geometry allows us to place a constraint on the level of differential rotation in the host star; we find that KELT-17 is consistent with both rigid-body rotation and solar differential rotation rates (alpha < 0.30 at 2 sigma significance). KELT-17 is only the fourth A-star with a confirmed transiting planet, and with a mass of 1.635 -0.061/+0.066 Msun, effective temperature of 7454 +/- 49 K, and projected rotational velocity v sin I_* = 44.2 -1.3/+1.5 km/s; it is amongst the most massive, hottest, and most rapidly rotating of known planet hosts.
We report the discovery of KELT-12b, a highly inflated Jupiter-mass planet
transiting a mildly evolved host star. We identified the initial transit signal
in the KELT-North survey data and ...established the planetary nature of the
companion through precise follow-up photometry, high-resolution spectroscopy,
precise radial velocity measurements, and high-resolution adaptive optics
imaging. Our preferred best-fit model indicates that the $V = 10.64$ host, TYC
2619-1057-1, has $T_{\rm eff} = 6278 \pm 51$ K, $\log{g_\star} =
3.89^{+0.054}_{-0.051}$, and Fe/H = $0.19^{+0.083}_{-0.085}$, with an
inferred mass $M_{\star} = 1.59^{+0.071}_{-0.091} M_\odot$ and radius $R_\star
= 2.37 \pm 0.18 R_\odot$. The planetary companion has $M_{\rm P} = 0.95 \pm
0.14 M_{\rm J}$, $R_{\rm P} = 1.79^{+0.18}_{-0.17} R_{\rm J}$, $\log{g_{\rm P}}
= 2.87^{+0.097}_{-0.098}$, and density $\rho_{\rm P} = 0.21^{+0.075}_{-0.054}$
g cm$^{-3}$, making it one of the most inflated giant planets known. The time
of inferior conjunction in ${\rm BJD_{TDB}}$ is $2457088.692055 \pm 0.0009$ and
the period is $P = 5.0316144 \pm 0.0000306$ days. Despite the relatively large
separation of $\sim0.07$ AU implied by its $\sim 5.03$-day orbital period,
KELT-12b receives significant flux of $2.93^{+0.33}_{-0.30} \times 10^9$ erg
s$^{-1}$ cm$^{-2}$ from its host. We compare the radii and insolations of
transiting gas-giant planets around hot ($T_{\rm eff} \geq 6250$ K) and cool
stars, noting that the observed paucity of known transiting giants around hot
stars with low insolation is likely due to selection effects. We underscore the
significance of long-term ground-based monitoring of hot stars and space-based
targeting of hot stars with the Transiting Exoplanet Survey Satellite (TESS) to
search for inflated giants in longer-period orbits.
We report the discovery of KELT-4Ab, an inflated, transiting Hot Jupiter orbiting the brightest component of a hierarchical triple stellar system. The host star is an F star with \(T_{\rm ...eff}=6206\pm75\) K, \(\log g=4.108\pm0.014\), \(\left{\rm Fe}/{\rm H}\right=-0.116_{-0.069}^{+0.065}\), \({\rm M_*}=1.201_{-0.061}^{+0.067} \ {\rm M}_{\odot}\), and \({\rm R_*}=1.610_{-0.068}^{+0.078} \ {\rm R}_{\odot}\). The best-fit linear ephemeris is \(\rm {BJD_{TDB}} = 2456193.29157 \pm 0.00021 + E\left(2.9895936 \pm 0.0000048\right)\). With a magnitude of \(V\sim10\), a planetary radius of \(1.699_{-0.045}^{+0.046} \ {\rm R_J}\), and a mass of \(0.902_{-0.059}^{+0.060} \ {\rm M_J}\), it is the brightest host among the population of inflated Hot Jupiters (\(R_P > 1.5R_J\)), making it a valuable discovery for probing the nature of inflated planets. In addition, its existence within a hierarchical triple and its proximity to Earth (\(210\) pc) provides a unique opportunity for dynamical studies with continued monitoring with high resolution imaging and precision radial velocities. In particular, the motion of the binary stars around each other and of both stars around the primary star relative to the measured epoch in this work should be detectable when it rises in October 2015.
We announce the discovery of a highly inflated transiting hot Jupiter discovered by the KELT-North survey. A global analysis including constraints from isochrones indicates that the V = 10.8 host ...star (HD 343246) is a mildly evolved, G dwarf with \(T_{\rm eff} = 5754_{-55}^{+54}\) K, \(\log{g} = 4.078_{-0.054}^{+0.049}\), \(Fe/H = 0.272\pm0.038\), an inferred mass \(M_{*}=1.211_{-0.066}^{+0.078}\) M\(_{\odot}\), and radius \(R_{*}=1.67_{-0.12}^{+0.14}\) R\(_{\odot}\). The planetary companion has mass \(M_P = 0.867_{-0.061}^{+0.065}\) \(M_{J}\), radius \(R_P = 1.86_{-0.16}^{+0.18}\) \(R_{J}\), surface gravity \(\log{g_{P}} = 2.793_{-0.075}^{+0.072}\), and density \(\rho_P = 0.167_{-0.038}^{+0.047}\) g cm\(^{-3}\). The planet is on a roughly circular orbit with semimajor axis \(a = 0.04571_{-0.00084}^{+0.00096}\) AU and eccentricity \(e = 0.035_{-0.025}^{+0.050}\). The best-fit linear ephemeris is \(T_0 = 2456883.4803 \pm 0.0007\) BJD\(_{\rm TDB}\) and \(P = 3.24406 \pm 0.00016\) days. This planet is one of the most inflated of all known transiting exoplanets, making it one of the few members of a class of extremely low density, highly-irradiated gas giants. The low stellar \(\log{g}\) and large implied radius are supported by stellar density constraints from follow-up light curves, plus an evolutionary and space motion analysis. We also develop a new technique to extract high precision radial velocities from noisy spectra that reduces the observing time needed to confirm transiting planet candidates. This planet boasts deep transits of a bright star, a large inferred atmospheric scale height, and a high equilibrium temperature of \(T_{eq}=1675^{+61}_{-55}\) K, assuming zero albedo and perfect heat redistribution, making it one of the best targets for future atmospheric characterization studies.
