Recent experiments carried out at the storage ring of GSI in Darmstadt reveal an unexpected oscillation in the orbital electron capture and subsequent decay of hydrogen-like 140Pr58+, 142Pm60+ and ...122I52+. The modulations have periods of 7.069(8) s, 7.10(22) s and 6.1 s respectively in the laboratory frame and are superimposed on the expected exponential decays.
In this paper we propose a semiclassical model in which the observed modulations arise from the coupling of rotation to the spins of electron and nucleus. We show that the modulations are connected to quantum beats and to the effect of the Thomas precession on the spins of bound electron and nucleus, the magnetic moment precessions of electron and nucleus and their cyclotron frequencies. We also show that the spin–spin coupling of electron and nucleus, though dominant relative to the magnetic moment coupling of electron and nucleus with the storage ring magnetic field, does not contribute to the modulation because these terms average out during the time of flight of the ions, or cancel out. The model also predicts that the anomaly cannot be observed if the motion of the ions is rectilinear, or if the ions are stopped in a target (decay of neutral atoms in solid environments). It also supports the notion that no modulation occurs for the β+-decay branch.
► Spin precession of the spin of nucleus and electron in storage ring. ► Coupling of rotation to the spin of electron and nucleus. ► Modulation in the decay probability of the heavy ions induced by quantum beats. ► Comparison with experimental data.
We propose a model in which a recently reported modulation in the decay of the hydrogenlike ions 140Pr58+, 142Pm60+ and 122I52+ arises from the coupling of rotation to the spin of electron and ...nucleus. The model shows that the spin–spin coupling of electron and nucleus does not contribute to the modulation and predicts that the anomaly cannot be observed if the motion of the ions is rectilinear, or if the ions are stopped in a target. It also supports the notion that the modulation frequency is proportional to the inverse of the atomic mass and that no modulation is expected for the β+-decay. The model predicts that for He-like ions the modulation is still present.
The Kilodegree Extremely Little Telescope (KELT) project has been conducting a photometric survey of transiting planets orbiting bright stars for over 10 years. The KELT images have a pixel scale of ...∼23″ pixel−1-very similar to that of NASA's Transiting Exoplanet Survey Satellite (TESS)-as well as a large point-spread function, and the KELT reduction pipeline uses a weighted photometric aperture with radius 3′. At this angular scale, multiple stars are typically blended in the photometric apertures. In order to identify false positives and confirm transiting exoplanets, we have assembled a follow-up network (KELT-FUN) to conduct imaging with spatial resolution, cadence, and photometric precision higher than the KELT telescopes, as well as spectroscopic observations of the candidate host stars. The KELT-FUN team has followed-up over 1600 planet candidates since 2011, resulting in more than 20 planet discoveries. Excluding ∼450 false alarms of non-astrophysical origin (i.e., instrumental noise or systematics), we present an all-sky catalog of the 1128 bright stars (6 < V < 13) that show transit-like features in the KELT light curves, but which were subsequently determined to be astrophysical false positives (FPs) after photometric and/or spectroscopic follow-up observations. The KELT-FUN team continues to pursue KELT and other planet candidates and will eventually follow up certain classes of TESS candidates. The KELT FP catalog will help minimize the duplication of follow-up observations by current and future transit surveys such as TESS.
We propose a model in which a recently reported modulation in the decay of the hydrogenlike ions 140Pr58+, 142Pm60+ and 122I52+ arises from the coupling of rotation to the spin of electron and ...nucleus. The model shows that the spinaspin coupling of electron and nucleus does not contribute to the modulation and predicts that the anomaly cannot be observed if the motion of the ions is rectilinear, or if the ions are stopped in a target. It also supports the notion that the modulation frequency is proportional to the inverse of the atomic mass and that no modulation is expected for the beta + -decay. The model predicts that for He-like ions the modulation is still present.
We present the discovery of KELT-21b, a hot Jupiter transiting the V = 10.5 A8V star HD 332124. The planet has an orbital period of P = 3.6127647 0.0000033 days and a radius of . We set an upper ...limit on the planetary mass of at confidence. We confirmed the planetary nature of the transiting companion using this mass limit and Doppler tomographic observations to verify that the companion transits HD 332124. These data also demonstrate that the planetary orbit is well-aligned with the stellar spin, with a sky-projected spin-orbit misalignment of . The star has K, , , and km s−1, the highest projected rotation velocity of any star known to host a transiting hot Jupiter. The star also appears to be somewhat metal poor and -enhanced, with and /Fe = 0.145 0.053; these abundances are unusual, but not extraordinary, for a young star with thin-disk kinematics like KELT-21. High-resolution imaging observations revealed the presence of a pair of stellar companions to KELT-21, located at a separation of 1 2 and with a combined contrast of with respect to the primary. Although these companions are most likely physically associated with KELT-21, we cannot confirm this with our current data. If associated, the candidate companions KELT-21 B and C would each have masses of ∼0.12 , a projected mutual separation of ∼20 au, and a projected separation of ∼500 au from KELT-21. KELT-21b may be one of only a handful of known transiting planets in hierarchical triple stellar systems.
We announce the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting the mildly evolved, V = 10.64 host star TYC 2619-1057-1. We followed up the initial transit signal in the ...KELT-North survey data with precise ground-based photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the host star has = 6279 51 K, = 3.89 0.05, Fe/H = , = , and = 2.37 0.17 . The planetary companion has = 0.95 0.14 , = , = , and density = g cm−3, making it one of the most inflated giant planets known. Furthermore, for future follow-up, we report a high-precision time of inferior conjunction in of 2,457,083.660459 0.000894 and period of days. Despite the relatively large separation of ∼0.07 au implied by its ∼5.03-day orbital period, KELT-12b receives significant flux of erg s−1 cm−2 from its host. We compare the radii and insolations of transiting gas giant planets around hot ( 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 to search for inflated gas giants in longer-period orbits.
We report the discovery of KELT-18b, a transiting hot Jupiter in a 2.87-day 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 K and a mass of , 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 , a radius of , and a density of , 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 (BJDTDB) 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.
The Kilodegree Extremely Little Telescope (KELT) project has been conducting a photometric survey for transiting planets orbiting bright stars for over ten years. The KELT images have a pixel scale ...of ~23"/pixel---very similar to that of NASA's Transiting Exoplanet Survey Satellite (TESS)---as well as a large point spread function, and the KELT reduction pipeline uses a weighted photometric aperture with radius 3'. At this angular scale, multiple stars are typically blended in the photometric apertures. In order to identify false positives and confirm transiting exoplanets, we have assembled a follow-up network (KELT-FUN) to conduct imaging with higher spatial resolution, cadence, and photometric precision than the KELT telescopes, as well as spectroscopic observations of the candidate host stars. The KELT-FUN team has followed-up over 1,600 planet candidates since 2011, resulting in more than 20 planet discoveries. Excluding ~450 false alarms of non-astrophysical origin (i.e., instrumental noise or systematics), we present an all-sky catalog of the 1,128 bright stars (6<V<10) that show transit-like features in the KELT light curves, but which were subsequently determined to be astrophysical false positives (FPs) after photometric and/or spectroscopic follow-up observations. The KELT-FUN team continues to pursue KELT and other planet candidates and will eventually follow up certain classes of TESS candidates. The KELT FP catalog will help minimize the duplication of follow-up observations by current and future transit surveys such as TESS.
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