Two Young Planetary Systems around Field Stars with Ages between 20 and 320 Myr from TESS

Planets around young stars trace the early evolution of planetary systems. We report the discovery and validation of two planetary systems with ages <∼300Myr from observations by the Transiting Exoplanet Survey Satellite (TESS). The 40 V320 Myr old G star TOI-251 hosts a 2.74+0.18-0.18 mini-Neptune with a 4.94 day period. The 20-160 Myr old K star TOI-942 hosts a system of inflated Neptune-sized planets, with TOI-942b orbiting in a period of 4.32 days with a radius of 4.81+0.20-0.20 and TOI-942c orbiting in a period of 10.16 days with a radius of 5.79-0.18+0.19 Though we cannot place either host star into a known stellar association or cluster, we can estimate their ages via their photometric and spectroscopic properties. Both stars exhibit significant photometric variability due to spot modulation, with measured rotation periods of .3.5 days. These stars also exhibit significant chromospheric activity, with age estimates from the chromospheric calcium emission lines and X-ray fluxes matching that estimated from gyrochronology. Both stars also exhibit significant lithium absorption, similar in equivalent width to well-characterized young cluster members. TESS has the potential to deliver a population of young planet-bearing field stars, contributing significantly to tracing the properties of planets as a function of their age

TIC 172900988: A transiting circumbinary planet detected in one sector of TESS data

We report the first discovery of a transiting circumbinary planet detected from a single sector of Transiting Exoplanet Survey Satellite (TESS) data. During Sector 21, the planet TIC 172900988b transited the primary star and then five days later it transited the secondary star. The binary is itself eclipsing, with a period P ≈ 19.7 days and an eccentricity e ≈ 0.45. Archival data from ASAS-SN, Evryscope, KELT, and SuperWASP reveal a prominent apsidal motion of the binary orbit, caused by the dynamical interactions between the binary and the planet. A comprehensive photodynamical analysis of the TESS, archival and follow-up data yields stellar masses and radii of M1 = 1.2384 ± 0.0007 Me and R1 = 1.3827 ± 0.0016 Re for the primary and M2 = 1.2019 ± 0.0007 Me and R2 = 1.3124 ± 0.0012 Re for the secondary. The radius of the planet is R3 = 11.25 ± 0.44 R (1.004 ± 0.039RJup). The planet's mass and orbital properties are not uniquely determined-there are six solutions with nearly equal likelihood. Specifically, we find that the planet's mass is in the range of 824 M3 981 M (2.65 M3 3.09MJup), its orbital period could be 188.8, 190.4, 194.0, 199.0, 200.4, or 204.1 days, and the eccentricity is between 0.02 and 0.09. At V = 10.141 mag, the system is accessible for high-resolution spectroscopic observations, e.g., the Rossiter-McLaughlin effect and transit spectroscopy

X-linked sideroblastic anaemia with ataxia: another mitochondrial disease?

Objectives: The syndrome of X-linked sideroblastic anaemia with ataxia is rare, described only twice in the literature. The aim was to obtain clinical neurological and haematological data about this rare syndrome throughout adult life.Methods: A family is described with two affected brothers and two affected maternal uncles. The family was evaluated clinically. Haematological investigations included full blood count, blood film, iron studies, free erythrocyte protoporphyrin (FEP) concentrations and a bone marrow examination where possible.Results: Core neurological features included motor delay, ataxia evident from early childhood, and dysarthria. Neurological features were non-progressive until the fifth decade when slow progression became evident. Some family members showed mild spasticity. Patients usually have a mild asymptomatic anaemia or a borderline decreased mean corpuscular volume. Blood film examination showed Pappenheimer bodies. Bone marrow examination showed ring sideroblasts, indicating raised erythrocyte iron. Free erythrocyte protoporphyrin (FEP) concentrations were raised.Conclusions: Haematological features are subtle and can be easily overlooked, and individual patients may not display all the abnormal features. X-linked ataxias are rare and incorrect genetic advice may be given if the diagnostic haematological features of X-linked sideroblastic anaemia are overlooked. Males with early onset ataxia should have a haematological evaluation including a blood film, with a bone marrow examination if abnormal blood count indices and measurement of FEP concentrations raise suspicion. The condition has parallels with Pearson's syndrome and Friedreich's ataxia. All three conditions are associated with mitochondrial iron handling defects and ataxia. The human ATP binding cassette gene (hABC7) is a candidate gene and requires further investigation

An empirical analysis of the retention of dissatisfied business services customers using structural equation modelling

This study extends the body of literature concerning service switching, complaint handling, dependence and commitment by investigating why dissatisfied B2B customers do not switch service providers. Specifically, it develops and tests a social exchange-based model examining how dissatisfied, but behaviourally loyal, customers act in terms of their repurchase intentions. A conceptual model, specifying a set of hypothesised relationships between dimensions of switching costs, interpersonal relationships, dimensions of complaint handling, satisfaction with complaint handling, attractiveness of alternatives, dependence, calculative commitment and repurchase intentions, was examined using AMOS 17.0 on a sample of 376 business directors/managers from responding organisations. The results show that satisfaction with complaint handling, benefit-loss costs, dependence and calculative commitment significantly increase customers’ repurchase intentions. The findings also indicate that dependence, interpersonal relationships and specific types of switching costs influence customers’ calculative commitment, and the latter influences intentions to repurchase services. The study builds on the Investment Model by including justice components, and examines the effects of different types of antecedents on calculative commitment that have previously not been examined