The Transiting Exoplanet Survey Satellite (TESS) mission searches for new exoplanets. The observing strategy of TESS results in high-precision photometry of millions of stars across the sky, allowing ...for detailed asteroseismic studies of individual systems. In this work, we present a detailed asteroseismic analysis of the giant star HD 76920 hosting a highly eccentric giant planet (\(e = 0.878\)) with an orbital period of 415 days, using 5 sectors of TESS light curve that cover around 140 days of data. Solar-like oscillations in HD 76920 are detected around \(52 \, \mu\)Hz by TESS for the first time. By utilizing asteroseismic modeling that takes classical observational parameters and stellar oscillation frequencies as constraints, we determine improved measurements of the stellar mass (\(1.22 \pm 0.11\, M_\odot\)), radius (\(8.68 \pm 0.34\,R_\odot\)), and age (\(5.2 \pm 1.4\,\)Gyr). With the updated parameters of the host star, we update the semi-major axis and mass of the planet as \(a=1.165 \pm 0.035\) au and \(M_{\rm p}\sin{i} = 3.57 \pm 0.22\,M_{\rm Jup}\). With an orbital pericenter of \(0.142 \pm 0.005\) au, we confirm that the planet is currently far away enough from the star to experience negligible tidal decay until being engulfed in the stellar envelope. We also confirm that this event will occur within about 100\,Myr, depending on the stellar model used.
The Sun and \(\alpha\) Cen A and B are the nearest stars to us. Despite the general agreement between their models and seismic and non-seismic constraints, there are serious problems pertaining to ...their interior. The good agreement between the sound speed and base radius of the convective zone of the Sun and the solar models is broken apart by a recent revision in solar chemical composition. For \(\alpha\) Cen A and B, however, it is not possible to fit models with the same age and chemical composition to all seismic and non-seismic observational constraints. At the age deduced from seismic constraints, the luminosity ratio (\(L_{\rm A}/L_{\rm B}\)) of the models is significantly lower than the ratio taken from the observed luminosities. Enhancement of opacity as a function of temperature is one way to restore the agreement between solar models and the Sun, but such an enhancement does not alter the situation for \(\alpha\) Cen A and B. The reason is that models of both components are influenced in a similar manner and consequently the luminosity ratio doesn't change much. In the present study, problems pertaining to the interior of these three stars with a single expression for opacity enhancement are modelled. The opacity enhancement is expressed as a function of density, ionization degree of heavy elements (oxygen), and temperature. According to this expression, for improvement of the models the required opacity enhancement for \(\alpha\) Cen A and B at \(\log(T)\)= 6.5, for example, is about 7 and 22 per cent, respectively. The enhancement tak es place in the region in which pressure ionization is effective, and is higher for low-mass stars than for high-mass stars. This result seems to be a possible explanation for the serious differences between models and observational results of cool stars.
Asteroseismology of bright stars has become increasingly important as a
method to determine fundamental properties (in particular ages) of stars. The
Kepler Space Telescope initiated a revolution by ...detecting oscillations in more
than 500 main-sequence and subgiant stars. However, most Kepler stars are
faint, and therefore have limited constraints from independent methods such as
long-baseline interferometry. Here, we present the discovery of solar-like
oscillations in $\alpha$ Men A, a naked-eye (V=5.1) G7 dwarf in TESS's Southern
Continuous Viewing Zone. Using a combination of astrometry, spectroscopy, and
asteroseismology, we precisely characterize the solar analog alpha Men A (Teff
= 5569 +/- 62 K, R = 0.960 +/- 0.016 Rsun, M = 0.964 +/- 0.045 Msun). To
characterize the fully convective M dwarf companion, we derive empirical
relations to estimate mass, radius, and temperature given the absolute Gaia
magnitude and metallicity, yielding M = 0.169 +/- 0.006, R = 0.19 +/- 0.01 and
Teff = 3054 +/- 44 K. Our asteroseismic age of 6.2 +/- 1.4 (stat) +/- 0.6 (sys)
Gyr for the primary places $\alpha$ Men B within a small population of M dwarfs
with precisely measured ages. We combined multiple ground-based spectroscopy
surveys to reveal an activity cycle of 13.1 +/- 1.1 years, a period similar to
that observed in the Sun. We used different gyrochronology models with the
asteroseismic age to estimate a rotation period of ~30 days for the primary.
Alpha Men A is now the closest (d=10pc) solar analog with a precise
asteroseismic age from space-based photometry, making it a prime target for
next-generation direct imaging missions searching for true Earth analogs.
Most previous efforts to calibrate how rotation and magnetic activity depend on stellar age and mass have relied on observations of clusters, where isochrones from stellar evolution models are used ...to determine the properties of the ensemble. Asteroseismology employs similar models to measure the properties of an individual star by matching its normal modes of oscillation, yielding the stellar age and mass with high precision. We use 27 days of photometry from the Transiting Exoplanet Survey Satellite to characterize solar-like oscillations in the G8 subgiant of the 94 Aqr triple system. The resulting stellar properties, when combined with a reanalysis of 35 yr of activity measurements from the Mount Wilson HK project, allow us to probe the evolution of rotation and magnetic activity in the system. The asteroseismic age of the subgiant agrees with a stellar isochrone fit, but the rotation period is much shorter than expected from standard models of angular momentum evolution. We conclude that weakened magnetic braking may be needed to reproduce the stellar properties, and that evolved subgiants in the hydrogen shell-burning phase can reinvigorate large-scale dynamo action and briefly sustain magnetic activity cycles before ascending the red giant branch.
The Maunakea Spectroscopic Explorer (MSE) is a planned 11.25-m aperture facility with a 1.5 square degree field of view that will be fully dedicated to multi-object spectroscopy. A rebirth of the ...3.6m Canada-France-Hawaii Telescope on Maunakea, MSE will use 4332 fibers operating at three different resolving powers (R ~ 2500, 6000, 40000) across a wavelength range of 0.36-1.8mum, with dynamical fiber positioning that allows fibers to match the exposure times of individual objects. MSE will enable spectroscopic surveys with unprecedented scale and sensitivity by collecting millions of spectra per year down to limiting magnitudes of g ~ 20-24 mag, with a nominal velocity precision of ~100 m/s in high-resolution mode. This white paper describes science cases for stellar astrophysics and exoplanet science using MSE, including the discovery and atmospheric characterization of exoplanets and substellar objects, stellar physics with star clusters, asteroseismology of solar-like oscillators and opacity-driven pulsators, studies of stellar rotation, activity, and multiplicity, as well as the chemical characterization of AGB and extremely metal-poor stars.
Asteroseismology of bright stars has become increasingly important as a method to determine fundamental properties (in particular ages) of stars. The Kepler Space Telescope initiated a revolution by ...detecting oscillations in more than 500 main-sequence and subgiant stars. However, most Kepler stars are faint, and therefore have limited constraints from independent methods such as long-baseline interferometry. Here, we present the discovery of solar-like oscillations in \(\alpha\) Men A, a naked-eye (V=5.1) G7 dwarf in TESS's Southern Continuous Viewing Zone. Using a combination of astrometry, spectroscopy, and asteroseismology, we precisely characterize the solar analog alpha Men A (Teff = 5569 +/- 62 K, R = 0.960 +/- 0.016 Rsun, M = 0.964 +/- 0.045 Msun). To characterize the fully convective M dwarf companion, we derive empirical relations to estimate mass, radius, and temperature given the absolute Gaia magnitude and metallicity, yielding M = 0.169 +/- 0.006, R = 0.19 +/- 0.01 and Teff = 3054 +/- 44 K. Our asteroseismic age of 6.2 +/- 1.4 (stat) +/- 0.6 (sys) Gyr for the primary places \(\alpha\) Men B within a small population of M dwarfs with precisely measured ages. We combined multiple ground-based spectroscopy surveys to reveal an activity cycle of 13.1 +/- 1.1 years, a period similar to that observed in the Sun. We used different gyrochronology models with the asteroseismic age to estimate a rotation period of ~30 days for the primary. Alpha Men A is now the closest (d=10pc) solar analog with a precise asteroseismic age from space-based photometry, making it a prime target for next-generation direct imaging missions searching for true Earth analogs.
We present initial results on some of the properties of open clusters NGC 6791 and NGC 6819 derived from asteroseismic data obtained by NASA's Kepler mission. In addition to estimating the mass, ...radius and log g of stars on the red-giant branch of these clusters, we estimate the distance to the clusters and their ages. Our model-independent estimate of the distance modulus of NGC 6791 is (m-M)_0= 13.11\pm 0.06. We find (m-M)_0= 11.85\pm 0.05 for NGC 6819. The average mass of stars on the red-giant branch of NGC 6791 is 1.20 \pm 0.01 M_sun, while that of NGC 6819 is 1.68\pm 0.03M_sun. It should be noted that we do not have data that cover the entire red-giant branch and the actual mass will be somewhat lower. We have determined model-dependent estimates of ages of these clusters. We find ages between 6.8 and 8.6 Gyr for NGC 6791, however, most sets of models give ages around 7Gyr. We obtain ages between 2 and 2.4 Gyr for NGC 6819.
BACKGROUND: Gastric cancer is one of the most common types of cancer
and one of the most frequent causes of cancer-related death. The
majority of gastric cancers show distant metastasis at the time ...of
diagnosis. At present, there is no general agreement over one standard
chemotherapy regimen for metastatic gastric cancer. AIMS: We evaluated
the activity and toxicity of the combination of 5-Fluorouracil (5-FU),
epirubicin and cisplatin (FEP) in previously untreated patients with
metastatic gastric cancer. SETTING AND DESIGN: Medical Oncology
Department of Uludag University Faculty of Medicine, Bursa;
retrospective study. MATERIAL AND METHODS: Sixty-eight patients
received 5-FU 300 mg/m2 on Days 1-5, epirubicin 50 mg/m2 on Day 1 and
cisplatin 60 mg/m2 on Day 1, every 4 weeks. A median of 3.5 cycles was
administered. The response rate, time to disease progression, survival
and toxic effects were analyzed. STATISTICAL ANALYSIS USED: Overall
survival and time to progression were estimated using Kaplan-Meier
method. RESULTS: There were 4 partial responses and 1 complete
response (overall response rate 7.3%); 16 patients had stable disease.
Median progression-free and overall survival rates were 3.1 months (95%
CI 1.9-4) and 6 months (95% CI 4.2-7), respectively. The principal
toxicity was myelosupression. Grade 3-4 neutropenia occurred in 27.9%,
anemia in 17.6%, and thrombocytopenia in 11.7% of patients.
Non-hematological toxicity was mild and manageable. CONCLUSIONS: We
concluded that FEP combination as used at the doses and schedules in
this study has inferior activity against metastatic gastric cancer.
Silk fibroin is a natural, protein-based biopolymer produced by silkworm and obtained from silkworm cocoons. It has such features as biocompatibility, biodegradability, high mechanical resistance, ...low immunogenicity and low inflammatory response. Owing to these properties, it attracts attention in various fields including tissue engineering and drug delivery. The silk fibroin production method basically consists of processes such as degumming, extraction, dialysis, centrifugation, and, if necessary, lyophilization. Since the production of silk fibroin from cocoons includes many steps, there are various parameters that affect the protein content of silk fibroin. In this study, it was aimed to validate the production process steps which mainly affect the silk fibroin content and to determine optimum parameters to obtain silk fibroin with higher protein content. For this purpose, the effects of the type of extraction agent (Ajisawa’s reagent or lithium bromide), the molecular weight cutoff value (MWCO) of the dialysis membrane, the dialysis time, and the centrifugation process were evaluated statistically with one-way analysis of variance method. According to the results, the highest protein content is obtained using, LiBr as extraction agent, 3500 Da as MWCO value of dialysis membrane, 2 days as dialysis time and 532 RCF for 5 min as conditions of centrifugation process.
Background and Objectives: There is a lack of studies examining balance problems and Achilles tendon thickness in prediabetes despite their common occurrence in diabetes mellitus. The aim of this ...study was to evaluate Achilles tendon size and static and dynamic balance, as well as the role of the Achilles tendon in balance, in prediabetic patients. Materials and Methods: A total of 96 participants were divided into three groups: (1) the control group, consisting of participants without diabetes mellitus; (2) the prediabetes group; and (3) the diabetes mellitus group. Ultrasonographic measurements of Achilles tendon sizes (thickness, width and area) were performed. Dynamic balance was assessed using the Berg Balance Scale, and static balance (the Fall and Stability Indices) was assessed using a Tetrax device. The Self-Leeds Assessment of Neuropathic Symptoms and Signs was utilized to identify neuropathic pain. Results: In the prediabetes group, the median dynamic balance scores 54.0 (51.0–56.0) were lower than those of the control group 55.0 (54.0–56.0) but higher than those of the patients with diabetes mellitus 52.50 (49.0–54.25); however, this difference did not reach statistical significance. The ultrasonographic measurements of the Achilles tendon size were similar among the three groups. On the other hand, in the prediabetes group, a positive correlation was observed between the bilateral Achilles tendon anterior–posterior thickness and Fall Index score (p = 0.045), while a negative correlation was found between the left Achilles tendon anterior–posterior thickness and the Berg Balance Score (p = 0.045). Conclusions: In prediabetes, neither Achilles tendon size nor static or dynamic balance appears to be significantly affected. However, in prediabetic patients, increased Achilles tendon thickness appears to be associated with increased risk of falls and decreased balance.
