Context. Despite the fact that VW Cephei is one of the most well-studied contact binaries in the literature, there is no fully consistent model available that can explain every observed property of ...this system. Aims. Our aims are to obtain new spectra along with photometric measurements, to analyze what kind of changes may have happened in the system in the past two decades, and to propose new ideas for explaining them. Methods. For the period analysis we determined ten new times of minima from our light curves, and constructed a new O–C diagram of the system. Radial velocities of the components were determined using the cross-correlation technique. The light curves and radial velocities were modeled simultaneously with the PHOEBE code. All observed spectra were compared to synthetic spectra and equivalent widths (EWs) of the Hα line were measured on their differences. Results. We re-determine the physical parameters of the system according to our new light curve and spectral models. We confirm that the primary component is more active than the secondary, and there is a correlation between spottedness and the chromospheric activity. We propose that the flip-flop phenomenon occurring on the primary component could be a possible explanation of the observed nature of the activity. To explain the period variation of VW Cep, we test two previously suggested scenarios: the presence of a fourth body in the system, and the Applegate-mechanism caused by periodic magnetic activity. We conclude that although none of these mechanisms can be ruled out entirely, the available data suggest that mass transfer with a slowly decreasing rate provides the most likely explanation for the period variation of VW Cep.
Aims.
Asymmetric features in exoplanet transit light curves are often interpreted as an effect of gravity darkening, especially if there is spectroscopic evidence of a spin-orbit misalignment. Since ...other processes can also lead to light-curve asymmetries, this may lead to inaccurate gravity darkening parameters. Here, we investigate the case of non-radial pulsations as possible sources of asymmetry and likely source of misinterpreted parameters through simulations.
Methods.
We obtained a series of simulated transit light curves of a hypothetical exoplanet-star system constructed to study the phenomenon: a host star with no gravity darkening exhibiting small amplitude pulsations and a typical hot Jupiter in a circular, edge-on orbit. Multiple scenarios of single- or multi-periodic, radial-, or non-radial pulsations of various amplitudes have been considered, and a proper account of the obscuring effect of transits on all the surface intensity components was carried out. The magnitude of amplitude and phase modulations of non-radial pulsations during transits was also also investigated. We then fit both a non-gravity-darkened and a gravity-darkened free spin-orbit axis model on the data. The Akaike and Bayesian information criteria were used for an objective selection of the most plausible model. We then explored the dependence of the parameter deviations on the pulsation properties to identify the specific configurations that may lead to falsely misaligned solutions.
Results.
The modulation of amplitudes of non-radial pulsations during transits have extremely low levels, so that the non-radial nature of pulsations can be safely ignored. Low-amplitude pulsations generally do not affect the determination of the system parameters beyond their noise properties. However, frequencies close to multiples of the orbital frequency (
n * f
orb
) are found to cause distortions, leading to solutions that involve a side tilted stellar rotational axis; therefore, it is preferable to clean them beforehand for the sake of a improved accuracy. Additionally, in cases with higher amplitude pulsations, a preprocessing and cleaning of the pulsations before the analysis is recommended.
Context. Stars can maintain their observable magnetic activity from the pre-main sequence (PMS) to the tip of the red giant branch. However, the number of known active giants is much lower than ...active stars on the main sequence (MS) since the stars spend only about 10% of their MS lifetime on the giant branch. Due to their rapid evolution it is difficult to estimate the stellar parameters of giant stars. A possibility for obtaining more reliable stellar parameters for an active giant arises when it is a member of an eclipsing binary system. Aims. We have discovered EPIC 211759736, an active spotted giant star in an eclipsing binary system during the Kepler K2 Campaign 5. The eclipsing nature allows us to much better constrain the stellar parameters than in most cases of active giant stars. Methods. We have combined the K2 data with archival HATNet, ASAS, and DASCH photometry, new spectroscopic radial velocity measurements, and a set of follow-up ground-based BVRCIC photometric observations, to find the binary system parameters as well as robust spot models for the giant at two different epochs. Results. We determined the physical parameters of both stellar components and provide a description of the rotational and long-term activity of the primary component. The temperatures and luminosities of both components were examined in the context of the Hertzsprung–Russell diagram. We find that both the primary and the secondary components deviate from the evolutionary tracks corresponding to their masses in the sense that the stars appear in the diagram at lower masses than their true masses. Conclusions. We further evaluate the proposition that traditional methods generally result in higher masses for active giants than what is indicated by stellar evolution tracks in the HR diagram. A possible reason for this discrepancy could be a strong magnetic field, since we see greater differences in more active stars.
We present a comparative study of absolute distances to a sample of very nearby, bright Type Ia supernovae (SNe) derived from high cadence, high signal-to-noise, multi-band photometric data. Our ...sample consists of four SNe: 2012cg, 2012ht, 2013dy and 2014J. We present new homogeneous, high-cadence photometric data in Johnson-Cousins BVRI and Sloan g′r′i′z′ bands taken from two sites (Piszkesteto and Baja, Hungary), and the light curves are analyzed with publicly available light curve fitters (MLCS2k2, SNooPy2 and SALT2.4). When comparing the best-fit parameters provided by the different codes, it is found that the distance moduli of moderately reddened SNe Ia agree within 0.2 mag, and the agreement is even better ( 0.1 mag) for the highest signal-to-noise BVRI data. For the highly reddened SN 2014J the dispersion of the inferred distance moduli is slightly higher. These SN-based distances are in good agreement with the Cepheid distances to their host galaxies. We conclude that the current state-of-the-art light curve fitters for Type Ia SNe can provide consistent absolute distance moduli having less than ∼0.1-0.2 mag uncertainty for nearby SNe. Still, there is room for future improvements to reach the desired ∼0.05 mag accuracy in the absolute distance modulus.
Context.
The nearby spiral galaxy NGC 3147 hosted three Type Ia supernovae (SNe Ia) in the past decades that have been the subjects of intense follow-up observations. Simultaneous analysis of their ...data provides a unique opportunity for testing different methods of light curve fitting and distance estimation.
Aims.
The detailed optical follow-up of SN 2021hpr allows us to revise the previous distance estimations to NGC 3147 and compare the widely used light curve fitting algorithms to each other. After the combination of the available and newly published data of SN 2021hpr, its physical properties can also be estimated with higher accuracy.
Methods.
We present and analyse new
BV griz
and
Swift
photometry of SN 2021hpr to constrain its general physical properties. Together with its siblings, SNe 1997bq and 2008fv, we cross-compared the individual distance estimates of these three SNe given by the Spectral Adaptive Lightcurve Template (SALT) code, and we also checked their consistency with the results from the Multi-Color Light Curve Shape (MLCS) code. The early spectral series of SN 2021hpr was also fit with the radiative spectral code
TARDIS
to verify the explosion properties and constrain the chemical distribution of the outer ejecta.
Results.
After combining the distance estimates for the three SNe, the mean distance to their host galaxy, NGC 3127, is 42.5 ± 1.0 Mpc, which matches with the distance inferred by the most up-to-date light curve fitters, SALT3 and BayeSN. We confirm that SN 2021hpr is a Branch-normal Type Ia SN that ejected ~1.12 ± 0.28
M
⊙
from its progenitor white dwarf and synthesized ~0.44 ± 0.14
M
⊙
of radioactive
56
Ni.
Aim
Various components of metabolic syndrome associate with cardiac intracellular calcium (Cai 2+) mishandling, a precipitating factor in the development of heart failure. We aimed to provide a ...thorough description of early stage Cai 2+‐cycling alterations in the fructose‐fed rat, an experimental model of the disorder, where insulin resistance, hypertension and dyslipidaemia act cooperatively on the heart.
Method
Rats were fed with fructose‐rich chow. After 6 weeks, echocardiography was performed, which was followed by measurements of myocardial Cai 2+ transients recorded by Indo‐1 surface fluorometry in isolated perfused hearts. Sarcoplasmic reticulum (SR) Ca2+‐ATPase (SERCA2a) activity was assessed by administration of its inhibitor cyclopiazonic acid (CPA). Mathematical model analysis of Cai 2+ transients was used to estimate kinetic properties of SR Ca2+ transporters. Protein levels of key Ca2+ handling proteins were also measured.
Results
Echocardiography showed signs of cardiac hypertrophy, but in vivo and ex vivo haemodynamic performance of fructose‐fed rat hearts were unaltered. However, a decline in Ca2+ sequestration capacity (‐dCai 2+/dt and decay time of Cai 2+ transients) was observed. Model estimation showed decreased affinity for Ca2+ (higher Km) and elevated Vmax for SERCA2a. Diseased hearts were more vulnerable to CPA application. Fructose feeding caused elevation in SERCA2a and phosphorylated phospholamban (PLB) expression, while total PLB level remained unchanged.
Conclusion
In early stage, metabolic syndrome primarily disturbs SERCA2a function in the heart, but consequential haemodynamic dysfunction is prevented by upregulation of SERCA2a protein level and phosphorylation pathways regulating PLB. However, this compensated state is very vulnerable to a further decline in SERCA2a function.
Objectives: Recent reports have unambiguously identified the presence and the growth‐modulatory role of transient receptor potential vanilloid‐1 (TRPV1), a central integrator of pain sensation, on ...numerous non‐neuronal cell types and, of great importance, in certain malignancies. In this study, we have investigated the molecular expression of TRPV1 in the human tongue and its high‐incidence malignant (squamous cell carcinoma, SCC) and premalignant (leukoplakia) conditions.
Methods: Immunohistochemistry, Western blotting and quantitative ‘real‐time’ Q‐PCR were performed to define the expression of TRPV1.
Results: A weak and sparse TRPV1‐specific immunoreactivity was identified in the basal layers of the healthy human tongue epithelium. By contrast, we observed a dramatically elevated TRPV1‐immunoreactivity in all layers of the epithelium both in precancerous and malignant samples. Furthermore, statistical analysis revealed that the marked overexpression of TRPV1 found in all grades of SCC showed no correlation with the degree of malignancy of the tumours. Finally, the molecular expression of TRPV1 was also identified in an SCC‐derived cell line and was shown to be increased in parallel with the accelerated growth of the cells.
Conclusion: Collectively, our findings identify TRPV1 as a novel, promising target molecule in the supportive treatment and diagnosis of human tongue SCC.
ABSTRACT We present extensive optical (UBV RI, , and open CCD) and near-infrared (ZY JH) photometry for the very nearby Type IIP SN 2013ej extending from +1 to +461 days after shock breakout, ...estimated to be MJD 56496.9 0.3. Substantial time series ultraviolet and optical spectroscopy obtained from +8 to +135 days are also presented. Considering well-observed SNe IIP from the literature, we derive UBV RIJHK bolometric calibrations from UBV RI and unfiltered measurements that potentially reach 2% precision with a B − V color-dependent correction. We observe moderately strong Si ii as early as +8 days. The photospheric velocity ( ) is determined by modeling the spectra in the vicinity of Fe ii whenever observed, and interpolating at photometric epochs based on a semianalytic method. This gives km s−1 at +50 days. We also observe spectral homogeneity of ultraviolet spectra at +10-12 days for SNe IIP, while variations are evident a week after explosion. Using the expanding photosphere method, from combined analysis of SN 2013ej and SN 2002ap, we estimate the distance to the host galaxy to be Mpc, consistent with distance estimates from other methods. Photometric and spectroscopic analysis during the plateau phase, which we estimated to be 94 7 days long, yields an explosion energy of erg, a final pre-explosion progenitor mass of 15.2 4.2 and a radius of 250 70 . We observe a broken exponential profile beyond +120 days, with a break point at +183 16 days. Measurements beyond this break time yield a 56Ni mass of 0.013 0.001 M .
Aim: The aim of the study was to examine the effects of testosterone and oestrogen on the ECG parameters and expression of cardiac ion channels in male and female dogs, and to compare the ...dofetilide‐induced lengthening of QTc interval in control, castrated and hormone‐treated animals.
Methods: ECG records were taken from male and female anaesthetized dogs (n = 10 in each group) before castration, after castration, and following inverted hormone substitution. The animals were challenged with dofetilide at each stage of the experiment. Finally, the hearts were excised and expression of ion channels was studied using Western blot technique.
Results: Heart rate was decreased and PQ interval increased by deprivation of sex hormones in both genders (orchiectomy or ovarectomy), while inverted hormonal substitution restored control values. Orchiectomy significantly increased the duration of QT and QTc intervals, QTc‐dispersion and the dofetilide‐induced lengthening of QTc, while testosterone treatment of castrated females had opposite effects. Intraventricular conduction (QRS duration) was independent of the endocrine status of the animals. Ovarectomy or oestrogen treatment of castrated males failed to alter significantly these parameters except for QTc‐dispersion. Expression of ion channel proteins responsible for mediation of IK1 and Ito currents (Kir2.1 and Kv4.3, respectively), was significantly higher in the testosterone‐treated castrated females and normal males than in the oestrogen‐treated castrated males and normal females.
Conclusion: Repolarization of canine ventricular myocardium is significantly modified by testosterone, but not oestrogen, in both genders. This effect is likely due to augmentation of expression of K+‐channel proteins, and thus may provide protection against arrhythmias via increasing the repolarization reserve.
Aims. The nearby, bright, almost completely unreddened Type Ia supernova 2011fe in M101 provides a unique opportunity to test both the precision and the accuracy of the extragalactic distances ...derived from SNe Ia light curve fitters. Methods. We applied the current, public versions of the independent light curve fitting codes MLCS2k2 and SALT2 to compute the distance modulus of SN 2011fe from high-precision, multi-color (BVRI) light curves. Results. The results from the two fitting codes confirm that 2011fe is a “normal” (not peculiar) and only slightly reddened SN Ia. New unreddened distance moduli are derived as 29.21 ± 0.07 mag (D ~ 6.95 ± 0.23 Mpc, MLCS2k2), and 29.05 ± 0.07 mag (6.46 ± 0.21 Mpc). Conclusions. Despite the very good fitting quality achieved with both light curve fitters, the resulting distance moduli are inconsistent by 2σ. Both are marginally consistent (at ~1σ) with the Hubble Space Telescope key project distance modulus for M101. The SALT2 distance is in good agreement with the recently revised Cepheid- and TRGB-distance to M101. Averaging all SN- and Cepheid-based estimates, the absolute distance to M101 is ~6.6 ± 0.5 Mpc.
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