Stellar parameters of Be stars observed with X-shooter

Aims. The X-shooter archive of several thousand telluric star spectra was skimmed for Be and Be-shell stars to derive the stellar fundamental parameters and statistical properties, in particular for the less investigated late type Be stars, and the extension of the Be phenomenon into early A stars. Methods. An adapted version of the BCD method is used, utilizing the Balmer discontinuity parameters to determine effective temperature and surface gravity. This method is optimally suited for late B stars. The projected rotational velocity was obtained by profile fitting to the Mg ii lines of the targets, and the spectra were inspected visually for the presence of peculiar features such as the infrared Ca ii triplet or the presence of a double Balmer discontinuity. The Balmer line equivalent widths were measured, but due to uncertainties in determining the photospheric contribution are useful only in a subsample of Be stars for determining the pure emission contribution. Results. A total of 78 Be stars, mostly late type ones, were identified in the X-shooter telluric standard star archive, out of which 48 had not been reported before. The general trend of late type Be stars having more tenuous disks and being less variable than early type ones is confirmed. The relatively large number (48) of relatively bright (V > 8.5) additional Be stars casts some doubt on the statistics of late type Be stars; they are more common than currently thought: The Be/B star fraction may not strongly depend on spectral subtype.Comment: Accepted for publication in A&

OH maser towards IRAS 06056+2131: polarization parameters and evolution status

We present high angular resolution observations of OH maser emission towards the high-mass star forming region IRAS 06056+2131. The observations were carried out using the UK radio interferometer array, Multi-Element Radio Linked Interferometer Network (MERLIN) in the OH main lines at 1665- and 1667-MHz, in addition to the OH satellite line at 1720-MHz. The results of this study revealed emission in the 1665 MHz line with an estimated total intensity of $\sim 4$ Jy. We did not detect any emission from the 1667-MHz and 1720-MHz lines. The full polarization mode of MERLIN enables us to investigate the magnetic field in the OH maser region. Our results show that IRAS 06056+2131 is a highly circularly polarized source. In this transition, a Zeeman pair is identified from which a magnetic strength of $\sim -1.5$ mG is inferred. The orientation of the linear polarization vectors suggests that the magnetic field lines at the location of the OH maser emission \textbf{might be} in agreement with the orientation of the outflow thought to be associated with this source. The star forming evolutionary status of the embedded proto-stellar object is discussed.Comment: 10 pages, 5 figure

Analysis of the fractional relativistic polytropic gas sphere

Abstract Many stellar configurations, including white dwarfs, neutron stars, black holes, supermassive stars, and star clusters, rely on relativistic effects. The Tolman–Oppenheimer–Volkoff (TOV) equation of the polytropic gas sphere is ultimately a hydrostatic equilibrium equation developed from the general relativity framework. In the modified Riemann Liouville (mRL) frame, we formulate the fractional TOV (FTOV) equations and introduce an analytical solution. Using power series expansions in solving FTOV equations yields a limited physical range to the convergent power series solution. Therefore, combining the two techniques of Euler–Abel transformation and Padé approximation has been applied to improve the convergence of the obtained series solutions. For all possible values of the relativistic parameters ( $$\sigma$$ σ ), we calculated twenty fractional gas models for the polytropic indexes n = 0, 0.5, 1, 1.5, 2. Investigating the impacts of fractional and relativistic parameters on the models revealed fascinating phenomena; the two effects for n = 0.5 are that the sphere’s volume and mass decrease with increasing $$\sigma$$ σ and the fractional parameter ( $$\alpha$$ α ). For n = 1, the volume decreases when $$\sigma$$ σ  = 0.1 and then increases when $$\sigma$$ σ  = 0.2 and 0.3. The volume of the sphere reduces as both $$\sigma$$ σ and $$\alpha$$ α increase for n = 1.5 and n = 2. We calculated the maximum mass and the corresponding minimum radius of the white dwarfs modeled with polytropic index n = 3 and several fractional and relativistic parameter values. We obtained a mass limit for the white dwarfs somewhat near the Chandrasekhar limit for the integer models with small relativistic parameters ( $$\alpha = 1$$ α = 1 , $$\sigma = 0.001$$ σ = 0.001 ). The situation is altered by lowering the fractional parameter; the mass limit increases to Mlimit = 1.63348 M⊙ at $$\alpha = 0.95$$ α = 0.95 and $$\sigma = 0.001$$ σ = 0.001

Incidence and Pre-Implant Predictors of Late Right Ventricular Failure in Patients Supported with Contineous-Flow LVADs

Patients with continuous-flow left ventricular assist devices (CF-LVAD) may develop heart failure (HF) with predominant right sided HF signs. We aimed to examine the incidence, clinical and echocardiographic predictors of late right ventricular failure (RVF). Medical records and pre-implant echocardiograms of patients who received CF-LVADs from 2008-2012 at our center were reviewed. Patients who expired within 30 days of implant were excluded. RVF was defined as a syndrome of HF including leg swelling/edema and jugular venous distention requiring in- or out-patient therapy (diuresis and/or pump speed change). Multivariate logistic regression analysis was performed to determine predictors of late RVF episodes. A total of 165 patients were implanted with CF-LVADs of whom 140 survived 30 days post-surgery. Mean age 54, 75% men, 60% ischemic. A total of 37 patients developed RVF with a mean time to event of 216 days (range 31-927). 11 (7.8%) patients required inpatient management. Pre-implant echo parameters that predicted these events were right atrial pressure (RAP) (p=0.001) and RAP/(E/e’) ratio (p=0.002). No clinical parameters, including a history of hypertension or baseline pump speed, were predictive of late RVF (Table). Late RVF after CF-LVAD implantation is not uncommon. The only pre-LVAD predictors of late RVF were echo-derived RAP and the ratio of RAP/(E/e’), surrogates of high right- relative to left-sided filling pressures