Angular size measurements of carbon Miras and S-type stars

In our continuing investigation of highly evolved stars, we report new interferometric angular diameter observations of 5 carbon and 4 S-type Mira variable stars, and 4 non-Mira S stars. From the data, effective temperatures and linear radii are calculated. We compare the values of these parameters obtained for stars discussed in this paper with the same parameters for oxygen-rich giants/supergiants, oxygen-rich Mira variables, and non-Mira carbon stars presented in Dyck et al. (1996a, AJ, 111, 1705), van Belle et al. (1996, AJ, 112, 2147), and Dyck et al. (1996b, AJ, 112, 294), respectively. There are two principal findings from a synthesis of these studies. First, the non-Mira variables of each chemical class are consistently hotter and smaller than their Mira-variable counterparts. Second, the S stars lie between the oxygen-rich and the carbon-rich stars in both effective temperature and linear radius, for both the Mira-type and non-Mira stars

The impact of the oblateness of Regulus on the motion of its companion

The fast spinning B-star Regulus has recently been found to be orbited by a fainter companion in a close circular path with orbital period P_b = 40.11(2) d. Being its equatorial radius R_e 32% larger than the polar one R_p, Regulus possesses a remarkable quadrupole mass moment Q. We investigate the effects of Q on the orbital period P_b of its companion in order to see if they are measurable, given the present-day level of accuracy in measuring P_b. Conversely, we will look for deviations from the third Kepler law, attributed to the quadrupole mass moment Q of Regulus, to constrain the ratio \gamma=m/M of the system's masses.Comment: LaTex, 6 pages, 5 figures, 1 table. Accepted by Astrophysics and Space Scienc

The L 98-59 System: Three Transiting, Terrestrial-Size Planets Orbiting A Nearby M Dwarf

We report the Transiting Exoplanet Survey Satellite (TESS) discovery of three terrestrial-size planets transiting L 98-59 (TOI-175, TIC 307210830)—a bright M dwarf at a distance of 10.6 pc. Using the Gaia-measured distance and broadband photometry, we find that the host star is an M3 dwarf. Combined with the TESS transits from three sectors, the corresponding stellar parameters yield planet radii ranging from 0.8 R⊕ to 1.6 R⊕. All three planets have short orbital periods, ranging from 2.25 to 7.45 days with the outer pair just wide of a 2:1 period resonance. Diagnostic tests produced by the TESS Data Validation Report and the vetting package DAVE rule out common false-positive sources. These analyses, along with dedicated follow-up and the multiplicity of the system, lend confidence that the observed signals are caused by planets transiting L 98-59 and are not associated with other sources in the field. The L 98-59 system is interesting for a number of reasons: the host star is bright (V = 11.7 mag, K = 7.1 mag) and the planets are prime targets for further follow-up observations including precision radial-velocity mass measurements and future transit spectroscopy with the James Webb Space Telescope; the near-resonant configuration makes the system a laboratory to study planetary system dynamical evolution; and three planets of relatively similar size in the same system present an opportunity to study terrestrial planets where other variables (age, metallicity, etc.) can be held constant. L 98-59 will be observed in four more TESS sectors, which will provide a wealth of information on the three currently known planets and have the potential to reveal additional planets in the system

Predicting Stellar Angular Sizes

Our survey of long-baseline infrared and optical interferometry measurements is producing considerable numbers of directly determined stellar angular sizes. We use our sample of 124 high-precision (5%) angular stellar diameter values and correlate them with stellar magnitude values from the literature to produce empirical relations for main-sequence stars between observed apparent magnitudes, stellar colors, and angular sizes (surface brightness relations). We find a significant dependence on stellar metallicity for (B − V) colors. The scatter in the calculated relations is small (∼5%), which makes them a robust tool for the prediction of main-sequence stellar angular sizes based on photometry. We apply these relations via the calculation of the radius of the multiplanet host star GJ 667 C

The PTI Carbon Star Angular Size Survey: Effective Temperatures, Linear Radii, and Oblateness

info:eu-repo/semantics/publishe

Comparison of prehospital scales for predicting large anterior vessel occlusion in the ambulance setting

IMPORTANCE The efficacy of endovascular thrombectomy (EVT) for symptomatic large anterior vessel occlusion (sLAVO) sharply decreases with time. Because EVT is restricted to comprehensive stroke centers, prehospital triage of patients with acute stroke codes for sLAVO is crucial, and although several prediction scales are already in use, external validation, head-to-head comparison, and feasibility data are lacking. OBJECTIVE To conduct external validation and head-to-head comparisons of 7 sLAVO prediction scales in the emergency medical service (EMS) setting and to assess scale feasibility by EMS paramedics. DESIGN, SETTING, AND PARTICIPANTS This prospective cohort studywas conducted between July 2018 and October 2019 in a large urban center in the Netherlands with a population of approximately 2 million people and included 2 EMSs, 3 comprehensive stroke centers, and 4 primary stroke centers. Participants were consecutive patients aged 18 years or older for whom an EMS-initiated acute stroke code was activated. Of 2812 acute stroke codes, 805 (28.6%) were excluded, because no application was used or no clinical data were available, leaving 2007 patients included in the analyses. EXPOSURES Applications with clinical observations filled in by EMS paramedics for each acute stroke code enabling reconstruction of the following 7 prediction scales: Los Angeles Motor Scale (LAMS); Rapid Arterial Occlusion Evaluation (RACE); Cincinnati Stroke Triage Assessment Tool; Prehospital Acute Stroke Severity (PASS); gaze-face-arm-speech-time; Field Assessment Stroke Triage for Emergency Destination; and gaze, facial asymmetry, level of consciousness, extinction/inattention. MAIN OUTCOMES AND MEASURES Planned primary and secondary outcomeswere sLAVO and feasibility rates (ie, the proportion of acute stroke codes for which the prehospital scale could be reconstructed). Predictive performance measures included accuracy, sensitivity, specificity, the Youden index, and predictive values. RESULTS Of 2007 patients who received acute stroke codes (mean [SD] age, 71.1 [14.9] years; 1021 [50.9%] male), 158 (7.9%) had sLAVO. Accuracy of the scales ranged from 0.79 to 0.89, with LAMS and RACE scales yielding the highest scores. Sensitivity of the scales ranged from 38% to 62%, and specificity from 80% to 93%. Scale feasibility rates ranged from 78% to 88%, with the highest rate for the PASS scale. CONCLUSIONS AND RELEVANCE This study found that all 7 prediction scales had good accuracy, high specificity, and low sensitivity, with LAMS and RACE being the highest scoring scales. Feasibility rates ranged between 78% and 88% and should be taken into account before implementing a scale