Echelle observations are presented of lithium in 63 F and G dwarfs of the Praesepe cluster. For stars earlier than about G0V, Praesepe follows the same trends seen in the Hyades, which has approximately the same age and composition. Stars in Praesepe later than about G5V have more Li than their Hyades counterparts, possibly because Praesepe is slightly younger than the Hyades or has slightly lower metallicity. Significant differences in the abundance of Li are seen among stars of the same color, and, as in the Hyades, there is a tendency for the deviant stars to be binaries to the extent that duplicity in Praesepe is known. There are also stars with much less Li than most cluster members yet which appear to be true members of Praesepe. The close binary KW 181 has a normal Li abundance, despite the fact that similar close binaries in the Hyades are Li rich.
The central region of the dark cloud L1482 is illuminated by LkH{alpha} 101, a heavily reddened (A_V_~10mag) high-luminosity (>=8x10^3^L_Sun_) star having an unusual emission-line spectrum plus a featureless continuum. About 35 much fainter (mostly between R=16 and >21) H{alpha} emitters have been found in the cloud. Their color-magnitude distribution suggests a median age of about 0.5Myr, with considerable dispersion. There are also at least five bright B-type stars in the cloud, presumably of about the same age; none show the peculiarities expected of HAeBe stars. Dereddened, their apparent V magnitudes lead to a distance of about 700pc. Radio observations suggest that the optical object LkH{alpha} 101 is in fact a hot star surrounded by a small H II region, both inside an optically thick dust shell.
Our previous identification and spectroscopic confirmation of 431 faint, new planetary nebulae (PNe) in the central 25deg^2^ region of the Large Magellanic Cloud (LMC) permit us to now examine the shape of the LMC planetary nebula luminosity function (PNLF) through an unprecedented 10mag range. The majority of our newly discovered and previously known PNe were observed using the 2dF, multi-object fibre spectroscopy system on the 3.9-m Anglo-Australian Telescope and the FLAMES multi-object spectrograph on the 8-m Very Large Telescope. We present reliable [OIII] 5007{AA} and H{beta} flux estimates based on calibrations to well-established PN fluxes from previous surveys and spectroscopic standard stars.
The aim of our study is to investigate the physical properties of the star-forming interstellar medium (ISM) in the Large Magellanic Cloud (LMC) by separating the origin of the emission lines spatially and spectrally. The LMC provides a unique local template to bridge studies in the Galaxy and high redshift galaxies because of its low metallicity and proximity, enabling us to study the detailed physics of the ISM in spatially resolved individual star-forming regions. Following Okada et al. (2015A&A...580A..54O), we investigate different phases of the ISM traced by carbon-bearing species in four star-forming regions in the LMC, and model the physical properties using the KOSMA-{tau} PDR model. We mapped 3-13 arcmin^2^ areas in 30 Dor, N158, N160, and N159 along the molecular ridge of the LMC in [C II] 158 {mu}m with GREAT on board SOFIA. We also observed the same area with CO(2-1) to (6-5), ^13^CO(2-1) and (3-2), [C I] ^3^P_1_-^3^P_0_ and ^3^P_2_-^3^P_1_ with APEX. For selected positions in N159 and 30 Dor, we observed [O I] 145 {mu}m and [O I] 63 {mu}m with upGREAT. All spectra are velocity resolved. In all four star-forming regions, the line profiles of CO, ^13^CO, and [C I] emission are similar, being reproduced by a combination of Gaussian profiles defined by CO(3-2), whereas [C II] typically shows wider line profiles or an additional velocity component. At several positions in N159 and 30 Dor, we observed the velocity-resolved [O I] 145 and 63 {mu}m lines for the first time. At some positions, the [O I] line profiles match those of CO, at other positions they are more similar to the [C II] profiles. We interpret the different line profiles of CO, [C II] and [O I] as contributions from spatially separated clouds and/or clouds in different physical phases, which give different line ratios depending on their physical properties. We modeled the emission from the CO, [C I], [C II], and [O I] lines and the far-infrared continuum emission using the latest KOSMA-{tau} PDR model, which treats the dust-related physics consistently and computes the dust continuum SED together with the line emission of the chemical species. We find that the line and continuum emissions are not well-reproduced by a single clump ensemble. Toward the CO peak at N159 W, we propose a scenario that the CO, [C II], and [O I] 63 {mu}m emission are weaker than expected because of mutual shielding among clumps.
We present optical spectroscopy in the range 3300-7400A for a total of 30 planetary nebulae in the LMC and 11 in the SMC, with measurements of line intensities down to ~1% of H{beta}. Agreement with other authors is on the whole excellent, especially for lines >+10%-20% of H{beta}. Reddening estimates from Balmer line ratios have been determined, and the line intensities dereddened accordingly. Nebular [O III] electron temperature and, where measurable, [N II] temperatures and [S II] densities are given. [O II] electron densities are recalculated using appropriate electron temperatures. A number of spectra exhibit interesting spectral features (including symbiotic-type profiles, unidentified emission lines, and nonsimple Balmer decrements). These objects are discussed in some detail. Zanstra temperatures are derived for a total of 25 objects possessing detectable stellar continua. These temperatures are in agreement with the few published values from various methods, and preliminary photoionization modeling of this sample. The homogeneity and size of the sample make it possible to investigate several interesting correlations between measured parameters.
We present optical spectroscopy in the range 3300-7400A for a total of 37 planetary nebulae in the LMC and seven in the SMC. Together with the object from the first paper in the series (1991ApJS...75..407M), we now have accurate emission-line intensities down to a few percent of H{beta} for 77 nebulae in the Magellanic Clouds. Agreement with other authors is excellent. Reddening estimates from Balmer line ratios have been determined, and the line intensities have been dereddened accordingly. Nebular [O III] electron temperature and, where measurable, [S II] densities, are derived. [O II] electron densities are recalculated using appropriate electron temperatures. The [S II] and [O II] electron densities correlate well, with n_e_([O II])>n_e_([S II]). Zanstra temperatures are in derived for 22 objects possessing detectable stellar continua. These temperatures are in agreement with photoionization modeling of this sample.
We present optical spectroscopy in the range 3300-7400A for a total of 52 planetary nebulae in the Large Magellanic Cloud (LMC) and 18 in the Small Magellanic Cloud (SMC). Together with the object from the first (1991ApJS...75..407M) and second (1991ApJS...76.1085M) papers, we now have accurate emission-line intensities for a total of 147 nebulae in the Magellanic Clouds. This sample contains a large selection of objects of low luminosity, with measurements of line intensities down to ~10% of H{beta}. Brighter objects have line intensities measured down to ~2% of H{beta}. Agreement with other authors is generally very good, especially for lines greater than approximately 10% of H{beta}. Reddening estimates from Balmer line ratios have been determined: unreddened and reddened line intensities are tabulated.
LOAO BV-bands photometry and BOES RVs of WASP 0131+28
Short Name:
J/AJ/160/49
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the first BV light curves and high-resolution spectra of the post-mass transfer binary star WASP0131+28 to study the absolute properties of extremely low-mass white dwarfs. From the observed spectra, the double-lined radial velocities were derived, and the effective temperature and rotational velocity of the brighter, more massive primary were found to be Teff_1_=10000{+/-]200K and v_1_sin_i_=55{+/-}10km/s, respectively. The combined analysis of the Transiting Exoplanet Survey Satellite (TESS) archive data and ours yielded the accurate fundamental parameters of the program target. The masses were derived to about 1.0% accuracy and the radii to 0.6%, or better. The secondary component's parameters of M_2_=0.200{+/-}0.002M_{sun}_, R_2_=0.528{+/-}0.003R_{sun}_, Teff_2_=11186{+/-}235K, and L_2_=3.9{+/-}0.3L_{sun}_ are in excellent agreement with the evolutionary sequence for a helium-core white dwarf of mass 0.203M_{sun}, and indicates that this star is halfway through the constant luminosity phase. The results presented in this article demonstrate that WASP0131+28 is an EL CVn eclipsing binary in a thin disk, which is formed from the stable Roche-lobe overflow channel and composed of a main-sequence dwarf with a spectral type A0 and a pre-He white dwarf.
Using spectroscopic and continuum data measured by the MIRO instrument on board Rosetta of comet 67P/Churyumov-Gerasimenko, it is possible to derive and track the change in the water production rate, to learn how the outgassing evolves with heliocentric distance. The MIRO data are well suited to investigate the evolution of 67P, in unprecedented spatial and temporal detail. To obtain estimates of the local effective Haser production rates we developed an efficient and reliable retrieval approach with precalculated lookup tables. We employed line area ratios (H_2_^16^O/H_2_^18^O) from pure nadir observations as the key variable, along with the Doppler shift velocity, and continuum temperature. This method was applied to the MIRO data from August 2014 until April 2016. Perihelion occurred on August 13, 2015 when the comet was 1.24AU from the Sun. During the perihelion approach, the water production rates increased by an order of magnitude, and from the observations, the derived maximum for a single observation on August 29, 2015 is (1.42+/-0.51)x10^28^. Modelling the data indicates that there is an offset in the peak outgassing, occurring 34+/-10 days after perihelion. During the pre-perihelion phase, the production rate changes with heliocentric distance as r_h_^-3.8+/-0.2^; during post- perihelion, the dependence is r_h_^-4.3+/-0.2^. The comet is calculated to have lost 0.12+/-0.06% of its mass during the perihelion passage, considering only water ice sublimation. Additionally, this method provides well- sampled data to determine the spatial distribution of outgassing versus heliocentric distance. The time evolution is definitely not uniform across the surface. Pre- and post-perihelion, the surface temperature on the southern hemisphere changes rapidly, as does the sublimation rate with an exponent of ~-6. There is a strong latitudinal dependence on the r_h_ exponent with significant variation between northern and southern hemispheres, and so the average over the comet surface may only be of limited importance. We present more detailed regional variation in the outgassing, thereby demonstrating that the highest derived production rates originate from the Wosret, Neith, and Bes regions during perihelion.
