136 research outputs found

    Hexaaqua­cobalt(II) bis­{[N-(4-meth­oxy-2-oxidobenzyl­idene)glycylglycinato]nickel(II)} hexa­hydrate

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    In the title compound, [Co(H2O)6][Ni(C12H11N2O5)]2·6H2O, the NiII atom has a nearly square-planar coordination with two N and two O atoms of the N-(4-meth­oxy-2-oxidobenzyl­idene)glycylglycinate Schiff base ligand (L 3−). The CoII atom sits on an inversion center and is coordinated to six aqua ligands in a slightly distorted octa­hedral geometry. The [Co(H2O)6]2+ cations and [NiL]− anions form columns along the a axis by O—H⋯O hydrogen bonds. Additional hydrogen bonds between the uncoordinated and coordinated water molecules help to consolidate the crystal packing

    On the Color-Metallicity Relation of the Red Clump and the Reddening Toward the Magellanic Clouds

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    The zero point of the reddening toward the Large Magellanic Cloud (LMC) has been the subject of some dispute. Its uncertainty propagates as a systematic error for methods which measure the extragalactic distance scale through knowledge of the absolute extinction of LMC stars. In an effort to resolve this issue, we used three different methods to calibrate the most widely-used metric to predict LMC extinction, the intrinsic color of the red clump, (VI)RC,0(V-I)_{RC,0}, for the inner \sim3 degrees of that galaxy. The first approach was to empirically calibrate the color zeropoints of the BaSTI isochrones over a wide metallicity range of Δ[Fe/H]1.10{\Delta}\rm{[Fe/H]} \approx 1.10 using measurements of red clump stars in 47 Tuc, the Solar Neighborhood, and NGC 6791. From these efforts we also measure these properties of the Solar Neighborhood red clump, (VIV-I, GBPKsG_{BP}-K_{s}, GKsG-K_{s}, GRPKsG_{RP}-K_{s}, JKsJ-K_{s}, HKsH-K_{s}, MIM_{I}, MKsM_{Ks})RC,0=_{RC,0} = (1.02, 2.75, 2.18, 1.52, 0.64, 0.15, -0.23, -1.63). The second and third methods were to compare the observed colors of the red clump to those of Cepheids and RR Lyrae in the LMC. With these three methods, we estimated the intrinsic color of the red clump of the LMC to be (VI)RC,0,LMC={0.93,0.91±0.02,0.89±0.02}(V-I)_{RC,0,\rm{LMC}} = \{ \approx 0.93,0.91 \pm 0.02,0.89 \pm 0.02\} respectively, and similarly using the first and third method we estimated (VI)RC,0,SMC={0.85,0.84±0.02} (V-I)_{RC,0,\rm{SMC}} = \{\approx 0.85,0.84 \pm 0.02 \} respectively for the Small Magellanic Cloud. We estimate the luminosities to be MI,RC,LMC=0.26M_{I,RC,\rm{LMC}}=-0.26 and MI,RC,SMC=0.37M_{I,RC,\rm{SMC}}=-0.37. We show that this has important implications for recent calibrations of the tip of the red giant branch in the Magellanic Clouds used to measure H0H_0.Comment: 20 pages, 5 figures, 4 tables. Accepted for Publication in The Astrophysical Journal as of February 9th, 202
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