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تسجيل مستخدم جديدRevisiting the Open Cluster M35
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D. Barrado y Navascues
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We present a photometric and spectroscopic study of the young open cluster M35, including very deep and accurate photometry of the stellar (including white dwarfs) and substellar population of the cluster, a complete mass function, rotational and radial velocities, and lithium abundances.
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We have obtained high resolution spectra of $sim$40 members of M35, determined the Lithium-T$_{rm{eff}}$ morphology and the distribution of the rotational velocity for G and K stars, and compared them to those of the Pleiades and other well-known open clusters.
We report the discovery of a hot DQ white dwarf, NGC 2168:LAWDS 28, that is a likely member of the 150-Myr old cluster NGC 2168 (Messier 35). The spectrum of the white dwarf is dominated by CII features. The effective temperature is difficult to esti
mate but likely > 20,000 K based on the temperatures of hot DQs with similar spectra. NGC2168:LAWDS 28 provides further evidence that hot DQs may be the ``missing high-mass helium-atmosphere white dwarfs. Based on published studies, we find that the DBA WD LP 475-242 is likely a member of the Hyades open cluster, as often assumed. These two white dwarfs are the entire sample of known He-atmosphere white dwarfs in open clusters with turnoff masses >2 solar masses. Based on the number of known cluster DA white dwarfs and a redetermination of the H-atmosphere:He-atmosphere ratio, commonly known as the DA:DB ratio, we re-examine the hypothesis that the H- to He-atmosphere ratio in open clusters is the same as the ratio in the field. Under this hypothesis, we calculate that five He-atmosphere WDs are expected to have been discovered, with a probability of finding fewer than three He-atmosphere white dwarfs of 0.08, or at the ~ 2-sigma level.
We present very deep RIc photometry of the M35 open cluster. We have covered 30 times 30, equivalent to about a fourth of the total area of the cluster. The data range from I_c=17.5 to 23.5 magnitudes, and the color interval is $0.5 le (R-I)_c le 2.5
$. Roughly, these values correspond from $0.6 M_odot$ to $0.1 M_odot$ in the cases of members of the cluster. By using the location of the stars on a Color-Magnitude Diagram, we have selected possible members of this cluster and obtained the Luminosity and Mass Functions of the M35 open cluster and compared them with those from the Pleiades.
Hydra spectra of 85 G-K dwarfs in the young cluster, M35, near the Li 6708 Angstrom line region are analyzed. From velocities and Gaia astrometry, 78 are likely single-star members which, combined with previous work, produces 108 members with T_eff r
anging from 6150 to 4000 K as defined by multicolor, broad-band photometry, E(B-V ) = 0.20 and [Fe/H] = -0.15, though there are indications the metallicity may be closer to solar. A(Li) follows a well-delineated decline from 3.15 for the hottest stars to upper limits <= 1.0 among the coolest dwarfs. Contrary to earlier work, M35 includes single stars at systematically higher A(Li) than the mean cluster relation. This subset exhibits higher V_ROT than the more Li-depleted sample and, from photometric rotation periods, is dominated by stars classed as convective (C); all others are interface (I) stars. The cool, high-Li rapid rotators are consistent with models that consider simultaneously rapid rotation and radius inflation; rapid rotators hotter than the sun exhibit excess Li depletion, as predicted by the models. The A(Li) distribution with color and rotation period, when compared to the Hyades/Praesepe and the Pleiades, is consistent with gyrochronological analysis placing M35s age between the older M34 and younger Pleiades. However, the Pleiades display a more excessive range in A(Li) and rotation period than M35 on the low-Li, slow-rotation side of the distribution, with supposedly younger stars at a given T_eff in the Pleiades spinning slower, with A(Li) reduced by more than a factor of four compared to M35.
We present a catalog of 1,143 periodic variables, compiled from our image-subtracted photometric analysis of the K2 Campaign-0 super stamp. This super stamp is centered on the open clusters M35 and NGC 2158. Approximately 46% of our periodic variable
s were previously unreported. Of the catalog variables, we find that 331 are members of M35 and 56 are members of NGC 2158 (${P_{mathrm{m}}~>~0.5}$). Our catalog contains two new transiting exoplanet candidates, both of which orbit field stars. The smaller planet candidate has a radius of $0.35~pm~0.04 rm R_{J}$ and orbits a K dwarf ($K_{mathrm{p}}=15.4$ mag) with a transit depth of 2.9 millimag. The larger planet candidate has a radius of $0.72~pm~0.02 rm R_{J}$ and orbits a late G type star ($K_{mathrm{p}}=15.7$ mag) with a transit depth of 2.2 millimag. The larger planet candidate maybe an unresolved binary or a false alarm. Our catalog includes 44 eclipsing binaries, including ten new detections. Of the eclipsing binaries, one is an M35 member and five are NGC 2158 members. Our catalog contains a total of 1,097 non-transiting variable stars, including a field $delta$ Cepheid exhibiting double mode pulsations, 561 rotational variables, and 251 pulsating variables (primarily $gamma$ Doradus and $delta$ Scuti types). The periods of our catalog sources range between 43 minutes to 24 days. The known ages of our reported cluster variables will facilitate investigations of a variety of stellar evolutionary processes.
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