Misty A. Brown

The Solar Neighborhood. X. New Nearby Stars in the Southern Sky and Accurate Photometric Distance Estimates for Red Dwarfs

Photometric (VJRCIC) and spectroscopic (6000–9500 A) observations of high–proper-motion stars discovered during the first phase of the SuperCOSMOS RECONS (SCR) search are used to estimate accurate distances to eight new nearby red dwarfs, including probable 10 pc sample members SCR 1845-6357 (M8.5 V at 4.6 pc), the binary SCR 0630-7643AB (M6.0 V J at 7.0 pc), and SCR 1138-7721 (M5.0 V at 9.4 pc). Distance estimates are determined using a suite of new photometric color-M relations defined using a robust set of nearby stars with accurate VRIJHKs photometry and trigonometric parallaxes. These relations are used with optical and infrared photometry to estimate distances on a uniform system (generally good to 15%) for two additional samples of red nearby star candidates: several recently discovered members of the solar neighborhood and known faint stars with proper motions in excess of 10 yr-1 south of decl. = -575. Of those without accurate trigonometric parallax measurements, there are five stars in the first sample and three in the second that are likely to be within 10 pc. The two nearest are SO 0253+1652 (M7.0 V at 3.7 pc) and DENIS 1048-3956 (M8.5 V at 4.5 pc). When combined with SCR 1845-6357, these three stars together represent the largest increase in the 5 pc sample in several decades. Red spectra are presented for the red dwarfs, and types are given on the RECONS standard spectral system. Red spectra are also given for two new nearby white dwarfs for which we estimate distances from the photometry of less than 20 pc: WD 0141-675 (LHS 145; 9.3 pc) and SCR 2012-5956 (17.4 pc). WD 0141-675 brings the total number of systems nearer than 10 pc discussed in this paper to 12.

The Solar Neighborhood. XIII. Parallax Results from the CTIOPI 0.9 Meter Program: Stars with μ ≥ 10 yr−1 (MOTION Sample)

We present the first set of definitive trigonometric parallaxes and proper motions from the Cerro Tololo Inter-American Observatory Parallax Investigation. Full astrometric reductions for the program are discussed, including methods of reference star selection, differential color refraction corrections, and conversion of relative to absolute parallax. Using data acquired at the 0.9 m telescope at CTIO, full astrometric solutions and VRIJHKs photometry are presented for 36 red and white dwarf stellar systems with proper motions faster than 10 yr-1. Of these, 33 systems have their first ever trigonometric parallaxes, which comprise 41% of MOTION systems (those reported to have proper motions greater than 10 yr-1) south of δ = 0° that have no parallaxes. Four of the systems are new members of the RECONS 10 pc sample for which the first accurate trigonometric parallaxes are published here: DENIS J1048-3956 (4.04 ± 0.03 pc), GJ 1128 (LHS 271, 6.53 ± 0.10 pc), GJ 1068 (LHS 22, 6.97 ± 0.09 pc), and GJ 1123 (LHS 263, 9.02 ± 0.16 pc). In addition, two red subdwarf–white dwarf pairs, LHS 193AB and LHS 300AB, are identified. The white dwarf secondaries fall in a previously uncharted region of the H-R diagram.

The Solar Neighborhood. XIV. Parallaxes from the Cerro Tololo Inter-American Observatory Parallax Investigation—First Results from the 1.5 m Telescope Program

Trigonometric parallaxes, proper motions, and VJ(RI)KC photometry are presented for 31 stars targeted by the Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI), a program of wide scope aimed at discovering and characterizing nearby stars. The data given are the first that have been obtained with the CTIO 1.5 m telescope, targeting a fainter subset of the CTIOPI input list. We present the first trigonometric parallaxes for 21 systems, of which one is within 10 pc (LP 647-013 at 9:59 � 0:22 pc) and six are between 10 and 25 pc. Concurrently with our Cerro Tololo 0.9 m program, we have determined parallaxes for DEN 1048� 3956 and LTT 6933 that place them at 4:00 � 0:03 and 16:24 � 0:43 pc from the Sun, respectively. We also present an improved parallax for the important nearby triple system GJ 2005ABC, placing it at 7:72 � 0:15 pc from the Sun. The remaining seven parallaxes are for calibration stars, whose values indicate that our results agree well with other parallax determinations. We present color-magnitude and color-color diagrams that, in combination with theoretical isochrones from the literature and other derived properties of the observed sample, have aided the identification of the general nature of each of our targets. We have in this way discovered five new subdwarfs and several very low mass stars, a few of which may be brown dwarfs.

The Solar Neighborhood. VIII. Discovery of New High Proper Motion Nearby Stars Using the SuperCOSMOS Sky Survey

Five new objects with proper motions between 10 and 26 yr-1 have been discovered via a new Research Consortium on Nearby Stars (RECONS) search for high proper motion stars using the SuperCOSMOS Sky Survey. The first portion of the search, discussed here, is centered on the south celestial pole and covers declinations -90° to -575. Photographic photometry from SuperCOSMOS and JHKs near-infrared photometry from the Two Micron All Sky Survey for stars nearer than 10 pc are combined to provide a suite of new M-color relations useful for estimating distances to main-sequence stars. These relations are then used to derive distances to the new proper motion objects, as well as previously known stars with μ ≥ 10 yr-1 (many of which have no trigonometric parallaxes) recovered during this phase of the survey. Four of the five new stars have red dwarf colors, while one is a nearby white dwarf. Two of the red dwarfs are likely to be within the RECONS 10 pc sample, and the white dwarf probably lies between 15 and 25 pc. Among the 23 known stars recovered during the search, there are three additional candidates for the RECONS sample that have no trigonometric parallaxes.

THE SOLAR NEIGHBORHOOD. XXII. PARALLAX RESULTS FROM THE CTIOPI 0.9 m PROGRAM: TRIGONOMETRIC PARALLAXES OF 64 NEARBY SYSTEMS WITH 0.″5 ⩽μ⩽ 1.″0 yr–1 (SLOWMO SAMPLE)

We present trigonometric parallaxes of 64 stellar systems with proper motions between 05 yr?1 and 10 yr?1 from the ongoing Research Consortium On Nearby Stars parallax program at the Cerro Tololo Inter-American Observatory. All of the systems are south of decl. =+30, and 58 had no previous trigonometric parallaxes. In addition to parallaxes for the systems, we present proper motions, Johnson-Kron-Cousins VRI photometry, variability measurements, and spectral types. Nine of the systems are multiple; we present results for their components, three of which are new astrometric detections. Of the 64 systems, 56 are within 25?pc of the Sun and 52 of those are in the southern hemisphere, comprising 5.7% of the total number of known southern 25?pc systems.

The Solar Neighborhood. XV. Discovery of New High Proper Motion Stars with μ ≥ 04 yr−1 between Declinations −47° and 00°

We report the discovery of 152 new high proper motion systems (μ ≥ 04 yr-1) in the southern sky (δ = -47° to 00°) brighter than UKST plate R59F = 16.5 via our SuperCOSMOS-RECONS (SCR) search. This paper complements Paper XII in the Solar Neighborhood series, which covered the region from δ = -90° to -47° and discussed all 147 new systems from the southernmost phase of the search. Among the total of 299 systems from both papers, there are 148 (71 in Paper XII, 77 in this paper) new systems moving faster than 05 yr-1 that are additions to the classic Luyten Half Second sample. These constitute an 8% increase in the sample of all stellar systems with μ ≥ 05 yr-1 in the southern sky. As in Paper XII, distance estimates are provided for the systems reported here based on a combination of photographic plate magnitudes and Two Micron All Sky Survey photometry, assuming that all stars are on the main sequence. Two SCR systems from the portion of the sky included in this paper are anticipated to be within 10 pc, and an additional 23 are within 25 pc. In total, the results presented in Paper XII and here for this SCR sweep of the entire southern sky include five new systems within 10 pc and 38 more between 10 and 25 pc. The largest number of nearby systems have been found in the slowest proper motion bin, 06 yr-1 > μ ≥ 04 yr-1, indicating that there may be a large population of low proper motion systems very near the Sun.

The Solar Neighborhood. XI. The Trigonometric Parallax of SCR 1845−6357

We present a trigonometric parallax for the nearby star SCR 1845� 6357, an extremely red, high proper motion object discovered by Hambly et al. and identified via accurate photoelectric photometry and spectroscopy to be an M8.5 dwarf with a photometric parallax of 4:6 � 0:8 pc by Henry et al. Using methods similar to those described in Deacon & Hambly, we have derived a full astrometric solution from SuperCOSMOS scans of eight survey and nonsurvey Schmidt photographs held in the United Kingdom Schmidt Telescope Unit plate library. We calculate the trigonometric parallax to be � ¼ 282 � 23 mas, yielding a distance of 3:5 � 0: 3p c, which implies an absolute Ks magnitude of 10.79. This distance calculation places SCR 1845� 6357 as the 16th closest stellar system to the Sun.