The Astrophysical Journal, 613:L000–L000, 2004 September 20 ᭧ 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A. THE AB DORADUS MOVING GROUP B. Zuckerman1 and Inseok Song1,2 Department of Physics and Astronomy, University of California at Los Angeles, Box 951547, Knudsen Hall, Los Angeles, CA 90095; [email protected], [email protected] and M. S. Bessell Research School of Astronomy and Astrophysics Institute of Advanced Studies, Australian National University, Cotter Road, Weston Creek, Canberra, ACT 2611, Australia; [email protected] Received 2004 June 30; accepted 2004 August 12; published 2004 August 23 ABSTRACT From radio to X-ray wavelengths, AB Doradus has been an intensively studied star. We have identified ∼30 nearby star systems, each with one or more characteristics of youth, that are moving through space together with AB Dor. This diverse set of ∼50 million year old star systems is the comoving, youthful group closest to Earth. The group’s nucleus is a clustering of a dozen stars ∼20 pc from Earth that includes AB Dor itself. The AB Dor moving group joins the previously known and somewhat younger and more distant Tucana/Horologium and TW Hydrae associations and the b Pictoris moving group as excellent laboratories for investigations of forming planetary systems. Subject headings: open clusters and associations: individual (AB Doradus moving group) — stars: kinematics — stars: pre–main-sequence 1. INTRODUCTION 2. OBSERVATIONS In 2001 we began a spectroscopic search for young stars The past few years have seen the identification of a variety near the Sun using the double-beam grating and echelle spec- of comoving stellar groups near the Sun with ages in the range trographs on the two Nasmyth foci of the Australian National 8–30 Myr, which is characteristic of the period during which University’s 2.3 m telescope (see, e.g., Zuckerman et al. 2001 the planets of the solar system were forming (see Jacobsen for a few early results) and the Hamilton echelle spectrograph 2003, Kasting & Catling 2003, and references therein). The at the coude´ focus of the 3 m telescope at Lick Observatory. first such group to be identified was the TW Hydrae association, Some spectra have also been obtained with the High Resolution ∼55 pc from Earth. Then the somewhat nearer Tucana/Horo- Echelle Spectrometer (Vogt et al. 1994) at the 10 m Keck logium association was discovered, followed soon after by the telescope and with an echelle spectrometer on the 2.5 m tele- even closer b Pictoris moving group whose stars are typically scope at Las Campanas Observatory. The primary goal of these ∼35 pc from Earth. With but a few exceptions, all stars in these observations is the measurement of radial velocity and v sin i groups and the somewhat more distant (97 pc) h Chamaeleontis along with the equivalent widths of the Ha and Li l6708 lines. cluster are located deep in the southern hemisphere (see Zuck- Radial velocity, in conjunction with proper motion and parallax, erman & Song 2004 for a recent review). enables us to calculate the three-dimensional Galactic space Given that nearby main-sequence stars are brighter and thus motionsU, V, W that are essential for the identification of in- more prominent and easier to study than more distant ones, we dividual moving groups. Details of our observations and results anticipated that no substantial stellar association closer than the can and will be found in Song et al. (2003) and I. Song et al. b Pictoris group would ever be identified. But we were wrong. (2004, in preparation). We have identified the ultrarapid rotator, quintessential active The spectral types in parentheses listed in the fifth column binary star, AB Doradus, only 15 pc from Earth, as the most of Table 1 are based onV Ϫ K colors in preference to SIMBAD- famous member of a young, comoving, stellar group that par- listed spectral types. Most of these stars have been little in- tially surrounds the Sun (Table 1). Many AB Dor group stars vestigated previously (few references in SIMBAD), and catalog are found in the northern hemisphere. spectral types are not necessarily reliable. Some, for example, Current adaptive optics (AO) systems on large telescopes HIP 26369 and 31878, are members of binary systems where and the Near-Infrared Camera and Multi-Object Spectrometer a companion with consistent spectral type andV Ϫ K can be on the Hubble Space Telescope (HST) become sensitive to faint used as a fiducial point. In addition, we can classify some of objects near bright ones at separations larger than about 1Љ.As the stars based on our own grating spectrometer data (I. Song may be seen in Table 1, about half the stars in the AB Dor et al. 2004, in preparation). moving group are sufficiently close to Earth that planets within Entries for radial velocity, lithium, Ha, andv sin i in Table 1 30 AU of these stars are accessible to AO and HST. Such are our own measurements. Additional measurements of some systems can be probed for warm (self-luminous) planets of a of these quantities may be found in the papers listed in the few Jupiter masses having semimajor axes comparable to those references/notes column, i.e., the last column of Table 1. A ques- of the giant planets of the solar system. tion mark in this column indicates questionable membership; for example, one component ofU, V, W may differ by a few kilo- 1 UCLA, Center for Astrobiology/Institute of Geophysics and Planetary meters per second from the group mean, or the lithium equivalent Physics, 3845 Slichter Hall, Los Angeles, CA 90095-1567. width or X-ray luminosity may be somewhat low for a typical 2 AURA/Gemini Observatory, 670 North A’ohoku Place, Hilo, HI 96720. star of age 50 Myr. We have not observed PW And or LO Peg. L000 L000 ZUCKERMAN, SONG, & BESSELL Vol. 613 TABLE 1 The AB Dor Moving Group Other R.A. Decl. V D RV Li Ha v sin i U, V, W HIP Name (J2000) (J2000) Sp. (mag) (pc) (km sϪ1) (mA˚ ) ()A˚ (km sϪ1) (km sϪ1) Refs./Notes PW And 00 18 20.9 ϩ30 57 22 K2 V 8.6 (28) … … … … Ϫ4.4, Ϫ27.1, Ϫ16.1 1–4 ϩ0.91 24 Ϫ8.9, Ϫ26.6, Ϫ15.8 3Љ.8 binary 119 0.5 ע HD 4277 00 45 50.9 ϩ54 58 40 F8 VϩK3 7.8 48.5 Ϫ15.4 3589 ϩ0.72 10 Ϫ8.6, Ϫ31.1, Ϫ9.3 ?; 23Љ binary 150 1.2 ע HD 6569 01 06 26.1 Ϫ14 17 47 K1 V 9.5 50.0 ϩ6.0 5191 ϩ0.76 10 Ϫ4.7, Ϫ27.8, Ϫ13.6 145 1.0 ע Ϫ11 28 04 (G8) 8.4 35.1 ϩ9.9 32.3 20 01 6276 ϩ0.80 !10 Ϫ7.1, Ϫ28.3, Ϫ11.8 ?; 3; 1Љ.8 binary 110 0.3 ע HD 13482 02 12 15.4 ϩ23 57 29 K1ϩK5 7.8 32.3 Ϫ1.3 10272 ϩ0.23 6 Ϫ8.7, Ϫ28.7, Ϫ13.1 146 0.3 ע ϩ38 37 22 (K3.5) 10.2 49.6 Ϫ4.1 20.9 42 02 12635 ϩ1.09 27?? Ϫ9.3, Ϫ28.3, Ϫ13.4 158 0.2 ע HD 16760 02 42 21.3 ϩ38 37 08 G5 8.7 49.6 Ϫ3.3 12638 ϩ0.90 13 Ϫ8.5, Ϫ28.5, Ϫ12.9 5,6;3Љ.6 binary 155 1.3 ע HD 17332 02 47 27.4 ϩ19 22 18 G0ϩG5 6.9 32.6 ϩ4.1 13027 ϩ0.10 … Ϫ5.1, Ϫ28.6, Ϫ16.1 34 0.3 ע ϩ22 25 24 (K6) 10.6 49.8 ϩ4.1 12.3 11 03 14807 ϩ0.87 … Ϫ6.0, Ϫ28.3, Ϫ16.7 145 0.2 ע ϩ22 24 58 G5 8.5 49.8 ϩ5.2 13.8 11 03 14809 ϩ0.70 7 Ϫ6.5, Ϫ25.6, Ϫ15.7 1,7,8 200 0.3 ע 16563A V577 Per 03 33 13.5 ϩ46 15 26 (G5) 8.2 33.8 Ϫ6.0 Ϫ2.50 20 Ϫ6.5, Ϫ25.6, Ϫ15.7 30 1.1 ע 16563B 03 33 14.0 ϩ46 15 19 M0 11.2 33.8 Ϫ6.1 Ϫ2.20 18 Ϫ7.4, Ϫ27.1, Ϫ10.6 ?0 1.7 ע Ϫ01 58 20 M3 11.6 16.3 ϩ16.0 23.3 47 03 17695 ϩ1.08 14 Ϫ7.2, Ϫ28.6, Ϫ11.6 1,9,10 100 0.3 ע GJ 159 04 02 36.7 Ϫ00 16 08 F5 V 5.4 19.2 ϩ17.0 18859 ϩ1.20 … Ϫ6.9, Ϫ27.8, Ϫ14.3 120 0.6 ע HD 25953 04 06 41.5 ϩ01 41 03 F5 7.8 55.3 ϩ17.6 19183 ϩ0.28 6 Ϫ7.1, Ϫ27.0, Ϫ14.5 0 1.0 ע HD 35650 05 24 30.2 Ϫ38 58 11 (K7) 9.1 17.7 ϩ30.9 25283 ϩ0.10 80 Ϫ7.5, Ϫ29.8, Ϫ16.0 1, 3, 8, 11; 9Љ binary 295 3.0 ע AB Dor 05 28 44.8 Ϫ65 26 55 K1 6.9 14.9 ϩ33.0 25647 Ϫ0.80 44 Ϫ7.2, Ϫ27.0, Ϫ13.9 30 1.1 ע Ϫ47 57 48 (K7) 9.8 23.9 ϩ31.1 55.1 36 05 26369 ϩ0.54 9 Ϫ7.2, Ϫ26.9, Ϫ13.9 1, 3 240 1.0 ע UY Pic 05 36 56.8 Ϫ47 57 53 K0 V 7.9 23.9 ϩ31.0 26373 ϩ1.05 16 Ϫ7.6, Ϫ26.7, Ϫ13.6 3,6,12 135 0.7 ע HD 45270 06 22 30.9 Ϫ60 13 07 G1 V 6.5 23.5 ϩ30.0 30314 Ϫ3.90 … Ϫ10.3, Ϫ27.7, Ϫ15.6 0 2.0 ע GSC 8894-426 06 25 55.9 Ϫ60 03 28 M2 11.7 (22) ϩ31.8 ϩ0.84 15 Ϫ7.1, Ϫ28.5, Ϫ15.0 1, 3, 12–14; 0Љ.8 binary 120 1.0 ע HR 2468 06 38 00.4 Ϫ61 32 00 G1.5 V 6.2 21.7 ϩ33.4 31711 ϩ0.26 12 Ϫ7.2, Ϫ27.4, Ϫ13.9 50 0.7 ע Ϫ61 28 41 (K7) 9.7 21.9 ϩ30.5 50.0 39 06 31878 Ϫ2.35 20 Ϫ7.4, Ϫ24.4, Ϫ15.7 0Љ.3 binary 0 1.0 ע V372 Pup 07 28 51.4 Ϫ30 14 48 (M3) 10.0 15.6 ϩ26.6 36349 ϩ0.74 6 Ϫ5.0, Ϫ28.8, Ϫ9.8 1,3,4,15 142 0.5 ע HD 113449 13 03 49.7 Ϫ05 09 42 (K1) 7.7 22.1 ϩ2.0 63742 Ϫ0.55 8 Ϫ7.5, Ϫ31.9, Ϫ15.6 ?; 0Љ.9 binary 110 0.4 ע HD 139751 15 40 28.4 Ϫ18 41 46 (K7) 10.1 42.6 Ϫ8.9 76768 ? Ϫ0.60 7 Ϫ7.0, Ϫ28.7, Ϫ13.4 0 0.4 ע Ϫ09 33 12 M0.5 11.3 31.9 Ϫ15.0 41.6 33 16 81084 ϩ1.18 15 Ϫ6.1, Ϫ28.8, Ϫ12.6 3 133 0.5 ע HD 152555 16 54 08.1 Ϫ04 20 25 G0 7.8 47.6 Ϫ17.1 82688 Ϫ1.09 17 Ϫ5.3, Ϫ27.6, Ϫ14.5 ?;1,4 40 0.7 ע HD 160934 17 38 39.6 ϩ61 14 16 M0 10.2 24.0 Ϫ35.6 86346 106231 LO Peg 21 31 01.7 ϩ23 20 07 K8 9.2 25.1 … … … … Ϫ5.7, Ϫ27.3, Ϫ15.0 1,3,8 Ϫ3.60 16 Ϫ6.8, Ϫ27.8, Ϫ15.0 1; 1Љ.8 binary 0 2.1 ע GJ 856A 22 23 29.1 ϩ32 27 34 M3 11 16.0 Ϫ20.6 110526 ϩ0.96 8 Ϫ3.1, Ϫ26.8, Ϫ14.1 ?;3,6 167 1.5 ע HD 217343 23 00 19.3 Ϫ26 09 13 G3 V 7.5 32.1 ϩ6.3 113579 ϩ0.18 7 Ϫ2.0, Ϫ24.5, Ϫ15.4 1Љ.8 binary 0 1.5 ע HD 217379 23 00 27.9 Ϫ26 18 43 (K8) 9.8 30.0 ϩ8.4 113597 Ϫ1.60 8 Ϫ6.8, Ϫ27.3, Ϫ15.9 1 30 0.8 ע ϩ63 55 34 (M1) 10.9 24.9 Ϫ23.7 04.8 06 23 114066 ? ϩ0.88 3 Ϫ7.9, Ϫ29.1, Ϫ11.3 220 1.2 ע HD 218860 23 11 52.0 Ϫ45 08 11 (G5) 8.8 50.5 ϩ10.3 114530 ϩ0.90 … Ϫ4.8, Ϫ27.5, Ϫ14.3 160 0.2 ע ϩ42 15 10 (G4) 8.9 49.4 Ϫ19.7 39.5 19 23 115162 ϩ0.78 6 Ϫ7.6, Ϫ27.9, Ϫ12.3 ?; 3 76 0.5 ע HD 224228 23 56 10.7 Ϫ39 03 08 K3 V 8.2 22.1 ϩ12.1 118008 Note.—We have not observed PW And and LO Peg; data are available in the listed references.