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Dm Stars) with Ages from ~10 Myr 9.36 0.94 0.07 V-Mag V-Mag to 13 Gyr

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Dm Stars) with Ages from ~10 Myr 9.36 0.94 0.07 V-Mag V-Mag to 13 Gyr GJ 176 FCAPT Photometry GJ 876 FCAPT Photometry GJ 205 FCAPT Photometry GJ 674 ASAS3 Photometry 1.84 Hosts 3 currently known planets dM1.5 2-4 Gyr 2 Gyr - HR 1614 M.G. Member 9.32 Possible planetary companion dM3.5 0.05 32.497-d dM2.5 dM2.5 1.86 114.95-d 33.1897-d 0.92 40.44-d 9.34 We report on the progress of the “Living with a Red Dwarf” Program, a 0.06 1.88 multi-frequency study of red dwarfs (dM stars) with ages from ~10 Myr 9.36 0.94 0.07 V-mag V-mag to 13 Gyr. dM stars are the most numerous stars in our Galaxy, 1.90 V-mag V-mag Δ Δ comprising >75% of all known stars. Recently, planets (including large Δ 9.38 0.08 1.92 terrestrial planets) have been discovered orbiting several nearby dM 0.96 9.40 stars. Our program aims to understand the magnetic activity, coronal physics, and XUV spectral irradiances of dM stars of different ages, and 1.94 0.09 9.42 -0.02 -0.03 what the effects would be on orbiting planets. As a part of this program, V-I Color Index V-I Color Index 0.00.51.01.5 0.0 0.5 1.0 1.5 -0.02 Phase Phase (33.1897-d) we are developing relationships among age, rotation and markers of -0.01 -0.01 magnetic activity (XUV emissions). Using our own photometry combined 0.00 0.00 GJ 4247 NSVS Photometry GJ 3379 ASAS3 Photometry with that of the ASAS3 program, we have determined the rotation periods 0.01 200 Myr - Castor M.G. Member 600 Myr - Hyades M.G. Member 0.01 -0.10 11.20 and possible activity cycles of an increasing number of dM stars. We are Index V-I Relative 0.02 Relative V-I IndexRelative V-I dM4 dM3.5 1.678-d 19.883-d using ROSAT, ASCA, XMM and Chandra X-ray observations and are 0.02 0.03 0.0 0.5 1.0 1.5 0.0 0.5 1.0 1.5 combining these with EUV, and FUV-UV data (from EUVE, FUSE and IUE Phase Phase -0.05 11.25 or HST) to form XUV spectral irradiance tables of dM stars covering a wide range of ages and XUV fluxes. From the relationships derived to 11.30 date, we have been able to provide age estimates for field dM0-5 stars 0.00 V-mag Here we have 6 selected lightcurves of the LWARD program. They range in length of based on their X-ray luminosities. Of particular importance is the Detrended V-mag rotation, and thus age, as well as spectral type. Lightcurves are shown from our three 11.35 determinations of ages for dM stars currently known to host planets. 0.05 current sources of photometry: the 0.8-m FCAPT located in Arizona, along with the ASAS-3 We gratefully acknowledge suport by grants from NSF/RUI AST- and NSVS programs. The two survey programs observe in one passband, but the color 11.40 0.0 0.5 1.0 1.5 0.0 0.5 1.0 1.5 507536 and NASA grants NNX06AD386 and NNG04G038G. curves obtained from the FCAPT will be used to conduct spot models. Phase Phase • Barnes (2007), ApJ, 669, 1167. “Ages for Illustrative Field Stars Using Gyro- chronology: Viability, Limitations and Errors” Living with a Red Dwarf Living with a Red Dwarf • Browning & Basri (2007), AIPC, 948, 157. Preliminary Age-Rotation Plot “Dynamo Action in Fully Convective Low- Preliminary Period-Activity Plot 250 Evolutionary Tracks for F-G-K-M-type Stars Mass Stars” 4 • Eggen (1998) AJ, 115, 2453. “The HR 1614 30 1.4 M.; F4-5 1.0 M.; G2 Kapteyn Group and Hipparcos Astrometry” 3 200 Pre-MS dM Stars • Lopez-Santiago, Montes, Crespo-Chacon and Barnard Fernandez-Figueroa (2006), ApJ, 643, 1160. Saturation Level for dM Stars 2 “The Nearest Young Moving Groups” 29 150 SZ UMa • Montes, Lopez-Santiago, Galvez, Fernandez- 1 L/L L/L . Figueroa, De Castro and Cornide (2001), MNRAS, X log 328, 45. “Late-Type Members of Young Stellar 0 100 Proxima Kinematic Groups – I. Single Stars” log L log 28 0.7 M.; K2-3 • Pierre & Frederic (2003), ESO Press Release. “A -1 Family Portrait of the Alpha Centauri System: 0.4 M.; M1-2 50 GJ 176 VLT Interferometer Studies the Nearest Stars” Proxima -2 (days) Period Rotation 0.0 5.0e+9 1.0e+10 1.5e+10 2.0e+10 • Reiners, Seifahrt, Kaufl, Siebenmorgan and 27 Age (years) GJ 3379 SZ UMa Smette (2007), A&A, 471, L5. “Spectral-type 0 Tracks used from BaSTI: A Bag of dependent rotational breaking and strong Kapteyn Stellar Tracks and Isochrones magnetic flux in three components of the late-M http://www.te.astro.it/BASTI/index.php multiple system LHS 1070” 26 0 100 200 300 02468101214 Period Age (Gyr) The above figure illustrates one of the most valuable research products of our study – The middle plot demonstrates the problem with determining the age of a dM star: their nuclear evolution is very slow. The luminosities of dM stars are essentially constant over the Age-Activity Relationship (example given is X-ray activity obtained from the • Continue and expand our photometry of single dM stars with the on-campus billions of years. This means we must find another way of estimating age – magnetic ROSAT archives). Despite the wide range of spectral types, the results are very CCD photometer and the 0.8-m FCAPT promising. Many of the stars with ages ≤ 2 Gyr are members of clusters, moving evolution shown in rotation and X-UV activity. The Age-Rotation plot will serve two main • Carry out photometry of dM stars in open clusters with known ages using the groups or associations whose ages have been extensively studied, including the purposes: delineating the spin-down of dM stars with age and acting as a sort of “Rosetta 1.3-m RCT Castor M.G. – 200Myr, the UMa Stream – 300 Myr, the Hyades Supercluster – 600 Stone” for translating our Activity-Rotation plots into Activity-Age plots. As mentioned in Myr and the HR 1614 M.G. – 2 Gyr). Unfortunately, Proxima Cen (dM5.5) is the only the Period-Activity section, there are numerous stars with well-determined ages < 1 Gyr. • Expand the target lists for both the ASAS-3 and NSVS archives old (> 2 Gyr) dM star with a reliable direct age determination (~5.8 Gyr) from its At any age older than this, there are only the poorly populated HR 1614 M.G., Proxima Cen • Propose new X-ray – UV observations of high-priority targets membership in the α Cen triple system. It is of later spectral type than some of the and a handful of other stars with kinematically estimated ages based on UVW motions. • Once rotation periods / ages are known for the larger sample, we will break younger, more massive and warmer dM stars and will reside in a specific spectral bin Through our photometry of old open clusters and WD-dM binaries, however, we hope to up the Age-Rotation and Age-Activity plots into more narrow spectral bins in our final results. At present, however, it has one of the best determined ages of enrich the sample of dM stars with well-determined ages > 2 Gyr. Our preliminary plot (M0-2, M2.5-4, M4.5-6…), giving us a more precise age calibrator illustrates that dM stars do in fact spin-down with age. Previous studies theorized that dM any dM star and, as such, is very important in our preliminary investigation. The stars • Determine the onset of “total convection” in dM stars through rotation, age stars would operate under a different dynamo mechanism than the solar - dynamo. The with ages ≥ 8 Gyr are all based upon UVW space motion statistical estimates. They α ω and activity determinations include SZ UMa (dM1; UVW: -137, -10, -2), Barnard’s Star (dM4; UVW: -141, 5, 18) “turbulent” dynamo present in dM stars was thought to not affect stellar rotation as the • Compare photometrically determined flare rates for young/old dM stars and Kapteyn’s Star (dM1; UVW: 19, -287, -54). Barnard and SZ UMa are reliably star aged. Our preliminary results would show that, despite which mechanism dM star estimated to be Old Disk stars and Kapteyn is a true Pop II Halo member. dynamos operate under, there is an obvious effect on their rotation rates. • Provide rich datasets (X-UV irradiences) for use in planetary evolution and habitability studies.
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