J/A+A/591/A43 Differential rotation in solar-like stars (Distefano+, 2016)
Lower limit for differential rotation in members of loose young stellar associations. Distefano E., Lanzafame. A.C., Lanza A.F., Messina S., Spada F. <Astron. Astrophys. 591, A43 (2016)> =2016A&A...591A..43D 2016A&A...591A..43D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Associations, stellar ; Stars, distances ; Effective temperatures ; Stars, masses Keywords: stars: solar-type - starspots - stars: rotation - galaxy: open clusters and associations: general - techniques: photometric Abstract: Surface differential rotation (SDR) plays a key role in dynamo models and determines a lower limit on the accuracy of stellar rotation period measurements. SDR estimates are therefore essential to constrain theoretical models and infer realistic rotation period uncertainties. We measure a lower limit to SDR in a sample of solar-like stars belonging to young loose stellar associations with the aim of investigating how SDR depends on global stellar parameters in the age range (4-95Myr). The rotation period of a solar-like star can be recovered by analyzing the flux modulation caused by dark spots and stellar rotation. The SDR and the latitude migration of dark-spots induce a modulation of the detected rotation period. We employed long-term photometry to measure the amplitude of such a modulation and to compute the quantity ΔΩphot=2π/Pmin-2π/Pmax that is a lower limit to SDR. We find that ΔΩphot increases with the stellar effective temperature and with the global convective turn-over timescale tauc, which is the characteristic time for the rise of a convective element through the stellar convection zone. We find that ΔΩphot is proportional to Teff2.18±0.65 in stars recently settled on the ZAMS. This power law is less steep than those found by previous authors, but closest to recent theoretical models. We investigate how ΔΩphot changes in time in a 1M☉ star. We find that ΔΩphot steeply increases between 4 and 30Myr and that it is almost constant between 30 and 95Myr. We find also that the relative shear increases with the Rossby number Ro. Although our results are qualitatively in agreement with hydrodynamical mean-field models, our measurements are systematically higher than the values predicted by these models. The discrepancy between ΔΩphot measurements and theoretical models is particularly large in stars with periods between 0.7 and 2d. Such a discrepancy, together with the anomalous SDR measured by other authors for HD 171488 (rotating in 1.31d), suggests that the rotation period could influence SDR more than predicted by the models. Description: The average rotation period, the parameters ωmin, ωmax, ΔΩphot and alphaphot are reported for 111 late-type stars belonging to loose young stellar associations. For each target, the main physical parameters are also reported. The Spectral types, the photometric data and the distances are taken by previous works. The masses, the effective temperatures and the convective turn-over time-scales have been inferred by comparing absolute magnitudes with different sets of theoretical isochrones. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 71 111 List of the target investigated in the present work table3.dat 94 111 Results table4.dat 62 111 Data used to compute absolute magnitudes table5.dat 85 109 Stellar parameters inferred by the comparison of J and H magnitudes with different theoretical models -------------------------------------------------------------------------------- See also: J/AJ/138/312 : Activity of bright solar analogs (Hall+, 2009) J/A+A/552/A78 : Solar like stars radial velocities (Zechmeister+, 2013) J/A+A/572/A34 : Pulsating solar-like stars in Kepler (Garcia+, 2014) J/A+A/520/A15 : RACE-OC project: YSOs within 100pc (Messina+, 2010) J/A+A/532/A10 : RACE-OC project. II. (Messina+, 2011) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 26 A26 --- ID ASAS or SuperwaspID (G1) 29- 45 A17 --- Name Other designation 46- 60 A15 --- Assoc Association 61- 64 F4.2 mag B-V B-V colour index (2) 66- 71 A6 --- SpType MK spectral type (2) -------------------------------------------------------------------------------- Note (2): The colour indexes and spectral types have been taken from Messina et al. (2010, Cat. J/A+A/520/A15 and 2011, Cat. J/A+A/532/A10). -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 26 A26 --- ID ASAS or SuperWasp ID (G1) 28- 32 F5.2 dAverage rotation period 34- 39 F6.3 rad/d omin Lowest angular frequency 41- 45 F5.3 rad/d e_omin Error on lowest angular frequency 47- 52 F6.3 rad/d omax Highest angular frequency 54- 58 F5.3 rad/d e_omax Error on highest angular frequency 60- 64 F5.3 rad/d DOp ΔΩphot = omax-omin 66- 70 F5.3 rad/d e_DOp Error on DeltaOmega_phot 72- 76 F5.3 --- alphap αphot = (omax-omin)/omax 78- 82 F5.3 --- e_alphap Errror on alpha_phot 84- 86 I3 --- Np Number of time-series points 89 A1 --- fQ [ABC] Quality flag (1) 93- 94 A2 --- fT Time-series flag (2) -------------------------------------------------------------------------------- Note (1): Quality flag as follows: A = stars with Np> 200 B = stars with Np between 100 and 200 C = stars with Np<100 Note (2): This flag indicates the time-series used to compute DeltaOmegaphot. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 26 A26 --- ID ASAS or SuperWasp ID (G1) 29- 34 F6.2 mas Plx ?=- Parallax 36- 42 F7.3 pc Dist Distance 46- 50 F5.2 mag DM Distance modulus 52- 55 F4.2 mag JMAG ?=- Absolute J magnitude (1) 57- 60 F4.2 mag HMAG ?=- Absolute H magnitude (2) 62 I1 --- Ref [1/6] Reference (3) -------------------------------------------------------------------------------- Note (1): This magnitude has been obtained by adding the Distance Modulus DM to the 2MASS J magnitude. The Distance Modulus has been inferred by using the parallax or the distance reported in other works Note (2): This magnitude has been obtained by adding the Distance Modulus DM to the 2MASS H magnitude Note (3): The reference number indicates the work from which the parallaxes and/or the distance have been taken, as follows: 1 = Torres et al., 2006, Cat. J/A+A/460/695 2 = Torres et al., 2008hsf2.book..757T 2008hsf2.book..757T 3 = Perryman et al., 1997A&A...323L..49P 1997A&A...323L..49P 4 = Zuckerman et al., 2000ApJ...544..356M 2000ApJ...544..356M 5 = De Silva et al., 2013, Cat. J/MNRAS/431/1005 6 = Murphy et al., 2013, Cat. J/MNRAS/435/1325 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 26 A26 --- ID ASAS or SuperWasp ID (G1) 28- 31 F4.2 Msun MSiess Mass from Siess et al. (2000A&A...358..593S 2000A&A...358..593S) models (1) 36- 42 F7.2 K TeffSiess Effective temperature from Siess et al. (2000A&A...358..593S 2000A&A...358..593S) models (1) 44- 47 F4.2 Msun MBar ?=- Mass from Baraffe et al. (1998, Cat. J/A+A/337/403) models (1) 50- 56 F7.2 K TeffBar ?=- Effective temperature from Baraffe et al. (1998, Cat. J/A+A/337/403) models (1) 58- 61 F4.2 Msun MSpada ?=- Mass from Spada et al. (2013ApJ...776...87S 2013ApJ...776...87S) models (1) 66- 72 F7.2 K TeffSpada ?=- Effective Temperature from Spada et al. (2013ApJ...776...87S 2013ApJ...776...87S) models (1) 74- 79 F6.2 d tauC ?=- Turnover convective time-scale from Spada et al. (2013ApJ...776...87S 2013ApJ...776...87S) models (1) 81- 85 F5.3 --- Ro ?=- Rossby number (2) -------------------------------------------------------------------------------- Note (1): Stellar parameters inferred by the comparison of the J and H magnitudes with the theoretical isochrones of Siess et al. (2000A&A...358..593S 2000A&A...358..593S), Baraffe el al. (1998, CaT. J/A+A/337/403) and Spada et al. (2013ApJ...776...87S 2013ApJ...776...87S). Note (2): The Rossby Number is computed as Ro=
/tauC -------------------------------------------------------------------------------- Global notes: Note (G1): ASAS_JHHMMSS+DDMM.m or SWASP1_JHHMMSS.SS+DDMMSS.s -------------------------------------------------------------------------------- Acknowledgements: Elisa Distefano, eds(at)oact.inaf.it
(End) Patricia Vannier [CDS] 15-Apr-2016
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