Parallax of ultra cool dwarfs with 2-meter class telescope

1. Parallax of ultra cool dwarfs with 2-meter class telescope Youfen Wang Shanghai Astronomical Observatory 2012.08.29

2. outline • Introduction • Parallax with robotic Liverpool telescope(LT) • parallax of 5 L dwarfs, submitted • Parallax with another 6-8 L,T dwarfs • Parallax with Lijiang 2.4 meter telescope • Test of precision and problems

3. Introduction mass between 13-72 Jupiter mass, bridge of stars and planets • L dwarfs: cooler then M dwarfs, most of them brown dwarfs • Brown dwarfs: with out steady hydrogen burning in its interior • derive absolute magnitude • Independent, allow to constrain model, thus to study mass, gravity, age, etallicity • only have measured parallax • Surveys for L、T dwarf hunting: 2MASS, SDSS, UKIDSS, CFHT, VISTA, WISE ~ of 1000 L dwarfs , many available to LT and Lijiang 2.4 Telescope Why parallax important? 800 L dwarfs discovered less then 80

4. Parallax with robotic LT • Liverpool Telescope(LT): 2m Ritchey-Chretien Cassegrain • Location and affiliation: • Observatorio del Roque de Los Muchachos on the Canary Island of La Palma in Spain • Liverpool John Moores University United Kingdom • Detector: RATCam, 2048x2048 pixel scale of 0.1395, 4.6 X4.6 arcmin, SDSS z • Robotic: flexibility in scheduling, less oversight

5. Parallax with robotic LT • Observations and data reduction: • Data between 2004 autumn and 2012 summer for 5 L dwarfs as well as another 6-8 targets Reduced through standard LT pipeline, deringed through IRAF rmfringe,bad pixel fixed,centroids using CASU, parallax derived through TOPP(Torino Observatorio Parallax program, Smart et al 2003) • Observed during twilight time, with in 30 minute from meridian, when targets have maximum parallax factor Expose 160 s, 3 exposures each observation ,S/N~50

6. 2M2238+4353 Parallax with robotic LT -5L dwarfs Target list: • Parallaxconsistent with photometric distances • proper motion consistent with the literature , smaller errors • normal solar metallicity, thin disk objects • Important: 3 objects derive Fbol, Lbol and Teff integrating observational and model spectra Paper submitted to MNRAS, referee require more high precision of position and calibration for parallax, we derived one calibration targets which has published value(2M1017+1308), will resubmit later.

7. Parallax with robotic LT - 6more L,T dwarfs 11 targets on SpT-mag diagram.Three binaries found Tardets list for another 6 L,T,derivedparallax • 2M1017+1308can work as calibrator. • Problem remained: check the reliability of these parallax. ps. 2M0034. try to derive parallax of the another 2 targets that have enough data.

8. Procuded by Same company Yunnan astronomical Observatory CCD 2048X2048, pixel scale 0.282 Target and data 2MASS J18212812+1414010 L4.5 J=13.431, H=12.396, K=11.65 Estimated z~17mag，photometry parallax~10pc ~ 100mas Four frames observed 2012,04,12，morning04:07，1h deviate from meridian,160s reduction： Flat field and bias ---iraf, centroids---Sextractor In every frame more than 2000 objects detected Parallax with Lijiang 2.4 telescope • X2=A*x1+B*y1+C，Y2=D*x1+E*y1+F • target instrumental mag ~12.7 • Common star 730 • σx σy 33mas for all object • and 28mas for that brighter than 12 mag (instrumental)

9. Parallax with Lijiang 2.4 telescope • Problem: not as flexible as LT, allocate time by whole night. • Plan: could apply in Sep. or latter, now doing maintence. Thanks!