Detalles de publicación
PP 06023
Resolved Hubble Space spectroscopy of ultracool binary systems
(1)IAC,(2)University of Central Florida,(3)Max-Planck Institut fur Astronomie,
Heidelberg,(4)Astronomy Department, University of California at Berkeley
Using the low-resolution mode of the Space Telescope Imaging
Spectrograph (STIS) aboard the Hubble Space Telescope (HST),
we obtain spectra from 20 spatially-resolved, ultracool dwarfs,
eighteen of which belong to nine very low-mass
binary systems with known angular separations in the range 0.37-0.098
arcseconds. For these dwarfs, we derive their spectral types to be
in the range dM7.5 to dL6 by either obtaining their PC3 index value or
by comparing our STIS spectra with ground-based spectra of similar spectral
resolution from Martin et al. (1999).
We have searched for Halpha emission in each object,
but the emission is clearly detected in only two of them. We find that the
distribution of Halpha emission in our sample is statistically
different from that of single field dwarfs, suggesting an intriguing
anti-correlation between chromospheric activity and binarity for M7--M9.5 dwarfs.
We provide strength measuments of the main photospheric features.
We derive calibrations of spectral subclasses versus F814W and K-band absolute
magnitudes for a subset of 10 dwarfs in 5 binaries that have known trigonometric parallaxes.
Spectrograph (STIS) aboard the Hubble Space Telescope (HST),
we obtain spectra from 20 spatially-resolved, ultracool dwarfs,
eighteen of which belong to nine very low-mass
binary systems with known angular separations in the range 0.37-0.098
arcseconds. For these dwarfs, we derive their spectral types to be
in the range dM7.5 to dL6 by either obtaining their PC3 index value or
by comparing our STIS spectra with ground-based spectra of similar spectral
resolution from Martin et al. (1999).
We have searched for Halpha emission in each object,
but the emission is clearly detected in only two of them. We find that the
distribution of Halpha emission in our sample is statistically
different from that of single field dwarfs, suggesting an intriguing
anti-correlation between chromospheric activity and binarity for M7--M9.5 dwarfs.
We provide strength measuments of the main photospheric features.
We derive calibrations of spectral subclasses versus F814W and K-band absolute
magnitudes for a subset of 10 dwarfs in 5 binaries that have known trigonometric parallaxes.