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The Close Binary Central Star of the Young
Planetary Nebula HB12
a
a
b
C. H. Hsia , W. H. Ip , J.Y. Hu
a
Institute of Astronomy, National Central University, Taiwan
b
Beijing Astronomical Observatory, Beijing, China
ABSTRACT
Young planetary nebulae play an important role when intermediate-mass stars (0.8~8M⊙) evolve from the proto-planetary nebula (PPN)
phase to the planetary nebula (PN) phase (Iben & Renzini, 1983, ARA&A, 21, 271). Many young planetary nebulae displayed marked bipolar
structures as they evolve away from the proto-planetary nebulae (PPNe) phase. One possible cause of their bipolarity might have to do with
the binary nature of the central stars. We report here our analysis of time-series LOT photometric measurements of the well-known young PN,
Hubble 12(HB 12), which is famous for its extended hourglass-like envelope. In addition to the potential presence of a close binary system ,
the characteristic absorption lines (MgⅠ,CN) of the spectrum show the possibility of a low-mass cool star.
WHY IMPORTANT?
RESULTS
 The dynamical structures of young planetary nebulae (PNe)
represent the end state of all kinds of low-mass stars. From
their spectral structures, we can study the dynamical ages,
history of evolution, physical nature of the central star(s), and
mass distribution.
 Some structures of young planetary nebulae still keep the
evolutionary signature of Asymptotic Giant Branch (AGB)
phase.
 Bond et al.(1990) found that half of 13 planetary nebulae with
binary nuclei show the butterfly or elliptical morphologies,
soker(1997) explained planetary nebula structures using
orbital interactions in binary system, and Marco et al.(2004)
used a radial-velocity (RV) survey to observe the planetary
-nebula nuclei (PNNi), they found that 10 out of 11 well
-observed PNNi are binary systems.
OBSERVATIONS
 Time-series photometric
measurements of HB 12
using the Lulin Onemeter Telescope (LOT).
Fig 2.Two phase plots of R band (Up) and I
band (Down) of the adjusted HB 12 data
to a frequency of 7.06 c/d ~ 0.14151775 d.
Fig 3. The power spectrum of the photometric data
of HB 12.
Fig 4. The observed spectrum of HB 12
in the wavelength range from ~
3500 A to 9050 A .The spectrum
can be decomposed into the
white dwarf and the cooler star
contributions.
 Medium spectral
resolution (R~5500) and
low spectral resolution
(R~2400) measurements
of HB 12 using the 2.16m
spectrograph at Beijing
Astronomical Observatory
(BAO).
Fig 1. The image of the young
p lanetary nebula HB 12
taken through the
narrowband filter [NII] with
the HST WFPC2
DATA REDUCTION
Data were calibrated using standard IRAF procedures.
 Photometry: The data were processed with the standard
APPHOT package. Differential photometric
measurements were carried out respect to three
comparison stars.
 Spectra: The spectral data were processed with standard
package, which includes bias and flat-field
correction , cosmic-ray removal, Wavelength
calibration and flux density calibration based on
two spectral standards.
ACKNOWLEDGMENT
This work was partially supported by the National Science Council of
Taiwan under NSC 93-2752-M-008-001-PAE and NSC 93-2112-M
-008-006.
We would like to thank Prof. Sun Kwok at University of Calgary, Prof.
Chou Yi at National Central University, and Dr. Jinzeng Li at Beijing
Astronomical Observatory for useful discussions.
Fig 5. (left) The spectral region centered at 4350 A. The characteristic absorption lines (CN λ4216, G band) of
late type star(G8~k2) can be easily identified. (right). The spectral region centered at 5450 A. The
characteristic absorption lines (the MgⅠ triplet λλ5167-72-83) of late type star(G8~k2) can be identified.
DISCUSSION
 According to our observation (photometry and spectra), the central object of HB 12 might be
a close binary (with a possible period of the multiple of 0.14157175 d.). This is the first
probable detection of the central stars at HB 12.
 We found no evidence of photometric variations over one day from our observational data. In
view of this, the nucleus of HB 12 is a short-period (< 1 day) binary system.
 According to our BAO spectra, the companion of central star of HB 12 might be a late type star.
FUTURE WORK
 The spectral type of the companion of central star of HB 12 will be clarified by obtaining a
comprehensive set of high resolution spectrographic measurements at BAO in Oct. 2005.
 A more accurate period of the central stars of HB 12 will be produced by obtaining a
comprehensive set of high-time series photometric measurements at LOT in 2005.
REFERENCES
Bond, Howard E.; Livio,Mario.,ApJ,355,568B,1990
Handler,G.; Mendez,R.H.; Medupe,R.; Costero,R.; Birch,P.V.; and 7 coauthors,A&A,320,125H,1997
Handler,G..,A&AS,135,57H,1999
Iben & Renzini, ARA&A,21, 271,1983
De Marco, Orsola; Bond, Howard E.; Harmer, Dianne; Fleming, Andrew J. ApJL, 93, 602, 2004
Soker, N.,ApJS,112,487,1997