NEW sdB Eclipsing Binary Systems
Subdwarf
B stars (sdB) are defined as having temperatures ranging from 20,000-42,000 K,
masses of about .5 Msun, and radii of about .2 Rsun (Randall
et al 2005). SdB stars belong to
the extended horizontal branch (EHB) with higher surface gravity and lower
luminosities than main sequence stars (Saffer et al 1994).
Combination of the
Northern Sky Variability Survey (NSVS; Wozniak et al., 2004) and the Two Micron
All Sky Survey (2MASS; Strutskie et al. 2006) allows for the search of binary
systems containing subdwarf B (sdB) stars. NSVS data was used to find light
curves for systems which contained narrow eclipses while the 2MASS data was
used to find color indices that matched for systems containing a sdB star. For periods longer than one day, we
searched for systems that would contain a sdB plus an M2 star or later due to
the fact that narrowness and color would be distinct in those systems. For periods shorter than one day, we
picked systems that exhibited reflection effect and showed variability and
appeared blue.
Below is a table with the
8 new possible sdB binaries that we have found. Linked to each star name is the NSVS page on that star. The last star listed is HW Vir and is a
already known eclipsing sdB system.
Also given is a light curve for each star. Please note that the epochs are not derived from one time of
minimum, but are rather from the aggregate phased light curve. The periods are from the shape of this
and not from several times of minimum.
Therefore, predictions at times of minimum at many epochs later than the
original observations should be viewed with caution. Also, the classification of the long period systems is
problematic. In a light curve with
a limited number of measures, a few bad points can masquerade as a narrow
eclipse.
Nicole Kelley: nicole_kelley [at] berkeley.edu University of California, Berkeley Summer REU Intern at UGA |
J. Scott Shaw: jss [at] physast.uga.edu University of Georgia Department of Physics and Astronomy |
Star Name |
LC |
RA (2000) |
DEC (2000) |
Magnitude |
Points |
Epoch |
Period |
2MASS ID |
Cross ID |
NSVS**** |
link |
deg |
deg |
HJD 2451000+ |
days |
||||
97.760818 |
+61.241322 |
10.690 |
167 |
426.306 |
9.74498 |
06310268+6114290 |
|||
314.365967 |
+56.767681 |
11.225 |
238 |
274.352 |
1.23981 |
20572772+5646059 |
GSC 03960-01027 |
||
130.249039 |
+39.933891 |
12.099 |
261 |
274.202 |
0.16004 |
08410015+3955545 |
PG0837+401 |
||
165.901794 |
+41.600521 |
10.627 |
250 |
274.206 |
3.63908 |
11033644+4136018 |
GSC 03012-01043 |
||
233.455994 |
+37.991459 |
13.608 |
167 |
273.374 |
0.16177 |
15334944+3759282 |
FBS 1531+381 |
||
270.800568 |
+32.186970 |
11.938 |
257 |
275.369 |
1.85363 |
18031193+3211137 |
|||
91.326370 |
+20.742229 |
11.772 |
182 |
409.439 |
4.74089 |
06051838+2044321 |
|||
166.277390 |
-9.025840 |
12.649 |
99 |
274.283 |
1.23235 |
11050663-0901335 |
|||
191.084351 |
-8.671140 |
11.212 |
121 |
274.287 |
0.11671 |
12442024-0840168 |
HW Vir |
Acknowledgements Thank you to M. Wood at Florida Institute for Technology and J. Coughlin at Emory University. This work has been funded by a partnership between the National Science Foundation (NSF AST-0552798) Research Experiences for Undergraduates (REU) and the Department of Defense (DoD) ASSURE (Awards to Stimulate and Support Undergraduate Research Experiences) programs. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Aeronautics and Space Administration and the National Science Foundation. We also thank Northern Sky Variability Survey (NSVS) and the University of California, operator of the Los Alamos National Laboratory under Contract No. W-7405-ENG-36 with the US Department of Energy.
References:
Randall, S.K.; Fontaine, G.; Brassard, P., and Bergeron, P. 2005, AJ, 161, 456-479
Saffer, R.; Bergerson, P.; Koester, D., and Liebert, J. 1994, ApJ, 432, 351
The Two Micron All Sky Survey (2MASS)
Skrutskie, M.F. et al. 2006, AJ, 131, 1163
Wozniak, P.R., et al., 2004, AJ, 127, 2436, Northern Sky Variability Survey: Public Data Release