Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Estimating stellar rotation from starspot detection during planetary
  transits   A new method for determining the stellar rotation period is proposed here,
based on the detection of starspots during transits of an extra-solar planet
orbiting its host star. As the planet eclipses the star, it may pass in front
of a starspot which will then make itself known through small flux variations
in the transit light curve. If we are lucky enough to catch the same spot on
two consecutive transits, it is possible to estimate the stellar rotational
period. This method is successfully tested on transit simulations on the Sun
yielding the correct value for the solar period. By detecting two starspots on
more than one transit of HD 209458 observed by the Hubble Space Telescope, it
was possible to estimate a period of either 9.9 or 11.4 days for the star,
depending on which spot is responsible for the signature in the light curve a
few transits later. Comparison with period estimates of HD209458 reported in
the literature indicates that 11.4 days is the most likely stellar rotation
period.

31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con