Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Blazhko-type modulation in the double-mode RR Lyrae stars of the OGLE
  Galactic bulge collection   We present the analysis of Blazhko-type modulation in double-mode RR Lyrae
(RRd) stars found in the OGLE photometry of the Galactic bulge. Modulation is
detected in 15 stars. Most of them have non-typical period ratio of the radial
modes. In the Petersen diagram, at a given period of the fundamental mode, they
are located significantly below or above the sequence formed by the majority of
RRd stars.
  Multi-periodic modulation is very frequent; two or three modulation periods
are detected in 8 stars. Modulation periods vary from ~20 to more than 300
days. Radial mode amplitudes can be modulated by a few to nearly hundred per
cent. Both radial modes may be modulated with the same period. More commonly
however, dominant modulation for the fundamental mode has different period than
dominant modulation for the first overtone. Quite often modulation of only one
mode is detected in the data. We find a clear feedback between pulsation
amplitude of the dominant mode and mean stellar brightness: lower the pulsation
amplitude, brighter the star. At phases of low pulsation amplitude, the mode
periods are prone to fast changes. All the stars share the common feature:
their pulsation properties are non-stationary. Amplitudes and phases of the
radial modes vary irregularly on a long time-scale of a few hundred or thousand
days. The short-term modulations are also irregular.
  One of the stars has switched the pulsation mode recently: from single-mode
fundamental mode pulsation to RRd state. In other star the non-radial mode with
characteristic ~0.61 period ratio to the first overtone is detected. This
non-radial mode is likely modulated with the same period as the radial modes.

24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th