  In this paper, we revisit the SN1987A neutrino data to see its constraints on
flavor conversion. We are motivated by the fact that most works that analyze
this data consider a specific conversion mechanism, such as the MSW
(Mikheyev-Smirnov-Wolfenstein) effect, although flavor conversion is still an
open question in supernovae due to the presence of neutrino-neutrino
interactions. In our analysis, instead of considering a specific conversion
mechanism, we let the electron antineutrino survival probability
$P_{\overline{e}\overline{e}}$ be a free parameter. We fit the data from
Kamiokande-II, Baksan, and IMB detected spectrum with two classes of models:
time-integrated and time-dependent. For the time-integrated model, it is not
possible to put limits above $1\sigma$ (68% confidence level) on the survival
probability. The same happens for the time-dependent model when cooling is the
only mechanism of antineutrino emission. However, for models considering an
accretion phase, $P_{\overline{e}\overline{e}}\sim0$ is strongly rejected,
showing a preference for the existence of an accretion component in the
detected antineutrino flux, and a preference for normal mass ordering when only
the MSW is present.
