Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Hourglass as seen with HST/WFPC2   We present a multi-filter HST/WFPC2 UV-optical study of the Hourglass region
in M8. We have extracted the stellar photometry of the sources in the area and
obtained the separations and position angles of the Herschel 36 multiple
system: for Herschel 36 D we detect a possible orbital motion between 1995 and
2009. We have combined our data with archival IUE spectroscopy and measured the
Herschel 36 extinction law, obtaining a different result from that of Cardelli
et al. (1989) due to the improvement in the quality of the optical-NIR data, in
agreement with the results of Ma\'iz Apell\'aniz et al. (2014). A large
fraction of the UV flux around Herschel 36 arises from the Hourglass and not
directly from the star itself. In the UV the Hourglass appears to act as a
reflection nebula located behind Herschel 36 along the line of sight. Finally,
we also detect three new Herbig-Haro objects and the possible anisotropic
expansion of the Hourglass Nebula.

1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat