[IAUC] CBET 690: 20061024 : NEW NEBULA NEAR IRAS 04376+5413

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                                                  Electronic Telegram No. 690
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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NEW NEBULA NEAR IRAS 04376+5413
     B. Stecklum, Thueringer Landessternwarte, Tautenburg, writes that
CCD imaging of the dark cloud LDN 1415 (Lynds 1962, Ap.J. Suppl. 7, 1),
performed with the 2-m Tautenburg telescope in its Schmidt configuration
(correction-plate diameter 1.34 m, f/2) on 2006 Apr. 2 revealed the
presence of a new compact arc-shaped nebula with a size of 20".  The
brightness peak of the nebula, located at R.A. = 4h41m35s.8, Decl. =
+54d19'20" (equinox 2000.0), is 4" north of 2MASS J04413594+5419168.
This 2MASS source and its southern companion, 2MASS J04413587+5419116,
are the reddest objects in this region of the dark cloud, and are within
the positional error ellipse of IRAS 04376+5413.  The 2MASS images show
that their morphology changes from bands J to K_s.  Thus, they are of
non-stellar origin and resemble bipolar outflow lobes of a young stellar
object that is seen close to edge-on.  On the detection CCD images, the
total magnitudes of the nebula within an aperture of 10" radius are R =
15.9 +/- 0.1 and I = 14.6 +/- 0.1.  The nebula is not seen on an
archival Kiso Schmidt telescope I-band image taken on 2001 Jan. 22
(limiting magnitude 18.4).  It is detected at the 2-sigma level on a
Palomar Sky Survey II N plate taken on 1996 Dec. 3, with a total
magnitude of 18.4 +/- 0.2.  Thus, it brightened by 3.8 mag within five
years.  Brightness monitoring showed a marginal decrease of the R and I
magnitudes by at most 0.1 mag between 2006 April and Oct. 16.  Optical
spectra of the nebula taken with the Tautenburg telescope at the Nasmyth
focus (f/10.5, resolution approximately 2500) on 2006 Sept. 21 reveal
the presence of a P-Cyg profile of the H_alpha line.  This indicates
that the nebula is the result of an 'FUor' or 'EXor' outburst from the
embedded source.  FUor and EXor eruptions of young stellar objects are
caused by strongly enhanced accretion from the surrounding disk (e.g.,
Hartmann and Kenyon 1996, ARAA 34, 207).  The pre-outburst optical,
near-infrared, and IRAS fluxes imply a luminosity of 0.16 that of the
sun in the range 0.9-60 microns for the likely distance of 170 pc.
Thus, the source is by far the least luminous among the known FUors and
EXors.  It is accompanied by two Herbig-Haro objects -- the brighter one
situated 30" north of the nebula, and the fainter one 1' to the south.
Both are aligned with the axis joining the two 2MASS sources.  A bent
tail of H_alpha emission stretches about 50" north of the bright
Herbig-Haro object.  To the north, the new nebula is surrounded by
fainter arcuate and extended emission.


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                         (C) Copyright 2006 CBAT
2006 October 24                  (CBET 690)               Daniel W. E. Green