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Alla tietoa upouudesta DS-kohteesta M78:ssa Orionissa. Tarkastakaapa vanhat
kuvat ja visuaalihavainnot. Milloin uusi sumu on ilmestynyt? Sumun
kehittymistä kannattaa seurata.
Arto Oksanen arto.oksanen at jklsirius.fi
Jyvaskylan Sirius ry, Kyllikinkatu 1, FIN-40100 Jyväskylä, Finland
Tel: +358-40-5659438 Fax: +358-14-4157803
Nyrola Observatory http://www.ursa.fi/sirius/nytt/nytt_info.html
From: Brian Skiff [mailto:Brian.Skiff_at_lowell.edu]
Sent: 9. helmikuuta 2004 6:02
Subject: ÄAAVSO-DISÅ Erupting star near Herbig-Haro 22
Jay McNeil (Paducah KY) recently noticed that a new nebula has appeared
in the region of M78 in Orion. This was observed with a small CCD camera
set-up. Passing this information along to Herbig-Haro expert Bo Reipurth
(Univ Hawaii), it has been found that the nebula has resulted from the
outburst of an embedded star behind the thick dark clouds in the region.
The event is possibly similar to eruptions of EX Lupi (prototype of the
EXor variables). Material has been submitted for an IAUC announcement,
but there is no reason follow-up observations should be delayed now that
the Moon is getting out of the way in the evening.
McNeil's Nebula (as it is being called for now) is about an arcminute
across, and is essentially a new deep-sky object---and is probably a visual
object. It is centered at roughly: 5 46 14 -00 05.8 (J2000). Those with
CCD cameras will immediately see what's going by comparing new images with
your favorite archive DSS images.
The erupting variable, which is too faint (at present) to appear in
McNeil's images, is located at the tapered southern tip of the new nebula,
and has been observed previously only from the near-IR and longward:
IRAS 05436-0007 = 2MASS J05461313-0006048: 5 46 13.14 -00 06 04.8 (J2000)
...where the position is from 2MASS. The 2MASS photometry is:
J = 14.74 +/- 0.03
H = 12.16 0.03
Ks = 10.27 0.02
...which was taken on 7 Oct 1998 (JD 2451093.8). Note the whopping red
J-K color (J-K=4.5). The star appears in no visible-light sky survey image
(even at I), and was thus much fainter than red magnitude 19 at least, but
now about R ü17.
There are two somewhat brighter stars about 1'.5 northeast, in fact,
the only two readily visible stars of any kind in a large area around the
new object. The pair are 20" apart. The brighter, northeastern star is
a T Tauri-type star of spectral type K2e. Various data are shown below.
LkHA 301 = GSC 4768-0171: 5 46 19.47 -00 05 20.0 (UCAC2)
2MASS: J=10.69, H=9.66, K=9.00 +/- 0.03
V=14.8 B-V=1.3 (Lick NPM2)
CMC12: Sloan r': 13.85 +/- 0.07 (n=3)
GSC-2.2: mr=12.3, mb=13.8
GSC: mb=15.8, mv=14.2
The star has an approximate V = 14.5 and R = 13.9 but note that there is
no genunine photometry available except the 2MASS data. (I'd have more
confidence in the Carlsberg (CMC12) red magnitude if there were more
observations.) The star does not appear in ASAS-3 or TASS MkIV; data in the
TASS MkII 'tenxcat' are clearly for the combined light of this star and its
companion. The star is not a known variable, but likely to have variations
of ü0.1 mag. due to spottedness and/or flaring.
The slightly fainter companion star appears to be not an emission-line
star, and is possibly an ordinary star and thus suitable as a comparison
for the erupting variable:
GSC 4768-0696: 5 46 18.90 -00 05 38.2 (UCAC2)
2MASS: J=11.20, H=10.17, K=9.72
CMC12: Sloan r': 14.80 +/- 0.38 (!) (n=3)
GSC-2.2: mr=13.5, mb=15.3
This star is approxiamtely V = 15.5, and R = 14.5, but these are especially
rough values. The 2MASS J-K color indicates the star is fairly red or
strongly reddened---or both.
This isn't a good set-up as far as differential comp stars, but on the
other hand, the Landolt standard fields in Selected Area 97 are only
2 degrees east at the same Declination.
The desiderata are perhaps obvious: VRIJHK etc photometry and spectra.
Another interesting aspect is to trace the development of the accompanying
nebula. Surely the region has been imaged often over, say, the last two
observing seasons. When did the nebula show up?
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