MisV1147: Quasi-Periodic Fading: Obscuration Events??
MisV1147 is a new emission-line object of unknown type, which was discovered
in 2001 by the MISAO project. It was observed on N. Ohkura's images taken
on 2001 Sept. 17. To be surprised, it was fainter than 14 mag in 2001 September.
Then it brightened rapidly to 12.5 mag within two weeks, and it kept
slow brightening during 2001 October (vsnet-campaign-unknown
4).
S. Yoshida reported the MISAO observations and that it is not a red variable
(vsnet-campaign-unknown
5, 27).
The bright state at 13th mag was terminated by a sudden fading on February
5 (vsnet-campaign-unknown
26, 36,
46),
when P. A. Dubovsky detected a fading to 13.9mag (vsnet-campaign-unknown
64). The object then gradually faded (vsnet-campaign-unknown
66), and it stopped at mag about 13.5-13.6 (vsnet-campaign-unknown
68).
M. Simonsen reported that the object was observed to be variable between
12.9-14.2 mag during June-August (vsnet-campaign-unknown
91, 92).
On August 28, M. Simonsen reported that MisV1147 has undergone an unexpected
dramatic fading again (14.2mag). The faint state was also confirmed on
August 31 at <14.7mag by M. Simonsen (vsnet-campaign-unknown
96). If the star is a Herbig Ae/Be star, this episode may be related
to "eclipse"-like fading of this class of stars (vsnet-campaign-unknown
95). The object was then quickly recovering from the deep minimum (vsnet-campaign-unknown
99, 104).
The next fading was reported on September 17 (vsnet-campaign-unknown
105).
It was in a very faint state during September 29 - October 2 (vsnet-campaign-unknown
106, 107,
108,
109,
110,
111).
The object then brightened to 13.7mag on October 5 (vsnet-campaign-unknown
112, 113,
114,
118).
The object again became fainter than 13.4mag since October 20. It further
faded to <14.7mag on October 29 (vsnet-campaign-unknown
121, 122).
T. Kato suspected that there may be a quasi-cycle of 30-40 d (vsnet-campaign-unknown
120). The object started brightening from a deep minimum in the early
November (vsnet-campaign-unknown
123). On November 10, the object was reported to be 14.5mag, which indicated
that the object became fainter again (vsnet-campaign-unknown
124, 125).
This new fading was observed as expected from its quasi-periodicity. The
object started to fade on Nov. 27. On Nov. 28, the objected was observed
1 mag fainter than two days before. T. Kato commented that this observation
may suggest that MisV1147 can be a rare deeply eclipsing system among (likely)
Herbig Ae/Be stars (vsnet-campaign-unknown
129, 130).
C. Lloyd commented that this feature may well be a true eclipse but some
Ae stars do show Algol-like fades and this star clearly has other dramatic
fades that look like obscuration events (vsnet-campaign-unknown
131).
The object brightened up on Dec. 1 images taken at the Kyoto team. The fading
episode from the end of November seems to be slightly earlier than expected
from the past (semi-?)periodicity (vsnet-campaign-unknown
132). The observation by the Kyoto team on December 6 detected the next
fading. It suggests that the fadings are not strictly periodic, but quasi-periodic
(vsnet-campaign-unknown
137, 148,
150,
151).
The object started recovering from the fading on December 12 (vsnet-campaign-unknown
155, 157,
162).
T. Kato reported that the object was again in a faint state on December
23, which may be inconsistent with the proposed quasi-periodic fadings. The
fadings may be obscuration events (vsnet-campaign-unknown
165, 166,
167).
The object had recovered on December 25 (vsnet-campaign-unknown
168).
C. Lloyd commented that it is quite likely that this is a binary, possibly
with some true periodic behaviour buried in the variations (vsnet-campaign-unknown
138). Based on measurements by A. Henden, the object gets redder in
V-R and R-I, but bluer in B-V as it fades (vsnet-campaign-unknown
139, 141).
T. Kato commented that it is one of the very signatures of deep Herbig Ae/Be-type
fadings (vsnet-campaign-unknown
142). J. Greaves mentioned that to measure polarization would be important
to determine whether the object is a Herbig Ae/Be star or not (vsnet-campaign-unknown
143, 144,
145,
146,
147,
149).
D. West estimated the spectral class of the object to be B4V or B2I from
de-reddened color from the A. Henden's observation #1 and A7V or F0I from
the observation II (vsnet-campaign-unknown
133, 134,
135,
136,
139,
140,
152,
153,
154,
156,
159,
158).
D. West reported that the object shows weak H_alpha emission, which is consistent
with the idea that this object is a YSO (vsnet-campaign-unknown
163, 164).
Links:
MisV1147 Charts provided by M. Simonsen:
http://joevp.20m.com/cgi-bin/i/charts/sxncharts/Cep_MisV1147_sxn.gif
http://joevp.20m.com/cgi-bin/i/charts/sxncharts/Cep_MisV1147_Rsxn.gif
[vsnet-campaign-unknown
21, 42]