J/A+AS/124/33 BN Ori UBV photometry & equivalent width (Shevchenko+ 1997)
The FUOR characteristics of the PMS star BN Orionis inferred from new
spectroscopic and photometric observations
Shevchenko V.S., Ezhkova O., Tjin A Djie H.R.E., van den Ancker M.E.,
Blondel P.F.C., de Winter D.
<Astron. Astrophys. Suppl. Ser. 124, 33 (1997)>
=1997A&AS..124...33S 1997A&AS..124...33S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Photometry, UBV ; Equivalent widths
Keywords: circumstellar matter - stars: emission-line - stars: BN Ori -
stars: pre-main-sequence
Abstract:
BN Ori is a young emission-line star with a peculiar light curve.
During the first half of this century the star showed strong irregular
brightness-variations, similar to those of Herbig Ae stars. In the
current half of the century the light curve resembles that of a
FU Ori-object (FUOR, after Ambartsumian 1971Afz.....7..557A 1971Afz.....7..557A). It can
be characterised by an initial large-scale rise in brightness followed
by a gradual decay over a period of about 15-years. From various
photometric patrol programmes we concluded that the star remained at
the same brightness level for the last 30-years. Between 1991 and 1995
the spectrum of BN Ori was intensively observed and was found to
exhibit some unique peculiarities. We have analysed the visual spectra
obtained with the 6m BTA telescope of the SAO, the 60cm and 48cm
telescopes at Mt. Maidanak, the 1.4m CAT and the 1.5m telescope of ESO
and the UV-spectra obtained with the IUE in 1984 and 1986. The spectra
show certain similarities with those of classical FUORs, such as a
large-scale thermal stratification, with Balmer lines showing A6-A7
spectral type wings, while other lines are typical for late F-type
stars. However, in contrast to classical FUORs, BN Ori is not of high
luminosity-class. On the other hand the spectrum also shows
similarities with those of Herbig A7e stars, although these stars have
much stronger absorption lines in the UV from their outer shell and
their circumstellar dust excesses are much larger than for BN Ori.
Also, the rotation rate vsinii of BN Ori is between 180 and 220km/s,
which is typical for A-type stars of 2-5M☉. This may indicate
that BN Ori is a fast rotating FUOR with an intermediate-mass
precursor on which the outburst had a different effect than in the
case of the classical FUORs (which are rotating slower and have a
low-mass T Tauri star as precursor). In the BN Ori outburst most of
the massive gas- and dust shell, characteristic for Herbig Ae stars,
seems to have been removed, except for the Hα- and MgII-emission
region close to the photosphere. The disappearance of the
circumstellar dust shell may explain the drastic variability-change in
the light curve of BN Ori. The mass-accretion rates of BN Ori and
several Herbig A7e stars (derived from the analysis of their
UV-spectra in terms of disc-accretion) suggest that the FUOR outburst
in BN Ori was due to a thermal runaway (Bell, 1994ApJ...427..987B 1994ApJ...427..987B) in
its inner accretion-disc which was triggered by a modest increase in
the accretion rate.
Objects:
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RA (2000) DE Designation(s)
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05 36 29.4 +06 50 01 BN Ori = HD 245465
16 08 34.2 -39 06 17 HR 5999 = HD 144668
05 45 22.5 +09 04 12 FU Ori
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table11 69 182 Identification and source of lines in the
high-resolution visual spectra of BN Ori,
HR 5999 and FU Ori.
table12 46 155 UBVR photometric data of BN Ori
tables.tex 113 564 LaTeX version of the tables
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Byte-by-byte Description of file: table11
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda Wavelength
9- 18 A10 --- Ident Line identification
20- 24 F5.2 eV Ex Excitation energy
26- 28 A3 --- S Line source (1)
30- 33 F4.2 0.1nm EW1 ? BN Ori equivalent width
34 A1 --- u_EW1 Uncertainty flag on EW1
35 A1 --- n_EW1 Note on EW1 (2)
37- 39 I3 km/s FW1 ? BN ORI Full width at half maximum
40 A1 --- u_FW1 Uncertainty flag on FW1
41- 45 F5.2 0.1nm EW2 ? HR 5999 equivalent width
46 A1 --- u_EW2 Uncertainty flag on EW2
47- 48 A2 --- n_EW2 Note on EW2 (2)
49- 51 I3 km/s FW2 ? HR 5999 Full width at half maximum
52 A1 --- n_FW2 [+:] + when two values of FW2,
: uncertainty flag
53- 55 I3 km/s FW2b ? Second FWHM value when n_FW2="+"
57- 60 F4.2 0.1nm EW3 ? FU Ori equivalent width
61- 62 A2 --- n_EW3 Note on FU Ori equivalent width (2)
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Note (1): p: photospheric
c: chromospheric
i: interstellar
s: shell, c.s. envelope
d: disc
Note (2): b: blended
vs: very strong
st: strong
m: medium
w: weak
vw: very weak
EW1 data are from BTO-spectrum Nov.21, 1991 data except when
n_EW1=2 where data are from Kolotilov & Zajtseva
(1976Afz....12...31K 1976Afz....12...31K)
EW2 data are from Tjin A Djie et al. (1989A&AS...78....1T 1989A&AS...78....1T)
EW3 data are from Herbig (1966VA......8..109H 1966VA......8..109H)
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Byte-by-byte Description of file: table12
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Heliocentric Julian date
14- 18 F5.3 mag Vmag V magnitude
21- 25 F5.3 mag U-B ? U-B colour index
27- 31 F5.3 mag B-V ? B-V colour index
34- 38 F5.3 mag V-R ? V-R colour index
43 I1 --- Tel [1,3] Telescope (1)
45 A1 --- Obs Observer (2)
46 A1 --- n_Obs [*] Note on observations (3)
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Note (1): 1: Zeiss 600 reflector (60cm)
3: AZT 14 reflector (48cm)
Note (2): C: A.V. Chernyshev
G: K.N. Grankin
I: M.A. Ibragimov
M: S.Yu Melnikov
P: D.L. Portnov
S: V.S. Shevchenko
Y: S.D. Yakubov
Note (3): Simultaneous with the high-resolution spectrum from SAO (Sect.4.3)
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Acknowledgements: P.F.C. Blondel
(End) Patricia Bauer [CDS] 12-Nov-1996