1997A&AS..124...33S


C.D.S. - SIMBAD4 rel 1.7 - 2020.05.26CEST06:42:01

1997A&AS..124...33S - Astron. Astrophys., Suppl. Ser., 124, 33-54 (1997/July-0)

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. and DE WINTER D.

Abstract (from CDS):

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). 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 pecularities. 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 v sini i 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) in its inner accretion-disc which was triggered by a modest increase in the accretion rate.

Abstract Copyright:

Journal keyword(s): circumstellar matter - stars: emission-line - stars: individual: BN Ori - stars: pre-main-sequence

VizieR on-line data: <Available at CDS (J/A+AS/124/33): table11 table12 tables.tex>

Status at CDS:  

Simbad objects: 17

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Number of rows : 17

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* XY Per Ae* 03 49 36.3362509899 +38 58 55.551266650 12.12 10.14 9.58 9.54 8.40 A2II+B6 141 0
2 V* UZ Tau ** 04 32 43.02168 +25 52 30.9036           M4Ve+M1/3Ve 283 0
3 V* VY Tau Or* 04 39 17.4208176970 +22 47 53.361809753     9.00     M0Ve 180 0
4 V* UX Ori Ae* 05 04 29.9881676817 -03 47 14.288047238 10.25 10.93 8.70 9.62 9.43 A4IVe 331 1
5 V* T Ori Ae* 05 35 50.4483740019 -05 28 34.923375739 12.724 11.637 11.248 10.09 10.043 A3IVeb 228 0
6 V* BN Ori Ae* 05 36 29.3483164157 +06 50 02.174009216   10.04 8.80     F4e 60 0
7 V* BF Ori Ae* 05 37 13.2623698298 -06 35 00.565420577 10.37 10.00 9.69 10.06 9.31 A7III 269 0
8 V* V351 Ori Ae* 05 44 18.7949420603 +00 08 40.411665342 9.44 9.22 8.87     A7V 98 0
9 V* FU Ori Or* 05 45 22.3650208559 +09 04 12.296285806   10.72 9.60     F0Iab 702 1
10 V* V646 Pup Or* 07 50 35.5923632458 -33 06 23.904713538   13.96 12.65 12.04   ~ 61 0
11 HD 325367 Or* 16 03 05.4914377137 -40 18 25.426543472   11.40 8.50     M0 274 0
12 V* V856 Sco Ae* 16 08 34.2868591379 -39 06 18.326059778 7.66 7.41 7.05 6.92   A7IIIne_sh 349 0
13 V* WW Vul Ae* 19 25 58.7494596284 +21 12 31.333220807 11.46 10.99 10.25 10.38 10.12 A2IVe 214 0
14 * 21 Vul dS* 20 14 14.5296180620 +28 41 41.335467713   5.365 5.189     A7IVn 87 0
15 V* V1515 Cyg Or* 20 23 48.0159810586 +42 12 25.780858811   15.26 13.39 12.03   G0/G2Ib 209 0
16 EM* LkHA 190 Or* 20 58 53.7336698326 +44 15 28.384667940   14.26 12.33 12.13   F7/G3I/IIe 474 0
17 EM* LkHA 120 Or* 21 01 09.2068364908 +50 21 44.803310926 13.37 13.09 11.99 11.75   F0/F4-G5 187 1

    Equat.    Gal    SGal    Ecl

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2020.05.26-06:42:02

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