J/A+A/702/A263 T CrB and RS Oph spectra and equivalent widths (Iijima+, 2025)
Pre-outburst spectroscopic phenomena of RS Oph and active state of T CrB.
Spectroscopic phenomena of RS Oph and T CrB.
Iijima T., Narusawa S.
<Astron. Astrophys. 702, A263 (2025)>
=2025A&A...702A.263I 2025A&A...702A.263I (SIMBAD/NED BibCode)
ADC_Keywords: Novae ; Stars, double and multiple ; Spectra, optical
Keywords: binaries: symbiotic - novae, cataclysmic variables -
stars: individual: RS Oph - stars: individual: T CrB
Abstract:
RS Oph and T CrB are well-known symbiotic recurrent novae. RS Oph
experiences outbursts every 10-20 years, and T CrB roughly every 80
years. Their next outbursts are predicted to take place in several
years.
We monitored spectral variations in these objects to investigate
whether there was any prevenient spectroscopic outburst phenomena.
High- and low-resolution optical spectra were obtained at the Asiago
Astrophysical Observatory.
A flare-up of the emission line He II 4686 was observed in April 1994
in a spectrum of RS Oph. This was probably the first sign of the 2006
outburst, because similar but weaker flare-ups followed in October.
1998, August 2001, April 2003, May 2004, and July 2005, namely, with
the same interval on a logarithmic scale (one flare-up expected in
February 2005 was not observable at our observatory). These flare-ups
were possibly related to the instability of the accretion disk. Other
signs of impending outbursts are the strengthening of the absorption
lines of an A-type star, which occurs about 950±50 days before an
outburst; this occurred in 2006, 2021, and probably in 1985. We
detected deep absorption lines of A-type star in March 2024 (on
JD2460392). We wished to determine whether these absorption lines
again strengthened 950 days before the next outburst, the expected
date of which is around JD2461342 (October-November 2026). This
would mean the interval from the last outburst in 2021 would be only 5
years which would be the shortest in the history of RS Oph. A more
precise forecast will be possible if we detect a flare-up of He II
4686 in March 2026 (JD2461116, which would be about 226 days before
the expected outburst. The most recent active state of T CrB lasted
from December 2014 to around November 2022. The emission line He II
4686 was prominent during the active state, but no flare-up was
observed.
Description:
Table 1: Low-resolution spectra of RS Oph were mainly obtained with a
Boller and Chivens grating spectrograph which had been mounted on the
182cm Copernics telescope at the Mount Ekar station of the
Astronomical Observatory of Padova until 1997. The spectrograph was
translated on the 122cm Galileo telescope at the Asiago Astrophysical
Observatory of the University of Padova in 1998. The spectral
resolution was λΔλ∼1000 with a 600 groove/mm
grating. A part of low-resolution spectra were obtained with a
prismatic spectrograph Camera VI which had been mounted on the Galileo
telescope until 1997. The spectral resolution was
λΔλ∼1000 on Hβ. High-resolution spectra,
λΔλ∼15000, were obtained with a Reosc Echelle
spectrograph mounted on the Copernics telescope.
Table2: All spectra of T CrB were obtained with the Boller and Chivens
spectrograph mounted on the 122cm Galileo telescope at the Asiago
Astrophysical Observatory of the University of Padova. The spectral
resolution was λΔλ∼1000 with a 600 groove/mm
grating.
Table 3: Equivalent widths of absorption lines of A type star (AVab)
were measured on high-resolution spectra,
λΔλ∼15000, obtained with a Reosc Echelle
spectrograph mounted on the 182 cm Copernics telescope at the Mount
Ekar station of the Astronomical Observatory of Padova. We measured
equivalent widths of CrI 480.49, TiI 484.82, MgI 517.27, CaI 518.87,
SiII 634.71 and SiII 637.14nm. These lines were rather free from
the blending with nearby absorption lines of the M type giant.
Table 4: Equivalent widths of HeII 4686 emission line were measured
on low-resolution and high-resolution spectra.
Table 5: Equivalent widths of HeII 4686 emission line and intensity
ratios I(HeII4686)/I(Hbeta) of T CrB were measured on
low-resolution. The effect of interstellar extinction is corrected by
E(B-V)=0.07.
RS Oph spectra:
The spectra are processed by IRAF.
The names of the spectra by Boller and Chivens spectrograph are:
bc(ID number).fit. The ID numbers are given in Table 1, where most
numbers consist of 5 figures until 18-October-2021 and 6 figures from
24-October-2021. If an ID number consists of 4 figures, one zero is
added at the top of the number in the name of the spectrum. For
example, if an ID number is 8930, the name is bc08930.fit.
The names of the spectra by the prismatic spectrograph Camera VI are
cm(ID number).fit. Most ID numbers consist of 4 figures. If an ID
number consists of 3 figures, one zero is added at the top of the
number in the name of the spectrum.
The names of the high-dispersion spectra by echelle spectrograph are
ec(ID number).fit. The ID numbers consist of 5 figures.
The interstellar extinction and the Doppler-shifts due to the orbital
motion and the rotation of the Earth are not corrected.
T CrB spectra:
The spectra are processed by IRAF.
The names of the spectra obtained by Boller and Chivens spectrograph
are: bc(ID number).fit. The ID numbers are given in Table 2, where
most numbers consist of 5 figures until 6-May-2020 and 6 figures from
19-December-2021. If an ID number consists of 4 figures, one zero is
added at the top of the number in the name of the spectrum. For
example, if a number in the table is 9488, the name of the spectrum is
bc09488.fit.
The interstellar extinction and the Doppler-shifts due to the orbital
motion and the rotation of the Earth are not corrected.
Objects:
------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------
15 59 30.16 +25 55 12.6 T CrB = HR 5958
17 50 13.15 -06 42 28.4 RS Oph = HD 162214
------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 60 272 Journal of spectroscopic observations of RS Oph
table2.dat 60 69 Journal of spectroscopic observations of T CrB
table3.dat 67 63 Equivalent widths of absorption lines of A type
star of RS Oph
table4.dat 33 208 Equivalent widths of HeII 4686 of RS Oph
table5.dat 35 69 Equivalent widths of HeII 4686 and intensity
ratios I(HeII/Hbeta) of T CrB
list.dat 103 340 List of T CrB fits spectra
fits/* . 340 Individual T CrB and RS Oph fits spectra
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Byte-by-byte Description of file: table1.dat table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 12 A10 "date" Date Observation date
15- 19 F5.2 "h:m" UT Universal time at beginning of exposure
23- 26 I4 s Exp Exposure time
29- 36 F8.2 d JD Julian date (JD-2400000)
38- 43 I6 --- spID Identification number of spectrum
46- 52 A7 --- Inst Instruments (1)
54- 60 A7 nm SpRange Spectral range
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Note (1): Instruments as follows:
B&C600 = Boller & Chivens spectrograph with grating 600 groove/mm
B&C1200 = Boller & Chivens spectrograph with grating 1200 groove/mm
CamVI = Prismatic spectrograph Camera VI
ech = Reosc Echelle spectrograph
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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3- 7 I5 --- spID Identification number of spectrum
10- 17 F8.2 d JD Julian date (JD-2400000)
20- 25 F6.1 d Time ?=- Days to outbursts in 2006 or 2021 (1)
28- 32 F5.3 nm CrI4804 ?=- CrI4804Å equivalent width (2)
35- 39 F5.3 nm TiI4848 ?=- TiI4848Å equivalent width (2)
42- 46 F5.3 nm MgI5172 ?=- MgI5172Å equivalent width (2)
49- 53 F5.3 nm CaI5188 ?=- CaI5188Å equivalent width (2)
55- 60 F6.3 nm SiII6347 ?=- SiII6347Å equivalent width (2)
62- 67 F6.3 nm SiII6371 ?=- SiII6371Å equivalent width (2)
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Note (1): "---" means observation after 2021 outburst.
Note (2): "---" means corresponding line was not detected or observed.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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2- 7 I6 --- spID Identification number of spectrum
10- 17 F8.2 d JD Julian date (JD-2400000)
20- 25 F6.1 d Time ?=- Days to outbursts in 2006 or 2021 (1)
28- 33 F6.3 nm HeII4686 HeII4686Å equivalent width
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Note (1): "---" means observation after 2021 outburst.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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3- 8 I6 --- spID Identification number of spectrum
12- 19 F8.2 d JD Julian date (JD-2400000)
23- 28 F6.3 nm HeII4686 HeII4686Å equivalent width
32- 35 F4.2 --- I(HeII/Hbeta) Intensity ratio I(HeII{4686}/Hbeta)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Star Star name, RS Oph or T CrB
8- 11 I4 --- Nx Number of pixels along X-axis
13- 14 I2 --- Ny Number of pixels along Y-axis
16 A1 --- Nz Number of slices
18- 38 A21 "datime" Obs.date Observation date
40- 46 F7.2 0.1nm blambda Lower value of wavelength interval
48- 54 F7.2 0.1nm Blambda Lower value of wavelength interval
56- 58 F3.1 0.1nm dlambda Wavelength resolution
61- 64 I4 Kibyte size Size of FITS file
66- 77 A12 --- FileName Name of FITS file, in subdirectory fits
79-103 A25 --- Title Title of the FITS file
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Acknowledgements:
Takashi Iijima, takashi.iijima1(at)gmail.com
(End) Patricia Vannier [CDS] 20-Oct-2025