J/A+A/670/A13 V838 Mon photometry and spectra (Liimets+, 2023)
V838 Mon: A slow waking up of Sleeping Beauty?
Liimets T., Kolka I., Kraus M., Eenmae T., Tuvikene T., Augusteijn T.,
Antunes Amaral L., Djupvik A.A., Telting J.H., Deshev B., Kankare E.,
Kankare J., Lindberg J.E., Amby T.M., Pursimo T., Somero A., Thygesen A.,
Strom P.A.
<Astron. Astrophys. 670, A13 (2023)>
=2023A&A...670A..13L 2023A&A...670A..13L (SIMBAD/NED BibCode)
ADC_Keywords: Novae ; Photometry, UBVRI ; Spectroscopy
Keywords: stars: individual: V838 Mon - stars: evolution - stars: peculiar -
stars: mass-loss - techniques: photometric - techniques: spectroscopic
Abstract:
V838 Monocerotis is a peculiar binary that underwent an immense
stellar explosion in 2002, leaving behind an expanding cool supergiant
and a hot B3V companion. Five years after the outburst, the B3V
companion disappeared from view, and so far did not recover.
We investigate the changes in the light curve and spectral features to
explain the behaviour of the V838 Mon during the current long-lasting
minimum.
A monitoring campaign has been performed during the past 13 years with
the Nordic Optical Telescope to obtain optical photometric and
spectroscopic data. The data sets are used to analyse the temporal
evolution of the spectral features and the spectral energy
distribution, and to characterise the object.
Our photometric data show a steady brightening in all bands during the
past 13 years, which is particularly prominent in the blue. This rise
is also reflected in the spectra, showing a gradual relative increase
in the continuum flux at shorter wavelengths. In addition, a slow
brightening of the Hα emission line starting in 2015 was
detected. These changes might imply that the B3V companion is slowly
reappearing. During the same time interval, our analysis reveals a
considerable change in the observed colours of the object along with a
steady decrease in the strength and width of molecular absorption
bands in our low-resolution spectra. These changes suggest a rising
temperature of the cool supergiant along with a weakening of its wind,
most likely combined with a slow recovery of the secondary due to the
evaporation of the dust and accretion of the material from the shell
in which the hot companion is embedded. From our medium-resolution
spectra, we find that the heliocentric radial velocity of the atomic
absorption line of TiI 6556.06Å has been stable for more than a
decade. We propose that Tii lines are tracing the velocity of the red
supergiant in V838 Mon, and not representing the infalling matter as
previously stated.
Description:
The bases of this paper are the data collected since 2009 with the
2.56m Nordic Optical Telescope1 (NOT) equipped with the cryogenically
cooled Alhambra Faint Object Spectrograph and Camera2 (ALFOSC). Bessel
UBVR filters and interference filter i (NOT ID no. 12) with a central
wavelength of 797 nm and FWHM 157 nm were exploited. The Bessel
filters are equivalent to the Johnson-Cousins UBVRC system.
Low-resolution long-slit spectra were regularly collected, with NOT
and ALFOSC, on a total of 28 nights starting from 2009. The
observations were typically carried out twice a year, occasionally
more frequently. Full optical coverage was achieved with grism 4 and a
slit width of mostly providing spectral dispersion of ∼3Å/pix
(R∼600 at 6600Å). Typical exposure times were 400 seconds which
provides a S/N between ∼10 and ∼100 over the usable spectral range
(4500-9000Å). In this way, the saturation of the red part of the
cool star spectrum was avoided.
Additional medium-resolution spectra were acquired on 28 nights. These
were taken around the Hα 6562.8Å line with grism 17 and a
slit width of mostly 0.5". The spectra cover the range between 6330
and 6870Å and have a dispersion of ∼0.26Å/pix (R∼9000 at
6600Å). The exposure times usually varied between 500 and 1200s
guaranteeing a S/N≥100. In addition, a spectrum from September 2007
with the similar set-up is used in this work for comparison purposes.
All spectra obtained with NOT were observed with the slit at the
parallactic angle.
Objects:
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RA (2000) DE Designation(s)
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07 04 04.82 -03 50 50.6 V838 Mon = NOVA Mon 2002
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 101 162 Photometric data of V838 Mon
table4.dat 32 22 Spectral measurements
list.dat 125 33 List of fits spectra
fits/* . 33 Individual fits spectra
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See also:
J/PAZh/28/764 : UBVR photometry of Nova Mon 2002 (V838 Mon) (Goranskii+, 2002)
J/ApJ/598/L43 : Polarimetry of V838 Mon and stars around (Wisniewski+, 2003)
J/A+A/434/1107 : UBV(RI)c photometry of stars around V838 Mon (Munari+, 2005)
J/AZh/84/147 : Light curves of V838 Mon and V4332 Sgr (Goranskii+, 2007)
J/A+A/532/A138 : V838 Mon spectrum in 2009 (Tylenda+, 2011)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 F16.8 d JD Julian Date
19- 24 F6.3 mag Umag ?=- U-band magnitude
28- 32 F5.3 mag e_Umag ?=- Error of U-band magnitude
35- 40 F6.3 mag Bmag ?=- B-band magnitude
44- 48 F5.3 mag e_Bmag ?=- Error of B-band magnitude
51- 56 F6.3 mag Vmag ?=- V-band magnitude
60- 64 F5.3 mag e_Vmag ?=- Error of V-band magnitude
67- 72 F6.3 mag Rmag ?=- R-band magnitude
76- 80 F5.3 mag e_Rmag ?=- Error of R-band magnitude
83- 88 F6.3 mag Imag ?=- I-band magnitude
92- 96 F5.3 mag e_Imag ?=- Error of I-band magnitude
98-101 A4 --- Tel Name of the telescope/instrument used
(NOT, SAAO or TO)
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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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1- 12 F12.4 d JD Julian Date
14- 17 F4.2 mag V-I V-I colour index
19- 22 F4.2 --- Rd5737 Relative depth of the 5737.703 line
24- 27 F4.1 0.1nm EWB-X(1-0) Pseudo-equivalent width of the B-X(1-0)
29- 32 F4.1 0.1nm EWB-X(0-0) Pseudo-equivalent width of the B-X(0-0)
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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- 4 I4 --- Nx Number of pixels along X-axis
6- 28 A23 "datime" Obs.date Observation date
30- 33 I4 0.1nm blambda Lower value of wavelength interval
35- 40 F6.1 0.1nm Blambda Upper value of wavelength interval
42- 44 F3.1 0.1nm dlambda Wavelength resolution
46- 47 I2 Kibyte size Size of FITS file
49- 75 A27 --- FileName Name of FITS file, in subdirectory fits
77-125 A49 --- Title Title of the FITS file
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Acknowledgements:
Tiina Liimets, liimets(at)asu.cas.cz
(End) Patricia Vannier [CDS] 30-Nov-2022