-
.4atronomical and Astrophysical Transactaonr, 1998, Vol. 15, pp.
101-115 Reprints available directly from the publisher Photocopying
permitted by license only
a 1 9 9 8 OPA (Overdeu Publidhers Association) Amalerdam B.V.
Publiahed under license
in The Netherlands under the Gordon and Breach Science
Publishers imprint.
Printed in India.
THE INVESTIGATION OF CONTEMPORARY CLASSICAL NOVAE
V. P. GORANSKIJ', E. A. KARITSKAYA2, A. V. KUSAKIN3, N. V.
METLOVA', T. M. POGROSHEVA3, and S. Yu. SHUGAROV'
Stersberg State Astronomical Institute, 19 Universitetskiy
Prospect Moscow 11 9899, Russia
'Institute of Astronomy, Russian Academy of Science, 48
Pyatnitskaya St., Moscow 10901 7, Russia
Tien-Shan High Altitude Observatory, Working Group of Sternberg
State Astronomical Institute
(Received July 12, 1996)
The investigation of five classid novae: N Cyg 1992 = V1974 Cyg,
N Ad 1993 = V1419 Aql, N Cas 1993 = V705 Cas, N Aql 1995 and N Cas
1995 is reported in this paper. The identifications of these novae
with faint stars in the Palomar Sky Survey were checked. N Aqll993
was identified with a star of 21 mag on the POSS 0 plate. The light
curves and the colour index variation curves were obtained using
original observations by the authors and other published data. The
behaviour of several type classical novae and X-ray novae in the
twa-colour diagrams is found to be considerably different. The
appearance of two light periodicities in N Cas 1992 in the late
stages of outburst is confirmed, but the observations can not be
fitted by any linear elements in a time interval of more than 200
d.
KEY WORDS two-colour disgluns, periods of novae
Novae, X-ray novae, identifications, photometric observations,
light curve, colou~s,
Five classical novae: N Cyg 1992 = V1974 Cyg, N Aqll993 = V1419
Aql, N Cas 1993 = V705 Cas, N Aql 1995 and N Cas 1995 are
investigated. For all the objects astrometric measurements were
carried out to identify them with faint stars from the PaloInar
Observatory Sky Survey (POSS). The novae fields taken from the blue
POSS 0 glass copies are reproduced i n Figure 1. POSS glass copies
were scanned and digitized with an autoniatical microdensitometer
(AMD). These densitograms were reproduced on a PC screen with the
help of our special computer program. The contrast has been
sharpened with a numerical method. The crosses denoting novae
positions have been plotted by astrometrical methods relative to
reference stars from GSC and PPM catalogues (see Figure 1).
N Aql 1993 is identified with a faint star of 21 mag on the POSS
0 plate (see Figure 1). The star is absent on the red POSS E plate.
The identifications of N Cas 4993 (Munari et d., 1994) and N Cas
1995 (Williams, 1995) are confirmed. Pre-
101
-
102 V. P. GOKANSIiIJ et al.
N Cyg 1992 = V1974 c y g N Aql 1993 = V1419 Aql
N Aql 1995
N Cas 1995
Figure 1 Reproductions of the novae fields Irolll the blue I’OSS
glass copies. North is at the top. Fig.ld dimensions are 4 arcmill
x 4 arcmin. The calculated aqtrometric positions are denoted by
crosses.
-
= 5.0 0
3 6.0 7.0
8.0
9.0
10.0
- ." r
CONTEMPORARY CLASSICAL NOVAE 103
I N Cy9 1992 x- Cl-Lut +- VdMl *- W w n .- ahw
12.0 lLO t
48800 49000 49200 13400 19600 49800 SOOW J.O. 2400000~
Figure 2 The light curves of five novae in V. The original
observations by the authors of tlus paper and by other observeis
have been used. The different symbols correspond t.o original
observations by the authors and other sources using different
photometers: Cr-Lut, the photometer of V. M. Lutyi in the Crimea;
Cr (or Moscow)-ShV, the photometer constructed by S. Yu. Shugarov
and I. M. Vokov used in the Crimea (or in Moscow); AA-Korn, the
photometer constructed by V. G. Kornilov used in Tien-Shan
(Alma-Ata); AA-Nadir, WBVR standard plant construct.ed photometer;
AA-unfilt, observations without filters but with dichroic plate
dividem in Tien-Shan. The small dots correspond to published
observations of other authors. The systematic differences of
observations using different equipment have not been taken into
account.
nova Cns 1993 is seen as a northern 17.0 B companion merged with
the southern one in the 2 arcsec pair. N Cas 1995 is reliably
identified with a star of magnitude 19.0 f 0.2 B and 17.5 f 0.5 R
before the outburst. (see Figure 1). The recent N Cyg 1992 position
is situated on the edge of a 19 niag star image (see Figure l) ,
the centre of which is displaced by 2 arcsec according to the
nova's position. It. may be that the pre-nova image blends with the
star's image. In the case of N Aql 1995 a faint, 20 mag star is
situated too far (by 2.5 arcsec) to the south-east from the recent
nova position (see Figure 1). So we assume that this star is not a
pre-nova.
Since 1992 we have monitored these five novae in the UBV and
WBVR pho- tometric systems. The light curves (Figure 2) and colour
index curves (Figure 3) obtained in the study allowed us to
investigate both the distinctions between classi- cal novae of
various types and those between clksical and X-ray novae. N Cyg
1992 is a 0-Ne-Mg nova and has unusual variations of colour
indices. For example, it has power UV excess up to A(W - B) = -4.0
mag (see Figure 3). N A l l 1993 and
-
104
= B.0
.: 9.0 co = 10.0
E -0
11.0
12.0
L3.0
14.0
15.0
16.0
V. P. CORANSKIJ et al.
I N Aql 1993 -5 X- 0 - L U < M X I *a&> *- cr-w
0- M-Korn 0- M-un~lll. 0 - other
x
1 - . : *( -
a - - +
L P' ;t. &r: 0
- .r=" 0 . X 8 X 88 a . - 0
- t I I I 1 . 1 1 ,
11.0
12.0
13.0
14.0
49200 49300 49400 49500 49600 49700 49800 49900 500GG 3.0.
2400000+
- - - -
3 6.0
4 7.0 2 .- 5 8.0 S
9.0
10.0
N Cas 1993 I!
. ...+P $ 6 * r w : * s * .
x- mscarsw e- M a n *- W d l r 9- othw
16.0 15-0 t --a I 1 I I I I I I I
49400 49500 49600 49700 49800 49900 50000 50100 2.0.
2400000+
Figure 2 Continued.
-
CONTEMPORARY CLASSICAL NOVAE 105
3 8.0
E 0
c .- & 9.0 n S
10.0
11.0
12.0
13.0
11.0
N A q l 1995 0- ~OrcOcrLMI
-- othmr -. *- Iu-mrn - - *. - .* .
9 . .. - .*
%. . .. - - *' 0 :/
* * a -
1 , I I 49760 49800 49840 49880 49920 49960 50000 50040 50080
50120
J.O. 2400000+
7.0
7.5 3
b; '0
.L 2 8.0 P $ 8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
- 0
N Cas 1995 0- noscorrBMI x- Cr-LUc .- * n *- w i -- othmr
I I I I 1 I 1 I
49940 49960 49980 50000 50020 50040 50060 50080 50100 50120
50140 J.D. 2400000+
Figure 2 Continued.
-
1 Of3 V. P. GORANSKIJ e t 01.
a -1.0
3
k
m
a -0.5 0
0.0
-
-
-
0.5
1.0
-4.a
F 5 -3.5
b
m
'' -3.0 =I
- u
-2.5
-2.0
-1.5
-i.Q
-0.5
. x x .. . -.. . X .. : t;: .. *.I :. p
z
N Cyq 1992 x - C r - L I i *- cr-M *- M-Korn 9 - o t h u
.
8
48800 49000 49200 49400 49600 49000 50000 J.O. 2100000+
X . I.. x
. N Cyq 1992
W
4saoo 49000 49200 49400 49600 49aoo 50000 J.0. 2400000+
Figure 3 The colour index variation curves. Symbols are the same
BP in Figure 2.
-
7 m
0.0 L 0 0 0
c
0.5
1.0
a A 0.5 b - 0
1 .o
1.5
2.0
CONTEMPORARY CLASSICAL NOVAE I07
I X
JF I . . x+ = 2:.
I 0
U U
. . . . . . . I 0 .
X
* * . 0. * . a r: .
. .
49200 49300 49400 49500 49600 49700 49800 49900 50000 J.0.
240M00+
3' J t
i T i 0
0
. . .
N Aql 1993 x- 0-Lut c-1 *.&> *- (ZaMI 0- M o r n 0-
M-Milt. .- other
. 0
49200 49300 49400 49500 49600 49700 49800 49900 50000 J.O.
2$00000+
Figure 3 Continued.
-
108 V. P. GORANSKIJ et 01.
3 m .. L 0 - s
0.5
t.0
8 3 7 -1.0 3
b d 0
-0.5
0.0
0.5
a a
I a
i +
a
a . 49400 49500 49600 49700 49800 49900 SO000 50100
J.D. 2100000+
t
t
N Cas 1993 x- lbKarSNl . M-Korn
t - m-mr a- other
b
a .
):I . I . . . a 9 I .
49400 49500 19600 49700 19800 I9900 50000 J.O. 2400000t
Figure 3 Continued.
-
CONTEMPORARY CLASSICAL NOVAE 109
-* 0.2 L 0.3 2 0.4
0.5 0.6 0.7 0.8 0.9 i .0 1.1 1.2 1.3 1.4 1.5 1.6
8
0.3 3 m
I) 0.4 L
8
0.5
0.6
0.7
0.8
-
- - - - - - - - - - - - -
d 0
0
e e a e ..
0
0
0
O
N Aql 1995 0- MacoL9-shu 0- M-Worn -- 0 t h
0
0
0
m m m e
I I I 1 I I
49840 19880 49920 49960 50000 50010 J.D. 2400000+
-0.4 - -0.3 - *
2 -0.1
il 0.1 - m 0.0 -
O O 0
0 0
0
0
iJ Aql 1995 0- w .- M-Yorn. =- other \
0 0
e m
19810 19880 49920 19960 50oMl . 50040 J.D. 2400000t
Figure 3 Continued.
-
110
-0.8 -0.7 -0.6
m 2 -0.5 .- -0.4
-0.3 -0.2 -0.1
0.0
0.1
0.2
0.3 0.4
0.5
0.6
b u
? (D
- - - - 8
- - - - - - - - - -
k 0.4 c
0
0.5-
0.6
0.7
V. P. GORANSKIJ et al.
e 3?
0 0
8
N Cas 1995 0- n D a o v s M l I- criurrp .- -Idlo* *- nvvi * -
0tk.c
I
JE: 0
e 0 0
0
0
0
X X
P 0
o e 0 0
0 0 0
49980 50000 50020. 50010 50060 50080 50100 50120 5011C J.O.
2100000+
0.7 1 N Cas 1995 0- nolwu-swI a- Cr-LUl 0- M-Korn *- w i .-
0th.r
0
0
0
49900 50000 50020 50040 50060 50080 50100 50120 50140 LO.
2400000t
Figure 3 Continued.
-
CONTEMPORARY CLASSICAL NOVAE 111
m I
3
- 2
- 1
0 .
+ 1 -
a
/ I / N cyg 1992
/
- 1 0 + l B - v
F igure 4 The clrifts of five novae under research in two-colour
diagrams (V - B)-(B - V ) , (W - B)-(B - V ) and (I? - V)-(V -
R).
N Cas 1993 are dust novae of DQ Her type. Their light curves
show the typical dips connected with dust envelope formation. The
disappearance of UV excess which is connected with UV light
absorption by large particles of dust is a typical feature of these
0bject.s. Also, the significant red excess is observed in episodcv
of dust envelope formation. Dust IR radiation has been revealed in
the case of N Aql 1995 but we did not observe the characteristic
light curve dip of DQ Her type in this object. Nevertheless the
significant R excess was observed in N Aql 1995.
N Cas 1995 shows unusual behaviour. Its oulburst demonstrates
very slow de- velopment and low velocity of envelope expansion
(Figure 1). During seven months the star had a normal photosphere.
In December 1995 a mini-outburst was observed with an amplitude of
1.5 mag, and bright Balmer Ha emission and UV excess were detected
photometrically. These light and colour changes in December, 1995
sugg-
-
112
m
L
- 3
I
- 2
- 1
0
+l
V. P. GORANSKIJ et 01.
i d t i B - v + 2 Figure 4 Continued.
est the formation of a dense atmosphere. It is interesting that
the shape. of the light curve of N Cas 1995 is.very similar to that
of slow Nova RR Pic. The last one had maxima due to three
short-living mini-outbursts over the flat prolonged maximum
finished with a slow fading. Upto until April, 1996 N Cas 1995 had
three mini-outbursts, too. An assumption that this object is not a
symbiotic nova but rather a classical nova is confirmed by
spectroscopic observations (Iijima and Rosino, 1996).
-
- 1
P I
>
0
t i
+ 2
CONTEMPORARY CLASSICAL NOVAE 113
C
N Cyg 1992
- * I I
- 1 0 + 1 B - Y + 2
Figure 4 Continued.
For all the classical novae under research there are systematic
deviations of ob- servations obtained with different photometers.
These deviations are changing with time and strongly increase in
the later stages of the outbursts. Note, that they reach 0.6-1.0
mag in the V band in spite of the equality of colour equation
coefficients to zero in all devices if the coefficients were
derived using normal stars. The devia- tions may be due to sinall
device-to-device and temperature changes in photometric bands which
cannot be controlled with convenient methods of photometry. When
the bright emissions are situated near the edge of a photometric
band the systematic deviation may increase up to 1.0 mag. Having
variations of power emission lines in the spectra one may expect
these deviations to change. So one may observe only the major
tendencies of star shifts in two-colour diagrams (Figure 4). Such
behaviour of the studied novae differs considerably from the
behaviour of X-ray novae which
-
114
a 13.22 - '0 a a * a
a
a 3 c 0 '$13.27 - .I
Il a I a a a
8 I Dm .D
13.32 - a . .. W a
13.37 - I a ~n
m W
13.42 - 4 I
V. P. GORANSKIJ et 01.
0 U 3 13.50 ." t 0
13.60
13.70
13.80
13.90
- W W
8 b * * . .. a . . a - 8
a a a
. W a D : s a a
a m . . a n , a a
a .*
-1 I W ' a* . # -
- . 0-0.08 '13 3 L .PI
i -0 .05 L
-0.02
0.01
0.01
1 0.0 0.5 1.0 Phase 1.5
a C
-
I. r.
a
a #
a
a
- a
-
- 8 , I 8
Figure 5 The folded light curves for N Cyg 1992 accodng to
ephemerides determined in this paper for three time intervale - a.
JD 2449202: T=HJD 2449202356 + 0.081985 d*E; b, JD 2449265369 T=HJD
2449369.085 + 0.0819853 d*E c, JD 244952CL560: T=HJD 2449533.210 +
0.0851306 d*E.
-
CONTEMPORARY CLASSICAL NOVAE 115
have spectra similar to high-temperature blackbody or accretion
discs (Bochkarev ei al., 1991; Goranskij ei ol., 1996) in all the
stages of outburst. X-ray novae are situated along the line of
interstellar reddening. They do not change their positions in
two-colour diagrams with time (Goranskij et ol., 1996).
Our observations confirm the appearance of two light-curve
periodicities in the late stages of N Cyg 1992 outburst. For time
interval JD 2449200-365 we revealed the period P = 0.081985 d
(Figure 5). This period differs from P = 0.81263 d, which had been
derived earlier by De Young and Schmidt (1994). In time interval JD
2449531-549 we revealed the period P = 0.085 d which is in
agreement with the period found by Semeniuk ef al. (1994) and
attributed to superhumps similar to SU UMa. The amplitude of
variation in V light is equal to 0.12-0.18 mag and increases with
wavelength. Over a time interval of 200 d these oscillations are
not coherent and can not be fitted by any linear elements.
Acknowledgements
This research was supported by Ministry of Science of the
Russian Federation Grant No. 3-201 of the programme Astronomy, and
also by the scientific budgetary item project The Optical
Monitoring of Unique Astrophysical Objects.
References
Bochkarev, N. G., Karitskaya, E. A., Shakura, N. I., and Zhekov,
S. A. (1991) Astror. .isfropAjs.
De Young, J. A. and Schmidt, R. E. (1994) Astrophys. J. 431,
L43. Goranslrij, V. P., Karitskaya, E. A., KurodrLin, N. E., and
'hnkovaky, E. M. (1996) Rrsr. A s f w n .
Iijima, T. and Rosino, L. (1996) IAU Circ. No. 6365. Munari, U.,
Tomov, T. V., Hric, L., and Hazucha, P. (1994) I f . Bull. Variable
Sfars No. 3977. Semeniuk, I., Pych, W., Olech, A., and R u b w r k
i , M. (1994) Acts Aitron. 44, No. 3,277. Williams, G. V. (1995)
IAU Circ. No. 6213.
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Left. 22, 371.