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Observational study of Hα in 31 RS CVn binary systems
Pergamon Journals. Printed in Great Britain 0275-1062/87$10.0+0.00
Chin.Astron.Astrophys.11 (1987) 64-73 Act.Astron.Sin.
27 (198v -
259-271
OBSERVATIONAL
STUDY
LIU
he-fu
TAN Hui-song
Department
OF Ha
IN
31
of Astronomy,
Yunnan Observatory,
RS
CVn
Beijing
Academia
BINARY
Normal
SYSTEMS
University
Sinica
Received 1985 May 30
ABSTRACT 90 spectral observations of the Ha regions of 31 RS CVn stars made with Reticon on the 2.1 metre McDonald Reflector in 1984 are reported here. Quantitative measurements were made on tAo Ho emission and absorption components. Combining with our previous observations in [ll, we have now observed 70% of the systems in Hall's catalogue. On the basis of the combined data, a statistical discussion is presented.
an image width 34~ corresponding to a spectral purity of 0.3A, a dispersion of 0.145 Over the whole range from X-rays to radio A/diode or 9.5A/mm and a signal-to-noiseratio waves, RS Canes Venaticorum stars show better than 60 - this high S/N ratio of characteristic features similar to sunspots, Reticon ensured good quality spectral profiles. Our data includes one piece of solar flares, solar radio bursts. They are objects of high stellar activity among data obtained by Dr. J. Tomkin with the binary stars, hence are pet objects of Reticon on the 2.7 metre telescope of McDonald Observatory, relating to the binary researchers. We have made observational studies of 33 such stars [1,2]. In this paper, HD 8357, on J.D. 2446 041.658. we include the observations on 31 RS CVn Data reduction and graphics were made on systems. Of these, 5 were observed in [l], the Cyber 170/750 computer of the University but here we include further observations on of Texas, using the program PFITS. The their Ha profile variations. In 1975, Hall heliocentric, Julian Date and the phase were gave a clear definition of these binaries calculated on a VAX computer. [3] and the 1984 catalogue of Hall et al. All the observational data are presented [4] contains 84 members. However, Ho in TABLE 1. Column 2 gives the spectrum of observation was indicated for only some 20 the hot component (before the slash) and of these systems. We have now observed a that of the cold component - only one system total of 59 systems, or 70% of Hall's had unknown spectrum for the secondary. Column 3 gives the heliocentric Julian Date catalogue; this has enabled us to make a statistical study of some features of the for the mid-instant of observation and the Ha emission. We hope to make a systematic Phase of Column 4 was generally calculated investigation of the Ha profile and its from the epoch and period given in Hall's emission characteristicsof this type of catalogue, the exceptions are referenced in the TABLE. Columns 5 and 6 give the binary star. equivalent widths of, respectively, the absorption component (below the continuum) of 2. OBSERVATIONS. DATA TREATMENT Ha and the emission component (above the continuum). The last column contains During two observing periods, 1984 Nov 29 references relevant to Ha observations of that Dee 3 and Dee 25 -Dee 27, the present writers star. used the Reticon detector at the conde focus of the 2.1 metre telescope of McDonald Observatory to observe the spectral region 3. Ha PROFILES AND EMISSION around Ha of 31 RS CVn type binaries. Our The 31 RS CVn systems are divided into 3 observations were made with Grating II (blazing angle 13.88', 600 lines/mm), first- groups and will be described separately. order spectrum, a slit of width 15OP~O.65", First, we analyse the four systems, HD 8357 1.
INTRODUCTION
Ha of
Table I. H Alpha Observations
star
SP. (h/c)
65
RS CVn Stars
1. D. (H) 2446000+
Phase
For 31 RS CVn Systems.
r
H Elba) absor.
Ref. emission
UX Ari
GSV/KOIV
59.643
0.466
0
30
HD 250810
GO
33.763
0.038
1019
0
34.809
0.136
980
0
35.681
0.218
1356
0
33.711
0.882
1606
0
34.773
0.892
1591
0
35.660
0.900
1655
0
36.729
0.911
1565
0
HR 1708
coIrr/G5rrr
HD 449982
G3V-IV/K3V
33.911
0.114
1266
0
HR 3119
F8V/compositc
33.937
0.569
1586
0
34.883
0.655
1473
0
35.786
0.736
1106
0
36.838
0.831
1409
0
HD 73343
KlIII/K3III
33.954
0.821
1177
0
SA 07552
G3V/KOV
35.996
0.058
961
0
37.032
0.249
1049
0
38.021
0.432
968
0
33.891
0.736
1006
0
35.780
0.832
1075
0
36.791
0.884
1142
0
34.911
0.607
997
0
35.837
0.865
1000
0
35.025
0.755
1225
0
35.973
0.769
876
0
37.018
0.783
1406
0
33.830
0.719
1296
0
34.854
0.888
1544
0
33.872
0.996
1550
0
35.869
0.090
1524
0
33.629
0.230
0
1222
34.612
0.376
0
921
35.602
0.523
0
800
36.567
0.667
0
715
37.580
0.817
0
635
60.558
0.234
0
857
33.673
0.841
1087
0
34.718
0.972
934
0
35.719
0.096
1080
0
36.712
0.220
1028
0
33.615
0.317
0
247
34.595
0.564
683
34
HR 2973
GK HyD HR 4527
VV Man HD 57364 II Peg
KlIII/
GO/GlIV A/GSIV-I11
GZV/KOIII G8III/K2III K2-3v-IV/
11 Peg
LX Per
sz
Psc
GOV/KOIV
F8V/KlIV
TY Pyx
G5lG5
35.926
0.609
1535
0
HR 1099
GSIV/KlIV
33.695
0.457
0
1191
34.764
0.833
0
1072
(b)
(cl
Cc>(4
(9)
w
(cl (f) (0)
(cl (h) (i)
LIU and TAN
66
Table
SW HR 1099
SP. (h/c)
ilV/KlIV
1. D. (H) 2446000+
Phase
r
I-I EWblo abror.
Ref.
emission
35.628
0.138
0
a41
36.727
0.727
0
836
37.912
0.942
0
al4
59.659
0.606
0
534
60.605
0.939
0
465
XY UMO
Z-sV/K5V
37.959
0.030
la27
0
HR 4374
3VI ZNII/KOIII
35.969
0.675
1269
0
3s. 031
0.178
1150
0
35.982
0.193
1203
0
37.011
0.209
1090
0
38.016
0.224
107s
0
35.041
0.710
lOS0
0
38.037
0.856
1205
0
33.558
0.183
1187
0
34.556
0.192
1198
0
35.553
0.201
1248
0
36.651
0.210
1394
0
59.560
0.422
1206
0
35.013
0.760
1037
0
3s. 099
0.589
1099
0 0
HR 4665
HR 5110 HR 7428
HD 86590
HD
108102
DM UMa
HD 175742
HD 37847
!IV/K
IV
?/K2111-II
OVl
36.863
0.489
1040
W/FaV
36.013
0.195
2287
0
IcGV-IV
35.951
0.830
0
2040
Ov/KS-M2\
/csrrr
36.036
0. a42
0
2030
36.895
0.956
0
2000
36.993
0.969
0
2000
37.996
0.103
0
2923
34.536
0.745
342
0
35.536
0.092
73
19
36.532
0.438
251
0
37.523
o.fa4
400
0
100
60
33.795 34.784
-
464
0
35.743
-
a35
0
35.767
-
835
0
36.741
-
767
0
767
0
36.779
HD 190540 HD 205249 HD 0357
/KOIV .lIII/ ;5/composite
1. (continued)
37.923
-
562
0
33.577
-
924
0
35.572
-
1232
0
33.598
-
1069
0
34.578
-
1064
0
33.644
0.280*
128
412
34.628
0.397
160
196
(cl 6)
(cl (i) Cc) (k)
Cc)
W
(h)
(k)
(4) Cm)
Ha of RS CVn Stars
67
Table
HD8357
FIV/KOIII
HK Lac * The
GS/compositc
phases
Referencea
are calculated in Table
(a)
E. J. Wciler,
(b)
P. W.
(c)
B. W. Bopp
(d)
S. E. Smith
(e)
S. S. Vogt,
37.595
0.711
136
123
41.658
0.156
0
728
59.617
0.118
302
112
60.590
0.225
250
129
61.608
0.336
193
13s
60.504
0.888
321
28
from the formula
J. D. 2445957.88
R. A. S., 182 (1978),
<
(h)
A. C. Collier,
A. J. Lerters.
(i)
(m).
(i)
869 H. L. Nations
(j)
B. W. Bopp
in Red-Dwarf 0.
and Tan Huisong, G. W. Henry,
22 (1982),-127
Stars>>,
~363.
S. C. Barden.
1983. Bull. Am. Astron.
B. Slee, A. E. Wright.
and L. W. Ramsey, and J. C. Talcott.
666
1517
975
L. W. Ramsey,
R. F. Hayncs.
83 (1978).
A. J., s5 (1980).
A. J.,
85 (1980),
I. B. V. S., 2606.
H. Louth,
D. J. Hillier,
Sac.,
15, 663,
1983.
M. N. R. A.S.,200(1982)
1086 55
1984.
Ap. J. Lrtrrrr.
HD 175742 and BD +61"1211. Because the first three systems are systems in which Ho emission was detected for the first time, we made further observations and analysis on the variation and features of this line. For binary BD +61'1211, Ho emission had been observed before, but no quantitative measurements were made because of low resolution; here, we give our determinations of the radial velocity and equivalent widths. It has the strongest Ho emission of all known RS CVn stars.
HR 7428,
(f)
+ 9.15 x n in reference
77
Ap. J., 270 (1983).
A. J..
J., 247 (1981),
D. P. Hucnemocrder,
Liu Xuefu
110
and B. W. Bopp, Ap.
B. W. Bopp,
D. S. Hall,
59
16
and J. C. Talcott,
(f)
(I)
0
0.600
and C. R. Canizarcs,
(g)
(k)
a.495
36.583
1. M. N.
Veddcr
35.617
1. (continued)
257
(1982),
91
from the metal lines of the secondary (primary) star. HD 8357 gives hard X-ray emission: it is the optical counterpart of the X-ray source H D123+075, [S]. Therefore, it is probable that its Ha emission is a secondary effect of its X-ray emissbon.
l(b) HR 7428 = HD 184398 This is a noneclipsing binary; the orbital period is 108.5707 d. In our previous paper [l], we found its Ha emission to show a steady double peak [cf. the profile on 1984 Sept 14 shown in Fig. 2 The Ha emission is l(a) HD 8357 = AR PSC there). Here, we re-observed it twice, on very strong. It also varies rapidly. Our 12 Nov 29 and Dee 25. Although there were no observations all showed strong Ha emission clear Ha emission, we could see a clear change above the continuum and twice it showed in the profile between these two days, and clear double peaks. See Fig. 1. HD 8357 is a two-spectrum binary and radial velocity on Dee 25, there seemed to be some emission in the red wing. On Dee 25, its phase was 0.42, measurements showed that the Ha emission while on the two previous occasions when it component has the same radial velocity as showed double peak emission, its phase was the primary star and the Ha absoprtion 0.48 and 0.51. Whether this means Ha emission component, the same as the secondary star; is more easily seen around phase 0.5 remains hence, the emission comes from the primary, to be confirmed by further observations. and the absorption, from the secondary. Should this be the case, we would infer that Because the two components of Ha mutually the Ha emission comes from the chromosphere compensate and overlap, the velocity curve determined from the absorption core (emission and transition region of the primary star. peak) has a larger amplitude than that from
LIU and TAN
68
J.I).(IO
J.D.(H) 2446000’
&
37.595
0.711
A
tJ.lln
d1.658
59.617 O.IIR --AT fio.590 \I. zz!:,
4
Fig. 1.
H-Alpha emission feature of HD 8357.
1.2
HK7428
k-----J 6560
Pig, 7.
6563
6560
6569
6572
th
Comparison of H-Alpha for HR 7426 observed in September, November and December,
1984.
Ha of RS CVn Stars
1
1
I
I
I
6554
6557
6560
6563
6566
Fig.3.
H-Alpha
variation for
HD
69
’ 6569
17574.7 (top)
--A 6572 C.i, and SZ Pac.
The Ha profile l(c) HD 175542 = V 775 Her showed rapid changes. The variation was complex and fast, and it was hard to see any regularity: sometimes the profile was above the continuum, sometimes there was emission in the wings, and other times it showed pure absorption features. This binary has an orbital period of 2.879 d, [4], but we could see no dependence of the Ha emission and the orbital phase during our observations.Hence it is probable that the emission comes mainly from active regions on the primary or both stars, similar to sunspots and solar flare; then the Ha emission wouldberandom and independent of the position in the orbital. The Ha profile is shown in Fig. 3.
2. HE 37847, HR 1099, IIPeg, UX Ari, LX Per, HK Lac, SZ Psc, HR 5110, HD 86590, HD 190540 The Ha profile of HD 37847 is shown in Fie. 5. The nrofile showed rapid variations in"shape and intensity, similar to HE 175742. Its period is not yet known and from the variations of the Ha profile we estimate its period cannot be very long. The other nine systems have been studied by many previous researchers:
The variable l(d) BD +61'1211 = DM UMa star designation was given in 1981, [6]. This system is-the optical counterpart of the X-ray source 2A 1052+606, [7]. It emits both in soft X-ray (X 10a) and hard X-ray, [8]. The Ha emission of this binary is very strong, having an equivalent width of more than 2A, much stronger than any other observed RS CVn binary. It is one with the highest activity. See Fig. 4.
Our observations are similar to the previous ones. In HR 1099, II Peg and UX Ari, the Ha emission was strong, and was seen to be above the continuum on all occasions. For the other 6 systems, it was a case of being above the continuum on some occasions, and otherwise on other occasions; when the emission portion was partially filled with the absorption lines. Figs. 6 and 7 show the profiles of HR1099 and II Peg. These graphs show that the Ha emission was strong, with equivalent widths
HR 1099 II Peg LX Peg SZ Psc Binary References [9,10] [11,12] [13,14] 111,15] HR 5110 HD 86590 HD 190540 UX Ari HK Lac 1161 [17,18] [17,19] [13,17][17,201
LIU and
TAN
V
0.8 I
6557
li5tilJ
I
6563
6566
wsve
Fig.
4.
pure
H-Alpha
I
I
length
emision
I
6569
I
I
6557
6560
I
6563 wave
(A)
of ED + 61°1211.
Fig.
5.
Fig.
6.
I
,*:4i”
H-Alpha
(i.llh~
I
I
G5tib
b569
emission of HR 1099.
L4J
,_I
6569 -
length profiles of HD 37847.
H-Alpha
I
4s
G566
,.\I
Ha
71
of RS CVn Stars
, -
ll
$/p 1.0 w 1.0 -
1.0 0.9
9
I
I
Fig.
I
I
I
I
I
6557
6560
6563
6566
6569
7. Pure H-Alpha
emission
(A)
of II Pega
0.80 t
Pig.
8.
Compxiron
of H-Alpha
for UX Ari observed
in September
and December,
1984.
72
LIU and TAN
generally greater than 0.5 A, and that the emission varied rapidly. HR 1099 showed double peak on several occasions while II Peg always showed single peak throughout our observations, and very sharp peak at that. The Ha profile of UX Ari is shown in Fig. 8. We see that the emission on Dee 25 was far weaker than that on Sept 14-17. Of the five RS CVn systems with strong Ha emission, (HR 1099, BD+61°1211, HD 224085, HD 8357, UX Ari), UX Ari is the weakest, and is the only one that is not a X-ray source. The Ha profiles of HK Lac and SZ Psc sometimes showed emission and sometimes absorption. For example, as Fig. 3 shows, SZ Psc had a slightlyabovecontinuum emission on Nov 29, yet on the next day, Ha showed the absorption line, with only a weak emission in the blue wing. For these 10 systems, we observed 36 times, and on 6 occasions we found above continuum Ha emission, that is, the probability of emission observation is 17%. This agrees with Bopp's estimate [17] of lo-20% based on HK Lac, SZ Lac and HD 86590. For more precise and stronger statements, we must await the results from longer term monitoring. These are 3. The Remaining 17 Systems systems that show Ha in absorption. Their Ha equivalent widths and radial velocities and other data are given in TABLE 1. It should be noted that the equivalent width of their Ha absorption line is always smaller than that of a standard star of the same spectral type. We think the main reason here is that the absorption line in such stars is partially filled by emission; other factors will be discussed below.
4.
EMISSION PROBABILITY STATISTICS DISCUSSION
Our observations of the Ha profiles and emission features of 59 RS CVn binaries reported in this paper and in [l] lead to the following statistical regularities: 1. Dependence of Ho Emission on the Period We observed above-continuumHa emission in 15 systems. Of these, apart from HD 185151, HD 190540 and HD 37847 for which no period could be found in the literature, the shortest period was that of HD 86590, at P = 1.07 d, and there were only 2 systems with periods greater than 2 weeks (HK Lac, 24.4 d; HR 7428, 108.6d). Thus, the majority are in the normal period group (ld
X-ray counterpart. The other four have corresponding X-ray sources as follows: RS CVn Binary HR BD HD HD
1099 +61'1211 224085 8357
X-ray Counterpart 4U 2A A H
0336 1052 0000 0123
+ + + +
01 606 28 075
tzj [231 u51
Such a tight correlation suggests to us that the strong Ha emission is a secondary effect arising rom the hard X-ray emission. 3. Relation between Ha and Soft X-Ray Emission Using space observations, Charles -obtained the soft X-ray flux in 45 RS CVn systems. Our statistical result is: H-ALPHA EMISSION
NO. OF SYSTEMS
Always Occasional Not seen
4 7 34
MEAN X-RAY LUMINOSITY 31.32 erg/s 31.19 30.84
It thus appears that the more intense the soft X-ray emission is, the greater the likelihood of Ha emission. Relation between Ho and Radio Emissions I171 noted the relation between the radio'flux and the Ha flux in HR 1009. For 3 systems with strong Ha emission, UX Ari, HR 1099 and II Peg, radio flashes have been observed [24]. 4.
BODD
5. Statistics on the Ha Absorption Equivalent Width It was noted that the equivalent width of Ha absorption is smaller in RS CVn stars than in standard stars of the same spectral type. For a total of 47 found the following frequency systems, .tie distribution of the equivalent width ratios. (EW)RS CVn (EW)standard 0.3 0.4 0.5 0.6 0.7 0.8 0.0
-
No. of Systems
0.4 0.5 0.6 0.7 0.8 0.9 1.0
2 4 10 4 7 9 11
total
47
Smith and Bopp [25] have pointed out that, even in systems with no clear above-continuum Ha emission, the equivalent width of the Ha absorption line is still smaller than that in standard stars of the same spectral type. Our observations lead to the same conclusion. There may be two reasons causing this:
Ho of
73
RS CVn Stars
First, as Bopp [21,26] pointed out, because chromospheric activity and high temperature corona have the conditions for providing Ho emission, the emission portion will partially fill the absorption component, thus decreasing its equivalent width relative to the normal stars. Next, as discussed by Vogt and Penrod [27] if there are cool spots on the stellar surface, then that will decrease the equivalent width of the Ha absorption. This effect will vary with the size of the spots, their temperature difference from the their distribution on the photosphere, surface and the rotation of the star, etc. But, generally speaking, this effect cannot We can make a rough estimate be very large. Suppose on a GO main sequence as follows.
star, spot groups occupy 50% of the surface and their temperature is 1200 K lower than the photosphere, then the equivalent width will be reduced to 82% of its normal value. According to our statistics above, of 47 systems, 20 have the equivalent width ratios above 0.8, and 27, below. For systems where this ratio is less than 0.8, it would be difficult to explain by this factor, especially for systems like HD 26337, with an equivalent width of only 432 mA, or only 27% of the value for the standard HR 8684, - in such a case, even if the star surface is completely covered with spot, we still cannot explain the small ratio. ACKNOWLEDGEMENT We thank Dr. Harlan J. Smith Director of McDonald Observatory for giving us valuable telescope time and Dr. J. Tomkin for providing an important piece of data.
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111 t2 1 I31 141
LIU Xue-fu and TAN Hui-song, Chin.Astron.Astrophys. 10 (1986) 221-229 = Act.Astrophys.Sin. 6 (1986) 132-142. TAN Hui-song and LIU Xue-fu, Chin.Astron.AstrophYs. 10 (1986) 342-346 = Act.Astron.Sin. 27 (1986) 130-136. D. 8. Hall, IAU colloquiumNo. 29. (1975), 287. D. S.Ha M. Mk E. R. Nelson,“Hall Catalogof RS CV” Binarystsr Systerm”,(lml (rce IBVS 2458, 1984).
I51 I61
S. Bdi-s, M. Cav. E. Ralph, W. Robenz,D. ~&WUU,md J. Tow, ,Q,. J. 240(1980), 107. P. M. ~olopov, M. M. Samus,N. P. Kukarkina, G. I. Medvedeva,N. B. perova, IBVS M. Gucis.
brmr,
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(1981). r71 W. LiBer, IAU Circ. No3176, (1979). [aI D. Gampton. AP. I., 234(1979), 993. I91 D. M. Popper. A. I., 83(1978), 1522. r101 D. A. Frsouclli, A. 1..83(1978), 1535. Ill1 H. L. Nations, L. W. Retnr9, A. J.. 85(1980), 1~. I121 s.s.VW, AP. I.,247( 1981), 975.
Ll)l t. J. Wciler, M. N. K. A. S.,l&2 (IY78), 77. I141 B. W. BoppandJ. C. Talcott,A. 1..83(1978), 1517. II51 B. W. Bopp, A. I.,86 (1981), 771. 1161
I’. A. L:cldman. IAU Symprwm, 88. (1979). 403.
[I71 B. W. Uopp, “Activity in Red-Dwarf Stan”, (1983). ~363. SOL, 16 (1984), 473. I181 S. C. Barden. ILN. Am. Asrron.
[ 191 A. C. Collier, 1201
r211 I221 I231 1241 I251 I261 I271
K. F. Hnynes, 0. B. Slcc. A. E W&t, D. J. HiBfu, hf. N. R A. S, X10(1982), 86Y. B. W. Bapp and J. C. Talmtt, A. I.,85(19@41).55. P. A. Charles, “Activity in Red-Dwarf Stan”, (1983), p415. N. E. White, P. W. Sanford, and E J. Weila, N&w. 274 (1978), 569. D. A. Schwartz, M. Garcia, M. Conroy, I?. Ralph, W. Robatr et al. Bull. Am. Aseon. Sac., 12 (1980). 513. P. A. Feldman, “Activity in Red-Dwarf Stan”, (1983), p429. S. E Smith and B. W. Bopp, A. 1.Letters. 22(1982). 127. B. W. Bopp. “Activity in Red-Dwarf Stars”, (1983), ~363. S. S. Voat, and G. D. Penrod, “Activity in Re&Dwarf Stars”, (1983). ~379.
Chin.Astron.Astrophys.11 (1987) 64-73 Act.Astron.Sin.
27 (198v -
259-271
OBSERVATIONAL
STUDY
LIU
he-fu
TAN Hui-song
Department
OF Ha
IN
31
of Astronomy,
Yunnan Observatory,
RS
CVn
Beijing
Academia
BINARY
Normal
SYSTEMS
University
Sinica
Received 1985 May 30
ABSTRACT 90 spectral observations of the Ha regions of 31 RS CVn stars made with Reticon on the 2.1 metre McDonald Reflector in 1984 are reported here. Quantitative measurements were made on tAo Ho emission and absorption components. Combining with our previous observations in [ll, we have now observed 70% of the systems in Hall's catalogue. On the basis of the combined data, a statistical discussion is presented.
an image width 34~ corresponding to a spectral purity of 0.3A, a dispersion of 0.145 Over the whole range from X-rays to radio A/diode or 9.5A/mm and a signal-to-noiseratio waves, RS Canes Venaticorum stars show better than 60 - this high S/N ratio of characteristic features similar to sunspots, Reticon ensured good quality spectral profiles. Our data includes one piece of solar flares, solar radio bursts. They are objects of high stellar activity among data obtained by Dr. J. Tomkin with the binary stars, hence are pet objects of Reticon on the 2.7 metre telescope of McDonald Observatory, relating to the binary researchers. We have made observational studies of 33 such stars [1,2]. In this paper, HD 8357, on J.D. 2446 041.658. we include the observations on 31 RS CVn Data reduction and graphics were made on systems. Of these, 5 were observed in [l], the Cyber 170/750 computer of the University but here we include further observations on of Texas, using the program PFITS. The their Ha profile variations. In 1975, Hall heliocentric, Julian Date and the phase were gave a clear definition of these binaries calculated on a VAX computer. [3] and the 1984 catalogue of Hall et al. All the observational data are presented [4] contains 84 members. However, Ho in TABLE 1. Column 2 gives the spectrum of observation was indicated for only some 20 the hot component (before the slash) and of these systems. We have now observed a that of the cold component - only one system total of 59 systems, or 70% of Hall's had unknown spectrum for the secondary. Column 3 gives the heliocentric Julian Date catalogue; this has enabled us to make a statistical study of some features of the for the mid-instant of observation and the Ha emission. We hope to make a systematic Phase of Column 4 was generally calculated investigation of the Ha profile and its from the epoch and period given in Hall's emission characteristicsof this type of catalogue, the exceptions are referenced in the TABLE. Columns 5 and 6 give the binary star. equivalent widths of, respectively, the absorption component (below the continuum) of 2. OBSERVATIONS. DATA TREATMENT Ha and the emission component (above the continuum). The last column contains During two observing periods, 1984 Nov 29 references relevant to Ha observations of that Dee 3 and Dee 25 -Dee 27, the present writers star. used the Reticon detector at the conde focus of the 2.1 metre telescope of McDonald Observatory to observe the spectral region 3. Ha PROFILES AND EMISSION around Ha of 31 RS CVn type binaries. Our The 31 RS CVn systems are divided into 3 observations were made with Grating II (blazing angle 13.88', 600 lines/mm), first- groups and will be described separately. order spectrum, a slit of width 15OP~O.65", First, we analyse the four systems, HD 8357 1.
INTRODUCTION
Ha of
Table I. H Alpha Observations
star
SP. (h/c)
65
RS CVn Stars
1. D. (H) 2446000+
Phase
For 31 RS CVn Systems.
r
H Elba) absor.
Ref. emission
UX Ari
GSV/KOIV
59.643
0.466
0
30
HD 250810
GO
33.763
0.038
1019
0
34.809
0.136
980
0
35.681
0.218
1356
0
33.711
0.882
1606
0
34.773
0.892
1591
0
35.660
0.900
1655
0
36.729
0.911
1565
0
HR 1708
coIrr/G5rrr
HD 449982
G3V-IV/K3V
33.911
0.114
1266
0
HR 3119
F8V/compositc
33.937
0.569
1586
0
34.883
0.655
1473
0
35.786
0.736
1106
0
36.838
0.831
1409
0
HD 73343
KlIII/K3III
33.954
0.821
1177
0
SA 07552
G3V/KOV
35.996
0.058
961
0
37.032
0.249
1049
0
38.021
0.432
968
0
33.891
0.736
1006
0
35.780
0.832
1075
0
36.791
0.884
1142
0
34.911
0.607
997
0
35.837
0.865
1000
0
35.025
0.755
1225
0
35.973
0.769
876
0
37.018
0.783
1406
0
33.830
0.719
1296
0
34.854
0.888
1544
0
33.872
0.996
1550
0
35.869
0.090
1524
0
33.629
0.230
0
1222
34.612
0.376
0
921
35.602
0.523
0
800
36.567
0.667
0
715
37.580
0.817
0
635
60.558
0.234
0
857
33.673
0.841
1087
0
34.718
0.972
934
0
35.719
0.096
1080
0
36.712
0.220
1028
0
33.615
0.317
0
247
34.595
0.564
683
34
HR 2973
GK HyD HR 4527
VV Man HD 57364 II Peg
KlIII/
GO/GlIV A/GSIV-I11
GZV/KOIII G8III/K2III K2-3v-IV/
11 Peg
LX Per
sz
Psc
GOV/KOIV
F8V/KlIV
TY Pyx
G5lG5
35.926
0.609
1535
0
HR 1099
GSIV/KlIV
33.695
0.457
0
1191
34.764
0.833
0
1072
(b)
(cl
Cc>(4
(9)
w
(cl (f) (0)
(cl (h) (i)
LIU and TAN
66
Table
SW HR 1099
SP. (h/c)
ilV/KlIV
1. D. (H) 2446000+
Phase
r
I-I EWblo abror.
Ref.
emission
35.628
0.138
0
a41
36.727
0.727
0
836
37.912
0.942
0
al4
59.659
0.606
0
534
60.605
0.939
0
465
XY UMO
Z-sV/K5V
37.959
0.030
la27
0
HR 4374
3VI ZNII/KOIII
35.969
0.675
1269
0
3s. 031
0.178
1150
0
35.982
0.193
1203
0
37.011
0.209
1090
0
38.016
0.224
107s
0
35.041
0.710
lOS0
0
38.037
0.856
1205
0
33.558
0.183
1187
0
34.556
0.192
1198
0
35.553
0.201
1248
0
36.651
0.210
1394
0
59.560
0.422
1206
0
35.013
0.760
1037
0
3s. 099
0.589
1099
0 0
HR 4665
HR 5110 HR 7428
HD 86590
HD
108102
DM UMa
HD 175742
HD 37847
!IV/K
IV
?/K2111-II
OVl
36.863
0.489
1040
W/FaV
36.013
0.195
2287
0
IcGV-IV
35.951
0.830
0
2040
Ov/KS-M2\
/csrrr
36.036
0. a42
0
2030
36.895
0.956
0
2000
36.993
0.969
0
2000
37.996
0.103
0
2923
34.536
0.745
342
0
35.536
0.092
73
19
36.532
0.438
251
0
37.523
o.fa4
400
0
100
60
33.795 34.784
-
464
0
35.743
-
a35
0
35.767
-
835
0
36.741
-
767
0
767
0
36.779
HD 190540 HD 205249 HD 0357
/KOIV .lIII/ ;5/composite
1. (continued)
37.923
-
562
0
33.577
-
924
0
35.572
-
1232
0
33.598
-
1069
0
34.578
-
1064
0
33.644
0.280*
128
412
34.628
0.397
160
196
(cl 6)
(cl (i) Cc) (k)
Cc)
W
(h)
(k)
(4) Cm)
Ha of RS CVn Stars
67
Table
HD8357
FIV/KOIII
HK Lac * The
GS/compositc
phases
Referencea
are calculated in Table
(a)
E. J. Wciler,
(b)
P. W.
(c)
B. W. Bopp
(d)
S. E. Smith
(e)
S. S. Vogt,
37.595
0.711
136
123
41.658
0.156
0
728
59.617
0.118
302
112
60.590
0.225
250
129
61.608
0.336
193
13s
60.504
0.888
321
28
from the formula
J. D. 2445957.88
R. A. S., 182 (1978),
<
(h)
A. C. Collier,
A. J. Lerters.
(i)
(m).
(i)
869 H. L. Nations
(j)
B. W. Bopp
in Red-Dwarf 0.
and Tan Huisong, G. W. Henry,
22 (1982),-127
Stars>>,
~363.
S. C. Barden.
1983. Bull. Am. Astron.
B. Slee, A. E. Wright.
and L. W. Ramsey, and J. C. Talcott.
666
1517
975
L. W. Ramsey,
R. F. Hayncs.
83 (1978).
A. J., s5 (1980).
A. J.,
85 (1980),
I. B. V. S., 2606.
H. Louth,
D. J. Hillier,
Sac.,
15, 663,
1983.
M. N. R. A.S.,200(1982)
1086 55
1984.
Ap. J. Lrtrrrr.
HD 175742 and BD +61"1211. Because the first three systems are systems in which Ho emission was detected for the first time, we made further observations and analysis on the variation and features of this line. For binary BD +61'1211, Ho emission had been observed before, but no quantitative measurements were made because of low resolution; here, we give our determinations of the radial velocity and equivalent widths. It has the strongest Ho emission of all known RS CVn stars.
HR 7428,
(f)
+ 9.15 x n in reference
77
Ap. J., 270 (1983).
A. J..
J., 247 (1981),
D. P. Hucnemocrder,
Liu Xuefu
110
and B. W. Bopp, Ap.
B. W. Bopp,
D. S. Hall,
59
16
and J. C. Talcott,
(f)
(I)
0
0.600
and C. R. Canizarcs,
(g)
(k)
a.495
36.583
1. M. N.
Veddcr
35.617
1. (continued)
257
(1982),
91
from the metal lines of the secondary (primary) star. HD 8357 gives hard X-ray emission: it is the optical counterpart of the X-ray source H D123+075, [S]. Therefore, it is probable that its Ha emission is a secondary effect of its X-ray emissbon.
l(b) HR 7428 = HD 184398 This is a noneclipsing binary; the orbital period is 108.5707 d. In our previous paper [l], we found its Ha emission to show a steady double peak [cf. the profile on 1984 Sept 14 shown in Fig. 2 The Ha emission is l(a) HD 8357 = AR PSC there). Here, we re-observed it twice, on very strong. It also varies rapidly. Our 12 Nov 29 and Dee 25. Although there were no observations all showed strong Ha emission clear Ha emission, we could see a clear change above the continuum and twice it showed in the profile between these two days, and clear double peaks. See Fig. 1. HD 8357 is a two-spectrum binary and radial velocity on Dee 25, there seemed to be some emission in the red wing. On Dee 25, its phase was 0.42, measurements showed that the Ha emission while on the two previous occasions when it component has the same radial velocity as showed double peak emission, its phase was the primary star and the Ha absoprtion 0.48 and 0.51. Whether this means Ha emission component, the same as the secondary star; is more easily seen around phase 0.5 remains hence, the emission comes from the primary, to be confirmed by further observations. and the absorption, from the secondary. Should this be the case, we would infer that Because the two components of Ha mutually the Ha emission comes from the chromosphere compensate and overlap, the velocity curve determined from the absorption core (emission and transition region of the primary star. peak) has a larger amplitude than that from
LIU and TAN
68
J.I).(IO
J.D.(H) 2446000’
&
37.595
0.711
A
tJ.lln
d1.658
59.617 O.IIR --AT fio.590 \I. zz!:,
4
Fig. 1.
H-Alpha emission feature of HD 8357.
1.2
HK7428
k-----J 6560
Pig, 7.
6563
6560
6569
6572
th
Comparison of H-Alpha for HR 7426 observed in September, November and December,
1984.
Ha of RS CVn Stars
1
1
I
I
I
6554
6557
6560
6563
6566
Fig.3.
H-Alpha
variation for
HD
69
’ 6569
17574.7 (top)
--A 6572 C.i, and SZ Pac.
The Ha profile l(c) HD 175542 = V 775 Her showed rapid changes. The variation was complex and fast, and it was hard to see any regularity: sometimes the profile was above the continuum, sometimes there was emission in the wings, and other times it showed pure absorption features. This binary has an orbital period of 2.879 d, [4], but we could see no dependence of the Ha emission and the orbital phase during our observations.Hence it is probable that the emission comes mainly from active regions on the primary or both stars, similar to sunspots and solar flare; then the Ha emission wouldberandom and independent of the position in the orbital. The Ha profile is shown in Fig. 3.
2. HE 37847, HR 1099, IIPeg, UX Ari, LX Per, HK Lac, SZ Psc, HR 5110, HD 86590, HD 190540 The Ha profile of HD 37847 is shown in Fie. 5. The nrofile showed rapid variations in"shape and intensity, similar to HE 175742. Its period is not yet known and from the variations of the Ha profile we estimate its period cannot be very long. The other nine systems have been studied by many previous researchers:
The variable l(d) BD +61'1211 = DM UMa star designation was given in 1981, [6]. This system is-the optical counterpart of the X-ray source 2A 1052+606, [7]. It emits both in soft X-ray (X 10a) and hard X-ray, [8]. The Ha emission of this binary is very strong, having an equivalent width of more than 2A, much stronger than any other observed RS CVn binary. It is one with the highest activity. See Fig. 4.
Our observations are similar to the previous ones. In HR 1099, II Peg and UX Ari, the Ha emission was strong, and was seen to be above the continuum on all occasions. For the other 6 systems, it was a case of being above the continuum on some occasions, and otherwise on other occasions; when the emission portion was partially filled with the absorption lines. Figs. 6 and 7 show the profiles of HR1099 and II Peg. These graphs show that the Ha emission was strong, with equivalent widths
HR 1099 II Peg LX Peg SZ Psc Binary References [9,10] [11,12] [13,14] 111,15] HR 5110 HD 86590 HD 190540 UX Ari HK Lac 1161 [17,18] [17,19] [13,17][17,201
LIU and
TAN
V
0.8 I
6557
li5tilJ
I
6563
6566
wsve
Fig.
4.
pure
H-Alpha
I
I
length
emision
I
6569
I
I
6557
6560
I
6563 wave
(A)
of ED + 61°1211.
Fig.
5.
Fig.
6.
I
,*:4i”
H-Alpha
(i.llh~
I
I
G5tib
b569
emission of HR 1099.
L4J
,_I
6569 -
length profiles of HD 37847.
H-Alpha
I
4s
G566
,.\I
Ha
71
of RS CVn Stars
, -
ll
$/p 1.0 w 1.0 -
1.0 0.9
9
I
I
Fig.
I
I
I
I
I
6557
6560
6563
6566
6569
7. Pure H-Alpha
emission
(A)
of II Pega
0.80 t
Pig.
8.
Compxiron
of H-Alpha
for UX Ari observed
in September
and December,
1984.
72
LIU and TAN
generally greater than 0.5 A, and that the emission varied rapidly. HR 1099 showed double peak on several occasions while II Peg always showed single peak throughout our observations, and very sharp peak at that. The Ha profile of UX Ari is shown in Fig. 8. We see that the emission on Dee 25 was far weaker than that on Sept 14-17. Of the five RS CVn systems with strong Ha emission, (HR 1099, BD+61°1211, HD 224085, HD 8357, UX Ari), UX Ari is the weakest, and is the only one that is not a X-ray source. The Ha profiles of HK Lac and SZ Psc sometimes showed emission and sometimes absorption. For example, as Fig. 3 shows, SZ Psc had a slightlyabovecontinuum emission on Nov 29, yet on the next day, Ha showed the absorption line, with only a weak emission in the blue wing. For these 10 systems, we observed 36 times, and on 6 occasions we found above continuum Ha emission, that is, the probability of emission observation is 17%. This agrees with Bopp's estimate [17] of lo-20% based on HK Lac, SZ Lac and HD 86590. For more precise and stronger statements, we must await the results from longer term monitoring. These are 3. The Remaining 17 Systems systems that show Ha in absorption. Their Ha equivalent widths and radial velocities and other data are given in TABLE 1. It should be noted that the equivalent width of their Ha absorption line is always smaller than that of a standard star of the same spectral type. We think the main reason here is that the absorption line in such stars is partially filled by emission; other factors will be discussed below.
4.
EMISSION PROBABILITY STATISTICS DISCUSSION
Our observations of the Ha profiles and emission features of 59 RS CVn binaries reported in this paper and in [l] lead to the following statistical regularities: 1. Dependence of Ho Emission on the Period We observed above-continuumHa emission in 15 systems. Of these, apart from HD 185151, HD 190540 and HD 37847 for which no period could be found in the literature, the shortest period was that of HD 86590, at P = 1.07 d, and there were only 2 systems with periods greater than 2 weeks (HK Lac, 24.4 d; HR 7428, 108.6d). Thus, the majority are in the normal period group (ld
X-ray counterpart. The other four have corresponding X-ray sources as follows: RS CVn Binary HR BD HD HD
1099 +61'1211 224085 8357
X-ray Counterpart 4U 2A A H
0336 1052 0000 0123
+ + + +
01 606 28 075
tzj [231 u51
Such a tight correlation suggests to us that the strong Ha emission is a secondary effect arising rom the hard X-ray emission. 3. Relation between Ha and Soft X-Ray Emission Using space observations, Charles -obtained the soft X-ray flux in 45 RS CVn systems. Our statistical result is: H-ALPHA EMISSION
NO. OF SYSTEMS
Always Occasional Not seen
4 7 34
MEAN X-RAY LUMINOSITY 31.32 erg/s 31.19 30.84
It thus appears that the more intense the soft X-ray emission is, the greater the likelihood of Ha emission. Relation between Ho and Radio Emissions I171 noted the relation between the radio'flux and the Ha flux in HR 1009. For 3 systems with strong Ha emission, UX Ari, HR 1099 and II Peg, radio flashes have been observed [24]. 4.
BODD
5. Statistics on the Ha Absorption Equivalent Width It was noted that the equivalent width of Ha absorption is smaller in RS CVn stars than in standard stars of the same spectral type. For a total of 47 found the following frequency systems, .tie distribution of the equivalent width ratios. (EW)RS CVn (EW)standard 0.3 0.4 0.5 0.6 0.7 0.8 0.0
-
No. of Systems
0.4 0.5 0.6 0.7 0.8 0.9 1.0
2 4 10 4 7 9 11
total
47
Smith and Bopp [25] have pointed out that, even in systems with no clear above-continuum Ha emission, the equivalent width of the Ha absorption line is still smaller than that in standard stars of the same spectral type. Our observations lead to the same conclusion. There may be two reasons causing this:
Ho of
73
RS CVn Stars
First, as Bopp [21,26] pointed out, because chromospheric activity and high temperature corona have the conditions for providing Ho emission, the emission portion will partially fill the absorption component, thus decreasing its equivalent width relative to the normal stars. Next, as discussed by Vogt and Penrod [27] if there are cool spots on the stellar surface, then that will decrease the equivalent width of the Ha absorption. This effect will vary with the size of the spots, their temperature difference from the their distribution on the photosphere, surface and the rotation of the star, etc. But, generally speaking, this effect cannot We can make a rough estimate be very large. Suppose on a GO main sequence as follows.
star, spot groups occupy 50% of the surface and their temperature is 1200 K lower than the photosphere, then the equivalent width will be reduced to 82% of its normal value. According to our statistics above, of 47 systems, 20 have the equivalent width ratios above 0.8, and 27, below. For systems where this ratio is less than 0.8, it would be difficult to explain by this factor, especially for systems like HD 26337, with an equivalent width of only 432 mA, or only 27% of the value for the standard HR 8684, - in such a case, even if the star surface is completely covered with spot, we still cannot explain the small ratio. ACKNOWLEDGEMENT We thank Dr. Harlan J. Smith Director of McDonald Observatory for giving us valuable telescope time and Dr. J. Tomkin for providing an important piece of data.
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111 t2 1 I31 141
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S. Bdi-s, M. Cav. E. Ralph, W. Robenz,D. ~&WUU,md J. Tow, ,Q,. J. 240(1980), 107. P. M. ~olopov, M. M. Samus,N. P. Kukarkina, G. I. Medvedeva,N. B. perova, IBVS M. Gucis.
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