�������� ���� �� ���� ��������� ������. ����� ������������� ��������� : http://star.arm.ac.uk/~ambn/269pbb.ps ���� ���������: Fri Apr 25 13:07:55 1997 ���� ��������������: Mon Oct 1 21:12:55 2012 ���������:

A&A manuscript no.
(will be inserted by hand later)
Your thesaurus codes are:
missing; you have not inserted them
ASTRONOMY
AND
ASTROPHYSICS
24.4.1997
The photosphere and chromosphere of the RSCVn star,
II Peg.
II. A multi�wavelength campaign in August/September 1992.
P.B. Byrne 1 , H. Abdul Aziz 6? , P.J. Amado 1 , M.J. Arevalo 7 , S. Avgoloupis 4 , J.G. Doyle 1 , M.T. Eibe 1 ,
K.H. Elliott 5 , R.D. Jeffries 5?? , A.C. Lanzafame 1??? , C. Lazaro 7 , H.M. Murphy 1 , J.E. Neff 3 , K.P. Panov 8 ,
L.M. Sarro 1;2 , J.H. Seiradakis 4 , R.E. Spencer 6
1 Armagh Observatory, Armagh BT61 9DG, N. Ireland
2 LAEFF, Vilspa, Madrid, Spain
3 Department of Astronomy, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USA
4 University of Thessaloniki, Department of Physics, Section of Astrophysics, Astronomy and Mechanics, GR�54006, Greece
5 School of Physics and Space Research, University of Birmingham, Birmingham B15 2TT, England
6 University of Manchester, Jodrell Bank, Macclesfield, SK11 9DL, England
7 Instituto de Astrofisica de Canarias, via Lactea, E�38200 La Laguna, Tenerife, Canary Islands, Spain
8 National Astronomical Observatory, Bulgarian Academy of Sciences, 72 Trakya Blvd., Sofia 1754, Bulgaria
Received 1996; accepted
Abstract. We describe multi�wavelength, simultaneous
observations of the RS CVn star, II Pegasi, most of which
were obtained during the first three weeks of Septem�
ber 1992. These observations were made using optical
and infra�red broad�band photometry, ultraviolet and op�
tical spectroscopy and microwave monitoring. We have
detected photospheric spots and chromospheric flares, as
well as deriving a description of mean conditions in the
quiet chromosphere. One of the flares, observed in opti�
cal photometry and ultraviolet spectroscopy is one of the
most energetic ever observed on this star. We demonstrate
that in its ``quiescent'' state II Peg is continually variable
in most of its chromospheric emissions, as well as in its
coronal output.
Key words: Late�type stars -- chromospheric activity --
RSCVn stars
Send offprint requests to: P.B. Byrne
? Present address: School of Physics, Universiti Sains
Malaysia, 11800 Penang, Malaysia
?? Present address: Dept. of Physics, Keele University,
Staffordshire ST5 5BG, UK
??? Present address: Instituto di Astronomia, Universit`a di
Catania, Viale A. Doria 6, I�95125 Catania, Italy
1. Introduction
Chromospheric and coronal heating on the Sun is highly
concentrated into localised active regions of enhanced
magnetic field. The distribution of such active regions
with solar longitude is highly non�uniform, with the global
brightness in high�temperature spectral features some�
times being dominated by a few very active regions. This
is especially true near the maximum of the Sun's magnetic
cycle.
Chromospherically active late�type stars exhibit most
of the characteristics of the active Sun but on a glob�
ally much enhanced scale. RSCVn stars are close late�
type binaries in which one component lies above the main
sequence and, forced into corotation through tidal in�
teraction, is chromospherically active as a result of dy�
namo generation of magnetic fields. RS CVn's exhibit a
wide range of solar�like activity phenomena. These include
non�radiatively heated chromospheres and X�ray emitting
coronae (Doyle et al. 1991, 1992a,b), cool surface spots
(Byrne 1992a,b) and frequent flares (Doyle et al. 1989b).
Based on the solar experience, it might be expected
that non�uniform distributions of magnetic heating on
RSCVn stars would lead to variability in the stars de�
tected flux in suitable chromospheric and coronal radia�
tions as the star rotates, i.e. rotational modulation. Such
effects have been very elusive, however, in spite of much
observational effort (Rodon'o et al. 1987, Andrews et al.
1988, Byrne et al. 1987, 1989, 1995 (hereafter Paper I),
Doyle et al.1989a, 1992a,b). However, since most previous

2 Please give a shorter version with: ``markboth--...�--...�
Table 1. Table of standard magnitudes and colours of II Peg derived from observations taken at Observatorio del Roque
de los Muchachos in September 1992, at the Stephanion Observatory in both July and September 1992 and at the Bul�
garian National Observatory in August 1992. Phases have been calculated according to the ephemeris of Vogt (1981), i.e.
JD=2443033.47+6.72422E.
Date UT JD Phase V B�V U�B V�R V�I
1992 2440000.0+
Jacobus Kapteyn Telescope
08 Sep 23:52 8874.4945 0.655 7.522 1.022 0.798 0.599 1.220
09 Sep 05:28 8874.7277 0.689 7.500 1.022 0.877 0.645 1.275
10 Sep 02:13 8875.5923 0.818 7.510 1.017 0.628 0.603 1.268
23:58 8876.4985 0.953 7.599 1.058 0.707 0.613 1.266
12 Sep 00:15 8877.5104 0.103 7.597 1.012 0.704 0.561 1.269
13 Sep 02:18 8878.5957 0.265 7.456 1.042 0.650 0.594 1.206
14 Sep 00:02 8879.5017 0.400 7.437 1.029 0.698 0.563 1.203
15 Sep 00:14 8880.5095 0.549 7.457 1.055 0.669 0.577 1.235
16 Sep 00:50 8881.5345 0.702 7.444 0.980 0.793 0.587 1.235
17 Sep 05:11 8882.7158 0.877 7.624 1.105 0.828 0.632 1.278
Stephanion Observatory
25 Jul 00:37 8828.526 0.818 7.551 1.050 0.727
27 Jul 00:34 8830.527 0.116 7.571 1.045 0.731
28 Jul 00:39 8831.527 0.265 7.484 1.021 0.740
29 Jul 00:41 8832.528 0.413 7.494 1.035 0.760
30 Jul 00:39 8833.527 0.562 7.500 1.033 0.717
31 Jul 00:42 8834.529 0.711 7.478 1.037 0.621
31 Jul 23:42 8835.488 0.854 7.563 1.047 0.706
03 Sep 21:58 8869.415 0.899 7.552 1.052 0.710
04 Sep 22:26 8870.435 0.051 7.646 1.058 0.739
05 Sep 21:05 8871.378 0.191 7.496 1.008 0.468
09 Sep 01:46 8874.574 0.666 7.462 1.016 0.652
11 Sep 01:29 8876.562 0.962 7.608 1.049 0.717
18 Sep 22:05 8884.420 0.131 7.630 1.047 0.726
Bulgarian National Observatory
26 Aug 01:23 8860.558 0.582 7.522 1.031 0.671
27 Aug 00:56 8861.539 0.728 7.497 1.030 0.653
28 Aug 00:32 8862.522 0.874 7.560 1.027 0.656
29 Aug 00:04 8863.503 0.020 7.652 1.057 0.704
30 Aug 00:42 8864.529 0.173 7.571 1.043 0.692
30 Aug 22:15 8865.427 0.306 7.518 1.036 0.694
efforts have been based on either sampling a single rota�
tion of the active star, or random sampling during many
different rotations, there is an obvious danger of any ro�
tational modulation being masked by short�term variabil�
ity, such as flaring, or longer�term variations, such as the
growth and decay of active regions.
In this paper we describe observations of the 6.72d
SB1 RSCVn K2IV binary, II Peg in the ultraviolet, optical
and microwave spectral regimes, over varying fractions of
2 stellar rotations, which are then used to examine these
issues. In this paper we present the data resulting from
these observations. In a forthcoming paper we will discuss
their implications more fully (Byrne et al. in prep). Note
that throughout this paper we use the orbital ephemeris of
Vogt (1981), i.e. JD = 2443033.47 + 6.72422E, which we
found in Paper I to be more accurate than any of the other
published ephemerides. We also assume, as have others,
that II Peg's axial rotation is tidally locked to the orbital
motion of its companion.
2. Observations
An extensive campaign of monitoring II Peg was organised
in the third quarter of 1992. The core of the coordinated
campaign took place during the two�week interval 5--19
September, but photometric observations were also made
in both July and August to establish the phase and am�
plitude of the spot modulation prior to the main phase of
the campaign.

Please give a shorter version with: ``markboth--...�--...� 3
2.1. Photometry
Visible and infra�red photometry was carried out at a
number of observing sites between July and September
1992. Standard photometry in Johnson UBV (Johnson,
1966), Cousins RIC (Cousins, 1976) and infra�red JHK
(Johnson, 1966) as well as continuous monitoring for flares
in the Johnson U band were achieved.
2.1.1. Photometry � Jacobus Kapteyn Telescope (JKT)
We observed II Peg at the 1m JKT at the Observatorio
del Roque de los Muchachos on the island of La Palma in
the Canary Islands, 7�16 September 1992. The telescope
was equipped with an EEV 1280\Theta1180 pxl CCD detector
and glass filters, which together approximated to the Cape
UBV(RI)C photometric system. Equatorial standard stars
from the lists of Menzies et al. (1991) were measured on
each night to relate the instrumental to the standard sys�
tem. The resulting magnitudes and colours are to be found
in Table 1
II Peg, along with two nearby comparison stars,
viz. SAO 91568 (= BD +28 ffi 4665) and SAO 91577 (=
HD224085 = BD+28 ffi 4667), were measured in all five
colours several times per night. These acted as compar�
ison and check star, respectively. Their mean magnitudes
and colours were found to be
SAO 91568: V = 8.507; (B�V) = 0.751; (U�B) = 0.474
(V�R)C = 0.372; (V�I) C = 0.752
SAO 91577: V = 8.243; (B�V) = 1.267; (U�B) = 1.420
(V�R)C = 0.614; (V�I) C = 1.243
The values for SAO 91577 may be compared with those
determined by the present authors over several seasons
(Rodon'o et al. 1986, Andrews et al. 1988, Byrne et al. 1989,
Doyle et al. 1989a, 1992a), viz.
SAO 91577: V = 8.23; (B�V) = 1.29; (U�B) = 1.41
(V�R)C = 0.65; (V�I) C = 1.24
and with those found from our other photometry below.
Continuous monitoring of II Peg in the Johnson U
band was also undertaken at the JKT on 8 nights between
6/7--15/16 September 1992 (Byrne et al. 1994). The tele�
scope was moved between individual exposures to create
up to ten images of the star before reading out the CCD,
thus reducing the overhead due to CCD readout. Details
of the coverage achieved, which totalled 31.7 hr, will be
found in Table 2. No flares were recorded in this time.
2.1.2. Photometry � Stephanion Observatory
Standard UBV photometry and U�band flare monitoring
were carried out at the Stephanion Observatory (SO),
Greece, using the 75cm Cassegrain reflector belonging
to the University of Thessaloniki between July 24--31 and
September 3�18, 1992. The telescope and photometer have
been described by Mavridis et al. (1982). Nightly mea�
Table 2. Flare monitoring times of II Peg at the Jacobus
Kapteyn Telescope, 6--16 September 1992, and at Stephanion
Observatory, 4--19 September 1992. Breaks of duration �3 min
have been ignored. Times in bold are those during which both
telescopes were observing for at least some of the time.
Date Monitoring Intervals Total
1992 UT
Jacobus Kapteyn Telescope
6/7 Sep 04:49--06:07 01 h 18 m
7/8 Sep 03:53--05:17 01 h 24 m
8/9 Sep 20:33--20:36 20:42--23:26
03:57--05:02 03 h 52 m
10/11 Sep 20:55--23:11 02 h 16 m
12/13 Sep 02:52--06:01 03 h 09 m
13/14 Sep 20:25--23:46 01:32--06:10 07 h 59 m
14/15 Sep 21:01--23:20 01:58--06:08 06 h 29 m
15/16 Sep 21:01--23:34 03:00--05:59 05 h 32 m
Stephanion Observatory
4/5 Sep 22:24--23:55 00:11--01:36
01:52--02:35 03 h 08 m
5/6 Sep 19:41--20:42 21:27--23 43
00:00--01:04 01:10--01:46 04 h 09 m
6/7 Sep 19:49--21:19 21 23--22:06
22:16--01:18 01:29--01:38 05 h 10 m
7/8 Sep 20:03--23:36 23:40--01:48
01:56--02:22 05 h 50 m
8/9 Sep 19:53--22:19 22:27--23:14
23:23--23:55 23:59--00:14
00:18--01:31 05 h 03 m
9/10 Sep 19:38--21:55 22:01--22:36
22:40--22:50 02 h 59 m
10/11 Sep 20:16--01:11 04 h 40 m
11/12 Sep 19:48--22:40 22:46--01:14
01:22--02:17 04 h 59 m
12/13 Sep 19:09--19:57 21:23--02:26 05 h 29 m
13/14 Sep 18:52--19:46 19:50--20:07
20:17--22:28 22:33--00:33
00:37--01:14 01:23--02:23 06 h 44 m
14/15 Sep 20:47--00:29 00:39--01:21
01:34--02:31 05 h 01 m
15/16 Sep 18:49--20:04 20:25--22:38
22:43--02:19 06 h 43 m
16/17 Sep 18:48--20:00 21:14--22:05
22:09--23:06 23:16--01:10
01:29--02:20 05 h 19 m
17/18 Sep 19:03--19:51 20:01--01:33
01:51--02:18 06 h 32 m
18/19 Sep 20:15--21:41 22:27--01:46 04 h 25 m

4 Please give a shorter version with: ``markboth--...�--...�
surements were referred to the same two local comparison
stars, i.e. SAO 91568 and SAO 91577, which in turn were
referred to standard stars on the best 3 nights photometri�
cally. Typical errors in V and B�V were �0.01, while those
for U�B were �0.04. The following mean magnitudes and
colours for these local comparisons were derived.
SAO 91568: V = 8.525; (B�V) = 0.781; (U�B) = 0.453
SAO 91577: V = 8.246; (B�V) = 1.253; (U�B) = 1.239
These may be compared with our magnitudes for these
same stars as measured at the JKT above (see Sec. 2.1.1
and Sec. 3.1.1). The resulting magnitudes and colours de�
rived for II Peg will be found in Table 1.
Continuous monitoring of II Peg in the Johnson U
band was also undertaken at Stephanion on 15 nights
between 4--19 September 1992. Details of the coverage
achieved, which totalled 76.2 hr, will be found in Table 2.
2.1.3. Photometry � Bulgarian National Observatory
Standard UBV photometry was also carried out at the
Bulgarian National Observatory's (BNO) 60 cm telescope
at Rozhen between 25--30 August 1992. These observa�
tions were made differentially with respect to the local
comparison star, SAO 91568, for which the standard mag�
nitudes and colours measured previously were also as�
sumed here as follows.
SAO 91568: V = 8.54; (B�V) = 0.79; (U�B) = 0.49
The resulting magnitudes and colours derived for II Peg
will be found in Table 1.
2.1.4. Photometry � Infra�red
Infra�red photometry of II Peg was carried out using the
1.5m Carlos Sanchez telescope at the Observatorio del
Teide of the Instituto de Astrofisica de Canarias (IAC)
at Mt. Teide, Tenerife (Canary Islands) on 13 nights be�
tween 30 July and 14 August 1992. A CVF photometer
with a focal plane chopper was used. The detector was
a liquid�nitrogen�cooled InSb device which, together with
filters, gave a good approximation to the standard J, H
and K bands (Johnson, 1966, Glass, 1985). Both the chop�
ping amplitude and the aperture diameter were 15 arcsec.
Each photometric measurement was performed exposing
the star for 10 sec in alternate beams until the signal�
to�noise of the integrated measurement was �500. The
comparison star was SAO 91577. Its standard magnitudes
were found to be
SAO 91577: J = 6.15; H = 5.84; K = 5.32; L = 5.17
Standard errors on each measurement were �0.01.
Standard reference stars were also observed to cali�
brate the observations to the standard system. A log of
this data will be found in Table 3.
2.2. Optical spectroscopy
Three optical spectroscopic data sets were taken during
the campaign. The first consisted of high�resolution spec�
tra, one per night, of Balmer Hff and Hfi, as well as
HeI D 3 . The second was in the blue at lower resolution and
included the higher members of the Balmer series and the
CaII H&K doublet. The third comprised a time sequence
of Hff spectra, also at a lower resolution.
2.2.1. Optical spectroscopy � high�resolution data
High�resolution (R�25 000) spectroscopy was carried out
using the Solar Stellar Spectrograph at the US National
Solar Observatory's 1.6m McMath Pierce Telescope at
Kitt Peak, Arizona on 5 nights between 11--16 September
1992. On all clear nights a single spectrum was recorded in
the region of the Balmer Hff line, while on a smaller num�
ber of nights spectra were recorded near Balmer Hfi and
HeI D 3 . A log of these spectra will be found in Table 4.
Table 4. A log of the optical high�resolution spectra recorded
at the McMath Pierce Telescope between 11--16 September and
of blue low�resolution spectra at the Isaac Newton Telescope
between 14--19 September 1992. Phases have been calculated
according to the ephemeris of Vogt (1981).
Date UT Exp JD Phase � c
1992 mid�exp min 2440000.0+ � A
McMath Pierce Telescope
11 Sep 04:57 30 8876.706 0.983 6562.8
06:55 30 8876.788 0.996 5975.7
08:52 30 8876.869 0.008 4861.3
12 Sep 08:47 40 8877.866 0.156 6562.8
09:57 30 8877.915 0.163 4861.3
11:39 35 8877.985 0.174 5975.7
14 Sep 08:47 30 8879.866 0.453 6562.8
10:04 35 8879.919 0.461 5975.7
15 Sep 08:35 40 8880.858 0.601 6562.8
16 Sep 08:28 07 8881.853 0.749 6562.8
Isaac Newton Telescope
15 Sep 02:00 20.0 8880.583 0.560 4128
16 Sep 01:56 16.7 8881.581 0.708 4128
17 Sep 02:00 16.7 8882.583 0.858 4128
18 Sep 02:01 16.7 8883.584 0.006 4128
20 Sep 01:56 16.7 8885.581 0.303 4128
2.2.2. Optical spectroscopy � blue low�resolution data
Low�resolution (R�4 500) spectroscopic data in the blue
region (�3 890--4365 � A) were obtained using the Interme�
diate Dispersion Spectrograph (IDS) on the 2.5m Isaac
Newton Telescope (INT) at the Observatorio del Roque
de los Muchachos on the island of La Palma on five nights
between 1992 September 14�19. A 2400 lines/mm grating,

Please give a shorter version with: ``markboth--...�--...� 5
Table 3. Table of nightly mean standard J, H and K magnitudes of II Peg derived from the observations taken at the Obser�
vatorio del Teide, Tenerife, in July and August 1992. Phases have been calculated according to the ephemeris of Vogt (1981),
i.e. JD=2443033.47+6.72422E.
Date UT JD Phase J H K
1992 2440000.0+
31 Jul 04:20 8834.681 0.734 5.412 4.802 4.628
1 Aug 03:23 8835.641 0.876 5.411 4.802 4.623
2 Aug 03:39 8836.652 0.027 5.455 4.842 4.662
3 Aug 02:54 8837.621 0.171 5.419 4.803 4.627
5 Aug 01:26 8839.560 0.459 5.407 4.788 4.599
6 Aug 03:00 8840.625 0.618 5.392 4.775 4.597
7 Aug 02:42 8841.612 0.765 5.400 4.782 4.604
8 Aug 00:41 8842.528 0.901 5.452 4.821 4.650
9 Aug 00:48 8843.533 0.050 5.441 4.811 4.642
10 Aug 03:21 8844.640 0.215 5.389 4.786 4.620
11 Aug 02:35 8846.607 0.507 5.395 4.780 4.605
12 Aug 03:51 8847.660 0.664 5.389 4.766 4.599
15 Aug 04:40 8850.694 0.115 5.441 4.825 4.649
Table 5. A log of the optical low�resolution Hff spectra
recorded at the University of Birmingham's Wast Hills Obser�
vatory between 7--20 September 1996. Phases have been calcu�
lated according to the ephemeris of Vogt (1981).
Date UT JD Phase
1992 2440000.0+
7/8 Sep 21:53--04:35 8873.412--.691 0.494--0.535
8/9 Sep 20:47--22:31 8874.366--.483 0.635--0.653
10/11 Sep 21:39--01:32 8876.402--.564 0.938--0.962
11/12 Sep 20:38--01:12 8877.360--.550 0.081--0.109
13/14 Sep 20:16--04:16 8879.343--.678 0.376--0.425
14/15 Sep 20:04--02:35 8880.336--.608 0.523--0.564
15/16 Sep 23:54--04:49 8881.496--.701 0.696--0.726
16/17 Sep 20:09--21:22 8882.340--.390 0.821--0.829
20/21 Sep 20:30--21:26 8886.353--.393 0.418--0.424
blazed at 3 500 � A was used and a slit width of 1.35 arcsec,
which projected to 2.2 pxl on the CCD detector. A log of
these spectra will be found in Table 4.
2.2.3. Optical spectroscopy � red low�resolution data
Low�resolution (R�3 300) Hff data were recorded on 9
nights between 7--20 September 1992 using the 40cm tele�
scope at the University of Birmingham's Wast Hills Ob�
servatory. The telescope was equipped with a zoom lens
spectrograph (Elliott, 1996) equipped with a GEC CCD
detector which gave 385 pixels in the dispersion direction,
corresponding to a wavelength coverage of �760� A. A log
of this data will be found in Table 5.
2.3. UV spectroscopy
Ultraviolet spectroscopy was obtained with the Interna�
tional Ultraviolet Explorer satellite (IUE) (Boggess et al.
1978) on 12 consecutive days between 1992 September
5--16. Data were obtained using both the IUE's long�
wavelength (�1900--3200 � A; LWP) and short�wavelength
(�1150--1950 � A; SWP) cameras in high� (R�45000 at
�2 800 � A; HIRES) and low�resolution (R�300 at �1 500 � A;
LORES), respectively. Between three and six spectra were
obtained on each date alternating between LWP HIRES
and SWP LORES. This observing scheme enabled us to
make maximumuse of the satellite as SWP exposures were
made while the LWP camera was being read to ground and
prepared for the next observation and vice versa. A log of
the spectra will be found in Table 6.
2.4. Microwave observations
II Peg was also monitored between 7--15 September
1992 using the Broad�band Interferometer (BBI) (Padin
et al. 1987) at the Nuffield Radio Astronomy Laboratory
(NRAL) at Jodrell Bank, England. The BBI operates at
5GHz (�=6cm) with a bandwidth of 384MHz and has a
sensitivity of 2mJy min \Gamma 1
2 .
The observations consisted of single scans of the
source, each nominally 45min but, due to telescope track�
ing errors (due, in turn, to high winds), actually achieved
a typical on�source integration time of 20--40min. Individ�
ual integrations each lasted 20sec. After averaging these
20sec integrations over a scan the typical noise level was
�0.3--1.0mJy.
The BBI was on 24hr scheduled operation observing
a number of objects including II Peg. Amplitude calibra�
tors, 3C48 and 3C286, were observed every �12hr. Their
flux densities were taken as 5.335Jy and 7.338Jy respec�

6 Please give a shorter version with: ``markboth--...�--...�
tively (Baars et al. 1977). A nearby object, 2004+403, was
chosen as a phase calibrator with an observing cycle of 15
minutes on phase calibrator and 45 minutes on II Peg
(referred to as a scan). A tracking window of 3 arcmin
was imposed which rejected the incoming data when the
observing source fell outside this window due to tracking
error.
Details of the coverage achieved will be found in Ta�
ble 7.
3. Results
3.1. Photometry
3.1.1. Standard photometry
A comparison of the mean magnitudes and colours of the
comparison star SAO 91568 in Section 2.1 above shows
that, for the three ground�based sets of photometry, zero
points are reasonably consistent. The differences indicated
by this comparison suggest mean differences as follows:
SO�JKT: \DeltaV=+0.017; \Delta(B�V)=+0.030; \Delta(U�B)=--0.021
SO�BNO: \DeltaV=--0.015; \Delta(B�V)=--0.009; \Delta(U�B)=--0.037
No comparison was possible for the (V�R)C and (V�I) C
data since these were measured at the JKT only. These
differences in the magnitudes and colours of SAO 91568
are within the errors expected in the three data sets and
so are unlikely to indicate systematic differences.
Intercomparison of the mean results for SAO 91577,
however, indicates a large discrepancy between SO and
JKT in respect of (U�B) colour (\Delta(U�B) SO\GammaJKT =�0.181).
This is uncomfortably large to be attributed to photomet�
ric errors. It is possible, of course, that the bluer photo�
metric transformations, particularly U, are uncertain at
the extreme red end of their range. On the other hand the
mean (U�B) colours for II Peg itself are in good agreement
(cf. Fig. 1). At present this anomaly is unresolved.
The V light curve, as presented in Fig. 1, is a super�
position of the data from all three sources. Its scatter is
larger than might be expected from the intercomparison
of the mean magnitudes for SAO 91568. It can, neverthe�
less, be readily seen that there is a minimum near phase
' �0.03 and a maximumnear ' �0.4. Thus the light curve
is clearly asymmetric, with a much steeper rise than fall.
However, there is a relatively slow fall between ' �0.4--
0.8, followed by a much more rapid decline to minimum.
The amplitude of the modulation, \DeltaV is �0.2.
The scatter in the B�V curve is reasonably uniform
with phase and is of amplitude \Delta(B�V)�0.02--0.03. Over�
all, the B�V curve shows evidence of a low�level modula�
tion (\Delta(B�V)�0.02) in phase with the V variation.
The U�B curve shows a uniform scatter with amplitude
of \Delta(U�B)�0.15--0.2 apart from one point which stands
out from the rest (near ' �0.2). This is associated with the
large optical flare on 5 September which will be discussed
further below (Section 3.2). It is indicated in both the U�B
Fig. 1. Nightly mean V and (B�V), (U�B), (V�R)C and (V�I)C
light curves for II Peg in September 1992. The filled squares
represent data from JKT in September, the open squares those
from Stephanion Observatory in July, the open triangles those
from the same source in September and the stars those from
the Bulgarian National Observatory. The point bracketted and
labelled `F' is that measured during the flare of 12 September.

Please give a shorter version with: ``markboth--...�--...� 7
Table 7. Log of the BBI 5GHz monitoring of II Peg obtained between 7--15 September 1992. Phases have been calculated
according to the ephemeris of Vogt (1981).
Day UT JD Flux oe Day UT JD (mid�exp) Flux oe
1992 (mid�exp) mJy mJy 1992 2440000.0+ mJy mJy
2440000.0+
7 Sep 17:35--18:00 8873.241 2.5 0.5 10 Sep 18:18--19:00 8876.277 1.111 0.4
7 Sep 18:24--19:00 8873.279 2.7 0.5 10 Sep 19:19--20:00 8876.319 2.584 0.5
7 Sep 19:19--20:00 8873.319 1.9 0.4 10 Sep 20:19--21:00 8876.361 2.485 0.5
7 Sep 20:18--21:00 8873.360 2.0 0.5 10 Sep 21:19--21:56 8876.401 3.524 0.6
7 Sep 21:18--22:00 8873.402 4.9 0.5 10 Sep 22:19--23:00 8876.444 3.718 1.1
7 Sep 22:18--22:59 8873.443 1.8 0.5 10 Sep 23:31--23:59 8876.490 4.797 1.0
7 Sep 23:23--23:59 8873.487 3.4 0.7
8 Sep 00:20--00:58 8873.527 5.1 0.6 11 Sep 19:18--20:00 8877.319 3.036 0.5
8 Sep 01:20--02:00 8873.569 3.8 0.5 11 Sep 20:18--21:00 8877.360 2.176 0.4
8 Sep 02:20--03:00 8873.611 5.7 0.6 11 Sep 21:20--22:00 8877.403 0.903 0.4
11 Sep 22:25--22:59 8877.446 1.1 0.6
8 Sep 17:11--18:00 8874.233 1.4 0.4 11 Sep 23:21--23:59 8877.486 3.851 0.8
8 Sep 18:18--19:00 8874.277 2.3 0.4
8 Sep 19:18--20:00 8874.319 1.6 0.4 12 Sep 19:18--20:00 8878.319 3.331 0.5
8 Sep 20:18--21:00 8874.360 2.1 0.5 12 Sep 20:18--21:00 8878.360 2.120 0.4
8 Sep 21:22--21:38 8874.396 1.0 0.7 12 Sep 21:19--22:00 8878.403 0.248 0.5
8 Sep 22:19--22:59 8874.444 2.4 0.5 12 Sep 22:19--23:00 8878.446 0.437 0.7
8 Sep 23:19--23:58 8874.485 5.2 0.8 12 Sep 23:19--23:58 8878.486 1.739 0.8
9 Sep 00:19--01:00 8874.527 5.9 0.6
9 Sep 01:20--01:59 8874.569 3.0 0.5 13 Sep 19:18--20:00 8879.319 11.159 0.9
9 Sep 02:20--03:00 8874.611 4.9 0.6 13 Sep 20:19--21:00 8879.361 12.901 1.0
9 Sep 03:19--04:00 8874.652 4.7 0.5 13 Sep 21:20--22:00 8879.403 14.976 1.1
9 Sep 04:19--05:00 8874.694 3.4 0.5 13 Sep 22:19--23:00 8879.444 9.523 0.9
13 Sep 23:19--23:59 8879.485 9.1 0.9
9 Sep 18:38--18:59 8875.280 1.4 0.7
9 Sep 19:18--20:00 8875.319 0.2 0.4 14 Sep 19:24--19:59 8880.320 5.181 0.6
9 Sep 20:18--21:00 8875.360 1.4 0.5 14 Sep 20:19--21:00 8880.361 2.769 0.5
9 Sep 21:20--22:00 8875.403 0.3 0.5 14 Sep 21:18--22:00 8880.402 5.245 0.6
9 Sep 22:20--23:00 8875.444 1.0 0.5 14 Sep 22:18--22:59 8880.443 2.169 0.7
9 Sep 23:29--23:56 8875.488 3.7 1.1 14 Sep 23:22--23:59 8880.486 1.923 0.6
10 Sep 00:19--00:59 8875.527 3.1 0.6
10 Sep 01:20--02:00 8875.569 2.5 0.6 15 Sep 19:20--19:58 8881.319 1.992 0.6
10 Sep 02:20--03:00 8875.611 2.8 0.5 15 Sep 20:24--21:00 8881.363 0.990 0.9
10 Sep 03:19--04:00 8875.652 2.2 0.4 15 Sep 21:19--22:00 8881.402 0.607 0.7
10 Sep 04:19--05:00 8875.694 1.1 0.4 15 Sep 22:20--22:57 8881.443 2.485 0.9
15 Sep 23:20--24:00 8881.486 0.7 0.6
and B�V colour curves and in the V light curve by an `F'.
We note that the scatter in the (U�B) measurements is
much larger than would be expected on the basis of the
uncertainty in the measurements themselves (i.e. �0.03).
This may be due to low�level flaring as has been suggested
in many active late�type stars (see e.g. Byrne, 1983 and
references therein).
Both the near�IR colour curves mirror the V variation
accurately in phase. V�R, however, has an amplitude of
only \Delta(V�R)�0.07, while \Delta(V�I)�0.11. Both are again in
phase with V, consistent in a general sense, with the spot
origin of the variations.
The light curves for the IR JHK bands will be found
in Fig.2 in the form of J magnitude and (J�H) and (J�K)
colour diagrams. The J light curve is similar to V but with
an amplitude of \DeltaJ�0.06. There is no evidence of system�
atic variation in either of the IR colours themselves, but,
given the different amplitudes in V and J, there is a strong
variation in (V�J). Because, however, simultaneous V and

8 Please give a shorter version with: ``markboth--...�--...�
Fig. 2. The J magnitude and (J�H) and (J�K) colour curves
for II Peg at the end of July and the first half of August 1992
as observed at the Teide Observatory of the IAC. Phases have
been calculated according to the ephemeris of Vogt (1981), i.e.
JD=2443033.47+6.72422E.
JHK measurements are not available, it is not possible to
get a direct measure of the (V�J) colour.
3.2. U�band flare monitoring
Two optical U�band flares were recorded, details of which
will be found in Table 8. The light curve of the largest of
these will be found in Fig. 3.
We have used the Equivalent Duration (ED) method
of Gershberg (1972) in calculating the total, time�
integrated energy in each flare. ED is defined as the time
during which the quiescent star emits the same energy as
the flare in the same passband. Thus the measurement of
the flare's energy is referred to the quiescent pre�flare level
as measured immediately preceding the flare itself. This
avoids many of the uncertainties involved in the absolute
calibration of the flare observations.
The energy of the flare is thus defined as
EU = ED \Theta F q;U
where F q;U is the quiescent energy emitted in the U band
per second. This, in turn, is related to the star's quiescent
U magnitude (taken as 9.3, see Table 1) by
F q;U = 4�d 2 10 \Gamma0:4U \Pi U
where d is the distance to the star, taken as 29pc (Strass�
meier et al. 1993), and \Pi U is the conversion factor from
U magnitude to energy, taken as 2.32 10 \Gamma6 erg cm \Gamma2 s \Gamma1
(Bessell, 1979). This yields F q;U =4.45 10 31 erg cm \Gamma2 s \Gamma1 .
Deriving the energy of each flare in absolute terms is then
a relatively simple procedure, the results of which will be
found in Table 8.
3.3. High�resolution Hff
The McMath high�resolution spectra were flat�fielded, and
wavelength calibrated using purpose built routines within
the IDL data analysis package (IDL Users' Guide, 1985).
All subsequent analysis was undertaken using routines
within the IRAF astronomical software suite (Tody et al.
1986) or within DIPSO (Howarth and Murray, 1987), a
software package available on the UK STARLINK network
(Bromage, 1984). Spectra were corrected for telluric lines
by reference to spectra of early�type stars taken specially
for this purpose.
Fig. 4. The overall mean profile of II Peg's Hff emission line
derived from four nights' data (upper solid curve). Note that
all spectra have been wavelength corrected to the rest frame
of the K�star primary and the vertical line gives the rest wave�
lengths of the Hff line. The dashed curve gives the ratio of
the mean 1992 spectrum to that for 1991 taken from Paper I
and displaced downward to aid visibility. Both spectra have
been smoothed by a gaussian of FWHM�0.18� A, less than the
nominal resolution of the spectrograph.
The resulting spectra were then corrected to the
rest frame of the K star primary of II Peg. This was
achieved by shifting a strong, isolated photospheric line

Please give a shorter version with: ``markboth--...�--...� 9
Fig. 3. Light curve of the large optical flare observed in the U�band at Stephanion Observatory on 5 September 1992.
Fig. 5. The overall mean profile of II Peg's Hfi emission line
derived from all three nights' data (upper curve). The dashed
curve gives the mean 1991 Hfi profile from Paper I which have
been displaced downward to aid visibility. Note that all spectra
have been wavelength corrected to the rest frame of the K�star
primary and the vertical line gives the rest wavelengths of the
Hfi line.
(FeI�6569.224 � A) to its laboratory wavelength. The spec�
tra were then normalized by fitting a spline function to
the local continuum and dividing through by this spline.
The points at which the spline was fit were those judged
to be free of lines when comparison was made with spec�
tra of a number of slowly rotating K giants, taken with
the same instrument and broadened to II Peg's rotational
Fig. 6. The overall mean profile of II Peg's HeI D3 line de�
rived from three nights' data (upper curve). The dashed curve
gives the mean 1991 HeI D3 profile from Paper I which have
been displaced downward to aid visibility. Note that all spectra
have been wavelength corrected to the rest frame of the K�star
primary and the vertical lines give the rest wavelengths of the
HeI D3 doublet.
vsini (=21km s \Gamma1 , Vogt (1981)). Fig.4 shows the mean of
all the Hff spectra.
From Fig. 4 it will be seen that the mean Hff line is
strongly in emission with a peak intensity �1.45 times
that of the local continuum and has a FWHM�1.6� A. Fur�
thermore, it is asymmetric, in the sense that it shows an
``absorption reversal'' whose red peak is depressed relative

10 Please give a shorter version with: ``markboth--...�--...�
Fig. 7. The EW of the II Peg's Hff emission as a function of
Julian Date measured at the Univeristy of Birmingham's Wast
Hills Observatory between 7--20 September 1992. Proposed
flares are indicated by bracketts around the flaring points.
to the blue peak, and a blue wing which exceeds the red
in total flux.
3.4. High�resolution Hfi
The McMath high�resolution spectra in the vicinity of the
chromospheric Hfi emission line were extracted and an�
alyzed similarly to those at Hff (Section 3.3). They are
shown after correction to the rest frame of the K�star pri�
mary in Fig.5 in the form of the overall mean spectrum
derived from the data on all three nights of observation.
As remarked in Paper I the line is blended with nearby
photospheric lines of CrI�4861.849 � A and FeI�4861.952 � A
on the red side and FeI�4860.986 � A on the blue. It is possi�
ble to ``see'' the lines to the red but the line to the blue is
inextricably blended with Hfi and impossible to deblend
without recourse to either synthetic spectra or inactive
templates. However, it is apparent that the Hfi line is
``filled in'' and is asymmetric to the blue, in the sense
that it is more ``filled in'' on that side of line centre.
3.5. High�resolution HeI D 3
The McMath high�resolution spectra in the vicinity of the
chromospheric HeI D 3 line were extracted and analyzed as
were those for Hff (Section 3.3). The resultant spectra are
shown in Fig.6 in the form of the overall mean spectrum
derived from the data on both nights of observation. The
line is in net weak emission with a peak intensity of �2�3%
of the continuum level.
3.6. Low�resolution Hff
These spectra were extracted in hardware in real�time at
the telescope to give 1�dimensional data, which were later
debiased, flat�fielded and wavelength calibrated. The re�
sults of the low�resolution Hff monitoring will be found in
Fig. 7 as a plot of EW(Hff) against time.
3.7. Blue low�resolution spectroscopy
The INT spectra were extracted from the CCD images
and wavelength calibrated within the STARLINK package
FIGARO (Meyerdicks, 1993). We illustrate the results in
Figs. 8 where the overall mean spectrum has been shifted
in wavelength to match the rest frame of the K star. A flux
calibration was achieved by reference to measurements of
flux standards before and after the exposures. Although
these spectra were not spectrophotometric, intercompari�
son between flux standards suggests that the accuracy of
this calibration is better than �20% in all cases.
We note the following general characteristics. The
CaII H&K and Balmer Hffl lines are strongly in emission.
However, we have examined carefully the spectra in the
region of the Balmer Hfl or Hffi lines (marked by vertical
lines in Figs. 8) and find that there is no obvious evidence
of either, whether in emission or absorption.
3.8. UV spectroscopy
The IUE spectra were extracted from the spectral images
and then wavelength and flux calibrated using the pro�
gram IUEDR (Giddings, 1983) which is available on the
UK STARLINK astronomical computing network (Bro�
mage, 1984). Subsequent analysis was performed using
the STARLINK program DIPSO (Howarth and Murray,
1987).
3.8.1. SWP
In the SWP spectra the stellar lines are unresolved and
their fluxes were estimated by fitting one or two gaus�
sian profiles to the data in the manner described in Byrne
et al. (1987). Two gaussians of fixed separation and rela�
tive intensity were used where the lines were partially re�
solved doublets (e.g. CIV�1549/52 � A). The line fluxes for
the most prominent SWP emission lines resulting from
this procedure will be found tabulated in Tables 9.
3.8.2. LWP
Extracting line fluxes from the LWP spectra was more
complex for a number of reasons. The most promi�
nent lines visible in the LWP spectra were those of the
MgII h&k resonance doublet (�2795.5/2802.7 � A) and some
lines of the FeII UV1 multiplet near �2 600 � A. In both cases
the emission lines were resolved. Furthermore, in the case
of the MgII h&k resonance doublet there is appreciable
interstellar (IS) absorption superimposed on the stronger
and broader stellar emission. Finally, the wavelength cali�
bration of IUE in HIRES may be subject to uncertainties
of order � \Sigma10km sec \Gamma1 (Byrne et al. 1989).

Please give a shorter version with: ``markboth--...�--...� 11
Table 9. Line fluxes at Earth for the most prominent emission lines in the SWP spectra of II Peg. Values given in bold type
were obtained from spectra during which we have deemed flares to be taking place. The phase of each observation is given
according to the ephemeris of Vogt (1981), i.e. JD=2443033.47+6.72422E.
JD Phase OI CII CIV HeII CI AlII SiII
mid�exp �1302/5/6 � A �1335/6 � A �1548/51 � A �1640 � A �1656--58 � A �1671 � A �1808/17/8 � A
2440000.0+ Line Flux at Earth (\Theta10 \Gamma13 erg cm \Gamma2 sec \Gamma1 )
8871.327 0.183 6.9 12.1 37.2 15.4 5.3 2.7 1.8 3.4
8871.411 0.196 6.7 12.2 25.3 15.0 5.6 2.9 1.4 2.9
8872.380 0.340 4.6 4.8 5.3 4.6 3.1 1.1 1.4 2.2
8873.368 0.487 3.2 3.7 3.9 3.3 2.1 1.1 1.0 1.6
8873.441 0.498 2.6 2.5 4.7 2.9 1.6 1.1 0.7 1.2
8874.221 0.614 3.2 4.5 4.2 4.3 3.0 2.2 1.3 1.7
8874.328 0.630 2.4 2.4 3.7 4.0 2.8 1.1 1.0 1.2
8874.424 0.644 3.2 4.6 5.9 4.3 3.0 0.7 1.4 1.8
8875.398 0.789 3.3 4.8 9.8 6.6 2.5 1.2 1.7 2.5
8876.335 0.928 3.9 3.3 5.0 4.6 2.7 1.0 1.2 2.0
8876.440 0.944 3.4 2.8 4.9 3.7 1.9 --- 1.3 2.3
8877.340 0.078 3.5 4.8 4.8 4.1 3.0 0.6 1.4 2.2
8877.440 0.093 2.7 2.8 3.0 3.7 2.8 0.7 1.0 1.8
8878.344 0.227 3.7 4.3 5.6 3.5 3.1 --- 1.4 2.3
8878.431 0.240 4.8 6.2 9.8 5.1 3.3 1.4 1.5 1.9
8879.347 0.376 4.3 3.5 5.1 3.0 2.5 0.8 1.2 1.8
8879.433 0.389 3.9 4.8 5.8 4.2 2.7 0.7 1.4 2.2
8880.319 0.521 3.5 4.2 5.1 3.3 2.2 0.8 1.2 2.0
8880.418 0.536 3.6 3.8 4.2 3.5 2.6 0.7 1.3 1.7
8881.303 0.667 3.2 2.3 5.1 3.9 2.0 0.8 1.5 1.6
8881.430 0.686 3.7 3.4 5.7 3.7 2.7 --- 1.7 3.0
8882.343 0.822 1.3 1.3 2.9 1.9 1.4 --- 0.8 1.3
8882.430 0.835 3.2 4.0 6.3 4.3 2.9 --- 1.3 2.1
We have adopted the following procedure for deriving
the flux of the MgII lines. We have assumed that the IS
line is unresolved at the resolution of IUE HIRES and
fitted it with a gaussian profile of fixed FWHM equal
to that of the instrumental profile of the IUE spectro�
graph in HIRES mode, while simultaneously fitting the
main emission profile with another gaussian whose cen�
tral wavelength, FWHM and intensity are all free to vary.
This procedure fits the IS line well but it is clear that there
is excess flux in the wings of the main stellar emission line
over and above a gaussian.
After this first round of fits the IS feature was used as
a fiducial to bring the entire set of spectra to a common
wavelength scale and the stellar emission fitted with the
sum of two gaussians, one to represent the main body of
the emission and the other to represent the wings. These
fits have been used to estimate the total flux in the stellar
emission line. The result will be found in Table 10.
The FeII lines were measured by fitting a number of
gaussians of fixed wavelength separation, corresponding to
the laboratory separation of the UV1 lines. Their FWHM
and intensities were, on the other hand, allowed to vary
freely. The resulting measured line fluxes will also be found
in Table 10.
3.9. Microwave observations
The data from each scan was vector integrated over the
whole scan period and a plot of these scan averages will
be found in Fig. 9. The star is detected at all times of
observation and shows evidence of continuous variability
in its flux at 5GHz at all time scales examined by the
data. This is true both on an hourly time scale and from
night�to�night. A strong flare with a peak flux density of
15 mJy was observed on September 13.
4. Discussion
4.1. Mean light curve
The mean V magnitude in 1991 (Paper I), !V?�7.45,
was clearly brighter than the current epoch, !V?�7.55.
Our measured mean is, however, very similar to those mea�
sured in 1986 (Byrne, 1986, Byrne and Marang, 1987),
!V?�7.53, and 1989 (Doyle et al. 1992a), !V?�7.54,
when II Peg showed a record large amplitude modulation.
Assuming that the fainter mean magnitude is caused by a
relatively larger global coverage by starspots, this implies

12 Please give a shorter version with: ``markboth--...�--...�
Table 10. Line fluxes at Earth for the most prominent emission lines in the LWP spectra of II Peg. Note that the MgII line
fluxes have been corrected for interstellar absorption. The values given in boldface are those associated with the flare discussed
in the text. Phase has been calculated using the ephemeris of Vogt (1981), i.e. JD=2443033.47+6.72422E.
JD Phase MgII Fe II
mid�exp 2795.5 � A 2802.7 � A 2620.7 � A 2621.7 � A 2625.7 � A 2628.3 � A 2631.1 � A
2440000.0+ \Theta10 \Gamma12 erg cm \Gamma2 sec \Gamma1 \Theta10 \Gamma13 erg cm \Gamma2 sec \Gamma1
8871.357 0.188 10.90 9.08 2.71 3.90 8.45 4.57 8.83
8872.328 0.332 7.13 5.05 3.13 1.78 4.31 2.33 2.98
8872.431 0.348 5.92 4.61 2.49 1.34 3.80 1.37 3.03
8873.316 0.479 5.85 5.47 3.41 2.56 3.20 1.88 2.25
8873.418 0.495 5.93 4.62 3.33 1.04 4.38 2.04 3.68
8874.171 0.606 5.40 4.68 1.85 1.66 3.08 2.03 2.76
8874.277 0.622 5.67 5.23 1.96 0.51 2.66 1.63 2.22
8874.381 0.638 5.45 5.67 2.46 1.84 3.69 2.63 1.64
8875.347 0.781 5.81 5.30 2.58 1.31 2.76 2.17 2.39
8875.443 0.796 5.68 5.29 2.55 2.17 3.18 2.94 4.57
8876.392 0.937 5.01 4.39 2.59 1.00 3.29 2.19 3.63
8877.390 0.085 5.90 4.92 1.75 1.30 3.64 2.19 3.64
8878.379 0.232 5.69 5.00 1.90 1.47 3.91 1.27 4.10
8879.390 0.383 5.86 5.02 1.93 0.97 3.87 1.64 3.17
8880.359 0.527 5.47 4.67 0.81 1.18 2.53 1.86 2.85
8881.383 0.679 4.75 4.17 1.83 1.14 3.04 1.66 3.42
8882.385 0.828 5.03 4.52 1.51 1.40 3.32 1.69 2.89
higher levels of global spot coverage than in the previous
year.
The phase of light minimum, ' min � 0:02, is the same
as in the previous season, perhaps supporting the hy�
pothesis that the dominant group of spots occurs at the
same longitude. The maximum in 1991, however,was dou�
ble peaked, with a secondary minimum at ' �0.5. This is
no longer seen in 1992.
Interestingly, the colour curves all show negligibly dif�
ferent mean values from the previous epoch, illustrating
the small overall effect of the relatively dark starspots on
the global colour of the star.
4.2. Optical flaring
The large optical flare of 5 September is among the largest
yet observed on II Peg. It may be compared in total op�
tical energy to the large flares observed by Doyle et al.
(1992a, 1993) whose observed total U�band energy were
both �1.8 10 35 erg, almost identical to the energy detected
in the present flare. All of these numbers are lower limits,
however, because the light curves were incomplete. The
flare light curves were complex and the events themselves
long�lived. The flare reported above showed at least three
separate light maxima. Its rise lasted �30 mins and its
total duration was �6.5 hr. These parameters are compa�
rable to those of the Doyle et al. flares. Note that this flare
was also detected in our UV spectra (Section 4.7.1).
4.3. Hff
A comparison of the overall mean Hff line profile from 1992
with that from 1991 (Paper I) is made in Fig. 4 and shows
dramatically that there is negligible difference between the
two, in spite of the intervening year. This reinforces the
conclusion of Paper I that the mean Hff profile of this and,
presumably, similar objects, are truly representative of a
mean chromosphere.
On the other hand, the results of the EW measure�
ments from the low�resolution data indicate quite clearly
that the Hff emission is almost continuously variable at
the 50% level about the mean. This agrees with the data
presented in Paper I, where the measured Hff EW's var�
ied between �0.6 � A and �1.1 � A. Our present data, by com�
parison, indicates variations over a slightly larger range,
i.e. �0.3 � A to �1.2 � A. Previous authors (cf. Paper I and refs.
therein) found values ranging between �0.2 � A and �2.0 � A.
Note that our largest value of EW(Hff) occurs in a single
point a factor of �2 larger than the mean, which we con�
sider likely to be due to a flare and is marked as such in
Fig. 7. A number of other measurements are marked like�
wise if they show a large deviation from the local trend.
It seems unlikely that the overall slow variations arrives
in flares, however, and perhaps the source of these lies in
gradual changes in the brightness of individual active re�
gions. Previously recorded large EW's were derived from
single, isolated spectra and so may also be due to individ�
ual flares.

Please give a shorter version with: ``markboth--...�--...� 13
4.4. Hfi
We have also compared the mean 1992 Hfi profile with
that from 1991 in Fig. 5. It is clear that, unlike the same
comparison for the Hff spectra, the agreement between the
two epoch's profiles is not nearly as good. This is in spite
of a good agreement between the nearby photospheric fea�
tures.
There appears to be an asymmetry towards the blue,
in the sense that there appears to be more emission (less
absorption) to the blue side of line centre. This same asym�
metry was noted in 1991 but at no part of the line was it
in net emission above the local continuum at either epoch.
Overall Hfi is more ``filled�in'' in the current epoch than
in 1991.
4.5. HeI D 3
In the same way we compare the mean 1992 HeI D 3 with
that recorded in 1991 from Paper I in Fig. 6. It is immedi�
ately obvious that the agreement between the two epochs
is poor, with the 1991 mean HeI profile being in strong
net absorption and that from 1992 in clear emission. Note
that the sense of this difference is similar to that of the
Hfi profiles.
4.6. Higher Balmer lines and CaII H&K
The mean profiles for the CaII H&K resonance doublet
and for the spectral region near Hfl and Hffi lines are given
in Fig. 8. Also included in Fig. 8 are spectra taken in 1991
(Paper I) in the same spectral regions. The agreement be�
tween the two epochs is excellent with no difference im�
mediately apparent.
These comparisons show a clear trend, i.e. the higher
the excitation of the line the greater the relative variability
of the line. We reached a similar conclusion in Paper I but
based on less comprehensive data.
4.7. Ultraviolet observations
Before comparing our current UV line fluxes with those
measured at previous epochs, we need to isolate individual
flare spectra and omit them from a calculation of the mean
flux.
4.7.1. Flares in UV spectra
The CIV�1548/51 � A resonance doublet is the strongest
feature in the SWP spectrum of all active late�type stars
(Byrne, 1995). It is also a sensitive indicator of flares
(Doyle et al. 1989b). Examination of Table 9 shows that
there are four CIV entries which deviate significantly from
the mean. These are indicated in the table as boldface
script. Similarly in Table 10 one spectrum also stands out
and is similarly indicated in the table. Note that the first
two SWP and the LWP flare spectra coincide in time with
the large optical flare on 5 September (Section 4.2. The
peak flux (37.5 10 \Gamma13 erg cm \Gamma2 s \Gamma1 averaged over 20 min)
is higher than that recorded by Doyle et al. (1992a) for
their largest II Peg flare by �30%.
4.7.2. Mean UV line fluxes
The overall mean CIV flux at Earth, excluding the
above flares, is 4.8\Sigma0.9 10 \Gamma13 erg cm \Gamma2 s \Gamma1 . This may
be compared to some previous values. In 1989 Doyle
et al. (1992a) recorded a value 6.7\Sigma1.0 10 \Gamma13 erg cm \Gamma2 s \Gamma1 ,
while in 1986, Doyle et al. (1989) found a value
6.2\Sigma1.0 10 \Gamma13 erg cm \Gamma2 s \Gamma1 . Therefore the 1992 mean flux
is significantly lower than either 1986 or 1989.
4.8. Microwave observations
The microwave radiation, which is coronal in origin, shows
the largest relative variability of any of the data, apart
from the obvious flare. As can be seen in Fig. 9, this vari�
ability takes place on all time�scales sampled, i.e. hours to
days.
There is a large flare on 13 September (Fig. 9) which
reached a peak flux of �15 mJy. Unfortunately the ob�
servations terminated while the flare was still in progress.
Nevertheless we can place a lower limit to its duration of
4.7 hr. Again unfortunately no simultaneous observations
at other wavelengths were being made during this time. It
may be compared to the peak flux at the same frequency
observed by Doyle et al. (1992a,b), i.e. �8 mJy.
The mean ``quiescent'' flux over the entire observing
interval, omitting the flare, is 2.6\Sigma1.5 mJy. This may
be compared to an upper limit of �5 mJy from Mutel
et al. (1985). Doyle et al. (1992a) observed II Peg over
6 hr on two consecutive nights. On the first night they
recorded a secular increase in 5 GHz flux from �1 mJy to
�2.5 mJy with a mean of 1.92\Sigma0.04 mJy. On their second
6 hr night they saw an opposite behaviour, i.e. a decline
in 5 GHz flux from �3.5 mJy to �2.0 mJy with a mean
of 2.34\Sigma0.08 mJy. Assuming this is typical of II Peg it is
consistent with our current data.
5. Conclusions
We have presented one of the most comprehensive multi�
wavelength data sets on an active late�type star, both in
the breadth of its wavelength coverage and its extent in
time. It has resulted in a characterisation of mean condi�
tions in the outer atmosphere of II Peg from the photo�
sphere to the corona for comparison with models and with
similar data from previous epochs.
We have detected flares on II Peg in optical broadband
photometry, in ultraviolet and optical spectroscopy and
in microwaves. One flare, recorded in optical broad band
photometry and in ultraviolet spectroscopy, is one of the
most energetic observed to date on the star.

14 Please give a shorter version with: ``markboth--...�--...�
We reinforce previous evidence that II Peg is highly
variable in virtually all spectral signatures, with the degree
of variability increasing to higher excitation.
Acknowledgements. Research at Armagh Observatory is sup�
ported by a Grant�in�Aid from the Department of Education
of Northern Ireland. This research utilised software and hard�
ware provided by the UK SERC STARLINK computing net�
work. MTE, PJA and ACL acknowledge financial support from
Armagh Observatory. MTE, PJA and LMS acknowledge sup�
port from the European Economic Community's COMETT
programme.
References
Andrews, A.D., Rodon'o, M., Linsky, J.L., Brown, A., Butler,
C.J., Catalano, S., Scaltriti, F., Busso, M., Nha, Il�S., Oh,
J.Y., Henry, M.C.D., Hopkins, J.L., Landis, H.J., Engel�
brektson, S. 1988, A&A, 204, 177
Baars, J.W.M., Genzel R., Pauliny�Toth, I.I.K., Witzen, A.
1977 A&A, 61, 99
Bessell, M.S. 1979, PASP, 91, 589
Boggess, A., et al. 1978, Nature, 275, 372
Bromage, G.E. 1984, Proc. 4th European IUE Conference,
ESA SP�218, p. 473
Byrne, P.B. 1983, in ''Activity in Red�Dwarf Stars'', eds. P.B.
Byrne & M. Rodon`o, Kluwer, p. 157
Byrne, P.B., 1986, IBVS, No. 2951
Byrne, P.B., 1992a, in ``Surface Inhomogeneities on Late�type
Stars'', eds. P.B. Byrne & D.J. Mullan, Springer, p. 3
Byrne, P.B. 1992b, in ``The Theory of Sunspots'', eds. J.H.
Thomas & N.O. Weiss, Kluwer, Dordrecht, p. 63
Byrne, P.B. 1995, in ``Flares and Flashes'', Proc. IAU Coll. 153,
eds. J. Greiner, H.W. Deurbeck, R.E. Gershberg, Springer,
p. 14
Byrne, P.B., Marang, F. 1987, Irish AJ, 18, 84
Byrne, P.B., Doyle, J.G., Brown, A., Linsky, J.L., Rodon'o, M.
1987, A&A, 176, 284
Byrne, P.B., Panagi, P.M., Doyle, J.G., Englebrecht, C.A.,
McMahan, R., Marang, F., Wegner, G. 1989, A&A, 214,
238
Byrne, P.B., Lanzafame, A.C., Sarro, L.M., Ryans, R. 1994,
MNRAS, 270, 427
Byrne, P.B., Panagi, P.M., Lanzafame, A.C., Avgoloupis, S.,
Huenemoerder, D.H., Kilkenny, D., Marang, F., Panov,
K.P., Roberts, G., Seiradakis, J.H., van Wyk, F. 1995, A&A,
299, 115 (Paper I)
Cousins, A.W.J. 1976, MemRAS, 81, 25
Doyle, J.G., Butler, C.J., Byrne, P.B., Rodon'o, M., Swank, J.,
Fowles, W. 1989a, A&A, 223, 219
Doyle, J.G., Byrne, P.B., van den Oord, G.H.J., 1989b, A&A,
224, 153
Doyle, J.G., Kellett, B.J., Byrne, P.B., Avgoloupis, S.,
Mavridis, L.N., Seiradakis, J.H., Bromage, G.E., Tsuru, T.,
Makashima, K., McHardy, I.M. 1991, MNRAS, 248, 503
Doyle, J.G., Kellett, B.J., Butler, C.J., Byrne, P.B., Neff,
J.E., Brown, A., Fox, D., Linsky, J.L., Bromage, G.E., Av�
goloupis, S., Mavridis, L.N., Seiradakis, J.H., Mathioudakis,
M., Murphy, H.M., Krzesinski, J., Pajdosz, G., Dadonas,
V., Sperauskas, J., van Wyk, F., Marang, F., Olah, K.,
Cameron, A.C., Antonopoulou, E., Rovithis, P., Rovithis�
Livaniou, H. 1992a, A&AS, 96, 351
Doyle, J.G., van den Oord, G.H.J., Kellett, B.J., 1992b, A&A,
262, 533
Doyle, J.G., Mathioudakis, M., Murphy, H.M., Avgoloupis, S.,
Mavridis, L.N., Seiradakis, J.H. 1993, A&A, 278, 499
Elliott, K.H. 1996, MNRAS, 281, 158
Gershberg, R.E. 1972, ApSS, 19, 75
Giddings, J.R. 1983, STARLINK User Note No. 37, Rutherford
Appleton Labs
Glass, I.S. 1985, Irish AJ, 17, 1
Howarth, I.D., Murray, M.J. 1987, STARLINK User Note
No. 50, Rutherford Appleton Labs
IDL Users' Guide, 1985, Research Systems Inc. Boulder
Johnson, 1966, A&AR, 4, 193
Mavridis, L.N., Asteriadis, G., Mahmoud, F.M. 1982, Com�
pendium in Astron. eds. E.G. Mariolopoulos, P.S. Theo�
caris, L.N., L.N. Mavridis. Reidel, Dordrecht, p. 253
Menzies, J.W., Marang, F., Laing, J.D., Coulson, I.M., Engle�
brecht, C.A., 1991, MNRAS, 248, 642
Meyerdicks, H. 1993, STARLINK User Note No. 86.9, Ruther�
ford Appleton Labs.
Mutel, R.L., Lestrade, J.F., Preston, R.A., Phillips, R.B. 1985,
ApJ, 289, 262
Padin, S., Davis, R.J., Lasenby, A.N. 1987, MNRAS, 224, 685
Rodon'o, M., Cutispoto, G., Pazzani, V., Catalano, S., Byrne,
P.B., Doyle, J.G., Butler, C.J., Andrews, A.D., Blanco, C.,
Marilli, E., Linsky, J.L., Scaltriti, F., Busso, M., Cellino,
A., Hopkins, J.L., Okazaki, A., Hayashi, S.S., Zeilik, M.,
Helston, R., Henson, G., Smith, P., Simon, T. 1986, A&A,
165, 135
Rodon'o, M., Byrne, P.B., Neff, J.E., Linsky, J.L., Simon, T.,
Butler, C.J., Catalano, S., Cutispoto, G., Doyle, J.G., An�
drews, A.D., Gibson, D.M. 1987, A&A, 176, 284
Strassmeier, K.S., Hall, D.S., Fekel, F.C., Scheck, M. 1993,
A&AS, 100, 173
Tody, D. et al. 1986, IRAF Users' Manual, National Optical
Astronomical Observatories
Vogt, S.S. 1981, ApJ, 247, 975
eMail addresses:
PBB: pbb@star.arm.ac.uk
LMS: lms@star.arm.ac.uk
MTE: mte@star.arm.ac.uk
PJA: pja@star.arm.ac.uk
JGD: jgd@star.arm.ac.uk
HMM: hmm@star.arm.ac.uk
ACL: alanzafame@alpha4.ct.astro.it
HAA: abdul@usm.my
RES: res@jb.man.ac.uk
JEN: jneff@astro.sunysb.edu
JHS: jhs@astro.auth.gr
SA: avgoloup@astro.auth.gr
RDJ: rdj@astro.keele.ac.uk
KHE: khe@star.sr.bham.ac.uk
MJA: mam@ll.iac.es
CL: clh@iac.es
This article was processed by the author using Springer�Verlag
L A T E X A&A style file L�AA version 3.

Please give a shorter version with: ``markboth--...�--...� 15
Table 6. Log of the IUE spectra of II Peg obtained between
1994 September 5--16. Phases have been calculated according
to the ephemeris of Vogt (1981).
Date IUE Image UT Exp. JD (mid�exp)
1992 No. Start min. 2440000.0+
5 Sep SWP45531 19:40:33 20 8871.327
LWP23854 20:19:41 30 8871.357
SWP45532 20:58:30 107 8871.411
6 Sep LWP23864 19:37:39 30 8872.328
SWP45543 20:17:32 100 8872.380
LWP23865 22:06:18 30 8872.431
7 Sep LWP23873 19:20:32 30 8873.316
SWP45553 19:59:17 100 8873.418
LWP23874 21:47:16 30 8873.368
SWP45554 22:22:56 25 8873.441
8 Sep LWP23875 15:51:00 30 8874.171
SWP45571 16:28:51 100 8874.221
LWP23876 18:23:12 30 8874.277
SWP45572 19:02:56 100 8874.328
LWP23877 20:53:37 30 8874.381
SWP45573 21:33:38 74 8874.424
9 Sep LWP23888 20:04:23 30 8875.347
SWP45586 20:42:53 100 8875.398
LWP23889 22:28:15 18 8875.443
10 Sep SWP45595 19:47:17 30 8876.335
LWP23898 20:33:49 100 8876.392
SWP45596 22:19:30 28 8876.440
11 Sep SWP45599 19:54:49 30 8877.340
LWP23907 20:32:13 100 8877.390
SWP45600 22:19:41 28 8877.440
12 Sep SWP45617 20:00:03 30 8878.344
LWP23912 20:35:24 60 8878.379
SWP45618 21:50:47 60 8878.431
13 Sep SWP45625 20:05:19 30 8879.347
LWP23923 20:51:21 60 8879.390
SWP45626 21:58:12 50 8879.433
14 Sep SWP45642 19:23:44 30 8880.319
LWP23938 20:06:15 60 8880.359
SWP45643 21:15:08 94 8880.418
15 Sep SWP45651 19:01:52 30 8881.303
LWP23945 20:41:13 60 8881.383
SWP45652 21:49:48 60 8881.430
16 Sep SWP45660 19:58:31 30 8882.343
LWP23958 20:43:58 60 8882.385
SWP45661 21:52:25 55 8882.430
Table 8. Details of the two optical flares recorded in Johnson
U on II Peg at Stephanion Observatory. See Section 3.2 for an
explanation of the derivation of the total integrated energy,
EU , of each flare.
Date UT \DeltaU ED EU
1992 max sec erg
05 Sep 20:39 0.32 \Lambda ?3925 ?1.75 10 35
12 Sep 21:49 0.29 59 2.63 10 33
\Lambda This flare is complex (see Fig. 3).

16 Please give a shorter version with: ``markboth--...�--...�
Fig. 8. Blue region spectra of II Peg taken at the Isaac Newton
Telescope 14--19 September 1992 shifted to the rest frame of the
K star. The top panel shows the five clear nights' spectra in the
region of the CaII H&K lines as the overall mean spectrum.
The middle and lower panels give the same data in the vicinity
of the Balmer Hffi and the Balmer Hfl lines. Also shown are
spectra in these same spectral regions taken in 1991 (Paper I)
smoothed to match the spectral resolution of the present data
(dashed curves). The vertical lines indicate the rest wavelengths
of the Balmer and CaII lines.
Fig. 9. The time sequence of BBI 5GHz observations of II Peg.
The flaring points discussed in the text are labelled with an `F'.