Photometric monitoring of late-type stars has proven to be a powerful tool
to discover cool starspots and to measure precise
stellar rotation periods with, in some favorable cases, even differential
rotation on the stellar surface (Hall [1972], [1994]).
The way the light and colors of a spotted star vary with time traces the
evolution of its starspots. Time-series light and color curves can then be
used to determine the approximate distribution of spots on the stellar
surface, their temperature contrast, and even their appearance and
disappearance marking the beginning and ending of a spot cycle
similar to the Sun's 11-year cycle.
In the past decade several studies were presented that attempted to model
long-term light-curve variations with an evolving spot distribution on the
basis of one stellar rotation to the next. Much literature could be cited
here but instead let us selflessly draw your attention to our own series of
papers on "Time-series photometric spot modeling'' and the many references
therein. Paper I on the RS CVn binary VY Ari (Strassmeier & Bopp
[1992]) included a description of the modeling technique and were
followed by Strassmeier et al. ([1994a]) on 15 years of photometry
of HR 7275, Olàh et al. ([1997]) on 30 years of HK Lac
and Olàh et al. ([1999]) on 10 years of V833 Tau. A particularly
important spot parameter extractable from these data is the spot's
lifetime and one result, still lively debatted, is that there
is no linear decay law for starspots as there is for sunspots, i.e. the
larger a sunspot the longer it lives (
= const; A being the
spot area). Various physically similar stars in terms of rotation
period and spectral type can host spots or spot groups
with a wide range of lifetimes.
For a set of four spotted RS CVn stars, Henry et al. ([1995a])
observed individual spot lifetimes between 0.5 years and over 6 years.
The same range of lifetimes was found for the stars in our previous
papers mentioned above. Maybe not surprising, the spotted star
with the longest photoelectric history (RS CVn with 45 years of broad-band
data) also shows the longest time scale: a cyclic change of the total
spotted area with a period of 20 years (Rodonó et al. [1995]).
All these phenomena are suggestive of a significantly non-solar magnetic
field topology and a dynamo process that might operate on many different
timescales.
Clearly, continuous photometric monitoring for a long period in time is
needed for conclusive analyses and automatic photoelectric telescopes
(APTs) are ideally suited for such a task.
In this paper, we present multicolor data from our two 0.75-m University
of Vienna twin APTs (Strassmeier et al. [1997b]) and the 0.25-m
Phoenix-10 APT (Boyd et al. [1984]) for 1996/97. Altogether,
47 program stars were observed in either by, UBV, or
.
Some special cases were targeted in all of these bandpasses
but with varying time and phase coverage on the individual telescopes.
Others had been observed only briefly and their aim was mostly
to support spectroscopic observations for Doppler imaging
with large telescopes (see, e.g., Rice & Strassmeier [1998]).
Table 1 presents a summary of the program stars and
their commonly known stellar parameters. A period
analysis for all stars from each individual telescope
gives a homogeneous set of stellar rotation
periods and the associated rotational light variations.
Star | V | Spectral type | Binary? |
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Radius | Variable type |
(mag) | (SB/S) | (days) | (days) | (kms-1) | (![]() |
|||
HR 5B (V640 Cas) | 6.6 | G8V | SB1 | 39.5 | n.det. | 4.7 | ... | solar-type SB |
SAO 91772 (LN Peg) | 8.6 | G8V | SB2 | 1.844 | 1.851 | 23 | ![]() |
RS CVn |
HD 4502 (![]() |
4.1 | K1IIIa | SB1 | 17.769 | 17.637 | 41 | ![]() |
RS CVn + ell. |
HD 12545 (XX Tri) | 8.1 | K0III | SB1 | 23.98 | 23.87 | 18.2 | ![]() |
RS CVn |
HD 17433 (VY Ari) | 6.8 | K3-4IV | SB1 | 13.198 | 16.23 | 10 | ![]() |
RS CVn |
HD 22468 (V711 Tau) | 5.7 | K1IV | SB2 | 2.8377 | 2.837 | 40 | 3.9 | RS CVn |
HD 26337 (EI Eri) | 7.0 | G5IV | SB1 | 1.947 | 1.913 | 50 | ![]() |
RS CVn |
HD 283518 (V410 Tau) | 11.2 | K4 | S | ... | 1.872 | 77 | 3.0 | WTTS |
HR 1362 (EK Eri) | 6.3 | G8III-IV | S | ... | (306.9) | 1.5 | 9 | single giant |
HD 283571 (RY Tau) | 10 | F8V | S | ... | n.det. | 49 | ... | CTTS |
HD 283572 (V987 Tau) | 9.3 | G5 | S | ... | 1.529 | 78 | ![]() |
WTTS |
HD 283750 (V833 Tau) | 8.2 | K5V | SB1 | 1.788 | 1.806 | 6.3 | ![]() |
BY Dra |
HD 282624 (SU Aur) | 8.9 | G2 | S | ... | n.det. | 66 | ![]() |
CTTS |
HD 31964 (![]() |
3.0 | F0Ia | ECL | 27yr | n.det. | ... | ... | puls. supergiant |
HD 31993 (V1192 Ori) | 7.5 | K2III | S | ... | 26.7 | 33 | ![]() |
single giant |
HD 33798 (V390 Aur) | 7.0 | G8III | S | ... | 9.69 | 33 | ![]() |
single giant |
HD 291095 (V1355 Ori) | 8.7 | K1IV | SB1 | ? | 3.87 | 46 | ![]() |
RS CVn-type |
HD 43989 (V1358 Ori) | 8.5 | G0IV | S | ... | (3.2:) | 42 | ![]() |
RS CVn-type |
HD 51066 (CM Cam) | 7.2 | G8III | SB1 | 3770. | 16.0 | 47 | 17.4 | eff. single giant |
HD 62044 (![]() |
4.3 | K1III | SB1 | 19.604 | 19.615 | 27 | 12 | RS CVn |
HD 81410 (IL Hya) | 7.5 | K1III | SB2 | 12.905 | 12.674 | 26.5 | 8.1 | RS CVn |
HD 82443 (DX Leo) | 7.0 | K0V | S | ... | 5.432 | 5 | ![]() |
BY Dra |
HD 82558 (LQ Hya) | 7.8 | K2V | S | ... | 1.60 | 28 | 0.94 | BY Dra |
HD 98230 (![]() |
3.8 | G5V | SB1 | 3.980 | n.det. | 2.8 | ... | solar-type SB |
HD 106225 (HU Vir) | 8.6 | K0III-IV | SB1 | 10.39 | 10.66 | 27 | ![]() |
RS CVn |
HD 111395 (HR 4864) | 6.3 | G5V | S | ... | 15.80 | 2.9 | ![]() |
solar type |
HD 111812 (31 Com) | 4.9 | G0III | S | ... | 6.96: | 57 | ![]() |
single giant |
HD 112313 (IN Com) | 8.0 | G5III-IV | SB1 | ? | 5.90 | 67 | ![]() |
RS CVn |
HD 112989 (37 Com) | 4.9 | G9III | S | ... | n.det. | 4 | ... | single giant |
HD 117555 (FK Com) | 8.1 | G2III | S | ... | 2.4067 | 160 | ![]() |
FK Comae |
HD 129333 (EK Dra) | 7.5 | G0-1V | S | ... | 2.598 | 17.5 | 0.92 | solar type |
HD 136901 (UV CrB) | 7.2 | K2III | SB1 | 18.665 | 18.657 | 42 | ![]() |
RS CVn + ell. |
BD-08![]() |
9.3 | K0III | SB1 | 4.77 | 4.75 | 67 | ![]() |
RS CVn |
HD 139006 (![]() |
2.2 | A0V+G5V | SB | 17.4 | n.det. | ![]() |
... | eclipsing |
HD 140436 (![]() |
3.8 | A0V | VB | 91yr | 0.44534 | 100 | ![]() |
Maia type |
HD 141714 (![]() |
4.6 | G3.5III-IV | S | ... | 57 | 5 | ![]() |
single giant |
HD 152178 (V2253 Oph) | 8.2 | K0III | SB1 | 314. | 22.07 | 28.8 | ![]() |
RS CVn |
HD 171488 (V889 Her) | 7.3 | G0V | S | ... | 1.337 | 33 | ![]() |
solar type |
HD 199178 (V1794 Cyg) | 7.2 | G5III-IV | S | ... | 3.342 | 67 | ![]() |
FK Comae |
HD 208472 (V2075 Cyg) | 7.3 | G8III | SB1 | 22.6 | 22.42 | 19.7 | ![]() |
RS CVn |
HD 209813 (HK Lac) | 6.9 | K0III | SB1 | 24.428 | 24.15 | 20 | ![]() |
RS CVn |
HR 9024 (OU And) | 5.9 | G1III | S | ... | 24.2 | 20 | ![]() |
single giant |
HD 216489 (IM Peg) | 5.6 | K2II-III | SB1 | 24.65 | 24.45 | 28.2 | ![]() |
RS CVn |
HD 216672 (HR Peg) | 6.3 | S | S | ... | irr. | ... | ... | semiregular |
HD 218153 (KU Peg) | 7.6 | G8II-III | SB1 | 1411. | 25.9 | 29 | ![]() |
RS CVn |
HD 224085 (II Peg) | 7.4 | K2-3IV | SB1 | 6.724 | 6.725 | 23.1 | ![]() |
RS CVn |
Variable | Comparison | Check | Time range |
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2 400 000+ | by | VRI | UBV | |||
HR 5B (V640 Cas)1 | HD 663 | HD 224784 | 50395 - 50635 | 52 | ... | ... |
SAO 91772 (LN Peg) | SAO 91775 | HD 977 | 50409 - 50635 | 35 | ... | ... |
HD 4502 (![]() |
HD 5516 | HD 3690 | 50395 - 50635 | 105 | ... | ... |
HD 12545 (XX Tri) | HD 12478 | SAO 55178 | 50395 - 50500 | ... | 116 | 53 |
HD 17433 (VY Ari) | HD 17572 | HD 17361 | 50386 - 50516 | ... | ... | 55 |
HD 22468 (V711 Tau)1 | HD 22484 | HD 22796 | 50395 - 50490 | 132 | 109 | ... |
HD 26337 (EI Eri) | HD 25852 | HD 26584 | 50395 - 50529 | ... | 128 | ... |
HD 283518 (V410 Tau) | HD 27159 | HD 27570 | 50395 - 50525 | ... | 125 | ... |
HR 1362 (EK Eri)1 | HD 27197 | HD 26409 | 50395 - 50500 | ... | 122 | ... |
HD 283571 (RY Tau) | HD 27159 | HD 27570 | 50395 - 50529 | ... | 128 | ... |
HD 283572 (V987 Tau) | HD 27570 | HD 28447 | 50395 - 50532 | 179 | 115 | ... |
HD 283750 (V833 Tau) | HD 283749 | HD 29169 | 50395 - 50521 | ... | 127 | ... |
HD 282624 (SU Aur) | HD 31565 | HD 31305 | 50395 - 50534 | ... | 147 | ... |
HD 31964 (![]() |
HD 33167 | ... | 50395 - 50426 | 100 | ... | ... |
HD 31993 (V1192 Ori) | HD 32191 | HD 32073 | 50395 - 50536 | ... | 140 | ... |
HD 33798 (V390 Aur) | HD 34248 | HD 33443 | 50396 - 50540 | ... | 26 | ... |
HD 291095 (V1355 Ori) | HD 41433 | HD 40347 | 50492 - 50551 | 36 | 64 | ... |
HD 43989 (V1358 Ori) | HD 44517 | HD 44019 | 50492 - 50554 | 34 | 39 | ... |
HD 51066 (CM Cam) | HD 48840 | HD 45947 | 50486 - 50562 | ... | 103 | ... |
HD 62044 (![]() |
HD 60318 | HD 58207 | 50395 - 50536 | 471 | ... | ... |
HD 81410 (IL Hya) | HD 81904 | HD 80991 | 50395 - 50594 | ... | 235 | ... |
HD 82443 (DX Leo) | HD 83098 | HD 83821 | 50392 - 50604 | ... | ... | 161 |
HD 82558 (LQ Hya) | HD 82477 | HD 82508 | 50395 - 50593 | ... | 202 | 145 |
HD 98230 (![]() |
HD 98262 | HD 94600 | 50408 - 50614 | 244 | ... | ... |
HD 106225 (HU Vir) | HD 106270 | HD 106332 | 50410 - 50633 | ... | 191 | 56 |
HD 111395 (HR 4864)1 | HD 111469 | HD 111812 | 50429 - 50636 | ... | 257 | ... |
HD 111812 (31 Com) | HD 111469 | HD 111395 | 50401 - 50636 | ... | ... | 169 |
HD 112313 (IN Com) | HD 112299 | HD 112706 | 50419 - 50636 | 168 | 226 | ... |
HD 112989 (37 Com)1 | HD 111469 | HD 111812 | 50415 - 50635 | ... | 274 | ... |
HD 117555 (FK Com) | HD 117567 | HD 117876 | 50421 - 50632 | 132 | ... | ... |
HD 129333 (EK Dra) | HD 129390 | HD 129798 | 50437 - 50576 | ... | 183 | 143 |
HD 136901 (UV CrB) | HD 136643 | HD 136655 | 50492 - 50636 | 90 | 146 | ... |
BD-08![]() |
SAO 140587 | SAO 140589 | 50451 - 50635 | ... | 139 | ... |
HD 139006 (![]() |
HD 1404363 | HD 1417144 | 50458 - 50568 | 267 | ... | ... |
HD 152178 (V2253 Oph) | HD 152501 | HD 151179 | 50468 - 50636 | ... | 120 | ... |
HD 171488 (V889 Her) | HD 171286 | HD 170829 | 50395 - 50636 | 93 | 179 | ... |
HD 199178 (V1794 Cyg) | HD 199956 | HD 199870 | 50395 - 50635 | ... | 67 | ... |
HD 208472 (V2075 Cyg) | HD 208341 | HD 208916 | 50395 - 50635 | ... | 96 | ... |
HD 209813 (HK Lac) | HD 210731 | HD 208728 | 50395 - 50635 | ... | 86 | ... |
HR 9024 (OU And)1 | HD 223848 | HD 222451 | 50395 - 50635 | ... | 89 | ... |
HD 216489 (IM Peg) | HD 216635 | HD 2166725 | 50395 - 50635 | ... | 73 | ... |
HD 218153 (KU Peg) | HD 218610 | SAO 91066 | 50395 - 50635 | ... | 75 | ... |
HD 224085 (II Peg) | HD 223332 | HD 224895 | 50395 - 50635 | ... | 26 | ... |
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