As has been seen1, the variability of some suspected variables has been confirmed by the Hipparcos results. What about the variables that were already "known". Did Hipparcos confirm their variability and periods ?
The following table shows a number of variables sorted according the the amount of variation detected and compares the periods found by Hipparcos with the GCVS data. n/a indicates that there was no entry for the variable in the Hipparcos Variability Annex. Periods are in days.
Variable HIP Hp scatter HIP GCVS data
period period type
IS Gem 32740 0.01 n/a 47 SRc
VW Dra 84496 0.02 n/a 170 SRd
d Ser 90441 0.03 n/a - I:
RX Cep 3905 0.03 n/a 55 SRd
BU Tau 17851 0.04 - - GCas
SW CrB 76791 0.05 n/a 100 SRb
V377 Cas 1543 0.05 n/a 0.030 DSct
BN Gem 37074 0.06 - - GCas
AB Aur 22910 0.06 - - Ina
W Boo 71955 0.09 35.33 450 SRb
XX Cam 19340 0.10 26 ? - RCB
Beta Per 14576 0.14 - 2.8673043 EA/SD
RW Cep 110504 0.16 - 346 SRd
Rho Cas 117863 0.18 - 320 SRd
Rho Per 14354 0.20 7.45 ?, 26.6 ? 50 SRb
TU CVn 63024 0.25 - 50 SRb
RR UMi 73199 0.26 1.5082 ? 43.3 SRb
TV UMa 57362 0.38 125 ? 42 SRb
BK Vir 61022 0.39 150 ? 150 SRb
AG Peg 107848 0.47 - - Nc
g Her 80704 0.48 - 89.2 SRb
RX Boo 70401 0.51 - 340 SRb
R CrB 77442 0.56 - - RCB
SW Vir 64569 0.65 153.6 150 SRb
SX Her 78994 0.74 206 ? 102.9 SRd
CH Cyg 95413 0.78 - - ZAnd/SR
U Del 102440 0.83 - 110 SRb
W Cyg 106642 0.85 132.0 131.1 SRb
Beta Lyr 92420 0.93 12.940 12.913834 EB
AC Her 90697 1.07 75.30 75.01 RVa
RZ Cas 13133 1.10 1.195250 1.195247 EA/SD
R Sct 92202 1.17 - 146.5 RVa
Z UMa 58225 1.19 202.0 195.5 SRb
V CVn 65006 1.39 191.5 191.89 SRa
U Ori 28041 3.43 367 368.3 Mira
RW Tau 18792 >3.80 2.76884 2.7688356 EA/SD
R UMa 52546 4.32 299.7 301.62 Mira
Chi Cyg 97627 5.19 402.3 408.05 Mira
Although the Hp photometric measures are not exactly the same as visual magnitudes, their scatter does give a good approximation as to the amount of variation seen in each variable by Hipparcos.
For some variables the amount of variation was clearly small - comparable with that seen for the less convincing suspected variables. Note also that the Mira variables will have faded below the detection limit at times.
The agreement on periods tends to be good for Mira type and eclipsing variables. For some semi-regular variables their is good agreement between the Hipparcos and GCVS values ; for others there is not. Hipparcos was able to detect short period and/or low amplitude variations in these variables more readily than can be done from visual estimates. The possible 26 day period in XX Cam is notable.
On the other hand, the 3 year mission duration and the limited number of measurements per star did make it difficult to detect longer periods or multiple periodicities. The limited number of measurements can also lead to minima being missed. This probably explains the failure to detect the periodicity in Beta Per and R Sct. Similarly, R CrB and AB Aur would have had larger ranges of Hp measures if sampled in other years.
Hence, although the Hipparcos data do provide some answers, there is still a lot of work for amateurs to do.
1 Suspected Binocular Variables in the Hipparcos data