TAP 26

TAP 26 was first reported by Feigelson et al. (1987) as a K7 PMS star. Walter et al. (1988) found a relatively high of about 70 km/s. It was first monitored for rotational modulation by Bouvier et al. (1993). They reported a 2.5 day rotation period for this star which they confirmed with their 1995 results (Bouvier et al. 1995). While acknowledging that their derived equatorial velocity was only 28 km/s, they suggested that they were seeing the orbital motion of a binary system. Mathieu et al. (1989) observed this star, yet did not report it as a spectroscopic binary. Prosser et al. (1995) were suspicious that Bouvier et al. may have missed the true period due to the fact that their sampling rate was not high enough. Since Bouvier et al. only averaged one measurement per night, they were not sensitive to periods of < 2 days. Prosser et al. monitored TAP 26 during a six day period in which they observed the star 12 times. They reported a 13 hour period. However, they noted that the confidence in the period was low because they did not obtain sufficient data.

TAP 26 was monitored from MTSB on 15 nights. On average, five observations were made of the star each night in each of three filters, V, R and I. During three of these 15 nights, the filter wheel failed and approximately 17 observations were made of the star, all in the I filter. From these data, I derived a 0.715 day period for the star. The MTSB data are displayed in Figure 1. The MTSB data indicate that the previously published period is an alias of the true, shorter, period. In Figure 2, MTSB data are compared with those of Bouvier et al. (1995). If one confines the period search range for the MTSB data to be greater than one day, the results are nearly identical to those for the data presented by Bouvier et al. Further, the Prosser et al. results are consistent with one of the aliases of our periodogram result, as expected in the case of insufficient data. Combining the period of TAP 26, with the published radius (1.1 R; Walter et al. 1988) one derives the sine of the inclination to Earth to be or about 68.