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Astron. Astrophys. 331, 187-192 (1998)

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5. Conclusions

We observed long-term variations of V1101 Aql in V magnitude, very likely triggered by disk activity. We have detected [FORMULA].46 as possible orbital period of V1101 Aql, with an important alias at [FORMULA].

The secondary of a DN with such an orbital period should have [FORMULA] (Warner 1995). This means that the V emission of the UV-heated secondary star is about 25 times lower than that of the whole system; i.e., any variation coming from the secondary could modify the total V luminosity of the system by a factor [FORMULA] 1/25 at most, corresponding to a full amplitude fluctuation of [FORMULA] 0.04 mag. This is smaller than the amplitude ([FORMULA] 0.1 mag) of the modulation in Fig. 3a, b, then indicating an extra contribution of [FORMULA] 0.06 mag due to the UV heating of the inner face of the secondary.

The discovery of a Z Cam-type DN with an orbital period just above to the 3-hr upper limit of the Period Gap of CVs is consistent with the presence of a sharp `luminosity bump', in the period-absolute magnitude plane of CVs between 3 and 3.5 hr as suggested by Zangrilli et al. (1997).

Our results then, complemented with data gathered from literature, allow us to set the standstill magnitude of this Z Cam star close to [FORMULA] and to estimate for this system a distance of about 300 pc.

The spectrum, taken during standstill, seems to confirm the cataclysmic binary nature of V1101 Aql, though the discovery of an asymmetric nebulosity, which seems to be associated to the object, does not rule out the possibility, already pointed out by Downes et al. (1995), that V1101 Aql could be a Herbig Ae/Be star rather than a CV. In this case, the presence of an associate nebulosity around the object is fully consistent with such a classification. However, due to the relatively poor seeing conditions ([FORMULA] 1".5), we cannot rule out that the image of V1101 Aql has been contamined by a background object.

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© European Southern Observatory (ESO) 1998

Online publication: February 4, 1998