Abstract Details
| Name: Sriram Krishna Affiliation: IIA, Bengaluru Conference ID: ASI2019_345 Title : UV imaging of the born-again planetary nebula A30 Authors and Co-Authors : N. Kameswara Rao, S. Krishna, J. Murthy, F. Sutaria, A. Ray, R. Mohan Abstract Type : Poster Abstract Category : Stars, ISM and Galaxy Abstract : The central star of A30 is believed to have undergone a very late thermal pulse that caused ejection of hydrogen deficient material, prominently seen in the light of [O ɪɪɪ] lines, about 850 years ago. The inner parts of the nebula are filled with this material whereas the outer rim of the nebula is of H-normal composition and of about 12,500 years of age. A30 is also an x-ray source showing both a diffuse source covering the inner few arc seconds region covering the hydrogen deficient knots and a point source located on the central star. To see the correspondence with the x-ray emission as well as with hydrogen deficient ejecta, we imaged A30 with UVIT (Ultraviolet imaging telescope) on board of Indian Astronomical satellite ASRTROSAT, in 3 FUV and 2 NUV filters. Two FUV filters, F154M (and F169M (λₑ 1608) allow the high excitation lines of He ɪɪ, C ɪᴠ etc. The other FUV filter F172M (λₑ 1717) allows mostly the nebular continuum. The NUV filters N219M (λₑ 2196) and N279N2 (λₑ 2796) allow mostly low excitation lines or continuum. In the present work We contrast the UV images with both X-ray contours as well as ground based [O ɪɪɪ] and H-alpha images. The most surprising result of our UV imaging is the presence of FUV halo in two FUV filters, F154M and F169M, extending beyond the known optical and NUV nebular size. The FUV halo might be a result of H2 molecular fluorescent emission (from the AGB ejecta). Despite the presence of very hot central star (Tₑ of 115,000 K) and an earlier excursion to hot PN stage (born-again), the nebula seems to possess still some unionized molecular gas. |