| Name: | Shatakshi Chamoli |
| Affiliation: | Indian Institute of Astrophysics |
| Conference ID : | ASI2024_386 |
| Title : | Exploring Image Subtraction Techniques to Search for Novae (and other Transients) in M31 |
| Authors : | Shatakshi Chamoli 1, Judhajeet Basu 1,2, Sudhanshu Barway 1, G.C. Anupama 1, Harsh Kumar 3,4,5, Vishwajeet Swain 3, Dhananjay Raman 6, Ravi Kumar 7, Aswin Suresh 3, Varun Bhalerao 3 |
| Authors Affiliation: | 1 Shatakshi Chamoli, Judhajeet Basu, Sudhanshu Barway, G.C. Anupama, Indian Institute of Astrophysics, Bengaluru-560034, India
2 Judhajeet Basu Pondicherry University, 605014-Puducherry, India
3 Harsh Kumar, Vishwajeet Swain, Varun Bhalerao, Aswin Suresh, Department of Physics, Indian Institute of Technology Bombay, Mumbai-400076, India
4 Harsh Kumar, Harvard College Observatory, Harvard University, Massachusetts-02158, USA
5 Harsh Kumar, Center for Astrophysics, Harvard University, 60 Garden St. Cambridge 02158 MA, USA
6 Dhananjay Raman, Department of Computer Science, Indian Institute of Technology Bombay, Mumbai-400076, India
7 Ravi Kumar, Department of Aerospace Engineering, Indian Institute of Technology Bombay, Mumbai-400076, India |
| Mode of Presentation: | Poster |
| Abstract Category : | Facilities, Technologies and Data science |
| Abstract : | We aim to search for transients in the bulge of M31 in the multi-epoch, UVIT archival images and GIT M31 survey data. The bulge is shrouded by galactic light, which must be removed to search for any object in this region. To do that, we have employed the following techniques to create a template image that can be subtracted from the science image to give a difference image free of galactic light contamination-
1) Median Combine Template subtraction: A template is made by a median combination of the multi-epoch observations. This template is subtracted from each observation to reveal sources present only in a particular epoch.
2) Ellipse Fit Template subtraction: An isophote model of the bulge in each observation serves as a template image. Subtracting this model image from the original image reveals all sources that lie above the constant brightness ellipses.
3) Image Subtraction using ZOGY: ZOGY is an image subtraction algorithm used by the GIT pipeline to search for transients.
Our focus is to search for novae, a class of cataclysmic variables with an accreting White Dwarf (WD) primary, specifically in the bulge of M31. Novae go into outburst due to a thermonuclear runaway on the surface of the WD as the accreted material accumulates on it, causing a sudden increase in its brightness. Depending on its speed class, the nova fades over days to months in the optical band. However, it can still be observed in UV and X-ray for weeks to years post-outburst. With our detection techniques mentioned above, we found UV-bright novae in the UVIT images. It is also being used to search for novae in the GIT images. An image subtraction pipeline can also be implemented for UVIT data for transient detection. |
