A Search for Periodicities from a ULX in the LINER Galaxy NGC 4736
Abstract
We present our results from the timing analysis of the transient Ultraluminous X-ray Source (ULX) X-2 in nearby galaxy NGC 4736 based on the Chandra and XMM-Newton archival data. The power density spectrum (PDS) of the source have been obtained using Fast Fourier Transform and examined to search periodicities. The PDS of X-2 reveals a QPO peak at 0.73_{-0.14}^{+0.16} mHz with an fractional rms variability of 16 percent using the Chandra data (ObsID 808) and the PDS obtained by using XMM-Newton-pn data (ObsID 0404980101) shows a peak at 0.53_{-0.35}^{+0.09} mHz with a fractional rms variation of 5 percent. These QPOs overlap within error limits and may be the same oscillation. Also, we detect a long periodicity or a QPO in the Chandra data of about (5.2±{2.0})×10^{-5} Hz (∼ 5.4 hrs) over 3 σ confidence level. If this is a QPO, it is the lowest QPO detected from a ULX. The mass of the compact object in ULX X-2 is estimated from Eddington luminosity and disk blackbody model in the range of (10-80) M_{sun}.
- Publication:
-
The X-ray Universe 2014
- Pub Date:
- July 2014
- Bibcode:
- 2014xru..confE..30A