Faint super-soft X-ray sources in XMM-Newton Large Magellanic Cloud fields

• Published in: Astronomy and astrophysics (Berlin) 2008-04, Vol.482 (1), p.237-245
• Main Authors: Kahabka, P., Haberl, F., Pakull, M., Millar, W. C., White, G. L., Filipović, M. D., Payne, J. L.
• Format: Article
• Language: English
• Subjects: Astronomy; binaries: general; Earth, ocean, space; Exact sciences and technology; galaxies: Magellanic Clouds; stars; stars: binaries: close; stars: general; X-rays: stars
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20078535

Aims. We report the discovery of three faint, super-soft X-ray sources in LMC fields observed with XMM-Newton. Methods. We analyse the three new sources together with RX J0537.7-7034 and RX J0507.1-6743, both known since ROSAT. Results. We identify XMMU J050803.1-684017 with the LMC planetary nebula LHA 120-N 102 = LMC SMP 29. The EPIC-pn spectrum of XMMU J050803.1-684017 can be fitted with a blackbody spectrum with an effective temperature of ~(26–51) eV and a bolometric luminosity of (0.1-30)$\times$1036 erg s-1, depending on the assumed absorption. The source is consistent with the nucleus of a planetary nebula. The EPIC-pn spectrum of XMMU J052530.5-671501 is characterized by a blackbody temperature of ~(38–120) eV, a best-fit bolometric luminosity of ~3$\times$1037 erg s-1 and absorbing LMC column of $\sim8^{+2}_{-8}$$\times$1021 cm-2. This most likely highly-absorbed super-soft source resembles the LMC super-soft source CAL 87. The EPIC-pn spectrum of XMMU J052215.0-701658 yields a blackbody temperature of ~(24–83) eV, but there are only about 40 source counts and the spectral parameters of the source are not well constrained. We observe RX J0537.7-7034 with EPIC-pn to be about a factor of 15 fainter compared to the ROSAT observation 11 years earlier. RX J0507.1-6743 is observed as an absorbed super-soft source by XMM-Newton and the improved X-ray position coincides with a MACHO star which is consistent with a symbiotic star.