Abstract
Aims. In an attempt to catch new X-ray transients while they are sti ll bright, the data taken by XMM-Newton as it slews between targets is being processed and cross-correlated with other X-ray obse rvations as soon as the slew data appears in the XMM-Newton archive. Methods. A bright source, XMMSL1 J070542.7-381442, was detected on 9 Oct 2007 at a position where no previous X-ray source had been seen. The XMM slew data and optical data acquired with the Magellan Clay 6.5 m telescope were used to classify the new object. Results. No XMM slew X-ray counts are detected above 1 keV and the source is seen to be∼750 times brighter than the ROSAT All-Sky Survey upper limit at that position. The normally mV∼16 star, USNO-A2.0 0450-03360039, which lies 3.5 ′′ from the X-ray position, was seen in our Magellan data to be very much enhanced in brightness. Our optical spectrum showed emission lines which identified t he source as a nova in the auroral phase. Hence this optical source is undoubtedly the progenitor of the X-ray source− a new nova (now also known as V598 Pup). The X-ray spectrum indicates that the nova was in a super-soft state (with kTeff≈35 eV). We estimate the distance to the nova to be∼3 kpc. Analysis of archival robotic optical survey data shows a rap id decline light curve consistent with that expected for a ve ry fast nova. Conclusions. The XMM-Newton slew data present a powerful opportunity to fi nd new X-ray transient objects while they are still bright. H ere we present the first such source discovered by the analysis of near real-time slew data.
Highlights
To date, the publicly available XMM-Newton slew data cover over 25% of the sky, while the soft band (0.2−2 keV) slew sensitivity limit (6 × 10−13 erg cm−2 s−1) is close to that of the RASS. (The hard-band [2−12 keV] limit is 4 × 10−12 erg cm−2 s−1.) For details of the slew data and catalogue and the first science results, see Saxton et al (2008) and Read et al (2006)
The XMM slew data and optical data acquired with the Magellan Clay 6.5 m telescope were used to classify the new object
No XMM slew X-ray counts are detected above 1 keV and the source is seen to be ∼750 times brighter than the ROSAT All-Sky Survey upper limit at that position
Summary
The publicly available XMM-Newton slew data cover over 25% of the sky, while the soft band (0.2−2 keV) slew sensitivity limit (6 × 10−13 erg cm−2 s−1) is close to that of the RASS. (The hard-band [2−12 keV] limit is 4 × 10−12 erg cm−2 s−1.) For details of the slew data and catalogue and the first science results, see Saxton et al (2008) and Read et al (2006). The near real-time comparison of XMM-Newton slew data with ROSAT data is giving, for the first time, the opportunity of finding all manner of high-variability X-ray objects, e.g. tidal disruption candidates (Esquej et al 2007), AGN, blazars, and Galactic sources such as novae, flare stars, cataclysmic variables, and eclipsing X-ray binaries It is only with a large-area survey, such as the XMM-Newton Slew Survey, that such rare events have a chance of being caught − within the first slew catalogue (XMMSL1, covering 14% of the sky; Saxton et al 2008), ∼40 individual slew sources are seen at fluxes >20 times greater than their corresponding ROSAT counterparts or 2σ upper limits (assuming a 70 eV black body model with Galactic NH). The discussion of these observations is deferred to a later paper
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