X‐ray emission from optical novae in M 31

Haberl

et al. 2011

A&A

Self Cite

Context. In the central part of M 31, a high number of optical novae can be targeted within the field of view of the XMM-Newton EPIC and Chandra HRC-I X-ray detectors. A special monitoring program of the area has allowed us to investigate supersoft emission of individual novae in detail and perform a statistical analysis of the sample. Aims. For the He/N nova M31N 2007-12b, we aimed to constrain the time of appearance of a supersoft source (SSS) and the duration of the SSS state as well as determine the spectral and time variability while the source was bright. Methods. We analyzed XMM-Newton EPIC and Chandra HRC-I observations of our monitoring program performed at intervals of ten days and added results of a XMM-Newton target of opportunity observation and Swift XRT observations. We performed source detection, determined long-term time and spectral variation of M31N 2007-12b, and searched for shorter-term time variability in the individual observations when the source was bright, using fast Fourier and folding techniques to analyze periodicities. Results. The SSS emission started between 21 and 30 d after the optical outburst and ended between 60 and 120 d after outburst, making M31N 2007-12b one of the few novae with the shortest SSS phase known. The X-ray spectrum was supersoft and can be fitted with a white dwarf (WD) atmosphere model with solar abundances absorbed by the Galactic foreground. The temperature of the WD atmosphere seems to increase at the beginning of the SSS phase from ∼70 to ∼80 eV. The luminosity of M31N 2007-12b during maximum was at the Eddington limit of a massive WD and dropped by ∼30% in the observation 60 d after outburst. The radius of the emission region is ∼6 × 10 8 cm. In the four bright state observations, we detected a stable 1110 s pulsation, which we interpret as the WD rotation period. In addition, we detect dips in three observations that might represent a 4.9 h or 9.8 h binary period of the system. Conclusions. Nova envelope models with < ∼ 50% mixing between solar-like accreted material and the degenerate core of the WD can be used to describe the data. We derive a WD mass of 1.2 M , as well as an ejected and burned mass of 2.0×10 −6 M and 0.2×10 −6 M , respectively. The observed periodicities indicate that nova M31N 2007-12b erupted in an intermediate polar (IP) system. The WD photospheric radius seems to be larger than expected for a non-magnetic WD but in the range for magnetic WDs in an IP system.

Section: Discussionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 86%

See 1 more Smart Citation

Nova M31N 2007-12b: supersoft X-rays reveal an intermediate polar?

Pietsch

Haberl

et al. 2011

A&A

Self Cite

“…Previously, there were only three other SSSs known in M 31 for which light curves indicated periodic variability. This small sample consists of the transient SSS XMMU J004319.4+411758 (865.5 s period; Osborne et al 2001), the persistent supersoft source XMMU J004252.5+411540 (217.7 s; Trudolyubov & Priedhorsky 2008), and the SSS counterpart of the CN M31N 2007-12b (1100Pietsch 2010). In M 31, M31N 2006-04a therefore is only the second nova to show a periodically variable X-ray flux at all and the only known SSS with a period longer than one hour.…”

Section: X-ray Variability Of Nova M31n 2006-04amentioning

confidence: 99%

X-ray monitoring of classical novae in the central region of M 31

Pietsch

Haberl

et al. 2010

A&A

Self Cite

Context. Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbour galaxy M 31. Aims. We carried out a dedicated monitoring of the M 31 central region with XMM-Newton and Chandra in order to find SSS counterparts of CNe, determine the duration of their SSS phase and derive physical outburst parameters. Methods. We systematically searched our data for X-ray counterparts of CNe and determined their X-ray light curves and spectral properties. Additionally, we determined luminosity upper limits for all novae from previous studies which are not detected anymore and for all CNe in our field of view with optical outbursts between May 2005 and March 2007. Results. We detected eight X-ray counterparts of CNe in M 31, four of which were not previously known. Seven sources can be classified as SSSs, one is a candidate SSS. Two SSSs are still visible more than nine years after the nova outburst, whereas two other nova counterparts show a short SSS phase of less than 150 days. Of the latter sources, M31N 2006-04a exhibits a short-time variable X-ray light curve with an apparent period of (1.6 ± 0.3) h. This periodicity could indicate the binary period of the system. There is no X-ray detection for 23 out of 25 CNe which were within the field of view of our observations and had their outburst from about one year before the start of the monitoring until its end. From the 14 SSS nova counterparts known from previous studies, ten are not detected anymore. Additionally, we found four SSSs in our XMM-Newton data without a nova counterpart, one of which is a new source. Conclusions. Out of eleven SSSs detected in our monitoring, seven are counterparts of CNe. We therefore confirm the earlier finding that CNe are the major class of SSSs in the central region of M 31. We use the measured SSS turn-on and turn-off times to estimate the mass ejected in the nova outburst and the mass burned on the white dwarf. Classical novae with short SSS phases seem to be an important contributor to the overall population.

“…But it is the nearby Andromeda Galaxy (M 31), with an annual nova rate of -+ 65 15 16 yr −1 (Darnley et al 2006), that provides the leading laboratory for the study of galaxy-wide nova populations (see, for example, Ciardullo et al 1987Ciardullo et al , 1990aShafter & Irby 2001;Darnley et al 2004Darnley et al , 2006Henze et al 2008Henze et al , 2010Henze et al , 2011Henze et al , 2014bShafter et al 2011aShafter et al , 2011bShafter et al , 2015aWilliams et al 2014Williams et al , 2016. Since the discovery of the first M 31 nova by Ritchey (1917, also spectroscopically confirmed) and the pioneering work of Hubble (1929), more than 1000 nova candidates have been discovered (see Pietsch et al 2007;Pietsch 2010, and their on-line database 46 ), with over 100 now spectroscopically confirmed (see, for example, Shafter et al 2011b).…”

Section: Introductionmentioning

confidence: 99%

M31N 2008-12a—THE REMARKABLE RECURRENT NOVA IN M31: PANCHROMATIC OBSERVATIONS OF THE 2015 ERUPTION

Darnley

Bode

et al. 2016

ApJ

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption 10 times, including yearly eruptions from 2008 to 2014. With a measured recurrence period of =  P 351 13 rec days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground-and space-based follow-up programs. In this paper we present the 2015 detection, visible to near-infrared photometry and visible spectroscopy, and ultraviolet and X-ray observations from the Swiftobservatory. The LCOGT 2 m (Hawaii) discovered the 2015 eruption, estimated to have commenced at August 28.28±0.12 UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities ∼13,000 km s −1 ,