Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userCXO J004318.8+412016, a steady supersoft X-ray source in M 31
73
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We obtained an optical spectrum of a star we identify as the optical counterpart of the M31 Chandra source CXO J004318.8+412016, because of prominent emission lines of the Balmer series, of neutral helium, and a He II line at 4686 Angstrom. The continuum energy distribution and the spectral characteristics demonstrate the presence of a red giant of K or earlier spectral type, so we concluded that the binary is likely to be a symbiotic system. CXO J004318.8+412016 has been observed in X-rays as a luminous supersoft source (SSS) since 1979, with effective temperature exceeding 40 eV and variable X-ray luminosity, oscillating between a few times 10(35) erg/s and a few times 10(37) erg/s. The optical, infrared and ultraviolet colors of the optical object are consistent with an an accretion disk around a compact object companion, which may either be a white dwarf, or a black hole, depending on the system parameters. If the origin of the luminous supersoft X-rays is the atmosphere of a white dwarf that is burning hydrogen in shell, it is as hot and luminous as post-thermonuclear flash novae, yet no major optical outburst has ever been observed, suggesting that the white dwarf is very massive (m>1.2 M(sol)) and it is accreting and burning at the high rate (mdot>10(-8)M(sol)/year) expected for type Ia supernovae progenitors. In this case, the X-ray variability may be due to a very short recurrence time of only mildly degenerate thermonuclear flashes.
rate research
Read More
[Abridged] Classical novae (CNe) represent the main class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M 31. Only three confirmed novae and three SSSs have been discovered in globular clusters (GCs) of any galaxy so far, of which one nova and two SSSs (including the nova) were found in M 31 GCs. To study the SSS state of CNe we carried out a high-cadence X-ray monitoring of the M 31 central area with XMM-Newton and Chandra. We analysed X-ray and optical data of a new transient X-ray source in the M 31 GC Bol 126, discovered serendipitously in Swift observations. Our optical data set was based on regular M 31 monitoring programmes from five different small telescopes. Additionally, we made use of Pan-STARRS 1 data obtained during the PAndromeda survey. Our observations reveal that the X-ray source in Bol 126 is the third SSS in an M 31 GC and can be confirmed as the second CN in the M 31 GC system. This nova is named M31N 2010-10f. Its properties in the X-ray and optical regimes agree with a massive white dwarf (M_WD >~ 1.3 M_sun) in the binary system. Incorporating the data on previously found (suspected) novae in M 31 GCs we used our high-cadence X-ray monitoring observations to estimate a tentative nova rate in the M 31 GC system of 0.05 /yr/GC. An optical estimate, based on the recent 10.5-year WeCAPP survey, gives a lower nova rate, which is compatible with the X-ray rate on the 95% confidence level. There is growing evidence that the nova rate in GCs is higher than expected from primordial binary formation and under conditions as in the field. Dynamical binary formation and/or additional accretion from the intracluster medium are possible scenarios for an increased nova rate, but observational confirmation for this enhancement has been absent, so far. Regular X-ray monitoring observations of M 31 provide a promising strategy to find these novae.
We report on observations of a luminous supersoft X-ray source (SSS) in M31, r1-25, that has exhibited spectral changes to harder X-ray states. We document these spectral changes. In addition, we show that they have important implications for modeling the source. Quasisoft states in a source that has been observed as an SSS represent a newly- discovered phenomenon. We show how such state changers could prove to be examples of unusual black hole or neutron star accretors. Future observations of this and other state changers can provide the information needed to determine the nature(s) of these intriguing new sources.
[Abridged] The central field of the Andromeda galaxy (M 31) has been monitored, using the Chandra HRC-I detector (about 0.1-10 keV energy range) from 2006 to 2012 with the main aim to detect X-rays from optical novae. We present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC-I observations available from the Chandra data archive starting in December 1999. Based on these observations, we studied the X-ray long-term variability of the source population and especially of X-ray binaries in M 31. We created a catalogue of sources, detected in the 64 available observations, which add up to a total exposure of about 1 Ms. We present a point-source catalogue, containing 318 X-ray sources with detailed long-term variability information, 28 of which are published for the first time. The spatial and temporal resolution of the catalogue allows us to classify 115 X-ray binary candidates showing high X-ray variability or even outbursts in addition to 14 globular cluster X-ray binary candidates showing no significant variability. The analysis may suggest, that outburst sources are less frequent in globular clusters than in the field of M 31. We detected 7 supernova remnants, one of which is a new candidate and in addition resolved the first X-rays from a known radio supernova remnant. Besides 33 known optical nova/X-ray source correlations, we also discovered one previously unknown super-soft X-ray outburst and several new nova candidates. The catalogue contains a large sample of detailed long-term X-ray light curves in the M 31 central field, which helps to understand the X-ray population of our neighbouring spiral galaxy M 31.
During a search for coherent signals in the X-ray archival data of XMM-Newton, we discovered a modulation at 1.2 s in 3XMM J004301.4+413017 (3X J0043), a source lying in the direction of an external arm of M 31. This short period indicates a neutron star (NS). Between 2000 and 2013, the position of 3X J0043 was imaged by public XMM-Newton observations 35 times. The analysis of these data allowed us to detect an orbital modulation at 1.27 d and study the long-term properties of the source. The emission of the pulsar was rather hard (most spectra are described by a power law with $Gamma < 1$) and, assuming the distance to M 31, the 0.3-10 keV luminosity was variable, from $sim$$3times10^{37}$ to $2times10^{38}$ erg s$^{-1}$. The analysis of optical data shows that, while 3X J0043 is likely associated to a globular cluster in M 31, a counterpart with $Vgtrsim22$ outside the cluster cannot be excluded. Considering our findings, there are two main viable scenarios for 3X J0043: a peculiar low-mass X-ray binary, similar to 4U 1822-37 or 4U 1626-67, or an intermediate-mass X-ray binary resembling Her X-1. Regardless of the exact nature of the system, 3X J0043 is the first accreting NS in M 31 in which the spin period has been detected.
Nova Vel 1999 (V382 Vel) was observed with BeppoSAX twice, 15 days and 6 months after the optical maximum. A hard X-ray source was detected in the first observation, while the second time also a very luminous supersoft X-ray source was detected. The continuum observed in the supersoft range with the BeppoSAX LECS cannot be fitted with atmospheric models of hot hydrogen burning while dwarfs. We suggest that we are observing instead mainly a ``pseudocontinuum, namely a blend of very strong emission lines in the supersoft X-ray range.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
