اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدNew outburst from the luminous supersoft source SSS1 in NGC 300 with periodic modulation
55
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The nearby galaxy NGC 300 is hosting two luminous transient supersoft X-ray sources with bolometric luminosities above 3x10^38 erg/s, assuming simple black-body spectra with temperatures around 60-70 eV. For one of these, SSS1, a periodic modulation of 5.4h was observed in an XMM-Newton observation from 1st of January 2001 lasting 47 ks, but not visible 6 days earlier when the luminosity was higher. We report here the detection of a new outburst from this source, which occurred during two more recent XMM-Newton observations performed on 17 to 20 December 2016 lasting for 310 ks. The luminosity was similar as in December 2000, and the 0.2-2.0 keV light curve revealed again a periodic modulation, with a period of 4.68+-0.26h, significant only in the first of the two observations. Taking into account the large uncertainties (the 2001 period was re-estimated at 5.7+-1.1h), the two values could be marginally compatible, and maybe associated with an orbital period, although the signal strength is highly variable. Thanks to the new long exposures, an additional absorption feature is now visible in the spectra, that we modelled with an absorption edge. This component decreases the bolometric luminosity below 3x10^38 erg/s and would therefore allow the presence of a white dwarf with a mass close to the Chandrasekhar limit. The system was found in outburst in 1992, 2000, 2008, and 2016 suggesting a possible recurrence period of about 8 years. We discuss viable models involving white dwarfs, neutron stars or black holes.
قيم البحث
اقرأ أيضاً
NGC 300 ULX1 is the fourth to be discovered in the class of the ultra-luminous X-ray pulsars. Pulsations from NGC 300 ULX1 were discovered during simultaneous XMM-Newton / NuSTAR observations in Dec. 2016. The period decreased from 31.71 s to 31.54 s
within a few days, with a spin-up rate of -5.56 x 10^{-7} s s^{-1}, likely one of the largest ever observed from an accreting neutron star. Archival Swift and NICER observations revealed that the period decreased exponentially from ~45 s to ~17.5 s over 2.3 years. The pulses are highly modulated with a pulsed fraction strongly increasing with energy and reaching nearly 80% at energies above 10keV. The X-ray spectrum is described by a power-law and a disk black-body model, leading to a 0.3-30 keV unabsorbed luminosity of 4.7 x 10^{39} erg s^{-1}. The spectrum from an archival XMM-Newton observation of 2010 can be explained by the same model, however, with much higher absorption. This suggests, that the intrinsic luminosity did not change much since that epoch. NGC 300 ULX1 shares many properties with supergiant high mass X-ray binaries, however, at an extreme accretion rate.
Context. Supersoft X-ray sources (SSSs) are characterised by very low temperatures (< 100 eV). Classical SSSs have bolometric luminosities in the range of 10^36-10^38 erg/s and are modelled with steady nuclear burning of hydrogen on the surfaces of w
hite dwarfs. However, several SSSs have been discovered with much higher luminosities. Their nature is still unclear. Aims. We report the discovery of a 4h modulation for an ultraluminous SSS in the nearby edge-on spiral galaxy NGC 4631, observed with XMM-Newton in 2002 June. Temporal and spectral analysis of the source is performed. Methods. We use a Lomb-Scargle periodogram analysis for the period search and evaluate the confidence level using Monte-Carlo simulations. We measure the source temperature, flux and luminosity through spectral fitting. Results. A modulation of 4.2+-0.4 h (3 sigma error) was found for the SSS with a confidence level >99%. Besides dips observed in the light curve, the flux decreased by a factor of 3 within ~10h. The spectrum can be described with an absorbed blackbody model with kT~67eV. The absorbed luminosity in the 0.2-2 kev energy band was 2.7x10^38 erg/sec while the bolometric luminosity was a hundred time higher (3.2x10^40 erg/s), making the source one of the most luminous of its class, assuming the best fit model is correct. Conclusions. This source is another very luminous SSS for which the standard white dwarf interpretation cannot be applied, unless a strong beaming factor is considered. A stellar-mass black hole accreting at a super Eddington rate is a more likely interpretation, where the excess of accreted matter is ejected through a strong optically-thick outflow. The 4 h modulation could either be an eclipse from the companion star or the consequence of a warped accretion disk.
A luminous optical transient (OT) that appeared in NGC 300 in early 2008 had a maximum brightness, M_V ~ -12 to -13, intermediate between classical novae and supernovae. We present ground-based photometric and spectroscopic monitoring and adaptive-op
tics imaging of the OT, as well as pre- and post-outburst space-based imaging with HST and Spitzer. The optical spectrum at maximum showed an F-type supergiant photosphere with superposed emission lines of hydrogen, Ca II, and [Ca II], similar to the spectra of low-luminosity Type IIn supernova impostors like SN 2008S, as well as cool hypergiants like IRC +10420. The emission lines have a complex, double structure, indicating a bipolar outflow with velocities of ~75 km/s. The luminous energy released in the eruption was ~10^47 ergs, most of it emitted in the first 2 months. By registering new HST images with deep archival frames, we have precisely located the OT site, and find no detectable optical progenitor brighter than broad-band V magnitude 28.5. However, archival Spitzer images reveal a bright, non-variable mid-IR pre-outburst source. We conclude that the NGC 300 OT was a heavily dust-enshrouded luminous star, of ~10-15 Msun, which experienced an eruption that cleared the surrounding dust and initiated a bipolar wind. The progenitor was likely an OH/IR source which had begun to evolve on a blue loop toward higher temperatures, but the precise cause of the outburst remains uncertain.
ASASSN-16oh is a peculiar transient supersoft X-ray source without a mass-ejection signature in the field of the Small Magellanic Cloud. Maccarone et al. (2019) concluded that ASASSN-16oh is the first dwarf nova with supersoft X-ray that originated f
rom an equatorial accretion belt on a white dwarf (WD). Hillman et al. (2019) proposed a thermonuclear runaway model that both the X-rays and $V$/$I$ photons are emitted from the hot WD. We calculated the same parameter models as Hillman et al.s and found that they manipulated on/off the mass-accretion, and their best fit $V$ light curves are 6 mag fainter, and decay about 10 times slower, than that of ASASSN-16oh. We propose a nova model induced by a high rate of mass accretion during a dwarf nova outburst, i.e., the X-rays originate from the surface of the hydrogen-burning WD whereas the $V/I$ photons are from the irradiated disk. Our model explains the main observational properties of ASASSN-16oh. We also obtained thermonuclear runaway models with no mass ejection for a wide range of parameters of the WD mass and mass accretion rates including both natural and forced novae in low-metal environments of $Z=0.001$ and $Z=0.0001$. They are a new type of periodic supersoft X-ray sources with no mass ejection, and also a bright transient in $V$/$I$ bands if they have a large disk. We suggest that such objects are candidates of Type Ia supernova progenitors because its mass is increasing at a very high efficiency $(sim 100 %)$.
We report on the results of X-ray observations of 4XMM J111816.0-324910, a transient ultra-luminous X-ray source located in the galaxy NGC 3621. This system is characterised by a transient nature and marked variability with characteristic time-scale
of ~3500 s, differently from other ULXs, which in the vast majority show limited intra-observation variability. Such a behaviour is very reminiscent of the so-called heartbeats sometimes observed in the Galactic black hole binary GRS 1915+105, where the variability time-scale is ~10-1000 s. We study the spectral and timing properties of this object and find that overall, once the differences in the variability time-scales are taken into account, they match quite closely those of both GRS 1915+105, and of a number of objects showing heartbeats in their light-curves, including a confirmed neutron star and a super-massive black hole powering an active galactic nucleus. We investigate the nature of the compact object in 4XMM J111816.0-324910 by searching for typical neutron star signatures and by attempting a mass estimate based on different methods and assumptions. Based on the current available data, we are not able to unambiguously determine the nature of the accreting compact object responsible for the observed phenomenology.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
