Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDiscovery of pulsations from the Be/X-ray binary RX J0101.3-7211 in the SMC by XMM-Newton
231
0
0.0
(
0
)
Authors
M. Sasaki
Ask ChatGPT about the research
No Arabic abstract
We report pulsations in the X-ray flux of RX J0101.3-7211 in the Small Magellanic Cloud (SMC) with a period of 455+/-2 s in XMM-Newton EPIC-PN data. The X-ray spectrum can be described by a power-law with a photon index of 0.6+/-0.1. Timing analysis of ROSAT PSPC and HRI archival data confirms the pulsations and indicates a period increase of ~5 s since 1993. RX J0101.3-7211 varied in brightness during the ROSAT observations with timescales of years with a maximum unabsorbed flux of 6 x 10^-13 erg cm^-2 s^-1 (0.1 - 2.4 keV). The flux during the XMM-Newton observation in the ROSAT band was lower than during the faintest ROSAT detection. The unabsorbed luminosity derived from the EPIC-PN spectrum is 2 x 10^35 erg s^-1 (0.2 - 10.0 keV) assuming a distance of 60 kpc. Optical spectra of the proposed counterpart taken at the 2.3 m telescope of MSSSO in Australia in August 2000 show strong Halpha emission and indicate a Be star. The X-ray and optical data confirm RX J0101.3-7211 as a Be/X-ray binary pulsar in the SMC.
rate research
Read More
Context. The Small Magellanic Cloud (SMC) is hosting many known high-mass X-ray binaries, all but one (SMC X-1) having Be companion stars. Through the calibration and verification phase of eROSITA on board the SRG spacecraft, the Be/X-ray binary XMMU J010429.4-723136 was in the field of view during observations of the supernova remnant 1E0102.2-7219, used as calibration standard. Aims. We report here a time and spectral analysis of XMMU J010429.4-723136, based on two eROSITA observations of the field, performed on 2019 November 7-9. We also reanalyse the OGLE light curve for that source, in order to determine the orbital period. Methods. The search for pulsations (from the X-ray data) and for the orbital period (from the OGLE data) is done via Lomb-Scargle periodogram analysis. X-ray spectral parameters and fluxes are retrieved from the best-fit model. Results. We detected for the first time, the pulsations of XMMU J010429.4-723136 at a period of 164 s, and therefore designate the source as SXP 164. From the spectral fitting, we derive a source flux of 1x10e-12 erg s-1 cm-2 for both observations, corresponding to a luminosity of 4x10e35 erg s-1 at the distance of the SMC. Furthermore, reanalysing the OGLE light curve including the latest observations, we found a significant periodic signal at 22.3d likely being the orbital period, which is shorter than the previously reported values.
Many X-ray accreting pulsars have a soft excess below 10 keV. This feature has been detected also in faint sources and at low luminosity levels, suggesting that it is an ubiquitous phenomenon. In the case of the high luminosity pulsars (Lx > 10^36 erg/s), the fit of this component with thermal emission models usually provides low temperatures (kT < 0.5 keV) and large emission regions (R > a few hundred km); for this reason, it is referred to as a `soft excess. On the other hand, we recently found that in persistent, low-luminosity (Lx ~ 10^34 erg/s) and long-period (P > 100 s) Be accreting pulsars the observed excess can be modeled with a rather hot (kT > 1 keV) blackbody component of small area (R < 0.5 km), which can be interpreted as emission from the NS polar caps. In this paper we present the results of a recent XMM-Newton observation of the Galactic Be pulsar RX J0440.9+4431, which is a poorly studied member of this class of sources. We have found a best-fit period P = 204.96(+/-0.02) s, which implies an average pulsar spin-down during the last 13 years, with dP/dt ~ 6x10^(-9) s/s. The estimated source luminosity is Lx ~ 8x10^(34) erg/s: this value is higher by a factor < 10 compared to those obtained in the first source observations, but almost two orders of magnitude lower than those measured during a few outbursts detected in the latest years. The source spectrum can be described with a power law plus blackbody model, with kTbb = 1.34(+/-0.04) keV and Rbb = 273(+/-16) m, suggesting a polar-cap origin of this component. Our results support the classification of RX J0440.9+4431 as a persistent Be/NS pulsar, and confirm that the hot blackbody spectral component is a common property of this class of sources.
We report on the discovery of X-ray pulsations in the Be/X-ray binary IGR J21343+4738 during an XMM-Newton observation. We obtained a barycentric corrected pulse period of 320.35+-0.06 seconds. The pulse profile displays a peak at low energy that flattens at high energy. The pulse fraction is 45+-3$% and independent of energy within the statistical uncertainties. The 0.2-12 keV spectrum is well fit by a two component model consisting of a blackbody with kT=0.11+-0.01 keV and a power law with photon index Gamma=1.02+-0.07. Both components are affected by photoelectric absorption with a equivalent hydrogen column density NH=(1.08+-0.15)x 10^{22} cm^{-2} The observed unabsorbed flux is 1.4x10^{-11} erg cm^{-2} s^{-1} in the 0.2-12 keV energy band. Despite the fact that the Be stars circumstellar disc has almost vanished, accretion continues to be the main source of high energy radiation. We argue that the observed X-ray luminosity (LX~10^{35} erg s^{-1}) may result from accretion via a low-velocity equatorial wind from the optical companion.
IGR J06074+2205 is a poorly studied X-ray source with a Be star companion. It has been proposed to belong to the group of Be/X-ray binaries. In Be/X-ray binaries, accretion onto the neutron star occurs via the transfer of material from the Be stars circumstellar disk. Thus, in the absence of the disk, no X-ray should be detected. The main goal of this work is to study the quiescent X-ray emission of IGR J06074+2205 during a disk-loss episode. We show that at the time of the XMM-Newton observation the decretion disk around the Be star had vanished. Still, accretion appears as the source of energy that powers the high-energy radiation in IGR J06074+2205. We report the discovery of X-ray pulsations with a pulse period of 373.2 s and a pulse fraction of ~50%. The $0.4-12$ keV spectrum is well described by an absorbed power law and blackbody components with the best fitting parameters: $N_{rm H}=(6.2pm0.5) times 10^{21}$ cm$^{-2}$, $kT_{rm bb}=1.16pm0.03$ keV, and $Gamma=1.5pm0.1$ The absorbed X-ray luminosity is $L_{rm X}=1.4 times 10^{34}$ erg s$^{-1}$ assuming a distance of 4.5 kpc. The detection of X-ray pulsations confirms the nature of IGR J06074+2205 as a Be/X-ray binary. We discuss various scenarios to explain the quiescent X-ray emission of this pulsar. We rule out cooling of the neutron star surface and magnetospheric emission and conclude that accretion is the most likely scenario. The origin of the accreted material remains an open question.
Context: Finding Active Galactic Nuclei (AGN) behind the Magellanic Clouds (MCs) is difficult because of the high stellar density in these fields. Although the first AGN behind the Small Magellanic Cloud (SMC) were reported in the 1980s, it is only recently that the number of AGN known behind the SMC has increased by several orders of magnitude. Aims: The mid-infrared colour selection technique has been proven to be an efficient means of identifying AGN, especially obscured sources. The X-ray regime is complementary in this regard and we use XMM-Newton observations to support the identification of AGN behind the SMC. Methods: We present a catalogue of AGN behind the SMC by correlating an updated X-ray point source catalogue from our XMM-Newton survey of the SMC with already known AGN from the literature as well as a list of candidates obtained from the ALLWISE mid-infrared colour selection criterion. We studied the properties of the sample with respect to their redshifts, luminosities and X-ray spectral characteristics. We also identified the near-infrared counterpart of the sources from the VISTA observations. Results: The redshift and luminosity distributions of the sample (where known) indicate that we detect sources from nearby Seyfert galaxies to distant and obscured quasars. The X-ray hardness ratios are compatible with those typically expected for AGN. The VISTA colours and variability are also consistent in this regard. A positive correlation was observed between the integrated X-ray flux (0.2--12 keV) and the ALLWISE and VISTA magnitudes. We further present a sample of new candidate AGN and candidates for obscured AGN. All of these make an interesting subset for further follow-up studies. An initial spectroscopic follow-up of 6 out of the 81 new candidates showed all six sources are active galaxies, albeit two with narrow emission lines.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
