This work represent the first major study of the optical and infrared characteristics of the mass donor companions to the X-ray pulsars in the Small Magellanic Cloud (SMC). In this work several new ...counterparts have been identified, and possible ones confirmed, as companions to X-ray pulsars in the SMC giving a total of 34 such objects now identified. In addition this work presents three new binary periods and confirms two X-ray periods using optical data for objects in this group. This homogeneous sample has been studied as a group to determine important general characteristics that may offer an insight into the evolution of such systems. In particular, the spectral class distribution shows a much greater agreement with those of isolated Be stars, and appears to be in some disagreement with the galactic population of Be stars in Be/X-ray binaries. Studies of the long-term optical modulation of the Be star companions reveal an extremely variable group of objects, a fact which will almost certainly make a major contribution to the pronounced X-ray variability. The spatial distribution of these systems within the SMC is investigated and strongly suggests a link between massive star formation and the Hi density distribution. Finally, studies of the circumstellar disc characteristics reveal a strong link with optical variability offering important clues into the long-term stability of such discs.
We have used Minor Planet Center (MPC) data and tools to explore the discovery circumstances and properties of the currently known population of over 10,000 NEAs, and to quantify the challenges for ...follow-up from ground-based optical telescopes. The increasing rate of discovery has grown to ∼1000/year as surveys have become more sensitive, by 1mag every ∼7.5 years. However, discoveries of large (H≤22) NEAs have remained stable at ∼365/year over the past decade, at which rate the 2005 Congressional mandate to find 90% of 140m NEAs will not be met before 2030 (at least a decade late). Meanwhile, characterization is falling farther behind: Fewer than 10% of NEAs are well characterized in terms of size, rotation periods, and spectral composition, and at the current rates of follow-up it will take about a century to determine them even for the known population. Over 60% of NEAs have an orbital uncertainty parameter, U≥4, making reacquisition more than a year following discovery difficult; for H>22 this fraction is over 90%. We argue that rapid follow-up will be essential to characterize newly discovered NEAs. Most new NEAs are found within 0.5mag of their peak brightness and fade quickly, typically by 0.5/3.5/5mag after 1/4/6 weeks. About 80% have synodic periods of <3 years that would bring them close to Earth several times per decade. However follow-up observations on subsequent apparitions will be difficult or impossible for the bulk of new discoveries, as these will be smaller (H>22) NEAs that tend to return 100× fainter. We show that for characterization to keep pace with discovery would require: quick (within days) visible spectroscopy with a dedicated ≥2m telescope; long-arc (months) astrometry, to be used also for phase curves, with a ≥4m telescope; and fast-cadence (<min) light curves obtained rapidly (within days) with a ≥4m telescope. For the already-known large (H≤22) NEAs that tend to return to similar brightness, subsequent-apparition spectroscopy, astrometry, and photometry could be done with 1–2m telescopes.
•We used MPC data to assess the challenges to follow-up observations of NEAs.•Discovery of H<22 NEAs has stagnated at a rate of ∼365/year.•NEAs fade rapidly in days/weeks post-discovery and take years to reappear as bright.•Characterization must take place within days of discovery.•2m and 4m telescopes can perform the multiple types of required characterization.
We have monitored 41 Be/X-ray binary systems in the Small Magellanic Cloud over image9 yr using PCA RXTE data from a weekly survey program. The resulting light curves were analyzed in search of ...orbital modulations with the result that 10 known orbital ephemerides were confirmed and refined, while 10 new ones where determined. A large number of X-ray orbital profiles are presented for the first time, showing similar characteristics over a wide range of orbital periods. Lastly, three pulsars, SXP 46.4, SXP 89.0, and SXP 165, were found to be misidentifications of SXP 46.6, SXP 91.1, and SXP 169, respectively.
We have monitored a type II outburst of the Be/X-ray binary MXB 0656-072 in a series of pointed RXTE observations during October through December 2003. The source spectrum shows a cyclotron resonance ...scattering feature at $32.8^{+0.5}_{-0.4}$ keV, corresponding to a magnetic field strength of $3.67^{+0.06}_{-0.04}\times 10^{12}$ G and is stable through the outburst and over the pulsar spin phase. The pulsar, with an average pulse period of $160.4\pm0.4$ s, shows a spin-up of 0.45 s over the duration of the outburst. From optical data, the source distance is estimated to be $3.9\pm0.1$ kpc and this is used to estimate the X-ray luminosity and a theoretical prediction of the pulsar spin-up during the outburst.
A 0535+26: back in business Coe, M. J.; Reig, P.; McBride, V. A. ...
Monthly notices of the Royal Astronomical Society,
20/May , Volume:
368, Issue:
1
Journal Article
Peer reviewed
Open access
In 2005 May/June, after 10 yr of inactivity, the Be/X-ray binary system A 0535+26 underwent a major X-ray outburst. In this paper, data are presented from 10 yr of optical, infrared and X-ray ...monitoring showing the behaviour of the system during the quiescent epoch and the lead up to the new outburst. The results show the system going through a period when the Be star in the system had a minimal circumstellar disc and then a dramatic disc recovery leading, presumably, to the latest flare up of X-ray emission. The data are interpreted in terms of the state of the disc and its interaction with the neutron star companion.
We report the association of the INTEGRAL source IGR J18027-2016 with the BeppoSAX source SAX J1802.7-2017. IGR J18027-2016 is seen to be a weak, persistent source by the IBIS/ISGRI instrument on ...board INTEGRAL with an average source count rate of 0.58 counts s-1 (~6.4 mCrab) in the 20-40 keV band. Timing analysis performed on the ISGRI data identifies an orbital period of of $4.5696 \pm 0.0009$ days and gives an ephemeris of mid-eclipse as, $T_{\rm mid} = 52\,931.37 \pm 0.04$ MJD. Re-analysis of archival BeppoSAX data has provided a mass function for the donor star, $f(m) = 16 \pm 1~M_{\odot}$ and a projected semimajor axis of $a_{x}\sin{i} = 68 \pm 1$ lt-s. We conclude that the donor is an OB-supergiant with a mass of 18.8-29.3 $M_{\odot}$ and a radius of 15.0-23.4 $R_{\odot}$. Spectra obtained by XMM-Newton and ISGRI indicate a high hydrogen column density of $N_{\rm H} = 6.8 \times 10^{22}$ cm-2, which suggests intrinsic absorption. The source appears to be a high mass X-ray binary with the neutron star emitting X-rays through wind-fed accretion while in an eclipsing orbit around an OB-supergiant.
Deep observations of the Small Magellanic Cloud (SMC) and region were carried out in the hard X-ray band by the INTEGRAL observatory in 2008–2009. The field of view of the instrument permitted ...simultaneous coverage of the entire SMC and the eastern end of the Magellanic Bridge. In total, INTEGRAL detected seven sources in the SMC and five in the Magellanic Bridge; the majority of the sources were previously unknown systems. Several of the new sources were detected undergoing bright X-ray outbursts and all the sources exhibited transient behaviour except the supergiant system SMC X-1. They are all thought to be high-mass X-ray binary systems in which the compact object is a neutron star.
In this paper, we report on Chandra observations of the starburst galaxy NGC 922. NGC 922 is a drop-through ring galaxy with an expanding ring of star formation, similar in many respects to the ...Cartwheel galaxy. The Cartwheel galaxy is famous for hosting 12 ultraluminous X-ray sources (ULXs), most of which are in the star-forming ring. This is the largest number of ULXs seen in a single system and has led to speculation that the low metallicity of the Cartwheel (0.3 Z sub(middot in circle)) may optimize the conditions for ULX formation. In contrast, NGC 922 has metallicity near solar. The Chandra observations reveal a population of bright X-ray sources, including seven ULXs. The number of ULXs in NGC 922 and the Cartwheel scales with the star formation rate: we do not find any evidence for an excess of sources in the Cartwheel. Simulations of the binary population in these galaxies suggest that the ULX population in both systems is dominated by systems with strong wind accretion from supergiant donors onto direct-collapse black holes. The simulations correctly predict the ratio of the number of sources in NGC 922 and the Cartwheel. Thus, it would appear that the metallicity of the Cartwheel is not low enough to see a difference in the ULX population compared to NGC 922.
Almost all Galactic black hole (BH) binaries with low-mass donor stars are transient X-ray sources; we expect most of the X-ray transients observed in external galaxies to be BH binaries also. ...Obtaining period estimates for extragalactic transients is challenging, but the resulting period distribution is an important tool for modeling the evolution history of the host galaxy. We have obtained periods, or upper limits, for 12 transients in M31, using an updated relation between the optical and X-ray luminosities. We have monitored the central region of M31 with Chandra for the last ~12 years, and followed up promising transients with the Hubble Space Telescope; 4sigma B-magnitude limits for optical counterparts are 26-29, depending on crowding. We obtain period estimates for each transient for both neutron star and BH accretors. Periods range from <0.4 to 490 + or - 90 hr (<0.97 to < 175 hr if all are BH systems). These M31 transients appear to be somewhat skewed toward shorter periods than the Milky Way (MW) transients; indeed, comparing the M31 and MW transients with survival analysis techniques used to account for some data with only upper limits yields probabilities of ~0.02-0.08 that the two populations are drawn from the same distribution. We also checked for a correlation between orbital period and distance from the nucleus, finding a 12% probability of no correlation. Further observations of M31 transients will strengthen these results.
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