X-ray outbursts of AXPs and SGRs

We show that the X‐ray enhancement light curves of transient AXP∕SGRs can be reproduced by the active fallback disk model. We solve the diffusion equation for the relaxation of a disk that has been pushed back by a soft gamma‐ray burst. Our preliminary results indicate that a critical temperature around 1500 K leads to a thermal‐viscous instability in the fallback disks of all AXP∕SGRs. The effect of the instability on the light curves are different for transient and persistent sources due to different pre‐burst disk conditions in these systems

Fallback disks, magnetars and other neutron stars

The presence of matter with angular momentum, in the form of a fallback disk around a young isolated neutron star will determine its evolution. This leads to an understanding of many properties of different classes of young neutron stars, in particular a natural explanation for the period clustering of AXPs, SGRs and XDINs. The spindown or spinup properties of a neutron star are determined by the dipole component of the magnetic field. The natural possibility that magnetars and other neutron stars may have different strengths of the dipole and higher multipole components of the magnetic field is now actually required by observations on the spindown rates of some magnetars. This talk gives a broad overview and some applications of the fallback disk model to particular neutron stars. Salient points are: (i) A fallback disk has already been observed around the AXP 4U 0142+61 some years ago. (ii) The low observed spindown rate of the SGR 0418+5729 provides direct evidence that the dipole component of the field is in the 1012G range. All properties of the SGR 0418+5729 at its present age can be explained by spindown under torques from a fallback disk. (iii) The anomalous braking index of PSR J1734-3333 can also be explained by the fallback disk model which gives the luminosity, period, period derivative and the period second derivative at the present age. (iv) These and all applications to a variety of other sources employ the same disk physics and evolution, differing only in the initial conditions of the disk

Optical and Infrared Emission from the AXPs and SGRs

We show that the irradiated accretion disk model can account for all the optical and infrared observations of the anomalous X-ray pulsars in the persistent state. Model fits do not constrain the outer disk radii, while placing an upper limit to the inner disk radii, and thus to the strength of the dipole component of the stellar magnetic field. While magnetar fields (B_* > 10^{14} G) in higher multipoles are compatible with the irradiated disk model, magnetic dipole components of magnetar strength are not consistent with optical data.Comment: 12 pages, accepted for publication in ApJ Letter

Natural storages versus modern storages in Nevsehir region

Depolama yapıları; yetiştirme mevsimi dışında üründen yararlanmayı, üreticinin pazar fiyatlarını izleyerek ürünün uygun zamanlarda uygun fiyatlarla pazara sürümünü, tüketicinin pazarda uzun süre daha nitelikli ve uygun fiyatlarla ürün bulmasını, üretim ve pazarlama işlerinin iş gücünün yıl içerisinde dengeli şekilde dağılımını, ürünü değerlendiren sanayinin daha uzun süre ve ekonomik olarak çalışma olanağı bulmasını sağlamaktadır. Bu çalışmada; Nevşehir yöresinde tarımsal ürünlerin depolanası amacıyla kullanılan volkanik tüf kaya depolama sistemi hakkında bilgi verilmiştir. Yöredeki tüf kayalarına oyulan depolarda yalnızca deponun soğuk havasından yararlanılarak sebze ve meyveler enerji harcanmadan depolanabilmekte, bu da büyük maliyet üstünlüğü sağlamaktadır. Bacasız fabrikalar özelliğindeki bu depolar, ülke ve bölge ekonomisine büyük katkı yapmakta, önemli istihdam olanağı sağlamaktadır.Storage structures allow the producers to benefit from the products out of the season, to market their products in proper periods with proper market prices through monitoring the market prices, to provide a balanced labor distribution in production and processing activities throughout the year, allow the consumer to find quality products in markets with proper prices for longer durations, allows the producers and finally allow the relevant industries to work economically for longer durations. Information provided in this study about the natural storages made of volcanic tufa rock storage system used to store agricultural products. The storages are carved into tufa rock in the region and used as cold storage for vegetables and fruits without using any energy. The system has significant cost-advantages over the conventional modern storages. Such systems are also called as “factories without chimneys”. They are able to provide significant contributions to local and country economy and also provide significant employment opportunities

On fallback disks and magnetars

The discovery of a disk around the anomalous X-ray pulsar 4U 0142+61, has rekindled the interest in fallback disks around magnetars. We briefly review the assumptions of fallback disk models and magnetar models. Earlier data in optical and near IR bands combined with new Spitzer data in the mid-IR range are compatible with a gas disk. Higher multipole fields with magnetar strengths together with a dipole field of 1012-1013 G on the neutron star surface are compatible with the presence of a disk around the neutron star. The possible presence and properties of a fallback disk after the supernova explosion is a likely initial condition to complement the initial rotation period and initial dipole field in determining the evolutionary paths and different types of isolated neutron stars

A natural limit on the observable periods of anomalous x-ray pulsars and soft gamma-ray repeaters

We investigate the dependence of the evolution of neutron stars with fallback disks on the strength of the magnetic dipole field of the star. Using the same model as employed by Ertan et al. (2009), we obtain model curves for different dipole fields showing that the neutron stars with magnetic dipole fields greater than ∼ 1013 G on the surface of the star are not likely to become anomalous X‐ray pulsars (AXPs) and soft gamma‐ray repeaters (SGRs). Other sources with conventional dipole fields evolve into the AXP phase if their disk can penetrate the light cylinder. The upper limits to the observed periods of AXP and SGRs could be understood if the disk becomes inactive below a low temperature around 100 K. We summarize our present and earlier results indicated by the evolutionary model curves of these sources with an emphasis on the importance of the minimum disk temperature and the X‐ray irradiation in the long‐term evolution of AXPs and SGRs with fallback disks

Long-term evolution of dim isolated neutron stars

The X-ray dim isolated neutron stars (XDINs) have periods in the same range as the anomalous X-ray pulsars (AXPs) and the soft gamma-ray repeaters (SGRs). We apply the fallback disc model, which explains the period clustering and other properties of AXP/SGRs, to the six XDINs with measured periods and period derivatives. Present properties of XDINs are obtained in evolutionary scenarios with surface dipole magnetic fields B-0 similar to 10(12) G. The XDINs have gone through an accretion epoch with rapid spin-down earlier, and have emerged in their current state, with the X-ray luminosity provided by neutron star cooling and no longer by accretion. Our results indicate that the known XDINs are not likely to be active radio pulsars, as the low B-0, together with their long periods place these sources clearly below the 'death valley'

On the X-ray Outbursts of Transient Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters

We show that the X-ray outburst light curves of four transient anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), namely XTE J1810-197, SGR 0501+4516, SGR 1627-41 and CXOU J164710.2-455216, can be produced by the fallback disk model that was also applied to the outburst light curves of persistent AXPs and SGRs in our earlier work. The model solves the diffusion equation for the relaxation of a disk which has been pushed back by a soft gamma-ray burst. The sets of main disk parameters used for these transient sources are very similar to each other and to those employed in our earlier models of persistent AXPs and SGRs. There is a characteristic difference between the X-ray outburst light curves of transient and persistent sources. This can be explained by the differences in the disk surface-density profiles of the transient and persistent sources in quiescence indicated by their quiescent X-ray luminosities. Our results imply that a viscous disk instability operating at a critical temperature in ~ 1300 - 2800 K range is a common property of all fallback disks around AXPs and SGRs. The effect of the instability is more pronounced and starts earlier for the sources with lower quiescent luminosities, which leads to the observable differences in the X-ray enhancement light curves of transient and persistent sources. A single active disk model with the same basic disk parameters can account for the enhancement phases of both transient and persistent AXPs and SGRs. We also present a detailed parameter study to show the effects of disk parameters on the evolution of the X-ray luminosity of AXPs and SGRs in the X-ray enhancement phases.Comment: 41 pages, 9 figures. Appeared in the Astrophysical Journal, 758, 98 (2012

Diatomit ve hidrofob kil ile üretilen prefabrik yapı malzemesinin bazı özellikleri

Bu çalışmada, prefabrike yapı elemanı üretiminde diatomit (D) ve su itici özelliğe sahip hidrofob kilin (HK) çimento ile farklı oranlardaki karışımlarının fiziksel ve mekanik özelliklerine etkileri araştırılmıştır. Bu amaçla diatomit tozu yerine diatomit ağırlığının %5, %10 ve %15’i oranında hidrofob kil ve %10, %20 ve %30’u oranlarında da çimento kullanılarak örnekler hazırlanmıştır. Pres ve buhar kürü uygulanmış örnekler üzerinde basınç dayanımı, birim hacim ağırlık ve su emme özellikleri incelenmiştir. Diatomitin düşük oranlı çimento ve hidrofob kil ile karıştırılmasıyla üretilen örneklerin 1000-1300 kg/m3 birim hacim ağırlık ve 4-18 MPa arasında değişen basınç dayanımlarına sahip olduğu görülmüştür. Geleneksel yapı malzemeleriyle karşılaştırıldıklarında ise, benzer fiziksel ve mekanik özelliklere sahip olduğu belirlenmiştir