PoS(Integral08)115 3 , 1 2 using − http://pos.sissa.it/ and C. Ferrigno 1 h flares close to orbital ASM lightcurve of the source. X-ray Binary GX 301 is determined and the spin down V) pulse phase resolved spectra. , val analysis of archival data which n flare of the source when the flux trum and the impact of the model on re (CRSF) energy with pulse phase. 290 Versoix,Switzerland ted observations with a total exposure RXTE , A. Santangelo 4 berg, Germany , ommel-Strasse 1, 91058 Erlangen, ngen, Germany 2 [3] observations is confirmed. Additionally , [email protected] INTEGRAL , BeppoSAX e Commons Attribution-NonCommercial-ShareAlike Licence. , I. Kreykenbohm 1 [1, 2], and INTEGRAL RXTE , R. Staubert 1 ∗ data. The source has a double-peaked orbital lightcurve wit 2 with − We present the results of an in depth analysis of the High Mass Speaker. we provide an updated orbital periodis value found based to on be time consistent arri with the period obtained from the INTEGRAL trend, established by The history of the pulse period since the launch of from the source is maximal. WeWe obtained discuss broad-band the spectral (2–100 ke models suitablethe to describe dependence the of spec the cyclotron resonance scattering featu time of 200 ksec were performed to observe the pre-periastro phases 0.5 and 0.9. In addition to archival data three dedica [email protected] [email protected] [email protected] ∗ Copyright owned by the author(s) under the terms of the Creativ ISDC Data Centre for Astrophysics, Chemin d’Écogia 16, CH-1 Erlangen Centre for Astroparticle Physics (ECAP), Erwin-R Institut für Astronomie und Astrophysik, Sand 1, 72076 Tübi Dr. Karl Remeis-Sternwarte, Sternwartstrasse 7, 96049 Bam c Germany E-mail: 7th INTEGRAL Workshop September 8-11 2008 Copenhagen, Denmark ° V. Doroshenko GX 301 3 4 1 2 PoS(Integral08)115 9). . 01 01 07 . . . 0 IBIS 680 s 0 0 0 ISGRI ∼ ∼ ( ± ± ± ). As the 1 37 12 17 5 keV [10]. ns we used . . . . − period, s. IBIS 6 V. Doroshenko yr ∼ ⊙ t the paper. The M 1 5 on star is a d at − − ring models with an r disk [8] as well as pectrum of the source 10 bserve the source with cts s ) launched in October, mask instruments: ssification of Wray 977, cus mainly on studying ∼ . The wind mass loss rate keV ˙ 60 M source is brightest, such that − assage (orbital phase 20 . The distance to the source is 1 5 [8]. Several hypotheses were . − 0 ISGRI ∼ INTEGRAL ergs 37 , [5]), the accretion rate is high enough 1 2 was within the half coded field of view . The updated orbital period value is used to 10 − − ∼ X L 2 300 kms INTEGRAL ∼ 62) is a High Mass X-ray Binary system, consisting 0 v − 2 by 9 to study the source during the pre-periastron flare. The − . 0 ∼ , [13]). In this paper, however, we rely on data from Satellite, [11] ), JEM-X (Joint European X-ray monitor, [12]), and 20 keV together with a deep and broad cyclotron resonance scattering ∼ MJD of Orbital exposure, rate, Pulse INTEGRAL 30–45 keV are present at higher energies. ∼ INTEGRAL 2 (also known as 4U 1223 during orbital phase − Pointed observations of GX 301 2 with INTEGRAL − archival data. We analyzed all data when GX 301 GX 301 To study the timing properties of the source in addition to our pointed observatio The International Gamma-Ray Astronomy Laboratory ( INTEGRAL 05180027-66 54110.52-12.22 0.96-1.02 91.66 98 684 05730048-60 54276.28-76.85 0.95-0.97 31.98 163 685 05740012-40 54277.63-78.91 0.99-1.02 69.38 76 685 science window observation phase ksec 2002 by the European Space Agency is equipped with 3 co-aligned coded parameters of the 3 observations are given in Table 2. Table 1: IBIS layer) and JEM-X only. AINTEGRAL set of pointed observations was performed to o (Imager on board GX 301 1. Introduction terminal velocity of the wind is very low ( of a neutron star orbiting the B-type optical companion Wray 977. The neutr X-ray pulsar [4], accreting from theof dense the wind of optical the component optical is companion one of the highest known in the galaxy ( to explain the observed luminosity of the order of estimated between 1.8 kpc [6] and 5.3with kpc the [7] latest depending on estimate the close spectral tosource cla 3 kpc exhibits [5]. regular We X-ray will adopt flares the about latter 1–2 value d throughou before periastron p There is also an indication for a second flare at orbital phase SPI (Spectrometer on calculate orbital phase and determine the pulse period. proposed to explain the observedthe orbital presence lightcurve, of including a athe quasi-stable circumstella properties accretion of the stream source [9]. duringthe the spectral In pre-periastron parameters flare, this can where paper the beis we obtained complex: with fo modelling very the high lowoptional significance. reflection energy component. part The An requires s iron line the with usage a complicated of shape partial is observe cove 2. Observations and data selection A high energy cutoff at feature (CRSF) at PoS(Integral08)115 n 1 1 1 2 4 1 3 = ...... 0 0 0 0 0 0 0 r of θ from , and , s. ± ± ± ± ± ± ± 0 epoch ◦ t 7 4 7 6 6 1 4 ...... spin P observations V. Doroshenko r a set of semi- obs an eccentric orbit: f a periodic signal is is measured, while . ) MJD θ hown in Table 3.1. It is , omplete binary cycle. τ n,obs observations continues. A INTEGRAL 4 54278 685 3 54276 685 2 54112 684 1 54110 684 5 54108 684 3 53549 684 1 53548 684 , t ...... 0 0 0 0 0 0 0 ω , , s. e , and the mean anomaly ± ± ± ± ± ± ± peak width in the periodogram ( τ 5 6 9 2 4 0 9 n 2 ...... spin RXTE F χ P ) i ( and sin is the orbit inclination), the eccentricity a ies correspond to our pointed observations. i obs data where the source was within 9 + 3 med are listed in Table 1. is the pulse period at the initial epoch . n 2 2 0 MJD 0 − IBIS P data. The updated orbital period value was used to ¨ 3 BeppoSAX ss PP from the center) to obtain the source lightcurve. To 5 4 53536 685 1 53534 684 0 53533 684 4 53529 684 4 53528 683 3 53527 684 3 53526 683 ...... 1 6 ◦ 11 0 0 0 1 0 0 0 0 − + , s. ± ± ± ± ± ± ± ± 2 10 1 7 3 4 2 3 8 8 n ...... spin 0 × P must be obtained. Usually only in light seconds ( 2 ˙ PP INTEGRAL ) , time of periastron passage n i 2 1 ( ω . The last term of Eq. 3.1 represents the Doppler delays caused ∼ − 0 + data was performed to obtain qualitative estimates for this trend: sin ¨ P P n obs a , 0 1 P − + MJD ss 0 t 8 − = 3 53547 684 3 53546 684 1 53545 684 1 53544 684 5 53542 684 2 53540 684 3 53539 683 3 53537 684 ...... n 10 t for each known 0 0 0 0 0 0 0 0 INTEGRAL × n , s. ± ± ± ± ± ± ± ± t 6 9 3 5 6 8 4 5 0 ...... spin . To obtain a solution for the unknown pulse and orbital parameters, a numbe ∼ P ˙ P orb , P / Period values obtained using 4s 2 with INTEGRAL ) . (554 science windows in total within 9 τ − is the time derivatives of obs − For the timing analysis we used all available To study timing properties on the shorter timescales it is no longer possible to use 681 ... t ¨ ( IBIS P 53525 683 53524 683 53088 683 53086 683 52796 680 52791 681 52790 681 52789 681 ∼ , MJD π , the longitude of the periastron ˙ measurements of must be found during the fitting procedure to obtain a self consistent solution as an estimate for theapparent error. that The the obtained spin down values trend for established the by pulse period are s the center of thecontinuous FOV. parts We of determined the the source lightcurve. pulse We period used using 10% of epoch the folding fo quadratic fit to the P referred to as time of arrival (TOA) below, where (revolutions 322-330, 283 scw in total) of the source, covering almost a3. c Data analysis 3.1 Timing analysis determine the orbital parameters, we used the longest almost continuous of Table 2: GX 301 e P the projected semi-major axis by the effects of the orbital motion as a function of the Kepler parameters for folding, instead the pulse phaseobserved connection at method times is used. A fixed phase o 2 Precise period values for the 3 pointed observations perfor correct the lightcurve for the binary motion. The last 5 entr PoS(Integral08)115 = ˙ P cutoff 2 we I − s, , which ) ) 2 2 ( ( tions within 1). For ind accreting V. Doroshenko re most often required. For 482 . 1618 < . onents include a different amount ¢ all of the orbital f 41 ) ssociated with the ptical depth profile dividual absorption E 684 < = ( Gaussian absorption ular change of orbital time reported by [14] fore also use only two Fe = I orb : P P erent absorption column confidence level). Orbital ve and periastron passage )) + σ ubject to strong photoelectric -ASM data of GX 301 E accounts for the photoelectric ( ) ) abs gabs f I 1 τ obtained above for constant period RXTE ). + − − 1 ( 1 − orb P fold . dd E 1 exp 6 / − ) )] + ( × − E 1 dd cut ( 10 value with that reported by [8] and assuming 6 E σ − cutoff × I 4 H − PA 2 10 . N T × E 3 (all uncertainties are at 1 − Γ × (( [ ) − 6 . 1 E an optional iron line, 3 ∼ − ( exp exp × f Fe 63 consistent with the I . Γ = ∼ − ) A = 4 ¡ is usually treated as a simple Gaussian line. ( ) abs × cutoff I I 53531 ) E 482 ( . E = ( Fe I 41 PA abs I T = orb )= and P E 1 ( − values by [14, 8] is NS I ss PA 8 T − is the equivalent hydrogen column and f is the covering fraction (0 10 is a normalization constant, 2 with INTEGRAL accounts for the photoelectric absorption at lower energies. In a clumpy w H × Γ − N ) A abs 2 I Due to the lack of high quality theoretical models, spectra of X-ray pulsars a We checked this also by measuring phases of the pre-periastron flares a Unfortunately span of even longest observation did not allow us to fit for ( 25 . absorption, and the last component[15]. models An a iron CRSF emission line with a Gaussian shaped o system we can expect that a part ofabsorption. the X-rays All from the radiation neutron emerging star is fromof s the absorption. emission region The is resulting alsodensities. subject It spectrum is to is clear a that a itcolumns superposition is almost such of impossible that to several separate only diff contributions from aexample in [2] small and number [3] of adopted two photoelectriccolumn columns absorption densities to components effectively, describe but their is fix spectra. one We to there zero (pcfabs model in XSPEC) constant period. It turns out to be significantly less than reported earlier makes the assumption of a constantperiod period using questionable. Our estimate for sec 4 orbital motion. Applying the technique described above to the parameters. We fixed all thetime parameters except of pulse the period, current its derivati cycle to published values.period may The be best calculated fit by values comparing are our obtained a value of 3.2 Spectral analysis Here case with timing measurements.ASM Although data, it the is period not derivativevalues obtained is possible consistent by to with fixing estimate see orbital above any ( period period value varia at where GX 301 [2] used the Fermi-Dirac cutoff [16] described with phenomenological multi-component models.power Typically used law, comp a high energyline cutoff, is and introduced photoelectric to absorption. account for Sometimes the a CRSF. PoS(Integral08)115 vely. V. Doroshenko cretion columns etailed treatment m. In a first step 3.2; the unfolded 5 1 . . riginal paper for a 0 3 6 7 5 4 5 6 5 8 . . 002 002 04 05 13 07 03 07 08 1 ...... 5 4 ...... e shown in Fig. 1. . . 18 19 0 2 5 1 0 2 0 2 0 0 0 0 0 42 0 0 0 0 28 0 0 0 from revolutions 518 + − , and the dimension- − − − + + + − + − + − + − − + + + − − + − + sulting parameters are ns. The corresponding 3 ˙ 2 5 6 — ters are used for fitting 1 . 1 . . . M . 98 . 26 55 42 56 . . . . . 4 026 0 14 17 40 . 6 0 0 59 0 219 ecut model in XSPEC 0 cut cut E E ≤ ≥ ion of the models and the parameters. e 0 E E δ ξ r T ) fold E 0 002 03 / . 4 . . . 3 4 4 7 03 4 3 0 14 1 0 2 ) 0 007 . 05 03 07 04 01 09 ...... 0 08 . . 0 4 ...... 6 0 0 1 1 0 1 1 − 1 11 6 − 0 . E 0 0 0 0 0 0 − 0 4 3 11 12 1 − − + − + + + − + − + − − + − + − + 5 + − − + + − 5 6 9 − −− + 0 2 3 ...... 6 01 39 03 13 . 0 74 . . . . 6 cut . 611 25 10 6 . 0 0 0 − 0 E 153 46 13 (( exp 1 ( accounts for a relative contribution from the thermal and bulk 4 3 02 . . 15 12 88 03 74 34 04 26 . . . = 002 007 001 005 48 ...... 04 04 04 05 4 1 . . . . . δ 0 0 ...... 1 1 10 2 1 1 1 17 0163 01 0 19 0 0 0 8 . . 0 0 0 0 0 0 − + − + − + + − − + 0 0 , the temperature of the electrons in the optically thin region above − + − + + − − + − + − + 0 2 − + — 15 . 2 r 61 cutoff 15 68 72 . . 04 35 46 . . . I . . . 5 53 determines the importance of the escape of photons from the accretion 0 020 020 . 1.17/146 1.33/147 1.18/147 . . 6 0 where 13 11 124 39 0 − 0 24 0 ξ δ , the magnetic field strength B, the accretion rate e are called cutoff and folding energy of the Fermi-Dirac cutoff, respecti T and fold ξ E do f / 2 Fe cut fold Fe Γ cyc Fe cyc fold H cyc and f χ A E E E A σ n σ τ σ Parameter Fermi-Dirac High-energy cutoff Becker& Wolf(2007) Γ E Fit results for phase averaged spectra. See text for discuss 2 with INTEGRAL cut − E In a next step we performed pulse phase resolved analysis using the data Using the standard OSA 6.1 pipeline we obtained a phase averaged spectru In addition we use a theoretical model developed by [17]; we refer to the o Table 3: less parameters and 573 as no evolution offit the results pulse for profile is the evident Fermi-Dirac during cutoffconsistent these model with revolutio the are values shown reported in by Table [2]. 3.2. Most re the thermal mound comptonizations, while column. [3] used a different model to describe the cutoff. It is based on the high where GX 301 detailed discussion of this modelof and both its bulk parameters. and The thermalof model Comptonization X-ray is of pulsars. based a Taking on seed allthe a radiation constraints data: d into occurring the account in column the the radius following ac parame but it was modified in a way that the transition region is smoothed to avoid cusps. we fitted it with thespectrum models and described the above. residuals for The fits fit with results and are without shown the in inclusion of Table a CRSF ar PoS(Integral08)115 t with the parameters V. Doroshenko has to be of the ˙ M The bolometric lumi- and the neutron star mass at therefore it only applies to the compatible, is the magnetic field strength in D gh energy cutoff, and the Becker-Wolf , 12 ˙ M B cyc . E ˙ z M usion of a CRSF. 1 + NS NS 1 R 6 57 GM . 11 = X = L 12 B 1 is the gravitational red shift and . The magnetic field strength can be obtained from the energy of the CRSF: − 1 − 2 GM gs Rc 2 17 1 − 1 8 10 G. The fit results of the variable parameters are shown in Table 3.2. These . q 0 12 Unfolded spectrum and residuals for the Fermi-Dirac, the hi [5]. To make the model flux and the estimate from 2 with INTEGRAL = ∼ − z ⊙ is one of model parameters, it is possible to check if the model flux is consisten M The self consistency of the model by [17], however, must be checked. ˙ M nosity can be estimated from the accretion rate, As where models (top to bottom), with (right) and without (left) incl Figure 1: GX 301 order of units of 10 observed flux. The model does notphase include averaged any spectra. angular dependence, The distance1.85 to the source was fixed at 3 kpc PoS(Integral08)115 nal 2 . 6 4 5 . 9 4 5 2 . . 05 1 16 05 09 08 . . . . Comptonized 2 4 5 1 6 5 V. Doroshenko ...... Even though 0 0 ...... 1 7 4 3 101 33 0 0 0 0 0 0 0 3 3 0 0 1 analyses of [2] − + further improve − + − + + − − + − + − + − + − + − + compatible with 8 7 9 0 . 6 8 7 . . . t cyclotron line is . . . 0 34 44 53 , respectively. It is del parameters, it is . . . 4 0 2 el by [17] implying ith earlier published 14 29 − 6 0 0 published values and 101 nergy is observed. We al parameters are mostly 2 can be fitted this model 08 21 5 . . 4 4 5 0 . − 06 05 1 03 06 15 11 4 03 . . . . 3 4 8 7 0 0 ...... 2 0 0 1 0 0 0 10 0 0 0 0 7 0 3 3 3 2 − + e results of the phase resolved − + − + − − + + − + + − − + BeppoSAX − + − + 1 4 6 9 8 . . 17 . . . . 35 87 38 71 . . . . 8 7 0 18 34 and 6 4 0 71 0 or the Fermi-Dirac cutoff model. All − pointed observations we were able to 2 61 2 2 . . 0 3 5 3 . . 05 1 07 05 08 04 . . . . 2 4 7 2 8 5 ...... 0 0 ...... RXTE 2 1 1 1 39 35 0 0 0 0 0 0 0 2 1 0 2 1 − + − + − + + − − + − + − + − + − + − + 9 7 8 1 . 7 6 7 ...... 0 33 58 45 . . . 4 8 6 12 36 − 6 0 0 7 118 2 we determined the evolution of the pulse period INTEGRAL − 5 38 1 3 . . 6 3 9 3 . . 05 09 05 05 05 13 09 03 . . . . 7 2 4 6 was revealed. The pulse time arrival analysis allowed us ...... 0 0 . . . . 1 2 1 1 26 23 0 0 0 0 0 0 0 0 0 2 0 1 1 − + − + − + + − − − + + − + − + − + − + 9 − 4 1 8 . 7 7 . . . . . 0 32 11 47 54 . . . . 9 7 11 38 − 6 5 0 0 116 2syr. data GX 301 ∼ 2 0 . . 2 2 7 0 9 1 . . 1 05 07 05 07 05 11 09 07 . . . . 7 4 ...... -ASM data. Using 0 0 1 . . 26 28 1 1 1 1 . 0 0 0 0 0 0 0 0 0 0 − + 19 2 + − − + − + − − + + − + − + − + 9 + − 5 7 7 . . 0 . . 7 1.13 1.51 1.36 1.28 1.30 . 0 32 48 44 57 . level. See text for a discussion of the model. . . . . 1 2 spectrum well in a self-consistent way and satisfy all known observatio − 0 RXTE σ − INTEGRAL ] 187 22 [keV] 4 [keV] 29 [keV] 3 [keV] 11 dof 0.92/41 1.58/44 1.0/43 1.19/45 1.15/46 [keV] 6 [keV] 0 [10 / 2 2 H Spectral fit results of the phase resolved analysis results f Fe fold cut cyc Fe cyc red 2 with INTEGRAL cyc f χ χ E N E E σ τ Par./PhaseE 0-0.2σ 0.2-0.4 0.4-0.6 0.6-0.8 0.8-1.0 Γ − Using archival therefore not surprising that the fit resultsspectral are analysis somewhat different. are Th alsoindeed compatible highly with variable with earlier phase; publications furthermore awere and correlation able with confirm the to tha cutoff obtain e athat self-consistent the spectrum description is of dominated by the athis spectrum thermally description Comptonized using is bremsstrahlung not a emission definitive mod due toalready the a strong highly correlations interesting between some result mo by itself that the spectrum of GX 301 obtain high quality broadband spectraconsistent of with the those source. found The in resultingour the spectr literature. results Any can discrepancies be betweenand attributed the [3] to were the based on known data variability from of different the instruments: source and that the and a spin-down of the order of describe the GX 301 Table 4: GX 301 uncertainties are on a 3 at all, as [17] make only qualitative estimates for a limited number of sources. To 4. Conclusions constraints. These parameters imply thatbremsstrahlung the emission spectrum. spectrum is dominated by a thermally to measure periastron passage time of thevalues neutron allows star. Comparing to this estimate value w values orbital obtained from period and possibly its derivative, which are PoS(Integral08)115 , , c 554 ° , y. Wray 01-2 line in the ity stream α V. Doroshenko (Dec, 2004) (May, 1980) 547. eded to be able to 427 191 A study of an orbital (Aug, 1995) 446. Periodic modulation of (Aug, 2005) 617. (Oct, 2006) 595. 300 The Astrophysical Journal 438 457 , (Nov, 2003) L37. (c) 2003: The . Sanford, V. Kämäräinen, O. Vilhu, 597 Ibis: The imager on-board integral en, P. B. Mogensen, I. Rasmussen, sta, M. Feroci, A. Rubini, en Heuvel, and E. J. Zuidervijk, , y. , R. Carli, C. Gomez, P. L. Jensen, ey, V. Reglero, L. Sabau, B. Sacco, schild, W. A. Heindl, P. Kretschmar, and ski, A. Castro-Tirado, P. Attina, A spectral study of wray 977, the optical Prince, B. A. Vaughan, M. H. Finger, , and M. Orlandini, T. Kohmura, U. Morita, F. Nagase, d, K. Broenstad, A. Goldwurm, G. L. Rosa, iciari, G. Loffredo, S. M. Núñez, dt, I. L. Rasmussen, A. Hornstrup, C. A. (Feb, 2008) 747. (c) Journal compilation (Nov, 1976) L119. A&AA ID. Astron. Astrophys. , Astronomy and Astrophysics 384 209 , Royal Astronomical Society , 8 Vlt/uves spectroscopy of wray 977, the hypergiant Astronomy and Astrophysics Astronomy and Astrophysics , , The Astrophysical Journal , (Nov, 2003) L131. (Apr, 1997) 933. (c) 1997: The American Astronomical Societ Rapid spin-up episodes in the wind-fed accreting pulsar gx 3 Detection of a fully resolved compton shoulder of the iron k 411 Astrophysical Journal Stellar wind accretion in gx 301-2: evidence for a high-dens 479 , An orbital light-curve model for gx 301-2 The variable cyclotron line in gx 301-2 2 with INTEGRAL − chandra x-ray spectrum of gx 301-2 American Astronomical Society. C. Labanti, P. Laurent, I. F. Mirabel,R. E. Staubert, M. L. Quadrini, Vigroux, M. B. C. Rams Weisskopf, and A. A. Zdziarski Astronomy and Astrophysics Oxborrow, J. Chenevez, P. A. Jensen, S. Laursen, K. H. Anders V. Reglero, T. Velasco, S. Larsson, R. Svensson, A. A. Zdziar K. Omø, S. M. Pedersen, J.J. Polny, Huovelin, H. S. Andersson, Maisala, T. M. Andersson, Morawski,M. G. Rapisarda, Juchnikowski, E. E. Morelli, Co V. Carassiti, F. Frontera, C. Pell M. Goria, G. Giulianelli, F. Cordero, M. Rezazad, M. Schmidt (Jun, 2001) 383. (c) 2001: The American Astronomical Societ R. Staubert, R. B. Wilson, and B. C. Rubin, 975. 977 (gx 301-2): a hypergiant with pulsar companion. Astrophysical Journal v.479 Monthly Notices of the Royal Astronomical Society cycle of gx 301-2 observed by bepposax F. Paerels, and T. Takahashi, 2008 RAS. three galactic x-ray sources companion to the x-ray pulsar gx301-2 A&AA ID. AAA027.114.057. counterpart of the binary x-ray pulsar 4u 1223-62 AAA018.142.100. [1] S. H. Pravdo and P. Ghosh, [2] I. Kreykenbohm, J. Wilms, W. Coburn, M. Kuster, R. E. Roth [8] D. T. Koh, L. Bildsten, D. Chakrabarty, R. W. Nelson, T. A. [3] A. La Barbera, A. Segreto, A. Santangelo, I. Kreykenbohm [9] D. A. Leahy and M. Kostka, [4] N. E. White, K. O. Mason, H. E. Huckle, P. A. Charles, and P. W [7] L. Kaper, H. J. G. L. M. Lamers, E. Ruymaekers, E. P. J. van d [5] L. Kaper, A. van der Meer, and F. Najarro, [6] G. E. Parkes, J. L. Culhane, K. O. Mason, and P. G. Murdin, GX 301 the spectral modeling with the modelfurther of constrain [17], the data spectral of parameters. much higher quality are ne References [11] P. Ubertini, F. Lebrun, G. D. Cocco, A. Bazzano, A. J. Bir [12] N. Lund, C. Budtz-Jørgensen, N. J. Westergaard, S. Bran [10] S. Watanabe, M. Sako, M. Ishida, Y. Ishisaki, S. M. Kahn, PoS(Integral08)115 , The , y. y pulsars y. V. Doroshenko Jem-x: The x-ray monitor ay timing explorer Orbital elements of the Spi: The spectrometer chnopper, Y. André, erer, P. Leleux, G. Weidenspointner, . Caraveo, B. Teegarden, P. von . Kreykenbohm, J. Wilms, P. Kretschmar, and N. E. White, (May, 1986) 241. G. G. Lichti, A. von Kienlin, B. Cordier, 304 Radiation Hydrodynamics in Stars and Compact (Nov, 2003) L63. (Nov, 2003) L231. , 9 411 411 (Jan, 2007) 435. (c) 2007: The American Astronomical Societ Thermal and bulk comptonization in accretion-powered x-ra Astrophysical Journal , (Nov, 2002) 394. (c) 2002: The American Astronomical Societ 654 580 Astronomy and Astrophysics Astronomy and Astrophysics Magnetic fields of accreting x-ray pulsars with the rossi x-r , , Observations of compact x-ray sources (Jan, 1986). 2 with INTEGRAL − S. Schanne, J. Knödlseder, G. Skinner,Ballmoos, P. Jean, L. F. Bouchet, Sanchez, P. Paul, P J.P. Matteson, Durouchoux, S. R. Boggs, Diehl, C. A. Wund Strong, M. Cassé, M. A. Clair, and aboard integral G. Sarri, A. Tiemon, A. Orr, R. Much, P. Kretschmar, and H. W. S and R. Staubert, binary x-ray pulsar gx 301-2 aboard integral Astrophysical Journal The Astrophysical Journal Objects [14] N. Sato, F. Nagase, N. Kawai, R. L. Kelley, S. Rappaport, [15] W. Coburn, W. A. Heindl, R. E. Rothschild, D. E. Gruber, I GX 301 [13] G. Vedrenne, J.-P. Roques, V. Schönfelder, P. Mandrou, [16] Y. Tanaka, [17] P. A. Becker and M. T. Wolff,