Engineering topics

Tomsick, John A.

Publications and source records attributed to Tomsick, John A..

45 records · Page 3

NASA NTRS2008

Monitoring the Black Hole Binary GRS 1758-258 with INTEGRAL and RXTE

The microquasar GRS 1758-258 is one of only three persistent black hole binaries that spend most of their time in the hard spectral state, the other two being Cyg X-l and 1E 1741.7-2942. It therefore provides the rare opportunity for an extensive long term study of this important black hole state which is associated with strong variability and radio jet emission. INTEGRAL has been monitoring the source since the first Galactic Center Deep Exposure season in spring 2003 during two 2-3 months long Galactic Center viewing epochs each year, amounting to 11 epochs including spring of 2008. With the exception of the last epoch quasi-simultaneous RXTE monitoring observations are available as well. Here we present an analysis of the epoch averaged broad band spectra which display considerable long term variability, most notably the occurrence of two soft/off states, extreme examples for the hysteretic behavior of black hole binaries. The hard source spectrum and long exposures allow us to extend the analysis for several epochs to approximately 800 keV using PICsIT data and address the question of the presence of a non-thermal Comptonization component.

Pottschmidt, Katja↗

NASA NTRS2008

Broadband X-Ray Spectra of GX 339-4 and the Geometry of Accreting Black Holes in the Hard State

A major question in the study of black hole binaries involves our understanding of the accretion geometry when the sources are in the "hard" state, with an X-ray energy spectrum dominated by a hard power-law component and radio emission coming from a steady "compact" jet. Although the common hard state picture is that the accretion disk is truncated, perhaps at hundreds of gravitational radii (Rg) from the black hole, recent results for the recurrent transient GX 339-4 by Miller and coworkers show evidence for disk material very close to the black hole's innermost stable circular orbit. That work studied GX 339-4 at a luminosity of approximately 5% of the Eddington limit (L(sub Edd) and used parameters from a relativistic reflection model and the presence of a thermal component as diagnostics. Here we use similar diagnostics but extend the study to lower luminosities (2.3% and 0.8% L(sub Edd)) using Swift and RXTE observations of GX 339-4. We detect a thermal component with an inner disk temperature of approximately 0.2 keV at 2.3% L (sub Edd). At both luminosities, we detect broad features due to iron K-alpha that are likely related to reflection of hard X-rays off disk material. If these features are broadened by relativistic effects, they indicate that the material resides within 10 Rg, and the measurements are consistent with the disk's inner radius remaining at approximately 4 Rg down to 0.8% L(sub Edd). However, we also discuss an alternative model for the broadening, and we note that the evolution of the thermal component is not entirely consistent with the constant inner radius interpretation. Finally, we discuss the results in terms of recent theoretical work by Liu and co-workers on the possibility that material may condense out of an Advection-Dominated Accretion Flow to maintain an inner optically thick disk.

Tomsick, John A.↗

NASA NTRS2007

The Discovery Outburst of the X-Ray Transient IGR J17497-2821 Observed with RXTE and ATCA

We report the results of a series of RXTE and ATCA observations of the recently discovered X-ray transient IGR J17497-2821. Our 3-200 keV PCA+HEXTE spectral analysis shows very little variations over a period of approx.10 days around the maximum of the outburst. IGR J17497-2821 is found in a typical low-hard state (LHS) of X-ray binaries (XRBs), well represented by an absorbed Comptonized spectrum with an iron edge at about 7 keV. The high value of the absorption (approx.4 x 10(exp 22/sq cm suggests that the source is located at a large distance, either close to the Galactic center or beyond. The timing analysis shows no particular features, while the shape of the power density spectra is also typical of the LHS of XRBs, with apprrox.36% rms variability. No radio counterpart is found down to a limit of 0.21 mJy at 4.80 and 8.64 GHz. Although the position of IGR J17497-2821 in the radio to X-ray flux diagram is well below the correlation usually observed in the LHS of black holes, the comparison of its X-ray properties with those of other sources leads us to suggest that it is a black hole candidate.

Rodriquez, Jerome↗

NASA NTRS2006

Identifications of Four Integral Sources in the Galactic Plane via CHANDRA Localizations

Hard X-ray imaging of the Galactic plane by the INTEGRAL satellite is uncovering large numbers of 20-100 keV "IGR" sources. We present results from Chandra, INTEGRAL, optical, and IR observations of four IGR sources: three sources in the Norma region of the Galaxy(1GR J16195-4945,IGR J16207-5129, and IGR J16167-4957) and one that is closer to the Galactic center (IGR 5171 95-4100). In all four cases, one relatively bright Chandra source is seen in the INTEGRAL error circle, and these are likely to be the soft X-ray counterparts of the IGR sources. They have hard 0.3-10 keV spectra with power-law photon indices of Gamma = 0.5-1.1. While many previously studied IGR sources show high column densities (NH approx. 10(exp 23)-10(exp 24)/sq cm), only IGR J16195-4945 has a column density that could be as high as 10(exp 23)/sq cm. Using optical and IR sky survey catalogs and our own photometry, we have obtained identifications for all four sources. The J-band magnitudes are in the range 14.9-10.4, and we have used the optical/IR spectral energy distributions (SEDs) to constrain the nature of the sources. Blackbody components with temperature lower limits of >9400 K for IGR J16195-4945 and >18,000 K for IGR J16207-5129 indicate that these are very likely high-mass X-ray binaries (HMXBs). However, for IGR 516167-4957 and IGR J17195-4100, low extinction and the SEDs indicate later spectral types for the putative companions, suggesting that these are not HMXBs.

Tomsick, John A.↗

NASA NTRS2006

Black Hole Spectral States and Physical Connections

The dramatic changes seen in the X-ray spectral and timing properties of accreting black hole candidates (BHCs) provide important clues about the accretion and jet formation processes that occur in these systems. Dividing the different source behaviors into spectral states provides a framework for studying BHCs. To date, there have been three main classification schemes with Luminosity-based, Component-based, or Transition-based criteria. The canonical, Luminosity-based criteria and physical models that are based on this concept do not provide clear explanations for several phenomena, including hysteresis of spectral states and the presence of jets. I discuss the re-definitions of states, focusing on an application of the Component-based states to more than 400 RXTE observations of the recurrent BHC 4U 1630^17. We compare the X-ray properties for the recent 2002-2004 outburst to those of an earlier (1998) outburst, during which radio jets were observed. The results suggest a connection between hysteresis of states and major jet ejections, and it is possible that both of these are related to the evolution of the inner radius of the optically thick accretion disk.

Tomsick, John A.↗

NASA NTRS2005

Black Hole Spectral States and Physical Connections

The dramatic changes seen in the X-ray spectral and timing properties of accreting black hole candidates (BHCs) provide important clues about the accretion and jet formation processes that occur in these systems. Dividing the different source behaviors into spectral states provides a framework for studying BHCs. To date, there have been three main classification schemes with Luminosity-based, Component-based, or Transition-based criteria. The canonical, Luminosity-based criteria and physical models that are based on this concept do not provide clear explanations for several phenomena, including hysteresis of spectral states and the presence of jets. I discuss the re-definitions of states, focusing on an application of the Component-based states to more than 400 RXTE observations of the recurrent BHC 4U 1630-47. We compare the X-ray properties for the recent 2002-2004 outburst to those of an earlier (1998) outburst, during which radio jets were observed. The results suggest a connection between hysteresis of states and major jet ejections, and it is possible that both of these are related to the evolution of the inner radius of the optically thick accretion disk.

Tomsick, John A.↗

NASA NTRS2005

X-RAY OBSERVATIONS OF THE BLACK HOLE TRANSIENT 4U 1630-47 DURING 2 YEARS OF X-RAY ACTIVITY

The black hole candidate (BHC) X-ray transient 4U 1630-47 continuously produced strong X-ray emission for more than 2 years during its 2002-2004 outburst, which is one of the brightest and longest outbursts ever seen from this source. We use more than 300 observations made with the Rossi X-Ray Timing Explorer (RXTE) to study the source throughout the outburst, along with hard X-ray images from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), which are critical for interpreting the RXTE data in this crowded field. The source exhibits extreme behaviors, which can be interpreted as an indication that the system luminosity approaches the Eddington limit. For 15 observations, fitting the spectral continuum with a disk-blackbody plus power-law model results in measured inner disk temperatures between 2.7 and 3.8 keV, and such temperatures are only rivaled by the brightest BHC systems, such as GRS 1915+105 and XTE J1550-564. If the high temperatures are caused by the dominance of electron scattering opacity in the inner regions of the accretion disk, it is theoretically required that the source luminosity be considerably higher than 20% of the Eddington limit. We detect a variety of high-amplitude variability, including hard 10-100 s flares, which peak at levels as much as 2-3 times higher than nonflare levels. The X-ray properties in 2002-2004 are significantly different from those seen during the 1998 outburst, which is the only outburst with detected radio jet emission. Our results support the "jet line" concept recently advanced by Fender and coworkers. Our study allows for a test of the quantitative McClintock & Remillard spectral state definitions, and we find that these definitions alone do not provide a complete description of the outburst. Finally, for several of the observations, the high-energy emission is dominated by the nearby sources IGR J16320-4751 and IGR J16358-4726, and we provide information on when these sources were bright and on the nature of their energy spectra.

Tomsick, John A.↗

NASA NTRS2005

X-ray Observations of the Black Hole Transient 4U 1630-47 During 2 Years of X-ray Activity

The black hole candidate (BHC) X-ray transient 4U 1630-47 continuously produced strong X-ray emission for more than 2 years during its 2002-2004 outburst, which is one of the brightest and longest outbursts ever seen from this source. We use more than 300 observations made with the Rossi X-Ray Timing Explorer (RM E) to study the source throughout the outburst, along with hard X-ray images from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), which are critical for interpreting the RXTE data in this crowded field. The source exhibits extreme behaviors, which can be interpreted as an indication that the system luminosity approaches the Eddington limit. For 15 observations, fitting the spectral continuum with a disk-blackbody plus power-law model results in measured inner disk temperatures between 2.7 and 3.8 key and such temperatures are only rivaled by the brightest BHC systems, such as GRS 1915+105 and XTE 51550-564. If the high temperatures are caused by the dominance of electron scattering opacity in the inner regions of the accretion disk, it is theoretically required that the source luminosity be considerably higher than 20% of the Eddington limit. We detect a variety of high-amplitude variability, including hard 10-100 s flares, which peak at levels as much as 2-3 times higher than nonflare levels. This flaring occurs at the highest disk luminosities in a regime in which the source deviates from the L(sub disk) infinity T(sup 4)(sub in) relationship that is seen at lower luminosities, possibly suggesting that we are seeing transitions between a Shakura & Sunyaev disk and a "slim" disk, which is predicted to occur at very high mass accretion rates. The X-ray properties in 2002-2004 are significantly different from those seen during the 1998 outburst, which is the only outburst with detected radio jet emission. Our results support the "jet line" concept recently advanced by Fender and coworkers. Our study allows for a test of the quantitative McClintock & Remillard spectral state definitions, and we find that these definitions alone do not provide a complete description of the outburst. Finally, for several of the observations, the high-energy emission is dominated by the nearby sources IGR 516320-4751 and IGR 516358-4726, and we provide information on when these sources were bright and on the nature of their energy spectra

Tomsick, John A.↗

NASA NTRS2005

X-Ray and Radio Studies of Black Hole X-Ray Transients During Outburst Decay

Black hole (BH) and black hole candidate (BHC) transients are X-ray binary systems that typically undergo bright outbursts that last a couple months with recurrence times of years to decades. For this ADP project, we are studying BH/BHC systems during the decaying phases of their outbursts using the Rossi X-ray Taming Explorer (RXTE), the Chandra X-ray Observatory, and multi-wavelength facilities. These systems usually undergo state transitions as they decay, and our observations are designed to catch the state transitions. The specific goals of this proposal include: 1. To determine the evolution of the characteristic frequencies present in the power spectrum (such as quasi-periodic oscillations, QPOs) during state transitions in order to place constraints on the accretion geometry; 2. To contemporaneously measure X-ray spectral and timing properties along with flux measurements in the radio band to determine the relationship between the accretion disk and radio jets; 3. To extend our studies of X-ray properties of BHCs to very low accretion rates using RXTE and Chandra. The work performed under this proposal has been highly successful, allowing the PI to lead, direct, or assist in the preparation of 7 related publications in refereed journals and 6 other conference presentations or reports. These items are listed below, and the abstracts for the refereed publications have also been included. Especially notable results include our detailed measurements of the characteristic frequencies and spectral parameters of BH/BHCs after the transition to the hard state (see All A3, and A5) and at low flux levels (see A4). Our measurements provide one of the strongest lines of evidence to date that the inner edge of the optically thick accretion disk gradually recedes from the black hole at low flux levels. In addition, we have succeeded in obtaining excellent multi-wavelength coverage of a BH system as its compact jet turned on (see Al). Our results show, somewhat unexpectedly, that the radio jet does not turn on until the hard X-ray emission is well past its peak hard state level, strongly constraining theoretical models for hard X-ray production and the spectrum emitted by the jet. Finally, the X-ray/radio results in A2 led us to propose a general picture about the relationship between jet production and X-ray spectral states .

Tomsick, John A.↗