scholarly journals A new transient ultraluminous X-ray source in NGC 7090

2020 ◽  
Vol 501 (1) ◽  
pp. 1002-1012
Author(s):  
D J Walton ◽  
M Heida ◽  
M Bachetti ◽  
F Fürst ◽  
M Brightman ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Broad Band ◽  
Small Population ◽  
Band Spectrum ◽  
X Ray ◽  
The Galaxy ◽  
Long Time ◽  
Complex Models ◽  
Peak Luminosity

ABSTRACT We report on the discovery of a new, transient ultraluminous X-ray source (ULX) in the galaxy NGC 7090. This new ULX, which we refer to as NGC 7090 ULX3, was discovered via monitoring with Swift during 2019–2020, and to date has exhibited a peak luminosity of LX ∼ 6 × 1039 erg s−1. Archival searches show that, prior to its recent transition into the ULX regime, ULX3 appeared to exhibit a fairly stable luminosity of LX ∼ 1038 erg s−1. Such strong long-time-scale variability may be reminiscent of the small population of known ULX pulsars, although deep follow-up observations with XMM–Newton and NuSTAR do not reveal any robust X-ray pulsation signals. Pulsations similar to those seen from known ULX pulsars cannot be completely excluded, however, as the limit on the pulsed fraction of any signal that remains undetected in these data is ≲20 per cent. The broad-band spectrum from these observations is well modelled with a simple thin disc model, consistent with sub-Eddington accretion, which may instead imply a moderately large black hole accretor (MBH ∼ 40 M⊙). Similarly, though, more complex models consistent with the super-Eddington spectra seen in other ULXs (and the known ULX pulsars) cannot be excluded given the limited signal-to-noise ratio of the available broad-band data. The nature of the accretor powering this new ULX therefore remains uncertain.

GW170817: Swift UV detection of a blue kilonova, and improving the search in O3

2017 ◽  
Vol 13 (S338) ◽  
pp. 53-60
Author(s):  
Aaron Tohuvavohu ◽  
Jamie A. Kennea ◽  
Keyword(s):  
Health And Safety ◽  
X Ray ◽  
Operational Capabilities ◽  
Observation Strategy ◽  
Ongoing Work ◽  
The Galaxy ◽  
Multi Wavelength ◽  
Flexible Planning ◽  
The Impact

AbstractSwift’s rapid slewing, flexible planning, and multi-wavelength instruments make it the most capable space-based follow-up engine for finding poorly localized sources. During O1 and O2 Swift successfully tiled hundreds of square-degrees of sky in the LVC localization regions, searching for, and identifying, possible X-ray and UV/O transients in the field. Swift made important contributions to the discovery and characterization of the kilonova AT 2017gfo, discovering the UV emission and providing the deepest X-ray upper limits in the first 24 hours after the trigger, strongly constraining the dynamics and geometry of the counterpart. Swift tiled 92% of the galaxy convolved error region down to average X-ray flux sensitivities of 10−12 erg cm−2 s−1, significantly increasing our confidence that AT 2017gfo is indeed the counterpart to GW 170817 and sGRB 170817. However, there remains significant room for improvement of Swift’s follow-up in preparation for O3. This will take the form of both revised observation strategy based on detailed analysis of the results from O2, and significant changes to Swift’s operational capabilities. These improvements are necessary both for maximizing the likelihood that Swift finds a counterpart, and minimizing the impact that follow-up activities have on other Swift science priorities. We outline areas of improvement to the observing strategy itself for optimal tiling of the LVC localization regions. We also discuss ongoing work on operational upgrades that will decrease latency in our response time, and minimize impact on pre-planned observations, while maintaining spacecraft health and safety.

scholarly journals NuSTAR view of Be/X-ray binary pulsar 2S 1417−624 during 2018 giant outburst

2019 ◽  
Vol 490 (2) ◽  
pp. 2458-2466 ◽  
Author(s):  
Shivangi Gupta ◽  
Sachindra Naik ◽  
Gaurava K Jaisawal
Keyword(s):  
Broad Band ◽  
Gaussian Function ◽  
Physical Models ◽  
Spectral Studies ◽  
Band Spectrum ◽  
X Ray ◽  
Binary Pulsar ◽  
Double Peak Structure ◽  
Peak Structure ◽  
Cyclotron Line

ABSTRACT We report the results obtained from a detailed timing and spectral studies of Be/X-ray binary pulsar 2S 1417−624 using data from Swift and NuSTAR observatories. The observations were carried out at the peak of a giant outburst of the pulsar in 2018. X-ray pulsations at ∼17.475 s were detected in the source light curves up to 79 keV. The evolution of the pulse profiles with energy was found to be complex. A four-peaked profile at lower energies gradually evolved into a double-peak structure at higher energies. The pulsed fraction of the pulsar, calculated from the NuSTAR observation was found to follow an anticorrelation trend with luminosity as observed during previous giant X-ray outburst studies in 2009. The broad-band spectrum of the pulsar is well described by a composite model consisting of a cut-off power-law model modified with the interstellar absorption, a thermal blackbody component with a temperature of ≈1 keV, and a Gaussian function for the 6.4 keV iron emission line. Though the pulsar was observed at the peak of the giant outburst, there was no signature of presence of any cyclotron line feature in the spectrum. The radius of the blackbody emitting region was estimated to be ≈2 km, suggesting that the most probable site of its origin is the stellar surface of the neutron star. Physical models were also explored to understand the emission geometry of the pulsar and are discussed in the paper.

scholarly journals The December 2015 re-brightening of V404 Cygni

2018 ◽  
Vol 616 ◽  
pp. A129 ◽  
Author(s):  
J. J. E. Kajava ◽  
S. E. Motta ◽  
C. Sánchez-Fernández ◽  
E. Kuulkers
Keyword(s):  
Broad Band ◽  
High Energy ◽  
Accretion Disc ◽  
Band Spectrum ◽  
Hard Photon ◽  
Time Resolved ◽  
X Ray ◽  
Spectral Behaviour ◽  
Black Hole Binary ◽  
Spectral Cut

In December 2015 the black hole binary V404 Cyg underwent a secondary outburst after the main June 2015 event. We monitored this re-brightening with the INTEGRAL and Swift satellites, and in this paper we report the results of the time-resolved spectral analysis of these data. The December outburst shared several characteristics with the June event. The well-sampled INTEGRAL light curve shows up to ten Crab flares, which are separated by relatively weak non-flaring emission phases when compared to the June outburst. The spectra are nicely described by absorbed Comptonization models, with hard photon indices, Γ ≲ 2, and significant detections of a high-energy cut-off only during the bright flares. This is in contrast to the June outburst, where the Comptonization models gave electron temperatures mostly in the 30–50 keV range, while some spectra were soft (Γ ~ 2.5) without signs of any spectral cut-off. Similarly to the June outburst, we see clear signs of a variable local absorber in the soft energy band covered by Swift/XRT and INTEGRAL/JEM-X, which causes rapid spectral variations observed during the flares. During one flare, both Swift and INTEGRAL captured V404 Cyg in a state where the absorber was nearly Compton thick, N H ≈ 1024 cm−2, and the broad-band spectrum was similar to obscured AGN spectra, as seen during the X-ray plateaus in the June outburst. We conclude that the spectral behaviour of V404 Cyg during the December outburst was analogous with the first few days of the June outburst, both having hard X-ray flares that were intermittently influenced by obscuration due to nearly Compton-thick outflows launched from the accretion disc.

scholarly journals Broad-band spectral analysis of LMXB XTE J1710−281 with Suzaku

2020 ◽  
Vol 496 (1) ◽  
pp. 197-205
Author(s):  
Prince Sharma ◽  
Rahul Sharma ◽  
Chetana Jain ◽  
Anjan Dutta
Keyword(s):  
Spectral Analysis ◽  
Broad Band ◽  
Emission Spectra ◽  
Band Spectrum ◽  
Surface Boundary ◽  
Hot Electron ◽  
Spectral Parameters ◽  
Surface Boundary Layer ◽  
X Ray ◽  
Single Temperature

ABSTRACT This work presents the broad-band time-averaged spectral analysis of neutron star (NS) low-mass X-ray binary, XTE J1710−281 by using the Suzaku archival data. The source was in a hard or an intermediate spectral state during this observation. This is the first time that a detailed spectral analysis of the persistent emission spectra of XTE J1710−281 has been done up to 30 keV with improved constraints on its spectral parameters. By simultaneously fitting the X-ray Imaging Spectrometer (0.6–9.0 keV) and the HXD-PIN (15.0–30.0 keV) data, we have modelled the persistent spectrum of the source with models comprising a soft component from accretion disc and/or NS surface/boundary layer and a hard Comptonizing component. The 0.6–30 keV continuum with neutral absorber can be described by a multicolour disc blackbody with an inner disc temperature of kTdisc = 0.28 keV, which is significantly Comptonized by the hot electron cloud with electron temperature of kTe ≈ 5 keV and described by photon index Γ = 1.86. A more complex three-component model comprising a multicolour disc blackbody ≈0.30 keV, single-temperature blackbody ≈0.65 keV, and Comptonization from the disc, partially absorbed (about 38 per cent) by an ionized absorber (log(ξ) ≈ 4) describes the broad-band spectrum equally well.

scholarly journals Broad view on hard X-ray background emission of the Galaxy

2009 ◽  
Vol 5 (H15) ◽  
pp. 810-810
Author(s):  
Roman Krivonos ◽  
Mikhail Revnivtsev ◽  
Sergey Tsygankov ◽  
Eugene Churazov ◽  
Rashid Sunyaev
Keyword(s):  
Near Infrared ◽  
Galactic Disk ◽  
Broad Band ◽  
Point Sources ◽  
X Rays ◽  
X Ray ◽  
Scientific Debate ◽  
The Galaxy ◽  
Background Emission ◽  
Galactic Background

AbstractThe nature of the Galactic Ridge X-Ray Emission (GRXE) has been under scientific debate since its discovery more than 30 years ago. It is observed as extended emission along the Galactic disk. The question was: is GRXE truly diffuse or is it composed from a large number of unresolved point sources? Using near-infrared Galaxy maps measured with the DIRBE experiment and data from the INTEGRAL observatory, we show that the galactic background in the energy range 20-60 keV originates from the stellar population of the Galaxy, which is in contrast to the diffuse nature believed before (Krivonos et al., 2007). Here we show preliminary results of studying the transition region from hard X-rays to gamma diffuse background of the Galaxy, revealing the broad band picture of Galactic Background emission.

scholarly journals The long-term enhanced brightness of the magnetar 1E 1547.0–5408

2020 ◽  
Vol 633 ◽  
pp. A31 ◽  
Author(s):  
Francesco Coti Zelati ◽  
Alice Borghese ◽  
Nanda Rea ◽  
Daniele Viganò ◽  
Teruaki Enoto ◽  
...  
Keyword(s):  
Thermal Emission ◽  
Broad Band ◽  
Spectral Shape ◽  
Band Spectrum ◽  
Pulse Profile ◽  
X Ray ◽  
Time Period ◽  
Order Of Magnitude ◽  
Cooling Trend

We present the evolution of the X-ray emission properties of the magnetar 1E 1547.0–5408 since February 2004 over a time period covering three outbursts. We analyzed new and archival observations taken with the Swift, NuSTAR, Chandra, and XMM–Newton X-ray satellites. The source has been observed at a relatively steady soft X-ray flux of ≈10−11 erg cm−2 s−1 (0.3–10 keV) over the last 9 years, which is about an order of magnitude fainter than the flux at the peak of the last outburst in 2009, but a factor of ∼30 larger than the level in 2006. The broad-band spectrum extracted from two recent NuSTAR observations in April 2016 and February 2019 showed a faint hard X-ray emission up to ∼70 keV. Its spectrum is adequately described by a flat power law component, and its flux is ∼7 × 10−12 erg cm−2 s−1 (10–70 keV), that is a factor of ∼20 smaller than at the peak of the 2009 outburst. The hard X-ray spectral shape has flattened significantly in time, which is at variance with the overall cooling trend of the soft X-ray component. The pulse profile extracted from these NuSTAR pointings displays variability in shape and amplitude with energy (up to ≈25 keV). Our analysis shows that the flux of 1E 1547.0–5408 is not yet decaying to the 2006 level and that the source has been lingering in a stable, high-intensity state for several years. This might suggest that magnetars can hop among distinct persistent states that are probably connected to outburst episodes and that their persistent thermal emission can be almost entirely powered by the dissipation of currents in the corona.

scholarly journals The origin of X-ray emission in the gamma-ray emitting narrow-line Seyfert 1 1H 0323+342

2020 ◽  
Vol 496 (3) ◽  
pp. 2922-2931 ◽  
Author(s):  
Sergio A Mundo ◽  
Erin Kara ◽  
Edward M Cackett ◽  
A C Fabian ◽  
J Jiang ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Broad Band ◽  
Band Spectrum ◽  
Narrow Line ◽  
Model Assumption ◽  
X Ray ◽  
Disc Model ◽  
Reflection Model ◽  
Superluminal Motion ◽  
Low Energies

ABSTRACT We present the results of X-ray spectral and timing analyses of the closest gamma-ray emitting narrow-line Seyfert 1 (γ-NLS1) galaxy, 1H 0323+342. We use observations from a recent, simultaneous XMM–Newton/NuSTAR campaign. As in radio-quiet NLS1s, the spectrum reveals a soft excess at low energies (≲2 keV) and reflection features such as a broad iron K emission line. We also find evidence of a hard excess at energies above ∼35 keV that is likely a consequence of jet emission. Our analysis shows that relativistic reflection is statistically required, and using a combination of models that includes the reflection model relxill for the broad-band spectrum, we find an inclination of $i=63^{+7}_{-5}$ degrees, which is in tension with much lower values inferred by superluminal motion in radio observations. We also find a flat (q = 2.2 ± 0.3) emissivity profile, implying that there is more reflected flux than usual being emitted from the outer regions of the disc, which in turn suggests a deviation from the thin disc model assumption. We discuss possible reasons for this, such as reflection off of a thick accretion disc geometry.

scholarly journals A Survey of the Interstellar Medium in Elliptical Galaxies: the Ionized Gas

1996 ◽  
Vol 171 ◽  
pp. 348-348
Author(s):  
N. Caon ◽  
F. Macchetto ◽  
M. Pastoriza
Keyword(s):  
Large Fraction ◽  
Broad Band ◽  
Elliptical Galaxies ◽  
Ionized Gas ◽  
X Ray ◽  
Lenticular Galaxies ◽  
The Galaxy ◽  
Extensive Program ◽  
Galaxy Center ◽  
S0 Galaxies

We have carried out an extensive program of observations of the ionized gas in 74 luminous elliptical and lenticular galaxies, selected to include a variety of properties in radio and X-ray emission, and in kinematical behavior. For each galaxy we have obtained broad-band R and V images and narrow-band images, centered at the Hα and [NII] emission lines, to derive the luminosity and distribution of the ionized gas. We found that a large fraction (≃ 70%) of E and S0 galaxies in our sample contain ionized gas. The gas morphology and size varies from small disks (mean diameter 1 – 4 kpc) to large filamentary structures (extending up to 10 kpc from the galaxy center). Comparison with previous measurements shows reasonable agreement for a few galaxies, but considerable scatter for a large fraction, possibly due to differences in the limiting flux thresholds.

scholarly journals First Results of Optical Monitoring of 3C 390.3

1997 ◽  
Vol 159 ◽  
pp. 163-164
Author(s):  
M. Dietrich ◽  
P.T. O’Brien ◽  
K. M. Leighly
Keyword(s):  
Time Scales ◽  
Broad Band ◽  
Emission Lines ◽  
High Temporal Resolution ◽  
Line Profiles ◽  
X Ray ◽  
First Results ◽  
Long Time ◽  
Flux Measurements ◽  
Calar Alto

In late autumn 1994, the International AGN Watch started a multiwavelength monitoring campaign on 3C 390.3, the first radio-loud AGN to be selected for high temporal-resolution monitoring from the radio domain to X-ray energies. This AGN is is of particular interest since significant variations have been observed on both short and long time scales in both the line fluxes and line profiles (Barr et al. 1980, Veilleux & Zheng 1991).In the optical, spectroscopic data and broad-band flux measurements in B, V, R, and I were obtained. The brightness of 3C 390.3 was calculated relative to the stars in the field. The R magnitudes are based on observations recorded at Calar Alto, Spain, in 1994 December. Generally, AGN spectra are intercalibrated using narrow forbidden emission lines since these lines can be taken as constant on time scales of decades (Peterson 1993). Since the [O III] λλ4959, 5007 flux is variable on time scales of several months (Zheng et al. 1995), these lines were studied in detail. We found that they were constant within ~2% during 1995 (Dietrich et al. 1996). The spectra were therefore intercalibrated by using the narrow forbidden emission lines. 3C 390.3 was also observed with IUE for 14 months (O’Brien et al. 1996) and with ROSAT for nine months in 1995 (Leighly et al. 1996). Radio data were also obtained during a 3-month MERLIN campaign.

Sign in / Sign up

Export Citation Format

Share Document