Three-band observations of the soft X-ray background and some implications of thermal emission models

The 1/4 keV diffuse X-ray background (SXRB) is discussed in relation to the local interstellar medium (LISM). The most likely source for these soft X-rays is thermal emission from a hot diffuse plasma. The existence of a non-zero flux from all directions and the short ISM mean free path of these X-rays (1020HI cm-2), coupled with ISM pressure constraints, imply that the plasma has a local component and that it must, at least locally (nearest hundred parsecs), have a large filling factor. Our understanding of the geometry and physical parameters of the LISM is therefore directly tied to our understanding of the SXRB.

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An unusual transient following the short GRB 071227

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2040 ◽

2019 ◽

Vol 489 (1) ◽

pp. 13-27

Author(s):

R A J Eyles ◽

P T O’Brien ◽

K Wiersema ◽

R L C Starling ◽

B P Gompertz ◽

...

Keyword(s):

Gamma Ray ◽

Thermal Emission ◽

Chemical Properties ◽

Major Axis ◽

Optical Observations ◽

X Ray ◽

Very Large Telescope ◽

The Galaxy ◽

Simple Extrapolation ◽

Emission Models

ABSTRACT We present X-ray and optical observations of the short duration gamma-ray burst GRB 071227 and its host at z = 0.381, obtained using Swift, Gemini South, and the Very Large Telescope. We identify a short-lived and moderately bright optical transient, with flux significantly in excess of that expected from a simple extrapolation of the X-ray spectrum at 0.2–0.3 d after burst. We fit the SED with afterglow models allowing for high extinction and thermal emission models that approximate a kilonova to assess the excess’ origins. While some kilonova contribution is plausible, it is not favoured due to the low temperature and high luminosity required, implying superluminal expansion and a large ejecta mass of ∼0.1 M$\odot$. We find, instead, that the transient is broadly consistent with power-law spectra with additional dust extinction of E(B − V) ∼ 0.4 mag, although a possibly thermal excess remains in the z band. We investigate the host, a spiral galaxy with an edge-on orientation, resolving its spectrum along its major axis to construct the galaxy rotation curve and analyse the star formation and chemical properties. The integrated host emission shows evidence for high extinction, consistent with the afterglow findings. The metallicity and extinction are consistent with previous studies of this host and indicate the galaxy is a typical, but dusty, late-type SGRB host.

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X-Ray Emission from Expanding Shells in NGC 3077

Symposium - International Astronomical Union ◽

10.1017/s0074180900197797 ◽

2004 ◽

Vol 217 ◽

pp. 310-311

Author(s):

Jürgen Ott ◽

Crystal L. Martin ◽

Fabian Walter

Keyword(s):

Thermal Emission ◽

Dwarf Galaxy ◽

Point Sources ◽

Starburst Galaxy ◽

Interstellar Gas ◽

X Ray ◽

Hot Gas ◽

Hα Emission ◽

Emission Models ◽

Expanding Shells

Deep Chandra observations of NGC 3077, a starburst dwarf galaxy in the M81 triplet, resolve the X-ray emission from several supershells. The emission is brightest in the cavities defined by expanding shells detected previously in Hα emission. Thermal emission models fitted to the data imply temperatures ranging from 1.3 to 4.9 × 106 K. The total 0.3–6.0 keV X-ray luminosity is 2 − 5 × 1039ergs−1 (depending on the selected thermal plasma model). Most (85%) of the X-ray luminosity in NGC 3077 comes from the hot interstellar gas; the remainder comes from six X-ray point sources. The radial density profile of the hot gas is not as steep as that expected in a freely expanding wind (e.g., as seen in the neighboring starburst galaxy M 82) implying that the hot gas is still confined by the Hα shells.

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Constraints on Thermal Emission Models of Anomalous X‐Ray Pulsars

The Astrophysical Journal ◽

10.1086/323777 ◽

2001 ◽

Vol 563 (1) ◽

pp. 255-266 ◽

Cited By ~ 40

Author(s):

Feryal Ozel ◽

Dimitrios Psaltis ◽

Victoria M. Kaspi

Keyword(s):

Thermal Emission ◽

X Ray ◽

Emission Models

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Chandra view on the active nucleus of CGCG 292–057: Jet-ISM interactions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318007445 ◽

2018 ◽

Vol 14 (S342) ◽

pp. 222-223

Author(s):

K. Balasubramaniam ◽

Ł. Stawarz ◽

V. Marchenko ◽

R. Thimmappa ◽

M. Sobolewska ◽

...

Keyword(s):

Power Law ◽

Thermal Emission ◽

Source Region ◽

Radial Profile ◽

Active Nucleus ◽

Iron Line ◽

X Ray ◽

The Galaxy ◽

Absorbed Power ◽

Emission Models

AbstractWe present the analysis of the 93 ksec Chandra ACIS–S data for the galaxy CGCG 292–057 (z = 0.054), with complex radio structure indicative of the intermittent jet activity. In order to characterize precisely the spectrum of the unresolved low-luminosity active nucleus in the source, we performed detailed MARX/PSF simulations and studied the radial profile of the source region surface brightness. In this way, we have detected an additional X-ray component extending from a few up to ∼10 kpc from the unresolved core, which could be associated with the hot gaseous medium compressed and heated (up to 0.9 keV) by the expanding inner lobes of the radio galaxy. We modeled the X-ray spectrum of the unresolved nucleus assuming various emission models, including an absorbed power-law, a power-law plus thermal emission component, and a two-temperature thermal plasma. The best fit was however obtained assuming a power-law emission scattered by a hot ionized gas, giving rise to the 6.7 keV iron line.

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Fe VIII, IX, and X Line Emission From the Soft X-ray Background: Previous Limits and a Future Measurement

International Astronomical Union Colloquium ◽

10.1017/s0252921100012276 ◽

1990 ◽

Vol 115 ◽

pp. 160-163

Author(s):

J. J. Bloch ◽

W. C. Priedhorsky ◽

Barham W. Smith

Keyword(s):

Broad Band ◽

Pulse Height ◽

Line Emission ◽

Elemental Abundance ◽

Cluster Emission ◽

X Ray ◽

Pulse Height Analysis ◽

Emission Models ◽

X Ray Background ◽

Imaging Sensors

AbstractWe discuss pulse height analysis of Be band data in relation to the important 72 eV Fe line cluster emission from the soft X-ray background (SXRB). Pulse height fits to the Be band data suggest that the Fe lines must be suppressed by a factor of ~10 with respect to the rest of the X-ray spectrum. The broad band rates and the mean energy of the pulse height data for the Be band can be brought into agreement by using depleted elemental abundance emission models. A planned measurement of the SXRB Fe lines using the Array of Low Energy X-ray Imaging Sensors (ALEXIS) experiment could resolve this issue.

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MAXI/SSC all-sky maps from 0.7 keV to 4 keV

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psz139 ◽

2020 ◽

Vol 72 (2) ◽

Cited By ~ 1

Author(s):

Satoshi Nakahira ◽

Hiroshi Tsunemi ◽

Hiroshi Tomida ◽

Shinya Nakashima ◽

Ryuho Kataoka ◽

...

Keyword(s):

Solid State ◽

Galactic Center ◽

Thermal Emission ◽

Brightness Distribution ◽

Point Sources ◽

X Ray ◽

The North ◽

Sky Survey ◽

Solar Wind Charge Exchange ◽

X Ray Background

Abstract By accumulating data from the Solid-state Slit Camera (SSC) on board the MAXI mission from 2009 to 2011, diffuse X-ray background maps were obtained in energies of 0.7–1.0, 1.0–2.0, and 2.0–4.0 keV. They are the first to be derived with a solid-state instrument, and to be compared with the previous ROSAT all-sky survey result. While the SSC map in the highest energy band is dominated by point sources and the Galactic diffuse X-ray emission, that in 0.7–1.0 keV reveals an extended X-ray structure, of which the brightness distribution is very similar to that observed with ROSAT about 20 years before. As in the ROSAT result, the emission is dominated by a bright arc-like structure, which appears to be part of a circle of ∼50° radius centered at about (l,b) ∼ (340°, 15°). In addition, the SSC map suggests a fainter and larger ellipse, which is elongated in the north–south direction and roughly centered at the Galactic center. The spectrum of these structures is explained as thin thermal emission from a plasma, with a temperature of ∼0.31 keV and an abundance of ∼0.3 solar. Based on SSC observation conditions including low solar activity, the solar wind charge exchange signals are estimated to be negligible in the present SSC maps, as well as in the >0.56 keV ROSAT map. A brief discussion is given on the results obtained.

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Eccentric tidal disruption event discs around supermassive black holes: dynamics and thermal emission

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3127 ◽

2020 ◽

Vol 499 (4) ◽

pp. 5562-5577

Author(s):

J J Zanazzi ◽

Gordon I Ogilvie

Keyword(s):

Thermal Emission ◽

Tidal Disruption ◽

X Ray ◽

General Relativistic ◽

Emission Models ◽

Heating Model ◽

Energy Dissipated ◽

Far Ultraviolet ◽

Nested Sequence ◽

Disruption Event

ABSTRACT After the tidal disruption event (TDE) of a star around a supermassive black hole (SMBH), if the stellar debris stream rapidly circularizes and forms a compact disc, the TDE emission is expected to peak in the soft X-ray or far ultraviolet (UV). The fact that many TDE candidates are observed to peak in the near UV and optical has challenged conventional TDE emission models. By idealizing a disc as a nested sequence of elliptical orbits that communicate adiabatically via pressure forces, and are heated by energy dissipated during the circularization of the nearly parabolic debris streams, we investigate the dynamics and thermal emission of highly eccentric TDE discs, including the effect of general-relativistic apsidal precession from the SMBH. We calculate the properties of uniformly precessing, apsidally aligned, and highly eccentric TDE discs, and find highly eccentric disc solutions exist for realistic TDE properties (SMBH and stellar mass, periapsis distance, etc.). Taking into account compressional heating (cooling) near periapsis (apoapsis), we find our idealized eccentric disc model can produce emission consistent with the X-ray and UV/optical luminosities of many optically bright TDE candidates. Our work attempts to quantify the thermal emission expected from the shock-heating model for TDE emission, and finds stream–stream collisions are a promising way to power optically bright TDEs.

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A new X-ray look into four old pulsars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732408 ◽

2018 ◽

Vol 615 ◽

pp. A73 ◽

Cited By ~ 9

Author(s):

Michela Rigoselli ◽

Sandro Mereghetti

Keyword(s):

Thermal Emission ◽

Power Laws ◽

High Energy ◽

Convincing Evidence ◽

X Ray ◽

Bolometric Luminosity ◽

Polar Caps ◽

Upper Limits ◽

Photon Index ◽

Emission Models

We report on the X-ray properties of four rotation-powered pulsars with characteristic ages in the range 0.3–5 Myr, derived from the analysis of XMM–Newton archival observations. We found convincing evidence of thermal emission only in the phase-averaged spectrum of PSR B0114+58, which is well fitted by a blackbody with temperature kT = 0.17 ± 0.02 keV and emitting radius R = 405+110−90 m, consistent with the size of its polar cap. The three other considered pulsars, PSR B0628−28, PSR B0919+06, and PSR B1133+16, have phase-averaged spectra that can be described well by single power laws with photon index Γ ~ 3. The 3σ upper limits on the bolometric luminosity of a possible thermal component with temperatures in the range ~0.05−2 keV are Lbol ≲ 3.2 × 1028 erg s−1 and Lbol ≲ 2.4 × 1029 erg s−1, for PSR B0628−28 and PSR B0919+06, respectively. On the other hand, we found possible evidence that the pulsed emission of PSR B0628−28 is thermal. Two absorption lines at ~0.22 keV and ~0.44 keV are detected in the spectrum of PSR B1133+16. They are best interpreted as proton cyclotron features, implying the presence of multipolar components with a field of a few 1013 G at the neutron star polar caps. We discuss our results in the context of high-energy emission models of old rotation-powered pulsars.

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Observations of Diffuse Emission from the Hot ISM

International Astronomical Union Colloquium ◽

10.1017/s0252921100036083 ◽

1996 ◽

Vol 152 ◽

pp. 269-275

Author(s):

W.T. Sanders ◽

R.J. Edgar

Keyword(s):

Galactic Plane ◽

Space Shuttle ◽

Data Sets ◽

Diffuse Emission ◽

X Ray ◽

Diffuse Background ◽

Thermal Origin ◽

Cosmic Abundance ◽

Emission Models ◽

X Ray Background

The Diffuse X-ray Spectrometer (DXS) is a Bragg-crystal spectrometer designed to obtain spectra of the diffuse x-ray background in the 83–44 Å (150–284 eV) range, with ~ 3 Å spectral resolution (10–25 eV), and ~ 15° angular resolution. It was flown successfully as an attached Shuttle payload on the STS 54 mission of NASA’s Space Shuttle Endeavour in January 1993, and spectra were obtained from the diffuse background along an arc extending roughly along the galactic plane from longitude 150° to longitude 300°. The primary conclusions so far from the analysis of the DXS data are: (1) The spectra of the diffuse background in the 83–44 Å range show emission lines or emission-line blends, indicating that the emission is thermal. Although most models of this emission have assumed that it is of thermal origin, this is the first detection of lines in the diffuse background in this wavelength range. (2) The detected spectra do not resemble the model spectra of cosmic abundance equilibrium plasmas at any temperature in the 105 – 107 K range. This is independent of the particular plasma model used, Raymond & Smith, Mewe & Kaastra, or Monsignori-Fossi & Landini. (3) The detected spectra do not resemble the model spectra of depleted abundance equilibrium plasmas at any temperature in the 105 – 107 K range, for a variety of assumed elemental depletions and the same emission models. This aspect of the analysis is not completed. (4) Tentative line identifications can be made, but other lines predicted to arise from the same ions must be of consistent strength in both the DXS and EUVE data sets.

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