scholarly journals ALMA observations of PSR B1259−63/LS 2883 in an inactive period: Variable circumstellar disk?

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Yutaka Fujita ◽  
Hiroshi Nagai ◽  
Takuya Akahori ◽  
Akiko Kawachi ◽  
Atsuo T Okazaki
Keyword(s):  
Binary System ◽  
Massive Star ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Circumstellar Disk ◽  
Inactive Period ◽  
Period Variable ◽  
Pulsar Winds

Abstract We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of the gamma-ray binary system containing the pulsar PSR B1259−63 orbiting around a massive star LS 2883 in an inactive period between the 2017 and 2021 periastron passages. We detected radio continuum emission from the binary system at 97 GHz (Band 3) and 343 GHz (Band 7). Compared with our previous ALMA observations performed soon after the 2017 periastron passage, the fluxes have decreased by a factor of six at 97 GHz and of two at 343 GHz. The flux at 343 GHz is large relative to that at 97 GHz and appears to be thermal emission from the circumstellar disk around LS 2883. The decrease of the 343 GHz flux may indicate that the disk has expanded and become partially optically thin since the disk is no longer affected by pulsar winds. The flux at 97 GHz is consistent with that expected from the pulsed emission from the pulsar, which indicates that the unpulsed emission that had been produced through pulsar-disk or pulsar-stellar wind interaction has disappeared. The image of the system is consistent with a point source and shows no sign of ejecta.

scholarly journals First detection of PSR B1259−63/LS 2883 in the millimeter and submillimeter wavelengths with ALMA

2019 ◽  
Vol 71 (5) ◽  
Author(s):  
Yutaka Fujita ◽  
Akiko Kawachi ◽  
Takuya Akahori ◽  
Hiroshi Nagai ◽  
Masaki Yamaguchi
Keyword(s):  
Binary System ◽  
Gamma Ray ◽  
High Energy ◽  
Radio Spectrum ◽  
Band 3 ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Submillimeter Wavelengths ◽  
Be Star ◽  
Lower Frequencies

Abstract We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of the binary system containing the pulsar PSR B1259−63 orbiting around a Be star LS 2883 after the 2017 periastron passage. We detected radio continuum emission from the binary system in the millimeter/submillimeter wavelengths for the first time. At Band 3 (97 GHz), the flux 84 days after the periastron is almost the same as that 71 days after the periastron. Although the binary system showed intense GeV gamma-ray flares during our observations, the Band 3 flux did not indicate any time correlation with them. The Band 3 fluxes are consistent with an extrapolation of the radio spectrum at lower frequencies. Assuming that it is synchrotron emission, we constrain magnetic fields (≲0.6 G) and the high-energy cutoff of the electrons (γ ≳ 360). The flux at Band 7 (343 GHz) 69 days after the periastron shows a significant excess from the extrapolation of the radio spectrum at lower frequencies. The flux may be associated with the circumstellar disk around the Be star. We also present the results of Australian Telescope Compact Array (ATCA) observations at 94 GHz for the 2014 periastron passage, which show that the radio spectrum was relatively soft when the pulsar passed the disk.

scholarly journals Discovery of recombining plasma inside the extended gamma-ray supernova remnant HB9

2019 ◽  
Vol 489 (3) ◽  
pp. 4300-4310 ◽  
Author(s):  
A Sezer ◽  
T Ergin ◽  
R Yamazaki ◽  
H Sano ◽  
Y Fukui
Keyword(s):  
Supernova Remnant ◽  
Gamma Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Area ◽  
Imaging Spectrometer ◽  
X Ray ◽  
East Region ◽  
X Ray Imaging ◽  
Collisional Ionization

ABSTRACT We present the results from the Suzaku X-ray Imaging Spectrometer observation of the mixed-morphology supernova remnant (SNR) HB9 (G160.9+2.6). We discovered recombining plasma (RP) in the western Suzaku observation region and the spectra here are well described by a model having collisional ionization equilibrium (CIE) and RP components. On the other hand, the X-ray spectra from the eastern Suzaku observation region are best reproduced by the CIE and non-equilibrium ionization model. We discuss possible scenarios to explain the origin of the RP emission based on the observational properties and concluded that the rarefaction scenario is a possible explanation for the existence of RP. In addition, the gamma-ray emission morphology and spectrum within the energy range of 0.2–300 GeV are investigated using 10 yr of data from the Fermi Large Area Telescope (LAT). The gamma-ray morphology of HB9 is best described by the spatial template of radio continuum emission. The spectrum is well fit to a log-parabola function and its detection significance was found to be 25σ. Moreover, a new gamma-ray point source located just outside the south-east region of the SNR’s shell was detected with a significance of 6σ. We also investigated the archival H i and CO data and detected an expanding shell structure in the velocity range of $-10.5$ and $+1.8$ km s−1 that is coinciding with a region of gamma-ray enhancement at the southern rim of the HB9 shell.

scholarly journals Radio observations of evaporating objects in the Cygnus OB2 region

2019 ◽  
Vol 627 ◽  
pp. A58 ◽  
Author(s):  
N. L. Isequilla ◽  
M. Fernández-López ◽  
P. Benaglia ◽  
C. H. Ishwara-Chandra ◽  
S. del Palacio
Keyword(s):  
Thermal Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Spectral Indices ◽  
Ionized Gas ◽  
Low Frequencies ◽  
Thermal Origin ◽  
Index Maps ◽  
Photoionization Rate ◽  
Gas Component

We present observations of the Cygnus OB2 region obtained with the Giant Metrewave Radio Telescope (GMRT) at frequencies of 325 and 610 MHz. In this contribution we focus on the study of proplyd-like objects (also known as free-floating evaporating gas globules or frEGGs) that typically show an extended cometary morphology. We identify eight objects previously studied at other wavelengths and derive their physical properties by obtaining their optical depth at radio-wavelengths. Using their geometry and the photoionization rate needed to produce their radio-continuum emission, we find that these sources are possibly ionized by a contribution of the stars Cyg OB2 #9 and Cyg OB2 #22. Spectral index maps of the eight frEGGs were constructed, showing a flat spectrum in radio frequencies in general. We interpret these as produced by optically thin ionized gas, although it is possible that a combination of thermal emission, not necessarily optically thin, produced by a diffuse gas component and the instrument response (which detects more diffuse emission at low frequencies) can artificially generate negative spectral indices. In particular, for the case of the Tadpole we suggest that the observed emission is not of non-thermal origin despite the presence of regions with negative spectral indices in our maps.

Metallicity Structure across the Galactic Disk: Radio Observations of H ii Regions

2017 ◽  
Vol 13 (S334) ◽  
pp. 275-276
Author(s):  
Dana S. Balser ◽  
Trey V. Wenger ◽  
T. M. Bania ◽  
L. D. Anderson
Keyword(s):  
Electron Temperature ◽  
Massive Star ◽  
Galactic Disk ◽  
Radio Continuum ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Thermal Electron ◽  
Radio Recombination Line ◽  
Nuclear Processing ◽  
Metallicity Distribution

AbstractHii regions are the sites of massive star formation and are the archetypal tracers of spiral arms. Because of their short lifetimes (<10 Myr) their abundances provide a measure of the nuclear processing of many stellar generations. Here we review our ongoing efforts to explore the metallicity structure of the Galactic disk by observing radio recombination line (RRL) and thermal radio continuum emission toward Hii regions. The RRL-to-continuum ratio provides an accurate measure of the electron temperature which is used as a proxy for metallicity. Since collisionally excited lines from metals (e.g., O, C) are the main coolant in Hii regions, the thermal electron temperature is well correlated with metallicity (e.g., [O/H]). We determine Hii region distances from maser parallax measurements when possible; otherwise we use kinematic distances. Such radio diagnostics of Hii regions yield an extinction free tracer to map the metallicity distribution across the entire Galactic disk.

scholarly journals Warped diffusive radio halo around the quiescent spiral edge-on galaxy NGC 4565

2019 ◽  
Vol 628 ◽  
pp. L3
Author(s):  
V. Heesen ◽  
L. Whitler ◽  
P. Schmidt ◽  
A. Miskolczi ◽  
S. S. Sridhar ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Thermal Emission ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Star Forming ◽  
Radio Halo ◽  
Gaussian Profile ◽  
Pure Diffusion

Context. Cosmic rays play a pivotal role in launching galactic winds, particularly in quiescently star-forming galaxies where the hot gas alone is not sufficient to drive a wind. Except for the Milky Way, not much is known about the transport of cosmic rays in galaxies. Aims. In this Letter, we present low-frequency observations of the nearby edge-on spiral galaxy NGC 4565 using the LOw-Frequency ARray (LOFAR). With our deep 144 MHz observations, we obtain a clean estimate of the emission originating from old cosmic-ray electrons (CRe), which is almost free from contamination by thermal emission. Methods. We measured vertical profiles of the non-thermal radio continuum emission that we fitted with Gaussian and exponential functions. The different profile shapes correspond to 1D cosmic-ray transport models of pure diffusion and advection, respectively. Results. We detect a warp in the radio continuum that is reminiscent of the previously known H I warp. Because the warp is not seen at GHz-frequencies in the radio continuum, its minimum age must be about 100 Myr. The warp also explains the slight flaring of the thick radio disc that can otherwise be well described by a Gaussian profile with an FWHM of 65 arcsec (3.7 kpc). Conclusions. The diffusive radio halo together with the extra-planar X-ray emission may be remnants of enhanced star-forming activity in the past where the galaxy had a galactic wind, as GHz-observations indicate only a weak outflow in the last 40 Myr. NGC 4565 could be in transition from an outflow- to an inflow-dominated phase.

scholarly journals CONSTRAINING THE PULSAR POWER IN GAMMA-RAY BINARIES THROUGH THERMAL X-RAY EMISSION

2012 ◽  
Vol 08 ◽  
pp. 132-137
Author(s):  
VÍCTOR ZABALZA ◽  
VALENTÍ BOSCH-RAMON ◽  
JOSEP MARIA PAREDES
Keyword(s):  
Stellar Wind ◽  
Binary Systems ◽  
Massive Star ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Mass Loss Rate ◽  
X Rays ◽  
Orbital Inclination ◽  
X Ray ◽  
Pulsar Wind

Gamma-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds collide producing non-thermal emission, most likely from the shocked pulsar wind. Thermal X-rays are expected from the shocked stellar wind, with a spectrum akin to the one observed in massive star binaries. The goal of this work is, through the study of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, constrain the pulsar spin-down luminosity and the stellar wind properties. A semi-analytic model is developed to compute the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries. The model results are compared with XMM-Newton observations of LS 5039, a candidate pulsar gamma-ray binary with a strong stellar wind. Exploring the range of possible values for the stellar mass-loss rate and orbital inclination, we obtain an upper limit on the pulsar spin-down luminosity of 6 × 1036 erg s-1. We conclude that, to explain the non-thermal luminosity of LS 5039 in the pulsar wind scenario, a non-thermal to spin-down luminosity ratio very close to unity may be required.

scholarly journals The soft X-ray landscape of gamma-ray bursts: thermal components

2011 ◽  
Vol 7 (S279) ◽  
pp. 175-182
Author(s):  
Rhaana Starling ◽  
Kim Page ◽  
Martin Sparre
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Gamma Ray Bursts ◽  
Continuum Emission ◽  
Line Of Sight ◽  
X Ray ◽  
Multiple Components ◽  
The Standard Model ◽  
New Discovery ◽  
The Continuum

AbstractThe repository of GRB (gamma-ray burst) observations made by the Swift X-ray Telescope, now consisting of over 650 bursts, is a valuable and unique resource for the study of GRB X-ray emission. The observed soft X-ray spectrum typically arises from an underlying power law continuum, absorbed by gas along the line-of-sight. However, particularly at early times in a burst's evolution the continuum emission is not always understood and may comprise multiple components including thermal emission unexpected in the standard model. A thermal X-ray component has been discovered in two very unusual GRBs, perhaps suggesting an association only with this subset of events. However, evidence exists for thermal emission from more typical examples and here we present a new discovery of one such case and describe a systematic search for thermal components among all early GRB X-ray spectra.

scholarly journals Distribution of Non-Thermal Emission in Galaxies

1981 ◽  
Vol 94 ◽  
pp. 209-214 ◽  
Author(s):  
R. Sancisi ◽  
P.C. van der Kruit
Keyword(s):  
Spiral Galaxies ◽  
Angular Resolution ◽  
Thermal Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Good Sensitivity ◽  
Physical Conditions ◽  
Large Samples ◽  
First Time

The properties of the radio continuum emission from spiral galaxies have been reviewed by Van der Kruit and Allen (1976) and by Van der Kruit (1978). In more recent years the major developments in the understanding of the radio continuum properties and the underlying physical conditions of galaxies have come from a number of surveys of large samples of objects. Some of these surveys (e.g. Hummel, 1980a) have good sensitivity and sufficiently high angular resolution to allow for the first time a clear separation of central sources and disk emission and a study of the properties of these components in a large number of galaxies. As a consequence some results already found, suggested or only suspected in previous detailed investigations of a limited number of objects are put on a firmer basis or entirely new aspects are revealed.

scholarly journals The link between broad emission line fluctuations and non-thermal emission from the inner AGN jet

2014 ◽  
Vol 10 (S313) ◽  
pp. 43-47 ◽  
Author(s):  
J. León Tavares ◽  
V. Chavushyan ◽  
A. Lobanov ◽  
E. Valtaoja ◽  
T. G. Arshakian
Keyword(s):  
Black Hole ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Line Emission ◽  
Emission Lines ◽  
Continuum Emission ◽  
Strong Impact ◽  
Broad Line ◽  
Reverberation Mapping ◽  
Broad Emission

AbstractAGN reverberate when the broad emission lines respond to changes of the ionizing thermal continuum emission. Reverberation measurements have been commonly used to estimate the size of the broad-line region (BLR) and the mass of the central black hole. However, reverberation mapping studies have been mostly performed on radio-quiet sources where the contribution of the jet can be neglected. In radio-loud AGN, jets and outflows may affect substantially the relation observed between the ionizing continuum and the line emission. To investigate this relation, we have conducted a series of multi-wavelength studies of radio-loud AGN, combining optical spectral line monitoring with regular VLBI observations. Our results suggest that at least a fraction of the broad-line emitting material can be located in a sub-relativistic outflow ionized by non-thermal continuum emission generated in the jet at large distances (> 1 pc) from the central engine of AGN. This finding may have a strong impact on black hole mass estimates based on measured widths of the broad emission lines and on the gamma-ray emission mechanisms.

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