Abstract Supernova remnants ($=$ SNR) are suggested to be sites of cosmic-ray acceleration. In particular, it has been an issue of keen interest whether cosmic ray protons are being accelerated in a SNR which emits TeV $\gamma$-rays. A crucial observational test for this is to find dense molecular gas towards the SNR, because such molecular gas can best verify the existence of cosmic-ray protons via pion decay to $\gamma$-rays. Here, we show that new high-resolution mm-wave observations of interstellar CO molecule have revealed molecular gas at 1 kpc distance interacting with the TeV $\gamma$-ray SNR G 347.3$-$0.5, and that a molecular cloud of $\sim 200$ solar masses is clearly associated with the TeV $\gamma$-ray peak, providing strong evidence for proton acceleration. We have estimated the total energy of accelerated protons to be $\sim 1048 \,\mathrm{erg}$, which corresponds to an acceleration efficiency of $\sim 0.001$, posing an observational constraint on the proton acceleration.

10.1093/pasj/55.5.l61

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Citations (135)

Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1

arXiv (Cornell University) (2023)

Fabio La Monaca Alessandro Di Marco Juri Poutanen Matteo Bachetti S. Motta

The Imaging X-ray Polarimetry Explorer (IXPE) measured with high significance the X-ray polarization of the brightest Z-source Scorpius X-1, resulting in the nominal 2-8 keV energy band in a polarization degree of 1.0(0.2)% and a polarization angle of 8(6){\deg} at 90% of confidence level. This observation was strictly simultaneous with observations performed by NICER, NuSTAR, and Insight-HXMT, which allowed for a precise characterization of its broad-band spectrum from soft to hard X-rays. The source has been observed mainly in its soft state, with short periods of flaring. We also observed low-frequency quasi-periodic oscillations. From a spectro-polarimetric analysis, we associate a polarization to the accretion disk at <3.2% at 90% of confidence level, compatible with expectations for an electron-scattering dominated optically thick atmosphere at the Sco X-1 inclination of 44{\deg}; for the higher-energy Comptonized component, we obtain a polarization of 1.3(0.4)%, in agreement with expectations for a slab of Thomson optical depth of ~7 and an electron temperature of ~3 keV. A polarization rotation with respect to previous observations by OSO-8 and PolarLight, and also with respect to the radio-jet position angle, is observed. This result may indicate a variation of the polarization with the source state that can be related to relativistic precession or to a change in the corona geometry with the accretion flow.

Position angle

Thomson scattering

10.48550/arxiv.2311.06359

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<title>New design concept of multilayer supermirrors for hard x-ray optics</title>

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1999)

Koujun Yamashita Hideyo Kunieda Yuzuru Tawara Keisuke Tamura Yasushi Ogasaka

It is important to enhance the reflectivity of multilayer supermirrors in 10-100 keV region used for hard x-ray optical systems. For this purpose design methods of multilayer supermirrors have been investigated at the grazing angle of 0.3 degrees by means of the x-ray etalon or phase matching configuration. It means that the 1st and higher order Bragg reflections emanated from different periodic lengths cooperatively enhance the reflectivity at energy bands concerned. The x-ray etalons method is useful for multi-band mirror with the band width of 5 keV or so, but becomes a bit difficult to make the energy band wider connecting gaps between isolated bands. Because heavy oscillation of reflectivity curve occurs due to adjacent destructive and constructive interference. The phase matching method is useful to get smooth reflectivity in the broad energy band and is possible to enhance the 2nd order Bragg reflection in higher energy region. We present the design of hard x-ray telescope sensitive in 25-40 keV region by means of multi-block supermirrors of Pt/C multilayers. The effective area was obtained to be more than 100 cm².

X-ray optics

Reflection

X-ray telescope

10.1117/12.363646

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Citations (16)

Magnetic Structures and Turbulence in SN 1006 Revealed with Imaging X-Ray Polarimetry

The Astrophysical Journal (2023)

Ping Zhou Dmitry Prokhorov Riccardo Ferrazzoli Yi-Jung Yang Patrick Slane

Abstract Young supernova remnants strongly modify the surrounding magnetic fields, which in turn play an essential role in accelerating cosmic rays (CRs). The X-ray polarization measurements probe magnetic field morphology and turbulence at the immediate acceleration site. We report the X-ray polarization distribution in the northeastern shell of SN 1006 from a 1 Ms observation with the Imaging X-ray Polarimetry Explorer. We found an average polarization degree of 22.4% ± 3.5% and an average polarization angle of −45.°4 ± 4.°5 (measured on the plane of the sky from north to east). The X-ray polarization angle distribution reveals that the magnetic fields immediately behind the shock in the northeastern shell of SN 1006 are nearly parallel to the shock normal or radially distributed, similar to that in the radio observations, and consistent with the quasi-parallel CR acceleration scenario. The X-ray emission is marginally more polarized than that in the radio band. The X-ray polarization degree of SN 1006 is much larger than that in Cas A and Tycho, together with the relatively tenuous and smooth ambient medium of the remnant, favoring that CR-induced instabilities set the magnetic turbulence in SN 1006, and CR acceleration is environment-dependent.

Degree of polarization

10.3847/1538-4357/acf3e6

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Citations (9)

Studying geometry of the ultraluminous X-ray pulsar Swift J0243.6+6124 using X-ray and optical polarimetry

Astronomy and Astrophysics (2024)

Juri Poutanen Sergey S. Tsygankov Victor Doroshenko Sofia V. Forsblom Peter Jenke

Discovery of pulsations from a number of ultra-luminous X-ray (ULX) sources proved that accretion onto neutron stars can produce luminosities exceeding the Eddington limit by several orders of magnitude. The conditions necessary to achieve such high luminosities as well as the exact geometry of the accretion flow in the neutron star vicinity are, however, a matter of debate. The pulse phase-resolved polarization measurements that became possible with the launch of the Imaging X-ray Polarimetry Explorer (IXPE) can be used to determine the pulsar geometry and its orientation relative to the orbital plane. They provide an avenue to test different theoretical models of ULX pulsars. In this paper we present the results of three IXPE observations of the first Galactic ULX pulsar Swift J0243.6+6124 during its 2023 outburst. We find strong variations in the polarization characteristics with the pulsar phase. The average polarization degree increases from about 5% to 15% as the flux dropped by a factor of three in the course of the outburst. The polarization angle (PA) as a function of the pulsar phase shows two peaks in the first two observations, but changes to a characteristic sawtooth pattern in the remaining data set. This is not consistent with a simple rotating vector model. Assuming the existence of an additional constant polarized component, we were able to fit the three observations with a common rotating vector model and obtain constraints on the pulsar geometry. In particular, we find the pulsar angular momentum inclination with respect to the line of sight of i p = 15°–40°, the magnetic obliquity of θ p = 60°–80°, and the pulsar spin position angle of χ p ≈ −50°, which significantly differs from the constant component PA of about 10°. Combining these X-ray measurements with the optical PA, we find evidence for at least a 30° misalignment between the pulsar angular momentum and the binary orbital axis.

Swift

10.1051/0004-6361/202450696

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ASCA and EUVE observations of II Pegasi: flaring and quiescent coronal emission

Astronomy and Astrophysics (1997)

R. Mewe J. S. Kaastra G. H. J. van den Oord J. S. Vink Yuzuru Tawara

We have analyzed X-ray and EUV spectra of both the quiescent and flaring state of II Peg, obtained from obser- vations with ASCA and EUVE. Coronal temperature structure and abundances have been derived from multi-temperature and differential emission measure (DEM) analyses of the spectra. The abundances are non-solar; in the case of ASCA for most el- ements(O,Ne,Mg,Si,S,Ar,Ca,Ni)weobtainabundancesthat areconsistentwithabout1/2-1/5ofthesolarphotosphericabun- dances of Anders and Grevesse (1989), but the Fe abundance is even lower, i.e. 0.1 solar. The multi-T and DEM tting analysis shows that the quiescent EUVE and ASCA spectra can be described by two temperature components: 4 and 10 MK (EUVE), 10 and 20 MK (ASCA). The two flares detected by EUVEandASCAshowpeaktemperaturesof20and > 35 MK, respectively. The latter flare has a total energy (0.1-10 keV) of 2.7 10 34 erg, a peak luminosity of 2.6 10 30 erg/s. There is evi- dence for an increase of a factor 4 of the iron abundance dur- ing the rise phase of the flare. Application of a cooling model yields a loop height of about 8 10 10 cm and a plasma density of 81 0 10 cm 3 .

Flare

Solar flare

Source

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Citations (9)

X-Ray Polarization of BL Lacertae in Outburst

The Astrophysical Journal Letters (2023)

Abel L. Peirson Michela Negro Ioannis Liodakis R. Middei Dawoon E. Kim

Abstract We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/ γ -ray outburst, a 287 ks observation (2022 November 27–30) was taken using the Imaging X-ray Polarimetry Explorer (IXPE), together with contemporaneous multiwavelength observations from the Neil Gehrels Swift observatory and XMM-Newton in soft X-rays (0.3–10 keV), NuSTAR in hard X-rays (3–70 keV), and optical polarization from the Calar Alto and Perkins Telescope observatories. Our contemporaneous X-ray data suggest that the IXPE energy band is at the crossover between the low- and high-frequency blazar emission humps. The source displays significant variability during the observation, and we measure polarization in three separate time bins. Contemporaneous X-ray spectra allow us to determine the relative contribution from each emission hump. We find >99% confidence X-ray polarization Π 2 – 4 keV = 21.7 − 7.9 + 5.6 % and electric vector polarization angle ψ 2–4keV = −28.°7 ± 8.°7 in the time bin with highest estimated synchrotron flux contribution. We discuss possible implications of our observations, including previous IXPE BL Lacertae pointings, tentatively concluding that synchrotron self-Compton emission dominates over hadronic emission processes during the observed epochs.

10.3847/2041-8213/acd242

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Citations (24)

X-ray Polarization Observations of BL Lacertae

arXiv (Cornell University) (2022)

R. Middei Ioannis Liodakis M. Perri Simonetta Puccetti E. Cavazzuti

Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus the Synchrotron emission to be responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae performed with the Imaging X-ray Polarimetry Explorer ({IXPE}), from which an upper limit to the polarization degree $Π_X<$12.6\% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac.

BL Lac object

Spectral energy distribution

Degree of polarization

10.48550/arxiv.2211.13764

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Discovery of a Hard X-Ray Flare from the Rho Ophiuchi Dark Cloud

Publications of the Astronomical Society of Japan (1992)

Katsuji Koyama Ikuko Asaoka T. Kuriyama Yuzuru Tawara

Flare

Source

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