86 research outputs found
Testing High-energy Emission Models for Blazars with X-Ray Polarimetry
Both leptonic and hadronic emission processes may contribute to blazar jet emission; which dominates in blazars' high-energy emission component remains an open question. Some intermediate synchrotron peaked blazars transition from their low- to high-energy emission components in the X-ray band making them excellent laboratories to probe both components simultaneously, and good targets for the newly launched Imaging X-ray Polarimetry Explorer (IXPE). We characterize the spectral energy distributions for three such blazars, CGRaBS J0211+1051, TXS 0506+056, and S5 0716+714, predicting their X-ray polarization behavior by fitting a multizone polarized leptonic jet model. We find that a significant detection of electron synchrotron dominated polarization is possible with a 300 ks observation for S5 0716+714 and CGRaBS J0211+1051 in their flaring states, while even 500 ks observations are unlikely to measure synchrotron self-Compton (SSC) polarization. Importantly, nonleptonic emission processes like proton synchrotron are marginally detectable for our brightest intermediate synchrotron peaked blazar (ISP), S5 0716+714, during a flaring state. Improved IXPE data reduction methods or next-generation telescopes like eXTP are needed to confidently measure SSC polarization.</p
An X-rays-to-radio investigation of the nuclear polarization from the radio-galaxy Centaurus A
Centaurus A is one of the closest radio galaxies to Earth. Its proximity allowed us to extensively study its active galactic nucleus but the core emission mechanism remains elusive because of local strong dust and gas obscuration. The capability of polarimetry to shave-off contaminating emission has been exploited without success in the near-infrared by previous studies but the very recent measurement of the 2â8 keV polarization by the Imaging X-ray Polarimetry Explorer (IXPE) brought the question back to the fore. To determine what is the prevalent photon generation mechanism to the multiwavelength emission from the core of Centaurus A, we retrieved from the archives the panchromatic polarization measurements of the central compact component. We built the total and polarized flux spectral energy distributions of the core and demonstrated that synchrotron self-Compton models nicely fit the polarized flux from the radio to the X-ray band. The linear polarization of the synchrotron continuum is perpendicular to the jet radio axis from the optical to the radio band, and parallel to it at higher energies. The observed smooth rotation of the polarization angle in the ultraviolet band is attributed to synchrotron emission from regions that are getting closer to the particle acceleration site, where the orientation of the jetâs magnetic fields become perpendicular to the jet axis. This phenomenon support the shock acceleration mechanism for particle acceleration in Centaurus A, in line with IXPE observations of several high-synchrotron peak blazars
An X-rays-to-radio investigation of the nuclear polarization from the radio-galaxy Centaurus A
Centaurus A is one of the closest radio-galaxies to Earth. Its proximity
allowed us to extensively study its active galactic nucleus but the core
emission mechanism remains elusive because of local strong dust and gas
obscuration. The capability of polarimetry to shave-off contaminating emission
has been exploited without success in the near-infrared by previous studies but
the very recent measurement of the 2 - 8 keV polarization by the Imaging X-ray
Polarimetry Explorer (IXPE) brought the question back to the fore. To determine
what is the prevalent photon generation mechanism to the multi-wavelength
emission from the core of Centaurus A, we retrieved from the archives the
panchromatic polarization measurements of the central compact component. We
built the total and polarized flux spectral energy distributions of the core
and demonstrated that synchrotron self-Compton models nicely fit the polarized
flux from the radio to the X-ray band. The linear polarization of the
synchrotron continuum is perpendicular to the jet radio axis from the optical
to the radio band, and parallel to it at higher energies. The observed smooth
rotation of the polarization angle in the ultraviolet band is attributed to
synchrotron emission from regions that are getting closer to the particle
acceleration site, where the orientation of the jet's magnetic fields become
perpendicular to the jet axis. This phenomenon support the shock acceleration
mechanism for particle acceleration in Centaurus A, in line with IXPE
observations of several high-synchrotron peak blazars.Comment: 10 pages, 6 figures, accepted for publication in MNRA
X-Ray Polarization of BL Lacertae in Outburst
Full list of authors: Peirson, Abel L.; Negro, Michela; Liodakis, Ioannis; Middei, Riccardo; Kim, Dawoon E.; Marscher, Alan P.; Marshall, Herman L.; Pacciani, Luigi; Romani, Roger W.; Wu, Kinwah; Di Marco, Alessandro; Di Lalla, Niccolo; Omodei, Nicola; Jorstad, Svetlana G.; Agudo, Ivan; Kouch, Pouya M.; Lindfors, Elina; Aceituno, Francisco Jose; Bernardos, Maria I.; Bonnoli, Giacomo; Casanova, Victor; Garcia-Comas, Maya; Agis-Gonzalez, Beatriz; Husillos, Cesar; Marchini, Alessandro; Sota, Alfredo; Casadio, Carolina; Escudero, Juan; Myserlis, Ioannis; Sievers, Albrecht; Gurwell, Mark; Rao, Ramprasad; Imazawa, Ryo; Sasada, Mahito; Fukazawa, Yasushi; Kawabata, Koji S.; Uemura, Makoto; Mizuno, Tsunefumi; Nakaoka, Tatsuya; Akitaya, Hiroshi; Cheong, Yeon; Jeong, Hyeon-Woo; Kang, Sincheol; Kim, Sang-Hyun; Lee, Sang-Sung; Angelakis, Emmanouil; Kraus, Alexander; Cibrario, Nicolo; Donnarumma, Immacolata; Poutanen, Juri; Tavecchio, Fabrizio; Antonelli, Lucio A.; Bachetti, Matteo; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolo; Capitanio, Fiamma; Castellano, Simone; Cavazzuti, Elisabetta; Chen, Chien-Ting; Ciprini, Stefano; Costa, Enrico; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Doroshenko, Victor; Dovciak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Heyl, Jeremy; Iwakiri, Wataru; Kaaret, Philip; Karas, Vladimir; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, Henric; La Monaca, Fabio; Latronico, Luca; Madejski, Grzegorz; Maldera, Simone; Manfreda, Alberto; Marin, Frederic; Marinucci, Andrea; Massaro, Francesco; Matt, Giorgio; Mitsuishi, Ikuyuki; Muleri, Fabio; Ng, C. -Y.; O'Dell, Stephen L.; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Perri, Matteo; Pesce-Rollins, Melissa; Petrucci, Pierre-Olivier; Pilia, Maura; Possenti, Andrea; Puccetti, Simonetta; Ramsey, Brian D.; Rankin, John; Ratheesh, Ajay; Roberts, Oliver J.; Sgro, Carmelo; Slane, Patrick; Soffitta, Paolo; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey; Turolla, Roberto; Vink, Jacco; Weisskopf, Martin C.; Xie, Fei; Zane, Silvia.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/Îł-ray outburst, a 287 ks observation (2022 November 27â30) 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 (0.3â10 keV), NuSTAR in hard X-rays (3â70 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 {{\rm{\Pi }}}_{2\mbox{--}4\mathrm{keV}}={21.7}_{-7.9}^{+5.6} \% and electric vector polarization angle Ï2â4keV = â28fdg7 ± 8fdg7 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. © 2023. The Author(s). Published by the American Astronomical Society.The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). Funding for this work was provided in part by contract 80MSFC17C0012 from the MSFC to MIT in support of the IXPE project. Support for this work was provided in part by the NASA through the Smithsonian Astrophysical Observatory (SAO) contract SV3-73016 to MIT for support of the Chandra X-Ray Center (CXC), which is operated by SAO for and on behalf of NASA under contract NAS8-03060. The IAA-CSIC coauthors acknowledge financial support from the Spanish "Ministerio de Ciencia e InnovaciĂłn" (MCIN/AEI/10.13039/501100011033) through the Center of Excellence Severo Ochoa award for the Instituto de AstrofĂisica de AndalucĂa-CSIC (CEX2021-001131-S), and through grants PID2019-107847RB-C44 and PID2022-139117NB-C44. Some of the data are based on observations collected at the Observatorio de Sierra Nevada, owned and operated by the Instituto de AstrofĂsica de AndalucĂa (IAA-CSIC). Further data are based on observations collected at the Centro AstronĂłmico Hispano-AlemĂĄn (CAHA), operated jointly by Junta de AndalucĂa and Consejo Superior de Investigaciones CientĂficas (IAA-CSIC). The POLAMI observations were carried out at the IRAM 30 m Telescope. I.R.A.M. is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). The Submillimetre Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Maunakea, the location of the SMA, is a culturally important site for the indigenous Hawaiian people; we are privileged to study the cosmos from its summit. The data in this study include observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku, and the University of Oslo, representing Denmark, Finland, and Norway, the University of Iceland, and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de AstrofĂsica de AndalucĂa (IAA) under a joint agreement with the University of Copenhagen and NOT. E.L. was supported by Academy of Finland projects 317636 and 320045. We acknowledge funding to support our NOT observations from the Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Finland (Academy of Finland grant nr 306531). The research at Boston University was supported in part by National Science Foundation grant AST-2108622, NASA Fermi Guest Investigator grants 80NSSC21K1917 and 80NSSC22K1571, and NASA Swift Guest Investigator grant 80NSSC22K0537. This study used observations conducted with the 1.8 m Perkins Telescope Observatory (PTO) in Arizona (USA), which is owned and operated by Boston University. The above study is based in part on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. We are grateful to the NuSTAR team for approving our DDT request. This work was supported under NASA contract No. NNG08FD60C, and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the NASA. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). This work was supported by JST, the establishment of university fellowships toward the creation of science technology innovation, grant No. JPMJFS2129. This work was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI grant No. JP21H01137. This work was also partially supported by Optical and Near-Infrared Astronomy Inter-University Cooperation Program from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan. We are grateful to the observation and operating members of Kanata Telescope. M.N. acknowledges the support by NASA under award number 80GSFC21M0002. C.C. acknowledges support by the ERC under the Horizon ERC Grants 2021 program under grant agreement no. 101040021. S.K., S.-S.L., W.Y.C., S.-H.K., and H.-W.J. were supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MIST; 2020R1A2C2009003). The KVN is a facility operated by the Korea Astronomy and Space Science Institute. The KVN operations are supported by KREONET (Korea Research Environment Open NETwork), which is managed and operated by KISTI (Korea Institute of Science and Technology Information). Partly based on observations with the 100 m telescope of the MPIfR (Max-Planck-Institut fĂŒr Radioastronomie) at Effelsberg. Observations with the 100 m radio telescope at Effelsberg have received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 101004719 (ORP). A.L.P. acknowledges support from NASA FINESST grant 80NSSC19K1407 and the Stanford Data Science Scholars program.Peer reviewe
Observations of 4U 1626-67 with the Imaging X-ray Polarimetry Explorer
We present measurements of the polarization of X-rays in the 2-8 keV band
from the pulsar in the ultracompact low mass X-ray binary 4U1626-67 using data
from the Imaging X-ray Polarimetry Explorer (IXPE). The 7.66 s pulsations were
clearly detected throughout the IXPE observations as well as in the NICER soft
X-ray observations, which we use as the basis for our timing analysis and to
constrain the spectral shape over 0.4-10 keV energy band. Chandra HETGS
high-resolution X-ray spectra were also obtained near the times of the IXPE
observations for firm spectral modeling. We find an upper limit on the
pulse-averaged linear polarization of <4% (at 95% confidence). Similarly, there
was no significant detection of polarized flux in pulse phase intervals when
subdividing the bandpass by energy. However, spectropolarimetric modeling over
the full bandpass in pulse phase intervals provide a marginal detection of
polarization of the power-law spectral component at the 4.8 +/- 2.3% level (90%
confidence). We discuss the implications concerning the accretion geometry onto
the pulsar, favoring two-component models of the pulsed emission.Comment: 19 pages, 7 figures, 7 tables; accepted for publication in the
Astrophysical Journa
X-ray polarimetry reveals the magnetic field topology on sub-parsec scales in Tycho's supernova remnant
Supernova remnants are commonly considered to produce most of the Galactic
cosmic rays via diffusive shock acceleration. However, many questions about the
physical conditions at shock fronts, such as the magnetic-field morphology
close to the particle acceleration sites, remain open. Here we report the
detection of a localized polarization signal from some synchrotron X-ray
emitting regions of Tycho's supernova remnant made by the Imaging X-ray
Polarimetry Explorer. The derived polarization degree of the X-ray synchrotron
emission is 9+/-2% averaged over the whole remnant, and 12+/-2% at the rim,
higher than the 7-8% polarization value observed in the radio band. In the west
region the polarization degree is 23+/-4%. The X-ray polarization degree in
Tycho is higher than for Cassiopeia A, suggesting a more ordered magnetic-field
or a larger maximum turbulence scale. The measured tangential polarization
direction corresponds to a radial magnetic field, and is consistent with that
observed in the radio band. These results are compatible with the expectation
of turbulence produced by an anisotropic cascade of a radial magnetic-field
near the shock, where we derive a magnetic-field amplification factor of
3.4+/-0.3. The fact that this value is significantly smaller than those
expected from acceleration models is indicative of highly anisotropic
magnetic-field turbulence, or that the emitting electrons either favor regions
of lower turbulence, or accumulate close to where the magnetic-field
orientation is preferentially radially oriented due to hydrodynamical
instabilities.Comment: 31 pages, 7 figures, 3 tables. Accepted for publication in ApJ.
Revised versio
IXPE and XMM-Newton observations of the Soft Gamma Repeater SGR 1806-20
Recent observations with the Imaging X-ray Polarimetry Explorer (IXPE) of two
anomalous X-ray pulsars provided evidence that X-ray emission from magnetar
sources is strongly polarized. Here we report on the joint IXPE and XMM-Newton
observations of the soft {\gamma}-repeater SGR 1806-20. The spectral and timing
properties of SGR 1806-20 derived from XMM-Newton data are in broad agreement
with previous measurements; however, we found the source at an all-time-low
persistent flux level. No significant polarization was measured apart from the
4-5 keV energy range, where a probable detection with PD=31.6\pm 10.5% and
PA=-17.6\pm 15 deg was obtained. The resulting polarization signal, together
with the upper limits we derive at lower and higher energies 2-4 and 5-8 keV,
respectively) is compatible with a picture in which thermal radiation from the
condensed star surface is reprocessed by resonant Compton scattering in the
magnetosphere, similar to what proposed for the bright magnetar 4U 0142+61.Comment: 11 pages, 3 figures, accepted for publication in Ap
Magnetic structures and turbulence in SN 1006 revealed with imaging X-ray polarimetry
Young supernova remnants (SNRs) strongly modify surrounding magnetic fields,
which in turn play an essential role in accelerating cosmic rays (CRs). 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 SN1006 from a 1 Ms observation with the Imaging X-ray
Polarimetry Explorer (IXPE). We found an average polarization degree of
and an average polarization angle of
(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 turbulence in SN 1006 and CR
acceleration is environment-dependent.Comment: 15 pages, 4 Figures, 2 Tables; accepted for publication in The
Astrophysical Journa
X-ray pulsar GRO J100857 as an orthogonal rotator
X-ray polarimetry is a unique way to probe geometrical configuration of
highly-magnetized accreting neutron stars (X-ray pulsars). GRO J100857 is
the first transient X-ray pulsar observed at two different flux levels by the
Imaging X-ray Polarimetry Explorer (IXPE) during its outburst in November 2022.
The polarization properties were found to be independent of the source
luminosity, with the polarization degree varying between non-detection to about
15% over the pulse phase. Fitting the phase-resolved spectro-polarimetric data
with the rotating vector model allowed us to estimate the pulsar inclination
(130 deg, which is in good agreement with the orbital inclination), the
position angle (75 deg) of the pulsar spin axis, and the magnetic obliquity (74
deg). This makes GRO J100857 the first confidently identified X-ray pulsar
as a nearly orthogonal rotator. The results are discussed in the context of the
neutron star atmosphere models and theories of pulsars' axis alignment.Comment: 11 pages, 7 figures, submitted to A&A. arXiv admin note: text overlap
with arXiv:2209.0244
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