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Register a new userA survey of X-ray emission from 100 kpc radio jets
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We have completed a Chandra snapshot survey of 54 radio jets that are extended on arcsec scales. These are associated with flat spectrum radio quasars spanning a redshift range z=0.3 to 2.1. X-ray emission is detected from the jet of approximately 60% of the sample objects. We assume minimum energy and apply conditions consistent with the original Felten-Morrison calculations in order to estimate the Lorentz factors and the apparent Doppler factors. This allows estimates of the enthalpy fluxes, which turn out to be comparable to the radiative luminosities.
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Recently, Diaz Trigo et al. reported an XMM-Newton detection of relativistically Doppler-shifted emission lines associated with steep-spectrum radio emission in the stellar-mass black hole candidate 4U 1630-47 during its 2012 outburst. They interpreted these lines as indicative of a baryonic jet launched by the accretion disk. Here we present a search for the same lines earlier in the same outburst using high-resolution X-ray spectra from the Chandra High-Energy Transmission Grating Spectrometer. While our observations (eight months prior to the XMM-Newton campaign) also coincide with detections of steep spectrum radio emission by the Australia Telescope Compact Array, we find no evidence for any relativistic X-ray emission lines. Indeed, despite $sim5times$ brighter radio emission, our Chandra spectra allow us to place an upper limit on the flux in the blueshifted Fe XXVI line that is $gtrsim20times$ weaker than the line observed by Diaz Trigo et al. We explore several scenarios that could explain our differing results, including variations in the geometry of the jet or a mass-loading process or jet baryon content that evolves with the accretion state of the black hole. We also consider the possibility that the radio emission arises in an interaction between a jet and the nearby ISM, in which case the X-ray emission lines might be unrelated to the radio emission.
Quiescent black hole X-ray binaries (X-ray luminosities <1e34 erg/s) are believed to be fed by hot accretion flows that launch compact, relativistic jets. However, due to their low luminosities, quiescent jets have been detected in the radio waveband from only five systems so far. Here, we present radio observations of two quiescent black hole X-ray binaries with the Australia Telescope Compact Array. One system, GS 1124-684, was not detected. The other system, BW Cir, was detected over two different epochs in 2018 and 2020, for which we also obtained quasi-simultaneous X-ray detections with Chandra and Swift. BW Cir is now the sixth quiescent X-ray binary with a confirmed radio jet. However, the distance to BW Cir is uncertain, and we find that BW Cir shows different behaviour in the radio/X-ray luminosity plane depending on the correct distance. Estimates based on its G-type subgiant donor star place BW Cir at >25 kpc, while initial optical astrometric measurements from Gaia Data Release 2 suggested likely distances of just a few kpc. Here, we use the most recent measurements from Gaia Early Data Release 3 and find a distance d=7.1(+4.8/-3.9) kpc and a potential kick velocity PKV=165(+81/-17) km/s, with distances up to ~20 kpc possible based on its parallax and proper motion. Even though there is now less tension between the parallax and donor-star based distance measurements, it remains an unresolved matter, and we conclude with suggestions on how to reconcile the two measurements.
We report the detection of extended X-ray emission from two high-redshift radio quasars. These quasars, J1405+0415 at $z$=3.208 and J1610+1811 at $z$=3.118, were observed in a Chandra snapshot survey selected from a complete sample of the radio-brightest quasars in the overlap area of the VLA-FIRST radio survey and the Sloan Digital Sky Survey. The extended X-ray emission is located along the line connecting the core to a radio knot or hotspot, favoring the interpretation of X-ray jets. The inferred rest frame jet X-ray luminosities from 2--30 keV would be of order 10$^{45}$ erg~s$^{-1}$ if emitted isotropically and without relativistic beaming. In the scenario of inverse Compton scattering of the cosmic microwave background (CMB), X-ray jets without a coincident radio counterpart may be common, and should be readily detectable to redshifts even beyond 3.2 due to the (1+$z$)$^4$ increase of the CMB energy density compensating for the (1+$z$)$^{-4}$ cosmological diminution of surface brightness. If these can be X-ray confirmed, they would be the second and third examples of quasar X-ray jets without detection of underlying continuous radio jets.
We present the results from a sensitive X-ray survey of 26 nearby hydrogen-poor superluminous supernovae (SLSNe-I) with Swift, Chandra and XMM. This dataset constrains the SLSN evolution from a few days until ~2000 days after explosion, reaching a luminosity L_x~10^40 erg/s and revealing the presence of significant X-ray emission at the location of PTF12dam. No SLSN-I is detected above L_x~10^41 erg/s, suggesting that the luminous X-ray emission L_x~10^45 erg/s associated with SCP60F6 is not common among SLSNe-I. We constrain the presence of off-axis GRB jets, ionization breakouts from magnetar central engines and the density in the sub-pc environments of SLSNe-I through Inverse Compton emission. The deepest limits rule out the weakest uncollimated GRB outflows, suggesting that IF the similarity of SLSNe-I with GRB/SNe extends to their fastest ejecta, then SLSNe-I are either powered by energetic jets pointed far away from our line of sight theta>30 deg, or harbor failed jets that do not successfully break through the stellar envelope. Furthermore, IF a magnetar central engine is responsible for the exceptional luminosity of SLSNe-I, our X-ray analysis favors large magnetic fields B>2x10^(14) G and ejecta masses M_ej>3 Msun in agreement with optical/UV studies. Finally, we constrain the pre-explosion mass-loss rate of stellar progenitors of SLSNe-I. For PTF12dam we infer Mdot<2x10^(-5) Msun/yr, suggesting that the SN shock interaction with the CSM is unlikely to supply the main source of energy powering the optical transient and that some SLSN-I progenitors end their life as compact stars surrounded by a low-density medium similar to long GRBs and Type Ib/c SNe.
The analysis of distributions of some parameters of radio pulsars emitting X-ray radiation was carried out. The majority of such pulsars has short spin periods with the average value $< P >$ = 133 msec. The distribution of period derivatives reveals a bimodality, dividing millisecond ($< log dfrac{dP}{dt}>$ = -19.69) and normal ($< log dfrac{dP}{dt}> $ = -13.29) pulsars. Magnetic fields at the surface of the neutron star are characterized by the bimodal distribution as well. The mean values of $<log B_s>$ are $8.48$ and $12.41$ for millisecond pulsars and normal ones, respectively. The distribution of magnetic fields near the light cylinder, it does not show the noticeable bimodality. The median value of $log B_{lc}$ = 4.43 is almost three orders higher comparing with this quantity ($<log B_{lc}>$ = 1.75) for radio pulsars without registered X-ray emission. Losses of rotational energy ($<log dfrac{dE}{dt}>$ = 35.24) are also three orders higher than corresponding values for normal pulsars. There is the strong correlation between X-ray luminosities and losses of rotational energies. The dependence of the X-ray luminosity on the magnetic field at the light cylinder has been detected. It shows that the generation of the non-thermal X-ray emission takes place at the periphery of the magnetosphere and is caused by the synchrotron mechanism. We detected the positive correlations between luminosities in radio, X-ray and gamma -ray ranges. Such correlations give the possibility to carry out a purposeful search for pulsars in one of these ranges if they radiate in other one.
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