scholarly journals The corona of GJ 1151 in the context of star–planet interaction

2020 ◽  
Vol 497 (1) ◽  
pp. 1015-1019
Author(s):  
G Foster ◽  
K Poppenhaeger ◽  
J D Alvarado-Gómez ◽  
J H M M Schmitt
Keyword(s):  
Radio Emission ◽  
Low Frequency ◽  
Mass Star ◽  
Coronal Temperature ◽  
X Ray ◽  
Upper Limit ◽  
Radio Signals ◽  
Low Mass ◽  
Time Periods

ABSTRACT The low-mass star GJ 1151 has been reported to display variable low-frequency radio emission, which has been interpreted as a signpost of coronal star–planet interactions with an unseen exoplanet. Here we report the first X-ray detection of GJ 1151’s corona based on the XMM–Newton data. We find that the star displays a small flare during the X-ray observation. Averaged over the observation, we detect the star with a low coronal temperature of 1.6 MK and an X-ray luminosity of LX = 5.5 × 1026 erg s−1. During the quiescent time periods excluding the flare, the star remains undetected with an upper limit of $L_{\mathrm{ X},\, \mathrm{ qui}} \le 3.7\times 10^{26}$ erg s−1. This is compatible with the coronal assumptions used in a recently published model for a star–planet interaction origin of the observed radio signals from this star.

scholarly journals BANYAN. III. RADIAL VELOCITY, ROTATION, AND X-RAY EMISSION OF LOW-MASS STAR CANDIDATES IN NEARBY YOUNG KINEMATIC GROUPS

2014 ◽  
Vol 788 (1) ◽  
pp. 81 ◽  
Author(s):  
Lison Malo ◽  
Étienne Artigau ◽  
René Doyon ◽  
David Lafrenière ◽  
Loïc Albert ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Mass Star ◽  
X Ray ◽  
Low Mass

scholarly journals Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4–650224

2021 ◽  
Vol 655 ◽  
pp. A52
Author(s):  
F. Coti Zelati ◽  
B. Hugo ◽  
D. F. Torres ◽  
D. de Martino ◽  
A. Papitto ◽  
...  
Keyword(s):  
Radio Emission ◽  
Flux Density ◽  
Millisecond Pulsar ◽  
Radio Emissions ◽  
X Ray ◽  
Link Type ◽  
Upper Limit ◽  
Variability Pattern ◽  
Average Flux ◽  
Compact Array

We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4–650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of LX ≃ 7 × 1033 erg s−1 over the 0.3−10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9σ with an average flux density of ≃33 μJy at 1.28 GHz. It showed variability over the course of hours and emitted a ≃10-min long flare just a few minutes after a brief sequence of multiple X-ray flares. No clear evidence for a significant correlated or anticorrelated variability pattern was found between the X-ray and radio emissions over timescales of tens of minutes and longer. CXOU J110926.4–650224 was undetected at higher radio frequencies in subsequent observations performed with the Australia Telescope Compact Array, when the source was still in the same X-ray sub-luminous state observed before, down to a flux density upper limit of 15 μJy at 7.25 GHz (at 3σ). We compare the radio emission properties of CXOU J110926.4–650224 with those observed in known and candidate tMSPs and discuss physical scenarios that may account for its persistent and flaring radio emissions.

scholarly journals Neutron star QPOs from oscillating, precessing hot, thick flow

2019 ◽  
Vol 491 (3) ◽  
pp. 3245-3250
Author(s):  
P Chris Fragile
Keyword(s):  
Neutron Star ◽  
Low Frequency ◽  
Outer Radius ◽  
Horizontal Branch ◽  
X Ray ◽  
Best Fitting ◽  
Low Mass ◽  
The Moment ◽  
X Ray Binaries ◽  
Simultaneous Oscillation

ABSTRACT Across black hole (BH) and neutron star (NS) low-mass X-ray binaries (LMXBs), there appears to be some correlation between certain high- and low-frequency quasi-periodic oscillations (QPOs). In a previous paper, we showed that for BH LMXBs, this could be explained by the simultaneous oscillation and precession of a hot, thick, torus-like corona. In the current work, we extend this idea to NS LMXBs by associating the horizontal branch oscillations (HBOs) with precession and the upper-kiloHertz (ukHz) QPO with vertical epicyclic motion. For the Atoll source 4U 1608-52, the model can match many distinct, simultaneous observations of the HBO and ukHz QPO by varying the inner and outer radius of the torus, while maintaining fixed values for the mass (MNS) and spin (a*) of the NS. The best-fitting values are MNS = 1.38 ± 0.03 M⊙ and a* = 0.325 ± 0.005. By combining these constraints with the measured spin frequency, we are able to obtain an estimate for the moment of inertia of INS = 1.40 ± 0.02 × 1045 g cm2, which places constraints on the equation of state. The model is unable to fit the lower-kHz QPO, but evidence suggests that QPO may be associated with the boundary layer between the accretion flow and the NS surface, which is not treated in this work.

scholarly journals Magnetically Driven Warping and Precession of Accretion Disks: Implications for Exotic Stellar Variabilities

2002 ◽  
Vol 187 ◽  
pp. 215-220
Author(s):  
Dong Lai
Keyword(s):  
Accretion Disks ◽  
Low Frequency ◽  
Disk Accretion ◽  
X Ray ◽  
T Tauri ◽  
Magnetic Stars ◽  
Low Mass ◽  
Inner Region ◽  
X Ray Binaries

AbstractThe inner region of the accretion disk around a magnetized star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the stellar field and the induced electric currents in the disk. These novel magnetic effects give rise to some “exotic” stellar variabilities, and may play an important role in explaining a number of puzzling behaviors related to disk accretion onto magnetic stars, such as mHz QPOs in X-ray pulsars, long-term periodicities of X-ray binaries (including precession of jets), low-Frequency (10-50 Hz) QPO’s in low-mass X-ray binaries, and photometric variabilities of T Tauri stars.

scholarly journals Broad-band spectral energy distribution of the X-ray transient Swift J1745−26 from outburst to quiescence

2020 ◽  
Vol 637 ◽  
pp. A2
Author(s):  
Sylvain Chaty ◽  
Francis Fortin ◽  
Alicia López-Oramas
Keyword(s):  
Energy Distribution ◽  
Light Curve ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
X Ray ◽  
Upper Limit ◽  
Spectral Break ◽  
Hard State ◽  
Low Mass

Aims. We aim to analyse our study of the X-ray transient Swift J1745−26, using observations obtained from its outburst in September 2012, up to its decay towards quiescence in March 2013. Methods. We obtained optical and infrared observations, through override programme at ESO/VLT with FORS2 and ISAAC instruments, and added archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, to build the light curve and the broad-band spectral energy distribution (SED) of Swift J1745−26. Results. We show that, during its outburst and also during its decay towards quiescence, Swift J1745−26 SED can be adjusted, from infrared up to X-rays, by the sum of both a viscous irradiated multi-colour black body emitted by an accretion disc, and a synchrotron power law at high energy. In the radio domain, the SED arises from synchrotron emission from the jet. While our SED fitting confirms that the source remained in the low/hard state during its outburst, we determine an X-ray spectral break at frequency 3.1 ≤ νbreak ≤ 3.4 × 1014 Hz, and a radio spectral break at 1012 Hz ≤ νbreak ≤ 1013 Hz. We also show that the system is compatible with an absorption AV of ∼7.69 mag, lies within a distance interval of D ∼ [2.6 − 4.8] kpc with an upper limit of orbital period Porb = 11.3 h, and that the companion star is a late spectral type in the range K0–M0 V, confirming that the system is a low-mass X-ray binary. We finally plot the position of Swift J1745−26 on an optical-infrared – X-ray luminosity diagram: its localisation on this diagram is consistent with the source staying in the low-hard state during outburst and decay phases. Conclusions. By using new observations obtained at ESO/VLT with FORS2 and ISAAC, and adding archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, we built the light curve and the broad-band SED of Swift J1745−26, and we plotted its position on an optical-infrared – X-ray luminosity diagram. By fitting the SED, we characterized the emission of the source from infrared, via optical, up to X-ray domain, we determined the position of both the radio and X-ray spectral breaks, we confirmed that it remained in the low-hard state during outburst and decay phases, and we derived its absorption, distance interval, orbital period upper limit, and the late-type nature of companion star, confirming Swift J1745−26 is a low-mass X-ray binary.

scholarly journals Radio observations of the merging galaxy cluster Abell 520

2019 ◽  
Vol 622 ◽  
pp. A20 ◽  
Author(s):  
D. N. Hoang ◽  
T. W. Shimwell ◽  
R. J. van Weeren ◽  
G. Brunetti ◽  
H. J. A. Röttgering ◽  
...  
Keyword(s):  
Mach Number ◽  
Radio Emission ◽  
Low Frequency ◽  
Galaxy Cluster ◽  
Shock Acceleration ◽  
Relativistic Electrons ◽  
Diffusive Shock Acceleration ◽  
Cluster Emission ◽  
X Ray ◽  
Extended Radio

Context. Extended synchrotron radio sources are often observed in merging galaxy clusters. Studies of the extended emission help us to understand the mechanisms in which the radio emitting particles gain their relativistic energies. Aims. We examine the possible acceleration mechanisms of the relativistic particles that are responsible for the extended radio emission in the merging galaxy cluster Abell 520. Methods. We performed new 145 MHz observations with the LOw Frequency ARay (LOFAR) and combined these with archival Giant Metrewave Radio Telescope (GMRT) 323 MHz and Very Large Array (VLA) 1.5 GHz data to study the morphological and spectral properties of extended cluster emission. The observational properties are discussed in the framework of particle acceleration models associated with cluster merger turbulence and shocks. Results. In Abell 520, we confirm the presence of extended (760 × 950 kpc2) synchrotron radio emission that has been classified as a radio halo. The comparison between the radio and X-ray brightness suggests that the halo might originate in a cocoon rather than from the central X-ray bright regions of the cluster. The halo spectrum is roughly uniform on the scale of 66 kpc. There is a hint of spectral steepening from the SW edge towards the cluster centre. Assuming diffusive shock acceleration (DSA), the radio data are suggestive of a shock Mach number of ℳSW = 2.6−0.2+0.3 that is consistent with the X-ray derived estimates. This is in agreement with the scenario in which relativistic electrons in the SW radio edge gain their energies at the shock front via acceleration of either thermal or fossil electrons. We do not detect extended radio emission ahead of the SW shock that is predicted if the emission is the result of adiabatic compression. An X-ray surface brightness discontinuity is detected towards the NE region that may be a counter shock of Mach number ℳNEX = 1.52±0.05. This is lower than the value predicted from the radio emission which, assuming DSA, is consistent with ℳNE = 2.1 ± 0.2. Conclusions. Our observations indicate that the radio emission in the SW of Abell 520 is likely effected by the prominent X-ray detected shock in which radio emitting particles are (re-)accelerated through the Fermi-I mechanism. The NE X-ray discontinuity that is approximately collocated with an edge in the radio emission hints at the presence of a counter shock.

scholarly journals SGR A* AND ITS ENVIRONMENT: LOW-MASS STAR FORMATION, THE ORIGIN OF X-RAY GAS AND COLLIMATED OUTFLOW

2016 ◽  
Vol 819 (1) ◽  
pp. 60 ◽  
Author(s):  
F. Yusef-Zadeh ◽  
M. Wardle ◽  
R. Schödel ◽  
D. A. Roberts ◽  
W. Cotton ◽  
...  
Keyword(s):  
Star Formation ◽  
Mass Star ◽  
X Ray ◽  
Low Mass ◽  
Sgr A

scholarly journals The spectacular cluster chain Abell 781 as observed with LOFAR, GMRT, and XMM-Newton

2019 ◽  
Vol 622 ◽  
pp. A19 ◽  
Author(s):  
A. Botteon ◽  
T. W. Shimwell ◽  
A. Bonafede ◽  
D. Dallacasa ◽  
F. Gastaldello ◽  
...  
Keyword(s):  
Radio Emission ◽  
Large Scale ◽  
Thermal Emission ◽  
Low Frequency ◽  
Current Data ◽  
Mass Relation ◽  
Radio Halo ◽  
Main Cluster ◽  
Upper Limit ◽  
Main Component

Context. A number of merging galaxy clusters show the presence of large-scale radio emission associated with the intra-cluster medium (ICM). These synchrotron sources are generally classified as radio haloes and radio relics. Aims. Whilst it is commonly accepted that mergers play a crucial role in the formation of radio haloes and relics, not all the merging clusters show the presence of giant diffuse radio sources and this provides important information concerning current models. The Abell 781 complex is a spectacular system composed of an apparent chain of clusters on the sky. Its main component is undergoing a merger and hosts peripheral emission that is classified as a candidate radio relic and a disputed radio halo. Methods. We used new LOw Frequency ARay (LOFAR) observations at 143 MHz and archival Giant Metrewave Radio Telescope (GMRT) observations at 325 and 610 MHz to study radio emission from non-thermal components in the ICM of Abell 781. Complementary information came from XMM-Newton data, which allowed us to investigate the connection with the thermal emission and its complex morphology. Results. The origin of the peripheral emission is still uncertain. We speculate that it is related to the interaction between a head tail radio galaxy and shock. However, the current data allow us only to set an upper limit of ℳ <  1.4 on the Mach number of this putative shock. Instead, we successfully characterise the surface brightness and temperature jumps of a shock and two cold fronts in the main cluster component of Abell 781. Their positions suggest that the merger is involving three substructures. We do not find any evidence for a radio halo either at the centre of this system or in the other clusters of the chain. We place an upper limit to the diffuse radio emission in the main cluster of Abell 781 that is a factor of 2 below the current radio power-mass relation for giant radio haloes.

scholarly journals LOFAR observations of the mode-switching pulsar B0943+10

2017 ◽  
Vol 13 (S337) ◽  
pp. 66-69
Author(s):  
Anna V. Bilous
Keyword(s):  
Radio Emission ◽  
Low Frequency ◽  
Single Pulse ◽  
Transparency Window ◽  
Mode Switching ◽  
Emission Region ◽  
Polar Cap ◽  
X Ray ◽  
Polar Gap ◽  
New Generation

AbstractPSR B0943+10 is an old non-recycled pulsar which for decades has been mostly known for its rapid and spontaneous radio mode switching. Recently, Hermsen et al. (2013) discovered correlated changes in the thermal X-ray emission from the polar cap, thus demonstrating that radio modes are not just a product of the local changes in the radio emission region, but a sign of some global magnetospheric transformation. At about the same time, owing to the commissioning of the new generation of low-frequency radio arrays, the broadband observations at the lowest edge of ionospheric transparency window became available. At these radio frequencies profile morphology and the single-pulse properties of PSR B0943+10’s emission become very dynamic, providing details not only about the emission itself, but also about the conditions in the polar gap. Here, I will present the recent results of the LOFAR observations of PSR B0943+10 and discuss their contribution to the multiwavelength picture.

Sign in / Sign up

Export Citation Format

Share Document