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Jerome Rodriguez

Publications and source records attributed to Jerome Rodriguez.

At least 37 records · Page 2Linked to original sources
arXiv2015

Chandra Observations of Eight Sources Discovered by INTEGRAL

We report on 0.3-10 keV observations with the Chandra X-ray Observatory of eight hard X-ray sources discovered within 8 degrees of the Galactic plane by the INTEGRAL satellite. The short (5 ks) Chandra observations of the IGR source fields have yielded very likely identifications of X-ray counterparts for three of the IGR sources: IGR J14091-6108, IGR J18088-2741, and IGR J18381-0924. The first two have very hard spectra in the Chandra band that can be described by a power-law with photon indices of Gamma = 0.6+/-0.4 and -0.7(+0.4)(-0.3), respectively (90% confidence errors are given), and both have a unique near-IR counterpart consistent with the Chandra position. IGR J14091-6108 also displays a strong iron line and a relatively low X-ray luminosity, and we argue that the most likely source type is a Cataclysmic Variable (CV), although we do not completely rule out the possibility of a High Mass X-ray Binary. IGR J18088-2741 has an optical counterpart with a previously measured 6.84 hr periodicity, which may be the binary orbital period. We also detect five cycles of a possible 800-950 s period in the Chandra light curve, which may be the compact object spin period. We suggest that IGR J18088-2741 is also most likely a CV. For IGR J18381-0924, the spectrum is intrinsically softer with Gamma = 1.5(+0.5)(-0.4), and it is moderately absorbed, nH = (4+/-1)e22 cm-2. There are two near-IR sources consistent with the Chandra position, and they are both classified as galaxies, making it likely that IGR J18381-0924 is an Active Galactic Nucleus (AGN). For the other five IGR sources, we provide lists of nearby Chandra sources, which may be used along with further observations to identify the correct counterparts, and we discuss the implications of the low inferred Chandra count rates for these five sources.

astro-ph.HE↗
arXiv2015

The On-Site Analysis of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) observatory will be one of the largest ground-based very high-energy gamma-ray observatories. The On-Site Analysis will be the first CTA scientific analysis of data acquired from the array of telescopes, in both northern and southern sites. The On-Site Analysis will have two pipelines: the Level-A pipeline (also known as Real-Time Analysis, RTA) and the level-B one. The RTA performs data quality monitoring and must be able to issue automated alerts on variable and transient astrophysical sources within 30 seconds from the last acquired Cherenkov event that contributes to the alert, with a sensitivity not worse than the one achieved by the final pipeline by more than a factor of 3. The Level-B Analysis has a better sensitivity (not be worse than the final one by a factor of 2) and the results should be available within 10 hours from the acquisition of the data: for this reason this analysis could be performed at the end of an observation or next morning. The latency (in particular for the RTA) and the sensitivity requirements are challenging because of the large data rate, a few GByte/s. The remote connection to the CTA candidate site with a rather limited network bandwidth makes the issue of the exported data size extremely critical and prevents any kind of processing in real-time of the data outside the site of the telescopes. For these reasons the analysis will be performed on-site with infrastructures co-located with the telescopes, with limited electrical power availability and with a reduced possibility of human intervention. This means, for example, that the on-site hardware infrastructure should have low-power consumption. A substantial effort towards the optimization of high-throughput computing service is envisioned to provide hardware and software solutions with high-throughput, low-power consumption at a low-cost.

astro-ph.IM↗
arXiv2015

Creating a high-resolution picture of Cygnus with the Cherenkov Telescope Array

The Cygnus region hosts one of the most remarkable star-forming regions in the Milky Way. Indeed, the total mass in molecular gas of the Cygnus X complex exceeds 10 times the total mass of all other nearby star-forming regions. Surveys at all wavelengths, from radio to gamma-rays, reveal that Cygnus contains such a wealth and variety of sources---supernova remnants (SNRs), pulsars, pulsar wind nebulae (PWNe), H II regions, Wolf-Rayet binaries, OB associations, microquasars, dense molecular clouds and superbubbles---as to practically be a galaxy in microcosm. The gamma-ray observations along reveal a wealth of intriguing sources at energies between 1 GeV and tens of TeV. However, a complete understanding of the physical phenomena producing this gamma-ray emission first requires us to disentangle overlapping sources and reconcile discordant pictures at different energies. This task is made more challenging by the limited angular resolution of instruments such as the Fermi Large Area Telescope, ARGO-YBJ, and HAWC and the limited sensitivity and field of view of current imaging atmospheric Cherenkov telescopes (IACTs). The Cherenkov Telescope Array (CTA), with its improved angular resolution, large field of view, and order of magnitude gain in sensitivity over current IACTs, has the potential to finally create a coherent and well-resolved picture of the Cygnus region between a few tens of GeV and a hundred TeV. We describe a proposed strategy to study the Cygnus region using CTA data, which combines a survey of the whole region at $65^{\circ} < l < 85^{\circ}$ and $-3.5^{\circ} < b < 3.5^{\circ} $ with deeper observations of two sub-regions that host rich groups of known gamma-ray sources.

astro-ph.HE↗
arXiv2015

Chandra Identification of Two AGN Discovered by INTEGRAL

Here, we report on observations of two hard X-ray sources that were originally discovered with the INTEGRAL satellite: IGR J04059+5416 and IGR J08297-4250. We use the Chandra X-ray Observatory to localize the sources and then archival near-IR images to identify the counterparts. Both sources have counterparts in the catalog of extended 2 Micron All-Sky Survey sources, and the counterpart to IGR J04059+5416 has been previously identified as a galaxy. Thus, we place IGR J04059+5416 in the class of Active Galactic Nuclei (AGN), and we suggest that IGR J08297-4250 is also an AGN. If this identification is correct, the near-IR images suggest that the host galaxy of IGR J08297-4250 may be merging with a smaller nearby galaxy. For IGR J04059+5416, the 0.3-86 keV spectrum from Chandra and INTEGRAL is consistent with an absorbed power-law with a column density of N_H = 3.1(+2.0)(-1.5)e22 cm-2 and a photon index of Gamma = 1.4+/-0.7, and we suggest that it is a Seyfert galaxy. For IGR J08297-4250, the photon index is similar, Gamma = 1.5+/-0.8, but the source is highly absorbed (N_H = 6.1(+10.1)(-4.3)e23 cm-2).

astro-ph.HE↗
arXiv2014

Evidence of Elevated X-Ray Absorption Before and During Major Flare Ejections in GRS 1915+105

We present time resolved X-ray spectroscopy of the microquasar GRS1915+105 with the MAXI observatory in order to study the accretion state just before and during the ejections associated with its major flares. Radio monitoring with the RATAN-600 radio telescope from 4.8 - 11.2 GHz has revealed two large steep spectrum major flares in the first eight months of 2013. Since, the RATAN receives one measurement per day, we cannot determine the jet forming time without more information. Fortunately, this is possible since a distinct X-ray light curve signature that occurs preceding and during major ejections has been determined in an earlier study. The X-ray luminosity spikes to very high levels in the hours before ejection then becomes variable (with a nearly equal X-ray luminosity when averaged over the duration of the ejection) during a brief 3 to 8 hour ejection process. By comparing this X-ray behavior to MAXI light curves, we can estimate the beginning and end of the ejection episode of the strong 2013 flares to within $\sim$3 hours. Using this estimate in conjunction with time resolved spectroscopy from the data in the MAXI archives allows us to deduce that the X-ray absorbing hydrogen column density increases significantly in the hours preceding the ejections and remains elevated during the ejections responsible for the major flares. This finding is consistent with an out-flowing wind or enhanced accretion at high latitudes.

astro-ph.GA↗
arXiv2013

Properties of unique hard X-ray dips observed from GRS 1915+105 and IGR J17091-3624 and their implications

We report a comprehensive study on spectral and timing properties of hard X-ray dips uniquely observed in some so-called variability classes of the micro-quasars GRS 1915+105 and IGR J17091-3624. These dips are characterized by a sudden decline in the 2.0-60.0 keV X-ray intensity by a factor of 4-12 simultaneous with the increase in hardness ratio by a factor of 2-4. Using 31 observations of GRS 1915+105 with RXTE/PCA, we show that different behavior are observed in different types of variability classes, and we find that a dichotomy is observed between classes with abrupt transitions vs those with smoother evolution. For example, both energy-lag spectra and frequency-lag spectra of hard X-ray dips in classes with abrupt transitions and shorter dip intervals show hard-lag (hard photons lag soft photons), while both lag spectra during hard dips in classes with smoother evolution and longer dip intervals show soft-lag. Both lag time-scales are of the order of 100-600 msec. We also show that timing and spectral properties of hard X-ray dips observed in light curves of IGR J17091-3624 during its 2011 outburst are consistent with the properties of the abrupt transitions in GRS 1915+105 rather than smooth evolution. A global correlation between the X-ray intensity cycle time and hard dip time is observed for both abrupt and smooth transition which may be due to two distinct physical processes whose time-scales are eventually correlated. We discuss implications of our results in the light of some generic models.

astro-ph.HE↗
arXiv2013

Calibrated Estimates of the Energy in Major Flares of GRS 1915+105

We analyze the energetics of the major radio flare of October 8 2005 in GRS 1915+105. The flare is of particular interest because it is one of the most luminous and energetic radio flares from a Galactic black hole that has ever been observed. The motivation is two-fold. One, to learn more about the energetics of this most extreme phenomenon and its relationship to the accretion state. The second is to verify if the calibrated estimates of the energy of major radio flares (based on the peak low frequency optically thin flux) derived from flares in the period 1996-2001 in Punsly & Rodriguez (2013), PR13 hereafter, can be used to estimate plasmoid energy beyond this time period. We find evidence that the calibrated curves are still accurate for this strong flare. Furthermore, the physically important findings of PR13 are supported by the inclusion of this flare: the flare energy is correlated with both the intrinsic bolometric X-ray luminosity, $L_{\mathrm{bol}}$, $\sim 1$ hour before ejection and $L_{\mathrm{bol}}$ averaged over the duration of the ejection of the plasmoid and $L_{\mathrm{bol}}$ is highly elevated relative to historic levels just before and during the ejection episode. A search of the data archives reveal that only the October 8 2005 flare and those in PR13 have adequate data sampling to allow estimates of both the energy of the flare and the X-ray luminosity before and during flare launch.

astro-ph.GA↗
arXiv2013

Gamma-ray observations of the microquasars Cygnus X-1, Cygnus X-3, GRS 1915+105, and GX 339-4 with the Fermi Large Area Telescope

Detecting gamma-rays from microquasars is a challenging but worthwhile endeavor for understanding particle acceleration, the jet mechanism, and for constraining leptonic/hadronic emission models. We present results from a likelihood analysis on timescales of 1 d and 10 d of ~4 years worth of gamma-ray observations (0.1-10 GeV) by Fermi-LAT of Cyg X-1, Cyg X-3, GRS 1915+105, and GX 339-4. Our analysis reproduced all but one of the previous gamma-ray outbursts of Cyg X-3 as reported with Fermi or AGILE, plus 5 new days on which Cyg X-3 is detected at a significance of ~5-sigma that are not reported in the literature. In addition, Cyg X-3 is significantly detected on 10-d timescales outside of known gamma-ray flaring epochs which suggests that persistent gamma-ray emission from Cyg X-3 has been detected for the first time. For Cyg X-1, we find three low significance excesses (~3-4-sigma) on daily timescales that are contemporaneous with gamma-ray flares reported (also at low significance) by AGILE. Two other microquasars, GRS 1915+105 and GX 339-4, are not detected and we derive 3-sigma upper limits of 2.3e-8 ph/cm2/s and 1.6e-8 ph/cm2/s, respectively, on the persistent flux in the 0.1-10 GeV range. These results enable us to define a list of the general conditions that are necessary for the detection of gamma-rays from microquasars.

astro-ph.HE↗
arXiv2013

GRS 1915+105 as a Galactic Analog of a Fanaroff-Riley II Quasar

We study the long term time averaged kinetic luminosity, $\bar{Q}$, of the major flares of the Galactic microquasar GRS 1915+105 and the relationship to the intrinsic X-ray (bolometric) luminosity, $L_{\mathrm{bol}}$, and scale it to that of a complete sample of SDSS/FIRST FR II quasars. If the scale invariance hypothesis for black holes (BHs) holds then we show that the expected distribution in the $\bar{Q}$ - $L_{\mathrm{bol}}$ scatter plane of GRS 1915+105 is consistent with FR II quasars for distances D = 10.7 - 11 kpc. We compare the specific values of kinetic luminosity and $L_{\mathrm{bol}}$ during flares of GRS 1915+105 to that predicted by several 3-D MHD simulations of BH accretion flows with relativistic ejections. If FR II quasars are a scaled up version of GRS 1915+105, the data are consistent with numerical models when they contain an ergospheric disk jet and the BH spin is $a/M= 0.99$ or $a/M=0.998$ (we estimate $a/M>0.984$). In the framework of scale invariance of BHs, our results may imply that FR II quasars also hold rapidly rotating BHs.

astro-ph.CO↗
arXiv2013

XTE J1752-223 in outburst: a persistent radio jet, dramatic flaring, multiple ejections and linear polarisation

The black hole candidate, XTE J1752-223, was discovered in 2009 October when it entered an outburst. We obtained radio data from the Australia Telescope Compact Array for the duration of the ~9 month event. The lightcurves show that the radio emission from the compact jet persisted for the duration of an extended hard state and through the transition to the intermediate state. The flux then rose rapidly by a factor of 10 and the radio source entered a series of at least 7 maxima, the first of which was likely to be emission associated with the compact jet. The subsequent 6 flares were accompanied by variable behaviour in terms of radio spectrum, degree of linear polarisation, morphology and associated X-ray behaviour. They were, however, remarkably similar in terms of the estimated minimum power required to launch such an ejection event. We compare the timing of radio peaks with the location of the ejecta, imaged by contemporaneous VLBI experiments. We then discuss the mechanism behind the events, in terms of whether discrete ejections is the most likely description of the behaviour. One ejection, at least, appears to be travelling with apparent superluminal motion. The range of properties, however, suggests that mutiple mechanisms may be relevant and that at least some of the emission is coming from shocked interactions amongst the ejecta and between the ejecta and the interstellar medium. We also compare the radio flux density with the X-ray source during the hard state and conclude that XTE J1752-223 is a radio-weak/X-ray-bright outlier on the universal correlation for black hole transient sources.

astro-ph.HE↗
arXiv2012

The Relationship Between X-ray Luminosity and Major Flare Launching in GRS 1915+105

We perform the most detailed analysis to date of the X-ray state of the Galactic black hole candidate GRS 1915+105 just prior to (0 to 4 hours) and during the brief (1 to 7 hour) ejection of major (superluminal) radio flares. A very strong model independent correlation is found between the 1.2 keV - 12 keV X-ray flux 0 to 4 hours before flare ejections with the peak optically thin 2.3 GHz emission of the flares. This suggests a direct physical connection between the energy in the ejection and the luminosity of the accretion flow preceding the ejection. In order to quantify this concept, we develop techniques to estimate the intrinsic (unabsorbed) X-ray luminosity, $L_{\mathrm{intrinsic}}$, from RXTE ASM data and to implement known methods to estimate the time averaged power required to launch the radio emitting plasmoids, $Q$ (sometimes called jet power). We find that the distribution of intrinsic luminosity from 1.2 keV - 50 keV, $L_{\mathrm{intrinsic}}(1.2 - 50)$, is systematically elevated just before ejections compared to arbitrary times when there are no major ejections. The estimated $Q$ is strongly correlated with $L_{\mathrm{intrinsic}}(1.2 - 50)$ 0 to 4 hours before the ejection, the increase in $L_{\mathrm{intrinsic}}(1.2 - 50)$ in the hours preceding the ejection and the time averaged $L_{\mathrm{intrinsic}}(1.2 - 50)$ during the flare rise. Furthermore, the total time averaged power during the ejection ($Q$ + the time average of $L_{\mathrm{intrinsic}}(1.2 - 50)$ during ejection) is strongly correlated with $L_{\mathrm{intrinsic}}(1.2 - 50)$ just before launch with near equality if the distance to the source is $ \approx 10.5$ kpc.

astro-ph.HE↗
arXiv2012

Investigating the Optical Counterpart Candidates of Four INTEGRAL Sources localized with Chandra

We report on the optical spectroscopic follow up observations of the candidate counterparts to four INTEGRAL sources: IGR J04069+5042, IGR J06552-1146, IGR J21188+4901 and IGR J22014+6034. The candidate counterparts were determined with Chandra, and the optical observations were performed with 1.5-m RTT-150 telescope (TÜBİTAK National Observatory, Antalya, Turkey) and 2.4-m Hiltner Telescope (MDM Observatory, Kitt Peak, Arizona). Our spectroscopic results show that one of the two candidates of IGR J04069+5042 and the one observed for IGR J06552-1146 could be active late-type stars in RS CVn systems. However, according to the likelihood analysis based on Chandra and INTEGRAL, two optically weaker sources in the INTEGRAL error circle of IGR J06552-1146 have higher probabilities to be the actual counterpart. The candidate counterparts of IGR J21188+4901 are classified as an active M-type star and a late-type star. Among the optical spectra of four candidates of IGR J22014+6034, two show Hαemission lines, one is a late-type star and the other is a M type. The likelihood analysis favors a candidate with no distinguishing features in the optical spectrum. Two of the candidates classified as M type dwarfs are similar to some IGR candidates claimed to be symbiotic stars. However, some of the prominent features of symbiotic systems are missing in our spectra, and their NIR colors are not consistent with those expected for giants. We consider the IR colors of all IGR candidates claimed to be symbiotic systems and find that low resolution optical spectrum may not be enough for conclusive identification.

astro-ph.HE↗
arXiv2012

Future Science Prospects for AMI

The Arcminute Microkelvin Imager (AMI) is a telescope specifically designed for high sensitivity measurements of low-surface-brightness features at cm-wavelength and has unique, important capabilities. It consists of two interferometer arrays operating over 13.5-18 GHz that image structures on scales of 0.5-10 arcmin with very low systematics. The Small Array (AMI-SA; ten 3.7-m antennas) couples very well to Sunyaev-Zel'dovich features from galaxy clusters and to many Galactic features. The Large Array (AMI-LA; eight 13-m antennas) has a collecting area ten times that of the AMI-SA and longer baselines, crucially allowing the removal of the effects of confusing radio point sources from regions of low surface-brightness, extended emission. Moreover AMI provides fast, deep object surveying and allows monitoring of large numbers of objects. In this White Paper we review the new science - both Galactic and extragalactic - already achieved with AMI and outline the prospects for much more.

astro-ph.IM↗
arXiv2012

Localizing INTEGRAL Sources with Chandra: X-Ray and Multi-Wavelength Identifications and Energy Spectra

We report on Chandra observations of 18 hard X-ray (>20 keV) sources discovered with the INTEGRAL satellite near the Galactic plane. For 14 of the INTEGRAL sources, we have uncovered one or two potential Chandra counterparts per source. These provide soft X-ray (0.3-10 keV) spectra and sub-arcsecond localizations, which we use to identify counterparts at other wavelengths, providing information about the nature of each source. Despite the fact that all of the sources are within 5 degrees of the plane, four of the IGR sources are AGN (IGR J01545+6437, IGR J15391-5307, IGR J15415-5029, and IGR J21565+5948) and four others are likely AGN (IGR J03103+5706, IGR J09189-4418, IGR J16413-4046, and IGR J16560-4958) based on each of them having a strong IR excess and/or extended optical or near-IR emission. We compare the X-ray and near-IR fluxes of this group of sources to those of AGN selected by their 2-10 keV emission in previous studies and find that these IGR AGN are in the range of typical values. There is evidence in favor of four of the sources being Galactic (IGR J12489-6243, IGR J15293-5609, IGR J16173-5023, and IGR J16206-5253), but only IGR J15293-5609 is confirmed as a Galactic source as it has a unique Chandra counterpart and a parallax measurement from previous optical observations that puts its distance at 1.56+/-0.12 kpc. The 0.3-10 keV luminosity for this source is 1.4e32 erg/s, and its optical/IR spectral energy distribution is well described by a blackbody with a temperature of 4200-7000 K and a radius of 12.0-16.4 Rsun. These values suggest that IGR J15293-5609 is a symbiotic binary with an early K-type giant and a white dwarf accretor. We also obtained likely Chandra identifications for IGR J13402-6428 and IGR J15368-5102, but follow-up observations are required to constrain their source types.

astro-ph.HE↗
arXiv2012

XMM-Newton observations of five INTEGRAL sources located towards the Scutum Arm

Results are presented for XMM-Newton observations of five hard X-ray sources discovered by INTEGRAL in the direction of the Scutum Arm. Each source received more than 20 ks of effective exposure time. We provide refined X-ray positions for all five targets enabling us to pinpoint the most likely counterpart in optical/infrared archives. Spectral and timing information (much of which are provided for the first time) allow us to give a firm classification for IGR J18462-0223 and to offer tentative classifications for the others. For IGR J18462-0223, we discovered a coherent pulsation period of 997+-1 s which we attribute to the spin of a neutron star in a highly-obscured (nH = 2e23 /cm2) high-mass X-ray binary (HMXB). This makes IGR J18462-0223 the seventh supergiant fast X-ray transient (SFXT) candidate with a confirmed pulsation period. IGR J18457+0244 is a highly-absorbed (nH = 8e23 /cm2) source in which the possible detection of an iron line suggests an active galactic nucleus (AGN) of type Sey-2 situated at z = 0.07(1). A periodic signal at 4.4 ks could be a quasi-periodic oscillation which would make IGR J18457+0244 one of a handful of AGN in which such features have been claimed, but a slowly-rotating neutron star in an HMXB can not be ruled out. IGR J18482+0049 represents a new obscured HMXB candidate with nH = 4e23 /cm2. We tentatively propose that IGR J18532+0416 is either an AGN or a pulsar in an HMXB system. The X-ray spectral properties of IGR J18538-0102 are consistent with the AGN classification that has been proposed for this source.

astro-ph.HE↗
arXiv2012

Is IGR J11014-6103 a Pulsar with the Highest Known Kick Velocity?

We report on Chandra X-ray and Parkes radio observations of IGR J11014-6103, which is a possible pulsar wind nebula with a complex X-ray morphology and a likely radio counterpart. With the superb angular resolution of Chandra, we find evidence that a portion of the extended emission may be related to a bow shock due to the putative pulsar moving through the interstellar medium. The inferred direction of motion is consistent with IGR J11014-6103 having been born in the event that produced the supernova remnant (SNR) MSH 11-61A. If this association is correct, then previous constraints on the expansion of MSH 11-61A imply a transverse velocity for IGR J11014-6103 of 2,400-2,900 km/s, depending on the SNR model used. This would surpass the kick velocities of any known pulsars and rival or surpass the velocities of any compact objects that are associated with SNRs. While it is important to confirm the nature of the source, our radio pulsation search did not yield a detection.

astro-ph.HE↗
arXiv2012

Chandra observations of five INTEGRAL sources: new X-ray positions for IGR J16393-4643 and IGR J17091-3624

The Chandra High Resolution Camera observed the fields of five hard X-ray sources in order to help us obtain X-ray coordinates with sub-arcsecond precision. These observations provide the most accurate X-ray positions known for IGR J16393-4643 and for IGR J17091-3624. The obscured X-ray pulsar IGR J16393-4643 lies at R.A. (J2000) = 16:39:05.47, and Dec. = -46:42:13.0 (error radius of 0.6" at 90% confidence). This position is incompatible with the previously-proposed counterpart 2MASS J16390535-4642137, and it points instead to a new counterpart candidate that is possibly blended with the 2MASS star. The black hole candidate IGR J17091-3624 was observed during its 2011 outburst providing coordinates of R.A. = 17:09:07.59, and Dec. = -36:24:25.4. This position is compatible with those of the proposed optical/IR and radio counterparts, solidifying the source's status as a microquasar. Three targets, IGR J14043-6148, IGR J16358-4726, and IGR J17597-2201, were not detected. We obtained 3σ upper limits of, respectively, 1.7, 1.8, and 1.5 \times 10^-12 erg cm^-2 s^-1 on their 2-10 keV fluxes.

astro-ph.HE↗
arXiv2012

XMM-Newton Finds That SAX J1750.8-2900 May Harbor the Hottest, Most Luminous Known Neutron Star

We have performed the first sensitive X-ray observation of the low-mass X-ray binary SAX J1750.8-2900 in quiescence with XMM-Newton. The spectrum was fit to both a classical black body model, and a non-magnetized, pure hydrogen neutron star atmosphere model. A power law component was added to these models, but we found that it was not required by the fits. The distance to SAX J1750.8-2900 is known to be D = 6.79 kpc from a previous analysis of photospheric radius expansion bursts. This distance implies a bolometric luminosity (as given by the NS atmosphere model) of (1.05 +/- 0.12) x 10^34 (D/6.79 kpc)^2 erg s^-1, which is the highest known luminosity for a NS LMXB in quiescence. One simple explanation for this surprising result could be that the crust and core of the NS were not in thermal equilibrium during the observation. We argue that this was likely not the case, and that the core temperature of the NS in SAX J1750.8-2900 is unusually high.

astro-ph.HE↗