News Article | May 12, 2017
News Article | May 15, 2017
This image from the NASA/ESA Hubble Space Telescope shows the unusual galaxy IRAS 06076-2139, found in the constellation Lepus (The Hare). Hubble's Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) instruments observed the galaxy from a distance of 500 million light-years. This particular object stands out from the crowd by actually being composed of two separate galaxies rushing past each other at about 2 million kilometers (1,243,000 miles) per hour. This speed is most likely too fast for them to merge and form a single galaxy. However, because of their small separation of only about 20,000 light-years, the galaxies will distort one another through the force of gravity while passing each other, changing their structures on a grand scale. Such galactic interactions are a common sight for Hubble, and have long been a field of study for astronomers. The intriguing behaviors of interacting galaxies take many forms; galactic cannibalism, galaxy harassment and even galaxy collisions. The Milky Way itself will eventually fall victim to the latter, merging with the Andromeda Galaxy in about 4.5 billion years. The fate of our galaxy shouldn't be alarming though: while galaxies are populated by billions of stars, the distances between individual stars are so large that hardly any stellar collisions will occur. Please follow SpaceRef on Twitter and Like us on Facebook.
News Article | May 15, 2017
A powerful space telescope orbiting Earth has spied on two galaxies in the midst of a cosmic close call 500 million light-years away. The Hubble Space Telescope spotted two galaxies — collectively called IRAS 06076-2139 — speeding past one another at about 1.2 million miles per hour, according to NASA. SEE ALSO: Countless galaxies billions of light-years away shine in new Hubble photo The two galaxies are moving so fast that they likely won't merge, but the two objects are so huge that they will distort each other as they pass about 20,000 light-years from one another. The immense gravity of the two objects will be able to influence the structure of the galaxies as they pass, changing the positions of stars and gas within them. "Such galactic interactions are a common sight for Hubble, and have long been a field of study for astronomers," NASA said in a statement. The Milky Way is actually on its way to a galactic collision itself with the Andromeda Galaxy. At some point in about 4.5 billion years the two galaxies will merge into one. That may sound slightly (or more-than-slightly) terrifying, but in reality, it shouldn't be too much cause for personal concern. "While galaxies are populated by billions of stars, the distances between individual stars are so large that hardly any stellar collisions will occur," NASA said of the Andromeda/Milky Way merger. Scientists working with the Hubble just celebrated the space telescope's 27th year in space, and the intrepid eye on the sky is still going strong. NASA has previously said that the telescope should be able to continue working in orbit through at least 2020, two years after the James Webb Space Telescope — Hubble's successor — is expected to get to space.
News Article | May 5, 2017
SBS Consulting Pte Ltd is a Singaporean software development company. It has an online payroll software Singapore for small businesses. Its other business software Singapore are CRM System, School Management System, & Clinic Management System. -- SBS Consulting Pte Ltd is a well-known Singaporean software development company. It has a feature-rich, online payroll software Singapore for the use of small and mid-sized businesses. The other business software Singapore offered by SBS are CRM System, School & Tuition Management System, & Clinic Management System."Our web-basedcan add to your credibility and enhance your statutory compliance. It can streamline your payroll processing and reduce your stress level," advised SBS Consulting Pte Ltd.Most of the small business owners, short in resources, always feel the pressure of maintaining the balance between the business needs and the need of executing their statutory compliance. They feel the pinch if they are doing their payroll manually. It is a situation they can resolve by implementing a module-rich"It is but natural that the implementation of aincreases the efficiency and productivity. The automation of the task saves the time, human resources, and money. It also leads to the disbursement of actual salaries to the employees of the business. For this reason, many companies are investigating top payroll software systems," prompted Ms. Meena, the Business Head of SBS Consulting Pte Ltd.• Employee Management• Master Setup Management• Company Management• Banking Compliant – Automated GIRO for almost all Major Banks• Compliant with the regulations issued by CPF Board, IRAS, Ministry of Manpower• Leaves Management• Attendance & Timesheet Management• Claims Management• Progression Planning• Enquiry Management• Email and SMS Management• Real-time Reports and Dashboards• Schedule Management• Tracking• Bio-metric (Finger Scan) Attendance support• Billing & Invoice Management• Itemized Pay slip• Multiple Company Setups & Document Upload• Connectivity withlike MYOB, QuickBooks, etc• Experienced 24X7 customer serviceInvesting in a toplike payroll software Singapore is a worthwhile investment. Some of the businesses even choosethat gives them payroll functionality. It enables the business owners and managers in streamlining payroll function of the firm. The software capably takes over the lengthy calculations that can quickly tire or fatigue a payroll executive. It is repetitive, mindless process and even the slightest loss of concentration can result in a mistake damaging the goodwill of the business."Ourstores many information parameters related to the employees like employee name, age, nationality, NRIC, race, religion, immigration status, education, training, certificates, details of family, emergency phone numbers, email address, etc.Also, the software also facilitates uploading and storing of unlimited employee photos & documents. It also allows unlimited company setups which are a plus point for a business owner having multiple businesses or for an umbrella organization that controls some companies," added Ms. Meena.Recording an employee's attendance and keeping accurate timesheet is a concern for the small as well as large businesses. The data enables them to justly compensate their employees. Inaccurate information not only leads to failed payday but can also sour the relations between the management and the employees. It can also affect the cash flow of the company. The traditional method is to manually track the employees, but it ties up the skilled human resources of the business and wastes them. In a technological era like ours, such wastes are unacceptable."Oursolves this problem by automating the process. It uses biometric finger scanners to maintain the attendance record and timesheet for each employee. The arrangement is tamper-free and tracks an employee's incoming and outgoing to the seconds.SBS'supports different timesheet formats; timesheet entry for one calendar day - one location, one calendar day - multiple locations, one calendar day - multiple employees, multiple employees - one calendar day. It is a useful payroll tool that you can trust," said Ms. Meena.SBS Consulting is a respected software development firm in Singapore. It offers business software Singapore like Payroll Software Singapore, Doctor & Clinic Management Software, CRM System & School Management Software.Contact:Ms. Meena,Visit:High Street Centre,#17-02, 1 North Bridge Road,Singapore - 179094Tel: (65) 6536 0036Email: firstname.lastname@example.org
News Article | March 3, 2017
Flash Physics is our daily pick of the latest need-to-know developments from the global physics community selected by Physics World's team of editors and reporters A new high-resolution map of dark matter – an invisible substance that appears to have a profound gravitational effect on galaxies and other large-scale structures in the cosmos – has been produced by an international team of astronomers using the Hubble Space Telescope. The map focuses on three galaxy clusters that act as cosmic telescopes by magnifying images of the more distant universe through gravitational lensing. The degree to which this magnification occurs gives an extremely precise measurement of the dark matter within the clusters. "We have mapped all of the clumps of dark matter that the data permit us to detect, and have produced the most detailed topological map of the dark-matter landscape to date," explains Priyamvada Natarajan of Yale University in the US, who led the team. An important feature of the map is that it is in close agreement with computer simulations of how cold dark matter (CDM) – a popular theoretical description of dark matter – is expected to be distributed within the galaxy clusters. The map is described in the Monthly Notices of the Royal Astronomical Society. A hard-to-detect pigment in melanoma skin cancer can be imaged using a laser-based technique. A team at Massachusetts General Hospital's Wellman Center for Photomedicine in the US has used a form of Raman spectroscopy to identify the pheomelanin molecule. Melanoma is the deadliest form of skin cancer and fair skin has a higher probability of developing the hard-to-detect variation of the disease called amelanotic melanoma. This is linked to the fact that fair skin contains a higher concentration of pheomelanin – a pigment, or melanin, within the skin. While the black-brown pigment found in most melanomas is easily observed, pheomelanin is essentially invisible. To detect the pigment, the team, led by Conor Evans, turned to a form of Raman spectroscopy called coherent anti-Stokes Raman Scattering (CARS) microscopy. Raman spectroscopy is a well-known technique that uses lasers to measure the unique chemical vibrations within molecules and hence identify them. CARS microscopy meanwhile, is a high-resolution imaging technique. It focuses two lasers on a sample and "tunes" the energy difference to specific molecular vibrations. This means a high-resolution image can be generated. Using CARS, the researchers successfully imaged the usually invisible pheomelanin by looking for its unique chemical structure. The method could be incorporated into a brand-new tool for early cancer diagnosis. The work will be presented at the OSA Biophotonics Congress: Optics in the Life Sciences meeting on 2–5 April in San Diego, US. It has also been described in Scientific Reports. A connection between the sudden outflows of gas from a supermassive black hole and X-ray bursts has been made by astronomers using two space telescopes – NASA's NuSTAR and the European Space Agency's XMM-Newton. Gas outflows are common features of supermassive black holes, which sit at the centre of large galaxies. These objects ingest vast amounts of material and the dynamics of this accretion process can lead to the ejection of gas in a burp-like ultrafast wind. The team trained the instruments on an outflow from the black hole at the centre of galaxy IRAS 13224-3809 and observed that the temperature of an outflow was changing much more rapidly than had previously been seen in other events – on a timescale of less than 1 h. According to team member Erin Kara of the University of Maryland, these fluctuations provide important clues about where the outflow was created. "Because we saw such rapid variability in the winds, we know that the emission is coming from very close to the black hole itself, and because we observed that the wind was also changing on rapid timescales, it must also be coming from very close to the black hole." The observations were made over several days and revealed that the temperature fluctuations were a response to changes in the intensity of X-rays emitted by the black hole. This information could provide important clues about where the X-rays and outflows are produced. The research is described in Nature.
News Article | March 1, 2017
We used all the available XMM-Newton data, both from our recent observing campaign (Principal Investigator A.C.F.) and from the archive. The EPIC-pn data are reduced using XMM-Newton’s Science Analysis System (SAS) version 15.0.0 EPPROC (https://www.cosmos.esa.int/web/xmm-newton/download-and-install-sas) tool. The EPIC observations were made in large-window mode. We extracted source counts from a 30″-diameter circular region centred on the source coordinates, and background counts from a circular region about 60″ in diameter nearby on the same chip, avoiding contaminating sources, chip edges, and the region where the internal background due to copper is high, and filter the data for background flares. We created separate stacked spectra of the archival and new data using the ADDSPEC ftool (available as part of NASA’s high-energy astrophysics software, HEASOFT; http://heasarc.nasa.gov/lheasoft/). We extracted full band (0.3–10 keV) lightcurves for each spectrum, shown in Extended Data Fig. 1, and divided the lightcurve into low-, medium- and high-flux intervals such that each flux band contained the same total number of counts (thus the low-flux intervals are much longer than the high-flux intervals). We then extracted spectra corresponding to each flux level from each observation, and combined them using ADDSPEC. We binned all the EPIC-pn spectra to achieve a signal-to-noise ratio of 6, after background subtraction, and to oversample the spectral resolution by a factor of 3. The RGS camera consists of two similar detectors, which have high effective area and high spectral resolution between 7 Å and 38 Å. The second-order spectra cover the wavelength range 7–18 Å and provide double the spectral resolution. We corrected for contamination from soft-proton flares following the XMM-SAS standard procedures. For each exposure, we extracted the first- and second-order RGS spectra in a cross-dispersion region of 1′ width, centred on IRAS sky coordinates. We extracted background spectra by selecting photons beyond 98% of the source point spread function. The background spectra were consistent with those from blank field observations. Using the SAS task RGSCOMBINE, we stacked all RGS 1 and 2 spectra, obtaining two high-quality spectra for both the first and the second order with a total, clean exposure of 1.529 Ms each. We grouped the RGS spectra in channels equal to one-third of the point spread function, and use C-statistics, because it provides optimal spectral binning and avoids over-sampling. RGS spectral fitting is performed using the SPEX package (https://www.sron.nl/astrophysics-spex), with contributions from XSPEC, in particular for reflection models. Flux-resolved spectra are extracted using the same good-time-interval files as used for the EPIC-pn analysis. The NuSTAR data were reduced using the NuSTAR data analysis software (NuSTARDAS) version 1.6.0 and CALDB version 20160731. We extracted source counts from a 30″-diameter circular region, centred on the source, and background counts from a large circular region on the same chip. We combined all the NuSTAR data into a single spectrum, given that the count rate is very low due to the extremely soft spectrum, and binned to achieve a signal-to-noise ratio of 6 and oversampling of 3. In the high-flux intervals, the source flux is above the nominal EPIC-pn large-window-mode pile-up limit of 3 counts s−1 (ref. 23), reaching about 9 counts s−1 at times. This risks distorting the spectrum and potentially affecting the detection of the ultrafast outflow. However, the count rate of IRAS 13224−3809 is dominated by photons from below 1 keV (the count rate from 0.5 keV to 1 keV is an order of magnitude higher than the count rate from 2 keV to 3 keV), because it is an extremely soft source. This means that the effects of pile-up are strongest below 2–3 keV. We tested this by extracting the same high-flux spectrum using an annular region, instead of a circle, with an excised core of 7″, which encircles the central four piled-up pixels. Above 2 keV, we found no difference in spectral shape between the two spectra, so we conclude that our analysis (restricted to E > 3 keV) is robust to this effect. The absorption feature is still present in both the mean spectrum and the low-flux spectrum when an annular extraction region is used. We also repeated this test using only single events, and again found no difference. The low-flux spectrum and the RGS spectra are not affected by pile-up. One potential cause of a false detection of an ultrafast outflow around 8 keV is the complex of emission lines, dominated by Cu Kα, in the instrumental background26. Over-subtracting these features would result in an artificial absorption feature at the corresponding energy, which would depend on the source to background flux ratio, giving an anticorrelation between the equivalent width of the line and the source flux. The copper background is only high in the outer regions of the detector, outside the central 300″, leaving a central ‘hole’ where contamination is minimal. We were careful to avoid the region where the copper background is high when selecting background regions, which should prevent contamination (see Extended Data Fig. 2). The easiest way to show that the ultrafast-outflow line is not an artefact of background over-subtraction is simply to not subtract the background and check the line remains. Although this is not always optimal (it may remove genuine but weak lines, or introduce new features), strong absorption features should remain in the spectrum. In Extended Data Fig. 3, we show the low-flux spectrum with no background subtraction, fitted with a power law. The iron line is weaker, owing to the additional high-energy contribution from the background, but the ultrafast-outflow line is clearly still present. If the observed line were produced by over-subtraction of the background, the (negative) flux of the line should be constant, the equivalent of an additional constant (positive) line in the background. This is trivial to test, by measuring the strength of an additive line with flux, rather than the multiplicative line we use elsewhere. We find clear variability, and an anti-correlation between the line flux and source flux (Fig. 3, inset), which is impossible if the line is a background feature. Finally, we note that the lines seen in the RGS spectrum are independent of this effect. We conclude that the line is genuine, and produced by absorption in the AGN spectrum. The potential secondary feature at about 8.7 keV (observer’s frame, 9.2-keV source frame) is coincidental with the Zn Kα line, and appears as an emission feature when the background is not subtracted. We cannot therefore robustly determine whether it is a genuine spectral feature, a statistical fluctuation, or due to the background. We fitted the stacked 2016 EPIC-pn spectrum in the range 3–10 keV (outside the band where pileup effects are present, and where the spectrum is relatively simple and unambiguous), and the stacked NuSTAR spectrum in the range 3–40 keV. We modelled the spectrum with the RELXILL relativistic reflection model27. The relativistic blurring parameters are consistent with those found by previous authors10 (see Extended Data Table 1), but a strong absorption feature remains at around 8.6 keV. When we included an additional Gaussian absorption line (modelled with GABS, with σ fixed at 0.1 keV), the fit improved by Δχ2 = 26, for two additional free parameters (degrees of freedom). Parameters for both these models are given in Extended Data Table 1. We also tested allowing σ to vary, but we found no significant difference in the fit statistic and no impact on the other fitting parameters. There are some differences between this result and those found by previous authors, which probably stem from the different energy range used. In particular, the photon index, the high-energy cut-off, and the iron abundance are different. The continuum parameters are not of great importance to this work, so long as the continuum is adequately described. The steeper Γ value in archival results (about 2.7; ref. 14) is probably due to the inclusion of the soft excess, which past authors10, 14 have fitted with a two-component reflection model. This requires a steep power law to produce enough soft photons to fit the soft excess. This model is not unique, because the soft excess generally has limited spectral features owing to the lower resolution of the EPIC-pn at these energies, and other factors, such as density of the disk, may alter the parameters from such a fit28. A visual comparison of the archival data and the new data (Extended Data Fig. 4a) does not show any major changes in the structure of the iron line or ultrafast-outflow absorption. Similarly, the iron abundance is largely determined by the relative strengths of the iron line and soft excess or Compton hump. Given the steep power law in the dual-reflection model, a high iron abundance is required to produce enough flux in the iron line. This is not required here, as we did not fit the soft excess and the Compton hump is only weakly constrained. This is important, as the iron abundance is potentially degenerate with the strength of the 8.6-keV absorption feature: an increased iron abundance produces a larger iron absorption edge in the reflection spectrum. We can be confident that this is not having a significant effect on our results, because the iron abundance is free to vary in all our fits, including the fits without the absorption modelled, and the feature still remains. We have explicitly searched for degeneracies using a Markov Chain Monte Carlo, and find no degeneracy between the strength of the line and the iron abundance. Following on from this, we performed a blind line scan over the 6–10-keV band, stepping an unresolved Gaussian line (σ = 0.01, allowed to be positive or negative) across the energy band, varying the normalization, and recording the Δχ2 at each point on this grid (Fig. 1a). We use the same underlying RELXILL model, allowing the same parameters to vary. We calculate the significance of this by taking the probability of the maximum Δχ2 for two additional free parameters, and correcting by the number of trials (that is, the number of resolution elements from 6.7 keV to 10 keV). This gives a final chance probability of 1.5 × 10−5, which corresponds to a 4.3σ detection. No other features are significant above about 1σ. We also fitted the absorption with a series of physical models—WARMABS in XSPEC (shown in Extended Data Fig. 4b), which uses grids of XSTAR photoionization models, and XABS and PION in SPEX. The three models give consistent results, with a degeneracy between two possible solutions with outflow velocities of v = 0.210 ± 0.009 and v = 0.244 ± 0.09, corresponding to Fe xxv and Fe xxvi. These solutions have different column densities and ionizations, which are summarized in Extended Data Table 2. The velocity broadening is not strongly constrained, but does not appear to affect any of the other wind parameters. We test this by fixing the broadening to lower and higher values, and find no change in the column density, velocity or ionization of the fit. The RGS spectrum is complex, showing several broad emission-like features at 15 Å and 18 Å. This spectrometer is the most sensitive to narrow (≲,000 Å) features, but higher effective area and broader energy range EPIC detectors are more efficient for determining the spectral continuum. We therefore performed an independent analysis of the RGS spectra using either a phenomenological spline continuum model fitted to the RGS spectrum or the physical reflection model provided by the best-fit reflection (RELXILL) model of the EPIC-pn stacked spectrum. When fitting the RGS spectrum, the spline is corrected for redshift and Galactic interstellar-medium absorption. We search for features in the RGS spectrum following an advanced procedure18. We include a Gaussian spanning the wavelength range 7–38 Å in increments of 0.05 Å, and assume a linewidth of 1,000 km s−1 (comparable to the RGS resolution). This broadening will also tend to strengthen the detection of any warm-absorber and ultrafast-outflow lines with respect to interstellar absorption lines, since the latter are typically narrower29 (≤200 km s−1). We take into account the absorption edges of neutral neon (14.3 Å), iron (17.5 Å), and oxygen (23.0 Å), but we exclude the corresponding 1s–2p absorption lines in order to detect and compare any spectral feature intrinsic to IRAS 13224−3809 or to the interstellar medium. The strongest non-Galactic absorption feature detected is a broad depression around 16 Å, which is also clear in the RGS stacked spectrum (see Extended Data Fig. 5). The other two putative, weaker, absorption-like features appear at 10 Å and 13 Å. Interestingly, the photoionization model of the EPIC spectrum predicts three broad (about 1,500 km s−1) ultrafast-outflow absorption lines that match the three RGS absorption features. We have tested different linewidths (from 100 km s−1 to 5,000 km s−1) without finding a major effect on their detection. The significance of the rest-frame absorption lines of Galactic O vii and O viii instead increase up to 5σ for narrower widths (<200 km s−1), confirming the results obtained with the grating spectra of the brightest X-ray binaries29. A full description of the RGS spectral modelling and the corresponding flux-resolved high-resolution X-ray spectroscopy will be discussed in a forthcoming paper. Here we provide the main result obtained with the overall spectrum and a first interpretation of the wind variability. We modelled the RGS stacked spectrum with both a spline and a reflection continuum in order to constrain the characteristics of the ultrafast outflow. The interstellar medium was modelled following the detailed multi-phase gas model constrained with the low-mass X-ray binaries29. We modelled the ultrafast-outflow absorption features in the RGS spectrum with an outflowing gas in photoionization equilibrium (XABS model in SPEX 3.02). The best fit of the RGS stacked spectrum provides the column density N = 9.5 ± 0.5 × 1022 cm−2 (90% error) the ionization parameter logξ = 4.0 ± 0.1 erg cm s−1 and the linewidth σ = 2,000 ± 1,000 km s−1. The RGS velocity shift v = −0.231c ± 0.007c fits between the EPIC Fe xxv (−0.244c ± 0.009c) and the Fe xxvi (−0.210c ± 0.009c) solutions, and does not fully constrain which solution is most likely, but slightly prefers the Fe xxv (−0.244c) solution, which is consistent within the 90% confidence level. We investigate a combined fit to both EPIC-pn and RGS spectra, fitting with the same absorption model but different continuum models for each spectrum (the physical reflection model for the EPIC-pn, and a spline for the RGS). We also include a photoionized emission component, modelled with the XSPEC PHOTEMIS model. The soft and hard absorption features are consistent with being from the same absorber (freeing the parameters between the two results in an improvement to the fit of only Δχ2 = 3, for four additional free parameters). The joint fit clearly prefers the Fe xxv solution, with final best-fit parameters of v = 0.236c ± 0.006c, σ = 4,000 ± 1,000, logξ = 4.14 ± 0.13 and . The increased broadening with respect to the individual spectrum fits may be due to a small offset between the EPIC-pn and RGS spectra, which could be caused by gain shift in the EPIC-pn. However, it is consistent at the 90% level with that found from the RGS alone. The inclusion of the emission component improves the fit significantly (Δχ2 = 21, for two additional free parameters), accounting for the residuals at about 8.3 keV and other possible features. The velocity of this component is 0.213c ± 0.015c, and the luminosity is (1.1 ± 0.5) × 1041 erg s−1. If this component is genuine, it is made up of scattered emission from the wind, and can in principle be used to determine the wind geometry. However, it is likely that much of the P Cygni profile, including any redshifted emission, is obscured by the relativistic iron line, which is very strong in this source. One possible approach to take here would be to search for the emission component of the P Cygni profile in the lag spectra, as the reverberation timescale should be much longer than for the relativistic reflection component, owing to the greater distance from the source. We also fitted the three flux-resolved spectra, tying parameters we expect to be constant (such as a and i) between the different spectra. The model parameters are consistent with those given in Extended Data Table 1, with the reflection fraction inversely proportional to flux. We performed the same line scan over these spectra simultaneously, stepping the line across in energy then recording the Δχ2 for each spectrum individually. The line is only significantly detected in the low flux spectrum, with a maximum Δχ2 of 59.7, for two additional free parameters. This gives a corrected probability of 1.96 × 10−12, and a significance of 7.0σ. We also check the robustness of the low-flux line detection using a Monte Carlo test. We draw parameters from a Markov chain Monte Carlo, used to evaluate the errors and degeneracies in the best-fit parameters, and use them to simulate 10,000 fake spectra. We then fitted these spectra using the same procedure. None of the simulated spectra have higher significance features, in either emission or absorption, setting a lower limit of P > 99.99% on the significance. Given the expected fraction of 4.6 × 10−12, it is not feasible to test sufficient spectra to establish the true significance using this method. We performed a similar analysis with ten flux-resolved spectra, again with the same number of counts in each. We fitted the spectra simultaneously, using RELXILL and a Gaussian absorption line, allowing the reflection fraction, power-law index, and normalizations of the reflection and Gaussian components to vary between each spectrum. This gives a reasonable fit (χ2/d.o.f. = 966/857 = 1.13, where d.o.f. is degrees of freedom). We then recorded the equivalent width and flux of the absorption line in each spectrum, and the 3–10-keV flux. These are plotted against each other in Fig. 3, showing a strong correlation. We used Bayesian regression to perform a linear fit, which incorporates the upper limits, and draw samples from the posterior distribution to calculate the uncertainty. We calculated the probability of a stronger correlation being found from a constant absorption feature by simulating 10,000 sets of points with the same errors, assuming that the line strength is constant in each case, and performing the same analysis. In no case did we find a stronger correlation. We performed high-resolution flux-resolved X-ray spectroscopy with the RGS data, consistent with that performed with EPIC: we extracted RGS 1 and 2 first- and second-order spectra with the good time intervals defined according to the EPIC flux prescriptions. We stacked the RGS 1 and 2 spectra for each flux range, obtaining three high-quality RGS spectra with comparable statistics. As previously seen for the overall stacked spectrum, there are some non-interstellar absorption-like features (at 9.5 Å, 13 Å and 16 Å) which show evidence of variability, being both stronger and possibly bluer in the low-flux spectrum. To probe the strength of the features in each spectrum, we applied the same technique used for the stacked spectrum by fitting a Gaussian over the wavelength range 7–38 Å in increments of 0.05 Å. In Fig. 2, we show the significance of the spectral features obtained adopting the (RGS fitted) spline continuum. The three broad features were still detected at 9.5 Å, 13.0 Å and 16 Å in the low-flux spectrum. They have less significance or are undetected in the higher-flux spectra with possible evidence of slight velocity change. Their wavelengths match with the strongest lines predicted by the 0.24c ultrafast outflow model in the RGS energy band: 10.0 ± 0.5 Å (Ne x + Fe xviii–Fe xxii blend), 13.2 ± 0.5 Å (O viii Kβ + Fe xviii) and 15.8 ± 0.5 Å (O viii Kα). The strength of the absorption lines anti-correlate with the flux in agreement with the EPIC result and therefore provides strong evidence in favour of a connection between the EPIC and RGS absorbers as being part of the same extreme wind. We computed the confidence level of the three main absorption lines in the low-flux spectrum, where they are significantly detected as in EPIC. Accounting for the number of trials due to bins of 0.05 Å and an outflow-velocity range from 0c to 0.3c, we obtain 2.1σ, 2.9σ and 3.4σ for the 9.5-Å, 13-Å and 16-Å absorption lines, respectively, which—since they have the same velocity shift—gives a cumulative 5.1σ detection. We can estimate the mass outflow rate by combining the velocity and column densities3, and the mass30 of 6 × 106M (estimated using the empirical reverberation relation31): where Ω is the solid angle of the wind and R is the radius of the wind. We cannot be confident of the value of Ω, as the emission from the P Cygni profile, if there is any, is obscured by the blue horn of the iron line, which is extremely strong in this source. However, given that the absorption line is found in the stacked archival data (most of which is from 2011), this implies that the feature has been present and roughly constant (as a function of flux) for at least 5 years, which would argue for a reasonably large covering fraction, otherwise any clump along the line of sight would probably have moved away. Similarly, we do not know the radius of the wind. However, we know that it must be variable on timescales ≲5 ks, which corresponds to 170 gravitational radii (R ). Assuming a radius of 100R , we find the accretion rate = 2 × 1023 × Ω g s−1 (0.03ΩM year−1) for Fe xxv, while the Eddington accretion rate for a black hole of this mass is 2.7 × 1024 g s−1, assuming an efficiency of 0.3 for near-maximal spin. In either case, a large fraction of the matter accreted by the disk is lost to the wind, possibly implying super-Eddington accretion at large radii (beyond R ). We can then calculate the power in the wind: For Ω = 2π, this gives a power of 4% of the Eddington luminosity L , implying that a non-negligible fraction of the accretion power must be lost into the wind. For the same assumed covering fraction, the power of the quasar PDS 456 is 15% of the Eddington luminosity3. The prevailing interpretation for highly blueshifted absorption features in the X-ray spectra of AGNs is that they are due to outflowing gas. However, it is possible that some of these features may instead be due to absorption by a diffuse absorbing surface layer on the approaching side of the accretion disk, which naturally gives relativistic velocities32. The absorption line then appears in the reflection component. Aberration means that the blue side is brighter than the red side. For a disk inclination of 60° the absorption layer needs to extend from about 5R to 10R to give an observed line at 8.2 keV. If the brighter parts of the light curve are associated with the corona rising above 10R , then reduced light bending and irradiation of the inner disk weakens both the reflection component and the absorption, consistent with observation. It is also possible that the variability is produced by a geometric effect. Previous authors have suggested that the relatively constant spectrum of the relativistic reflection component can be produced by changes in the height or extent of the X-ray corona above the disk33, and the covering fraction of a wind at a small angle to the disk could similarly depend on the size or position of the compact X-ray source. All the code used for the data reduction is available from the respective websites. XSPEC and SPEX are freely available online. Code used for generating figures, calculating flux-resolved extraction intervals, and calculating line significance, is available upon request to M.L.P. All data used in this work is publicly available. The XMM-Newton observations can be accessed from the XMM-Newton science archive (http://nxsa.esac.esa.int/nxsa-web/) and the NuSTAR data from the HEASARC archive (http://heasarc.gsfc.nasa.gov/docs/archive.html). Figure data are available from the authors.
News Article | March 1, 2017
Gas outflows are common features of active supermassive black holes that reside in the center of large galaxies. Millions to billions of times the mass of the Sun, these black holes feed on the large disks of gas that swirl around them. Occasionally the black holes eat too much and burp out an ultra-fast wind, or outflow. These winds may have a strong influence on regulating the growth of the host galaxy by clearing the surrounding gas away and suppressing star formation. Scientists have now made the most detailed observation yet of such an outflow, coming from an active galaxy named IRAS 13224-3809. The outflow's temperature changed on time scales of less than an hour, which is hundreds of times faster than ever seen before. The rapid fluctuations in the outflow's temperature indicated that the outflow was responding to X-ray emissions from the accretion disk, a dense zone of gas and other materials that surrounds the black hole. The new observations are published in the journal Nature on March 2, 2017. "Although we have seen these outflows before, this observation was the first time we were able to see the launching of the gases being connected with changes in the luminosity of black holes," said Erin Kara, a postdoctoral researcher in astronomy at the University of Maryland and a co-author of the study. Scientists made these measurements using two space telescopes, NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) telescope and the European Space Agency's (ESA) XMM-Newton. To capture the variability of these signals, scientists focused the XMM-Newton on the black hole for 17 days in a row, and observed the black hole with NuSTAR for six days. To measure the temperatures of these winds, scientists studied X-rays coming from the edge of the black hole. As they travel towards Earth, these X-rays pass through the outflows. Elements such as iron or magnesium present in the outflows can absorb specific parts of the X-ray spectrum, creating signature "dips" in the X-ray signal. By observing these dips, called absorption features, astronomers can learn what elements exist in the wind. The team noticed that the absorption features disappeared and reappeared in the span of a few hours. The researchers concluded that the X-rays were heating up the winds to millions of degrees Celsius, at which point the winds became incapable of absorbing any more X-rays. The observations that the outflows appear to be linked with X-rays, and that both are so highly variable, provide possible clues for locating where exactly the X-rays and outflows originate. "The radiating gas flows into black holes are most variable at their centers," Kara said. "Because we saw such rapid variability in the winds, we know that the emission is coming from very close to the black hole itself, and because we observed that the wind was also changing on rapid time scales, it must also be coming from very close to the black hole." To further study galaxy formation and black holes, Chris Reynolds, a professor of astronomy at UMD and a co-PI on the project, noted the need for more detailed data and observations. "We need to observe this black hole with better and more spectrometers, so we can get more details about these outflows," Reynolds said. "For instance, we don't know whether the outflow is composed of one or multiple sheets of gas. And we need to observe on multiple bands in addition to X-rays--that would allow us to detect molecular gases, and colder gases, that can be driven by these high-energy outflows. All that information will be crucial to understanding how these outflows are connected to galaxy formation." This research was supported by NASA, the European Space Agency, the European Research Council (Award No. 340492), the European Union Seventh Framework Programme (Award No. n.312789, StrongGravity), and the United Kingdom Science and Technology Facilities Council. The content of this article does not necessarily reflect the views of these organizations. The research paper, "Relativistically outflowing gas responds to the inner accretion disk of a black hole," Michael Parker, Ciro Pinto, Andrew Fabian, Anne Lohfink, Douglas Buisson, William Alston, Erin Kara, Edward Cackett, Chia-Ying Chiang, Thomas Dauser, Barbara De Marco, Luigi Gallo, Javier Garcia, Fiona Harrison, Ashley King, Matthew Middleton, Jon Miller, Giovanni Miniutti, Christopher Reynolds, Phil Uttley, Ranjan Vasudevan, Dominic Walton, Daniel Wilkins and Abderahmen Zoghbi, was published in the journal Nature on March 2, 2017. Media Relations Contact: Irene Ying, 301-405-5204, email@example.com University of Maryland College of Computer, Mathematical, and Natural Sciences 2300 Symons Hall College Park, MD 20742 http://www. @UMDscience About the College of Computer, Mathematical, and Natural Sciences The College of Computer, Mathematical, and Natural Sciences at the University of Maryland educates more than 7,000 future scientific leaders in its undergraduate and graduate programs each year. The college's 10 departments and more than a dozen interdisciplinary research centers foster scientific discovery with annual sponsored research funding exceeding $150 million.
News Article | March 3, 2017
A team of scientists detected temperature swings in ultrafast “burps” of hot winds emitted by a black hole's accretion disk. These outflows could be responsible for preventing the birth of stars. Black holes, as we all know, are voracious eaters. These objects are so dense that nothing, not even light, can escape once ensnared by their immense gravitational pull. Occasionally, though, young and overeager black holes gobble down so much material so fast that they produce ultrafast “burps” of hot winds. Observations now conducted using NASA’s NuSTAR and the European Space Agency’s XMM-Newton telescopes indicate that these outflows, which can travel at nearly a quarter of the speed of light, could be suppressing the birth of stars in galaxies. Although it has previously been suggested that black hole-driven jets and winds can inhibit star formation, this is the first time the temperature swings of these outflows has been measured and their interactions with a black hole’s radiation studied. “We know that supermassive black holes affect the environment of their host galaxies, and powerful winds arising from near the black hole may be one means for them to do so,” NuSTAR principal investigator Fiona Harrison, a professor of physics at the California Institute of Technology, said in a statement released Wednesday. “The rapid variability, observed for the first time, is providing clues as to how these winds form and how much energy they may carry out into the galaxy.” For the purpose of this study, which was published in the March 2 issue of the journal Nature, the researchers trained their telescopes on IRAS 13224-3809 — an active galaxy located in the constellation Centaurus. This revealed that the ultrafast outflows emanating from the vicinity of the supermassive black hole at the galaxy’s center were heating up and cooling down in a span of just a few hours — hundreds of times faster than ever seen before. This, the researchers said, was an indication that the outflows were responding to X-ray emissions from the accretion disk, which is an orbiting disk of dust, gas and debris that surrounds active black holes. The X-rays were heating up the winds to millions of degrees, pushing them past a point where they become incapable of absorbing any more X-rays. These high-speed winds, in turn, could be responsible for suppressing star formation — a process that occurs at a temperature of roughly 10 Kelvin (-442 degrees Fahrenheit), at which point clouds of gas and dust cool down enough to condense. However, further observations would be needed to better understand the role these winds play in regulating the environment within their host galaxies. “We need to observe this black hole with better and more spectrometers, so we can get more details about these outflows,” study co-author Christopher Reynolds, a professor of astronomy at the University of Maryland, said in a statement. “For instance, we don't know whether the outflow is composed of one or multiple sheets of gas. And we need to observe on multiple bands in addition to X-rays — that would allow us to detect molecular gases, and colder gases, that can be driven by these high-energy outflows.”
News Article | March 1, 2017
An artist impression illustrating a supermassive black hole with X-ray emission emanating from its inner region (pink) and ultrafast winds streaming from the surrounding disk (purple). Credit: The European Space Agency (ESA) Gas outflows are common features of active supermassive black holes that reside in the center of large galaxies. Millions to billions of times the mass of the Sun, these black holes feed on the large disks of gas that swirl around them. Occasionally the black holes eat too much and burp out an ultra-fast wind, or outflow. These winds may have a strong influence on regulating the growth of the host galaxy by clearing the surrounding gas away and suppressing star formation. Scientists have now made the most detailed observation yet of such an outflow, coming from an active galaxy named IRAS 13224-3809. The outflow's temperature changed on time scales of less than an hour, which is hundreds of times faster than ever seen before. The rapid fluctuations in the outflow's temperature indicated that the outflow was responding to X-ray emissions from the accretion disk, a dense zone of gas and other materials that surrounds the black hole. The new observations are published in the journal Nature on March 2, 2017. "Although we have seen these outflows before, this observation was the first time we were able to see the launching of the gases being connected with changes in the luminosity of black holes," said Erin Kara, a postdoctoral researcher in astronomy at the University of Maryland and a co-author of the study. Scientists made these measurements using two space telescopes, NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) telescope and the European Space Agency's (ESA) XMM-Newton. To capture the variability of these signals, scientists focused the XMM-Newton on the black hole for 17 days in a row, and observed the black hole with NuSTAR for six days. To measure the temperatures of these winds, scientists studied X-rays coming from the edge of the black hole. As they travel towards Earth, these X-rays pass through the outflows. Elements such as iron or magnesium present in the outflows can absorb specific parts of the X-ray spectrum, creating signature "dips" in the X-ray signal. By observing these dips, called absorption features, astronomers can learn what elements exist in the wind. The team noticed that the absorption features disappeared and reappeared in the span of a few hours. The researchers concluded that the X-rays were heating up the winds to millions of degrees Celsius, at which point the winds became incapable of absorbing any more X-rays. The observations that the outflows appear to be linked with X-rays, and that both are so highly variable, provide possible clues for locating where exactly the X-rays and outflows originate. "The radiating gas flows into black holes are most variable at their centers," Kara said. "Because we saw such rapid variability in the winds, we know that the emission is coming from very close to the black hole itself, and because we observed that the wind was also changing on rapid time scales, it must also be coming from very close to the black hole." To further study galaxy formation and black holes, Chris Reynolds, a professor of astronomy at UMD and a co-PI on the project, noted the need for more detailed data and observations. "We need to observe this black hole with better and more spectrometers, so we can get more details about these outflows," Reynolds said. "For instance, we don't know whether the outflow is composed of one or multiple sheets of gas. And we need to observe on multiple bands in addition to X-rays—that would allow us to detect molecular gases, and colder gases, that can be driven by these high-energy outflows. All that information will be crucial to understanding how these outflows are connected to galaxy formation." More information: The response of relativistic outflowing gas to the inner accretion disk of a black hole, Nature, nature.com/articles/doi:10.1038/nature21385
News Article | March 1, 2017
Scientists have made the most detailed observation yet of a black hole outflow, from the active galaxy IRAS 13224-3809. The outflow's temperature changed on time scales of less than an hour -- hundreds of times faster than ever seen before. The rapid fluctuations in the outflow's temperature also indicated that the outflow was responding to X-ray emissions from the accretion disk, a dense zone of gas and other materials that surrounds the black hole.