Netherlands Institute for Space Research

About: Netherlands Institute for Space Research is a facility organization based out in Utrecht, Netherlands. It is known for research contribution in the topics: Galaxy & Neutron star. The organization has 737 authors who have published 3026 publications receiving 106632 citations. The organization is also known as: SRON & Space Research Organisation Netherlands.

Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6-0.4 (W31C), W49N, and W51

Abstract: We report the detection of the ground state N, J = 1, 3/2 → 1, 1/2 doublet of the methylidyne radical CH at ∼532 GHz and ∼536 GHz with the Herschel/HIFI instrument along the sight-line to the massive star-forming regions G10.6–0.4 (W31C), W49N, and W51. While the molecular cores associated with these massive star-forming regions show emission lines, clouds in the diffuse interstellar medium are detected in absorption against the strong submillimeter background. The combination of hyperfine structure with emission and absorption results in complex profiles, with overlap of the different hyperfine components. The opacities of most of the CH absorption features are linearly correlated with those of CCH, CN, and HCO + in the same velocity intervals. In specific narrow velocity intervals, the opacities of CN and HCO + deviate from the mean trends, giving rise to more opaque absorption features. We propose that CCH can be used as another tracer of the molecular gas in the absence of better tracers, with [CCH]/[H2] ∼3.2 ± 1.1 × 10 −8 . The observed [CN]/[CH], [CCH]/[CH] abundance ratios suggest that the bulk of the diffuse matter along the lines of sight has gas densities nH = n(H) + 2n(H2) ranging between 100 and 1000 cm −3 .

Detailed high-energy characteristics of AXP 4U 0142+61: Multi-year observations with INTEGRAL, RXTE, XMM-Newton, and ASCA

Abstract: 4U 0142+61 is one of the Anomalous X-ray Pulsars exhibiting hard X-ray emission above 10 keV discovered with INTEGRAL In this paper we present detailed spectral and temporal characteristics both in the hard X-ray (> 10 keV) and soft X-ray (<10 keV) domains obtained using data from INTEGRAL, XMM-Newton, ASCA and RXTE Accumulating data collected over four years with the imager IBIS-ISGRI aboard INTEGRAL, the time-averaged total spectrum shows a power-law like shape with photon index Gamma = 093 +/- 006 4U 0142+61 is detected up to 229 keV and the flux between 20 keV and 229 keV is (1501 +/- 082) x 10(-11) erg cm(-2) s(-1), which exceeds the energy flux in the 2-10 keV band by a factor of similar to 23 Using simultaneously collected data with the spectrometer SPI of INTEGRAL the combined total spectrum yields the first evidence for a spectral break above 100 keV Assuming a logparabolic function for the spectral shape above 20 keV the peak energy of 4U 0142+61 is 228(-41)(+65) keV There is no evidence for significant long-term time variability of the total emission from 4U 0142+61 Both the total flux and the spectral index are stable within the 17% level (1 sigma) Pulsed emission is measured with ISGRI up to 160 keV The 20-160 keV profile shows a broad double-peaked pulse with a 62 sigma detection significance The total pulsed spectrum can be described with a very hard power-law shape with a photon index G = 040 +/- 015 and a 20-150 keV flux of (268 +/- 134) x 10(-11) erg cm(-2) s(-1) To perform accurate phase-resolved spectroscopy over the total X-ray window, we produced pulse profiles in absolute phase for INTEGRAL-ISGRI, RXTE-PCA, XMM-Newton-PN and ASCA-GIS The two known pulses in all soft X-ray profiles below 10 keV are located in the same phases Three XMM-Newton observations in 2003-2004 show statistically identical profiles However, we find a significant profile morphology change between an ASCA-GIS observation in 1999 following a possible glitch of 4U 0142+61 This change can be accounted for by differences in relative strengths and spectral shapes (08-10 keV) of the two pulses The principle peak in the INTEGRAL pulse profile above 20 keV is located at the same phase as one of the pulses detected below 10 keV The second pulse detected with INTEGRAL is slightly shifted with respect to the second peak observed in the soft X-ray band We performed consistent phase-resolved spectroscopy over the total high-energy band and identify at least three genuinely different pulse components with different spectra The high level of consistency between the detailed results from the four missions is indicative of a remarkably stable geometry underlying the emission scenario Finally, we discuss the derived detailed characteristics of the high-energy emission of 4U 0142+61 in relation to three models for the non-thermal hard X-ray emission

A Sub-arcsecond Survey Toward Class 0 Protostars in Perseus: Searching for Signatures of Protostellar Disks

Abstract: We present a 1.3 mm dust continuum survey toward nine Class 0 protostars and two Class I protostars in the Perseus molecular cloud, using CARMA with a resolution of ∼0.″3 (70 AU). This sample approximately doubles the number of Class 0 protostars observed with spatial resolutions 100 AU around two sources (L1448 IRS2 and Per-emb-14), and these sources may be strong disk candidates. Marginally resolved structures within 30° of perpendicular to the outflow are found toward three protostars (L1448 IRS3C, IRAS 03282+3035, L1448C) and are considered disk candidates. Two others (L1448 IRS3B, IRAS 03292+3039) have complex resolved structures, possibly indicative of massive, fragmenting inner envelopes or disks; L1448 IRS3B also has evidence for a companion separated by 0.″9 (∼210 AU). The candidate first hydrostatic core L1451-MMS is marginally resolved on 1″ scales and the Class 0 protostar IC 348-MMS and does not have strong indications of resolved structure at any scale. The strong disk candidate sources were followed up with C18O () observations; we detect velocity gradients that are consistent with the expected rotation axis, but without enough sensitivity to determine if it is Keplerian. We compare the observed visibility amplitudes to radiative transfer models of protostellar envelopes and disks. The visibility amplitude ratios show that a compact component (possibly a disk) is necessary for five of nine Class 0 sources. An envelope-only scenario cannot be ruled out for the other four Class 0 sources. We conclude that there is evidence for the formation of large disks in the Class 0 phase, but Class 0 disks likely have a range of radii and masses that depend on the initial conditions of their parent cores.

Kinetic Inductance Detectors

Abstract: Microwave kinetic Inductance Detectors, MKIDs, combine device simplicity, intrinsic multiplexing capability and a good sensitivity for radiation detection from the X-ray to the sub-mm part of the electromagnetic spectrum. As a consequence MKIDs are now being developed in several varieties and for many different applications. The paper will shortly address the fundamentals of the physics of MKIDs and will elaborate on the various applications of MKID arrays currently under development.

A kilo-pixel imaging system for future space based far-infrared observatories using microwave kinetic inductance detectors

Abstract: spectrum will require very large arrays of ultra-sensitive detectors in combination with high multiplexing factors and effcient lownoise and low-power readout systems. We have developed a demonstrator system suitable for such applications. Methods. The system combines a 961 pixel imaging array based upon Microwave Kinetic Inductance Detectors (MKIDs) with a readout system capable of reading out all pixels simultaneously with only one readout cable pair and a single cryogenic amplifier. We evaluate, in a representative environment, the system performance in terms of sensitivity, dynamic range, optical efficiency, cosmic ray rejection, pixel-pixel crosstalk and overall yield at an observation centre frequency of 850 GHz and 20% fractional bandwidth. Results. The overall system has an excellent sensitivity, with an average detector sensitivity hNEPdeti = 3 - 10