53 research outputs found
Resolution and sensitivity of a Fabry-Perot interferometer with a photon-number-resolving detector
With photon-number resolving detectors, we show compression of interference
fringes with increasing photon numbers for a Fabry-Perot interferometer. This
feature provides a higher precision in determining the position of the
interference maxima compared to a classical detection strategy. We also
theoretically show supersensitivity if N-photon states are sent into the
interferometer and a photon-number resolving measurement is performed.Comment: 8 pages, 12 figures, 1 table, minor extensions, title changed, new
figures added, reference correcte
Instrumental vetoes for transient gravitational-wave triggers using noise-coupling models: The bilinear-coupling veto
LIGO and Virgo recently completed searches for gravitational waves at their
initial target sensitivities, and soon Advanced LIGO and Advanced Virgo will
commence observations with even better capabilities. In the search for short
duration signals, such as coalescing compact binary inspirals or "burst"
events, noise transients can be problematic. Interferometric gravitational-wave
detectors are highly complex instruments, and, based on the experience from the
past, the data often contain a large number of noise transients that are not
easily distinguishable from possible gravitational-wave signals. In order to
perform a sensitive search for short-duration gravitational-wave signals it is
important to identify these noise artifacts, and to "veto" them. Here we
describe such a veto, the bilinear-coupling veto, that makes use of an
empirical model of the coupling of instrumental noise to the output strain
channel of the interferometric gravitational-wave detector. In this method, we
check whether the data from the output strain channel at the time of an
apparent signal is consistent with the data from a bilinear combination of
auxiliary channels. We discuss the results of the application of this veto on
recent LIGO data, and its possible utility when used with data from Advanced
LIGO and Advanced Virgo.Comment: Minor changes; To appear in Phys. Rev.
Landsat 9 Thermal Infrared Sensor 2 Subsystem-Level Spectral Test Results
Results from the Thermal Infrared Sensor 2 (TIRS-2) prelaunch spectral characterization at telescope and detector subsystem level are presented. The derived relative spectral response (RSR) shape is expected to be very similar to the instrument-level spectral response and provides an initial estimate of the RSR and its differences to the component-level RSR measurements. Such differences were observed at TIRS- 1 and are likely a result of angular dependence of the spectral response of the detector. The subsystem RSR measurements also provide an opportunity for a preliminary assessment of the spectral requirements. Final requirements verification will be performed at future thermal vacuum environmental testing with the fully assembled TIRS-2 instrument
Multiwavelength Radio Observations of Two Repeating Fast Radio Burst Sources: FRB 121102 and FRB 180916.J0158+65
The spectra of fast radio bursts (FRBs) encode valuable information about the source's local environment, underlying emission mechanism(s), and the intervening media along the line of sight. We present results from a long-term multiwavelength radio monitoring campaign of two repeating FRB sources, FRB 121102 and FRB 180916.J0158+65, with the NASA Deep Space Network (DSN) 70 m radio telescopes (DSS-63 and DSS-14). The observations of FRB 121102 were performed simultaneously at 2.3 and 8.4 GHz, and spanned a total of 27.3 hr between 2019 September 19 and 2020 February 11. We detected two radio bursts in the 2.3 GHz frequency band from FRB 121102, but no evidence of radio emission was found at 8.4 GHz during any of our observations. We observed FRB 180916.J0158+65 simultaneously at 2.3 and 8.4 GHz, and also separately in the 1.5 GHz frequency band, for a total of 101.8 hr between 2019 September 19 and 2020 May 14. Our observations of FRB 180916.J0158+65 spanned multiple activity cycles during which the source was known to be active and covered a wide range of activity phases. Several of our observations occurred during times when bursts were detected from the source between 400 and 800 MHz with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope. However, no radio bursts were detected from FRB 180916.J0158+65 at any of the frequencies used during our observations with the DSN radio telescopes. We find that FRB 180916.J0158+65's apparent activity is strongly frequency-dependent due to the narrowband nature of its radio bursts, which have less spectral occupancy at high radio frequencies (≳ 2 GHz). We also find that fewer or fainter bursts are emitted from the source at high radio frequencies. We discuss the implications of these results for possible progenitor models of repeating FRBs
A Dual-band Radio Observation of FRB 121102 with the Deep Space Network and the Detection of Multiple Bursts
The spectra of repeating fast radio bursts (FRBs) are complex and time-variable, sometimes peaking within the observing band and showing a fractional emission bandwidth of about 10%–30%. These spectral features may provide insight into the emission mechanism of repeating FRBs, or they could possibly be explained by extrinsic propagation effects in the local environment. Broadband observations can better quantify this behavior and help to distinguish between intrinsic and extrinsic effects. We present results from a simultaneous 2.25 and 8.36 GHz observation of the repeating FRB 121102 using the 70 m Deep Space Network radio telescope, DSS-43. During the 5.7 hr continuous observing session, we detected six bursts from FRB 121102, which were visible in the 2.25 GHz frequency band. However, none of these bursts were detected in the 8.36 GHz band, despite the larger bandwidth and greater sensitivity in the higher-frequency band. This effect is not explainable by Galactic scintillation and, along with previous multi-band experiments, clearly demonstrates that apparent burst activity depends strongly on the radio frequency band that is being observed
A Dual-band Radio Observation of FRB 121102 with the Deep Space Network and the Detection of Multiple Bursts
The spectra of repeating fast radio bursts (FRBs) are complex and
time-variable, sometimes peaking within the observing band and showing a
fractional emission bandwidth of about 10-30%. These spectral features may
provide insight into the emission mechanism of repeating fast radio bursts, or
they could possibly be explained by extrinsic propagation effects in the local
environment. Broadband observations can better quantify this behavior and help
to distinguish between intrinsic and extrinsic effects. We present results from
a simultaneous 2.25 and 8.36 GHz observation of the repeating FRB 121102 using
the 70 m Deep Space Network (DSN) radio telescope, DSS-43. During the 5.7 hr
continuous observing session, we detected 6 bursts from FRB 121102, which were
visible in the 2.25 GHz frequency band. However, none of these bursts were
detected in the 8.36 GHz band, despite the larger bandwidth and greater
sensitivity in the higher-frequency band. This effect is not explainable by
Galactic scintillation and, along with previous multi-band experiments, clearly
demonstrates that apparent burst activity depends strongly on the radio
frequency band that is being observed.Comment: 8 pages, 3 figures, 1 table. Accepted for publication in ApJL on 2020
June 8. v2: Updated to match published versio
Bright X-ray and Radio Pulses from a Recently Reactivated Magnetar
Magnetars are young, rotating neutron stars that possess larger magnetic fields (B ≈ 10¹³-10¹⁵G) and longer rotational periods (P ≈ 1-12 s) than ordinary pulsars. In contrast to rotation-powered pulsars, magnetar emission is thought to be fueled by the evolution and decay of their powerful magnetic fields. They display highly variable radio and X-ray emission, but the processes responsible for this behavior remain a mystery. We report the discovery of bright, persistent individual X-ray pulses from XTE J1810-197, a transient radio magnetar, using the Neutron star Interior Composition Explorer (NICER) following its recent radio reactivation. Similar behavior has only been previously observed from a magnetar during short time periods following a giant flare. However, the X-ray pulses presented here were detected outside of a flaring state. They are less energetic and display temporal structure that differs from the impulsive X-ray events previously observed from the magnetar class, such as giant flares and short X-ray bursts. Our high frequency radio observations of the magnetar, carried out simultaneously with the X-ray observations, demonstrate that the relative alignment between the X-ray and radio pulses varies on rotational timescales. No correlation was found between the amplitudes or temporal structure of the X-ray and radio pulses. The magnetar's 8.3 GHz radio pulses displayed frequency structure, which was not observed in the pulses detected simultaneously at 31.9 GHz. Many of the radio pulses were also not detected simultaneously at both frequencies, which indicates that the underlying emission mechanism producing these pulses is not broadband. We find that the radio pulses from XTE J1810-197 share similar characteristics to radio bursts detected from fast radio burst (FRB) sources, some of which are now thought to be produced by active magnetars
Bright X-ray and Radio Pulses from a Recently Reactivated Magnetar
Magnetars are young, rotating neutron stars that possess larger magnetic fields (B ≈ 10¹³-10¹⁵G) and longer rotational periods (P ≈ 1-12 s) than ordinary pulsars. In contrast to rotation-powered pulsars, magnetar emission is thought to be fueled by the evolution and decay of their powerful magnetic fields. They display highly variable radio and X-ray emission, but the processes responsible for this behavior remain a mystery. We report the discovery of bright, persistent individual X-ray pulses from XTE J1810-197, a transient radio magnetar, using the Neutron star Interior Composition Explorer (NICER) following its recent radio reactivation. Similar behavior has only been previously observed from a magnetar during short time periods following a giant flare. However, the X-ray pulses presented here were detected outside of a flaring state. They are less energetic and display temporal structure that differs from the impulsive X-ray events previously observed from the magnetar class, such as giant flares and short X-ray bursts. Our high frequency radio observations of the magnetar, carried out simultaneously with the X-ray observations, demonstrate that the relative alignment between the X-ray and radio pulses varies on rotational timescales. No correlation was found between the amplitudes or temporal structure of the X-ray and radio pulses. The magnetar's 8.3 GHz radio pulses displayed frequency structure, which was not observed in the pulses detected simultaneously at 31.9 GHz. Many of the radio pulses were also not detected simultaneously at both frequencies, which indicates that the underlying emission mechanism producing these pulses is not broadband. We find that the radio pulses from XTE J1810-197 share similar characteristics to radio bursts detected from fast radio burst (FRB) sources, some of which are now thought to be produced by active magnetars
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