Author(s)
Bae, Yeong-Bok, Park, Chan, Son, Edwin J., Ahn, Sang-Hyeon, Jeong, Minjoong, Kang, Gungwon, Kim, Chunglee, Kim, Dong Lak, Kim, Jaewan, Kim, Whansun, Lee, Hyung Mok, Lee, Yong-Ho, Norton, Ronald S., Oh, John J., Oh, Sang Hoon, Paik, Ho JungAbstract
Mid-frequency band gravitational-wave detectors will be complementary for the existing Earth-based detectors (sensitive above 10 Hz or so) and the future space-based detectors such as LISA, which will be sensitive below around 10 mHz. A ground-based superconducting omnidirectional gravitational radiation observatory (SOGRO) has recently been proposed along with several design variations for the frequency band of 0.1 to 10 Hz. For three conceptual designs of SOGRO (e.g., pSOGRO, SOGRO and aSOGRO), we examine their multi-channel natures, sensitivities and science cases. One of the key characteristics of the SOGRO concept is its six detection channels. The response functions of each channel are calculated for all possible gravitational wave polarizations including scalar and vector modes. Combining these response functions, we also confirm the omnidirectional nature of SOGRO. Hence, even a single SOGRO detector will be able to determine the position of a source and polarizations of gravitational waves, if detected. Taking into account SOGRO's sensitivity and technical requirements, two main targets are most plausible: gravitational waves from compact binaries and stochastic backgrounds. Based on assumptions we consider in this work, detection rates for intermediate-mass binary black holes (in the mass range of hundreds up to $10^{4}$$M_\odot$) are expected to be $0.0014-2.5 \,\, {\rm yr}^{-1}$. In order to detect stochastic gravitational wave background, multiple detectors are required. Two aSOGRO detector networks may be able to put limits on the stochastic background beyond the indirect limit from cosmological observations.
Figures
Responses of each channel in the SOGRO detector for plus ($+$), cross ($\times$), $x$, $y$, breathing ($b$), and longitudinal ($\ell$) polarization modes. The $+$ and $\times$ polarizations correspond to tensor modes, the $x$ and $y$ are vector modes, and the $b$ and $\ell$ polarizations are relevant to scalar modes. The responses of the (22) and the (31) channels are the same with the (11) and the (23) channels, respectively, up to $\pi/2$ rotation along the $z$-axis. The (33) channel is not shown as this is not used in sensitivity calculation. Combined (total) responses of all 5 channels are also depicted. The total responses show the omnidirectional nature of SOGRO; however, the total response of a terrestrial SOGRO to the $\ell$ mode vanishes in the direction of $z$-axis. In the last column, the general responses of a laser interferometer such as LIGO, Virgo or KAGRA are presented for comparison.
Responses of each channel in the SOGRO detector for plus ($+$), cross ($\times$), $x$, $y$, breathing ($b$), and longitudinal ($\ell$) polarization modes. The $+$ and $\times$ polarizations correspond to tensor modes, the $x$ and $y$ are vector modes, and the $b$ and $\ell$ polarizations are relevant to scalar modes. The responses of the (22) and the (31) channels are the same with the (11) and the (23) channels, respectively, up to $\pi/2$ rotation along the $z$-axis. The (33) channel is not shown as this is not used in sensitivity calculation. Combined (total) responses of all 5 channels are also depicted. The total responses show the omnidirectional nature of SOGRO; however, the total response of a terrestrial SOGRO to the $\ell$ mode vanishes in the direction of $z$-axis. In the last column, the general responses of a laser interferometer such as LIGO, Virgo or KAGRA are presented for comparison.
Responses of each channel in the SOGRO detector for plus ($+$), cross ($\times$), $x$, $y$, breathing ($b$), and longitudinal ($\ell$) polarization modes. The $+$ and $\times$ polarizations correspond to tensor modes, the $x$ and $y$ are vector modes, and the $b$ and $\ell$ polarizations are relevant to scalar modes. The responses of the (22) and the (31) channels are the same with the (11) and the (23) channels, respectively, up to $\pi/2$ rotation along the $z$-axis. The (33) channel is not shown as this is not used in sensitivity calculation. Combined (total) responses of all 5 channels are also depicted. The total responses show the omnidirectional nature of SOGRO; however, the total response of a terrestrial SOGRO to the $\ell$ mode vanishes in the direction of $z$-axis. In the last column, the general responses of a laser interferometer such as LIGO, Virgo or KAGRA are presented for comparison.
Responses of each channel in the SOGRO detector for plus ($+$), cross ($\times$), $x$, $y$, breathing ($b$), and longitudinal ($\ell$) polarization modes. The $+$ and $\times$ polarizations correspond to tensor modes, the $x$ and $y$ are vector modes, and the $b$ and $\ell$ polarizations are relevant to scalar modes. The responses of the (22) and the (31) channels are the same with the (11) and the (23) channels, respectively, up to $\pi/2$ rotation along the $z$-axis. The (33) channel is not shown as this is not used in sensitivity calculation. Combined (total) responses of all 5 channels are also depicted. The total responses show the omnidirectional nature of SOGRO; however, the total response of a terrestrial SOGRO to the $\ell$ mode vanishes in the direction of $z$-axis. In the last column, the general responses of a laser interferometer such as LIGO, Virgo or KAGRA are presented for comparison.
Responses of each channel in the SOGRO detector for plus ($+$), cross ($\times$), $x$, $y$, breathing ($b$), and longitudinal ($\ell$) polarization modes. The $+$ and $\times$ polarizations correspond to tensor modes, the $x$ and $y$ are vector modes, and the $b$ and $\ell$ polarizations are relevant to scalar modes. The responses of the (22) and the (31) channels are the same with the (11) and the (23) channels, respectively, up to $\pi/2$ rotation along the $z$-axis. The (33) channel is not shown as this is not used in sensitivity calculation. Combined (total) responses of all 5 channels are also depicted. The total responses show the omnidirectional nature of SOGRO; however, the total response of a terrestrial SOGRO to the $\ell$ mode vanishes in the direction of $z$-axis. In the last column, the general responses of a laser interferometer such as LIGO, Virgo or KAGRA are presented for comparison.
Responses of each channel in the SOGRO detector for plus ($+$), cross ($\times$), $x$, $y$, breathing ($b$), and longitudinal ($\ell$) polarization modes. The $+$ and $\times$ polarizations correspond to tensor modes, the $x$ and $y$ are vector modes, and the $b$ and $\ell$ polarizations are relevant to scalar modes. The responses of the (22) and the (31) channels are the same with the (11) and the (23) channels, respectively, up to $\pi/2$ rotation along the $z$-axis. The (33) channel is not shown as this is not used in sensitivity calculation. Combined (total) responses of all 5 channels are also depicted. The total responses show the omnidirectional nature of SOGRO; however, the total response of a terrestrial SOGRO to the $\ell$ mode vanishes in the direction of $z$-axis. In the last column, the general responses of a laser interferometer such as LIGO, Virgo or KAGRA are presented for comparison.
Responses of each channel in the SOGRO detector for plus ($+$), cross ($\times$), $x$, $y$, breathing ($b$), and longitudinal ($\ell$) polarization modes. The $+$ and $\times$ polarizations correspond to tensor modes, the $x$ and $y$ are vector modes, and the $b$ and $\ell$ polarizations are relevant to scalar modes. The responses of the (22) and the (31) channels are the same with the (11) and the (23) channels, respectively, up to $\pi/2$ rotation along the $z$-axis. The (33) channel is not shown as this is not used in sensitivity calculation. Combined (total) responses of all 5 channels are also depicted. The total responses show the omnidirectional nature of SOGRO; however, the total response of a terrestrial SOGRO to the $\ell$ mode vanishes in the direction of $z$-axis. In the last column, the general responses of a laser interferometer such as LIGO, Virgo or KAGRA are presented for comparison.
Responses of each channel in the SOGRO detector for plus ($+$), cross ($\times$), $x$, $y$, breathing ($b$), and longitudinal ($\ell$) polarization modes. The $+$ and $\times$ polarizations correspond to tensor modes, the $x$ and $y$ are vector modes, and the $b$ and $\ell$ polarizations are relevant to scalar modes. The responses of the (22) and the (31) channels are the same with the (11) and the (23) channels, respectively, up to $\pi/2$ rotation along the $z$-axis. The (33) channel is not shown as this is not used in sensitivity calculation. Combined (total) responses of all 5 channels are also depicted. The total responses show the omnidirectional nature of SOGRO; however, the total response of a terrestrial SOGRO to the $\ell$ mode vanishes in the direction of $z$-axis. In the last column, the general responses of a laser interferometer such as LIGO, Virgo or KAGRA are presented for comparison.
: $h_{ij}$ only
: SNR: 167.9
: SNR: 83.94
: SNR: 55.96
: SNR: 41.97
: SNR: 33.57
Amplitude spectral densities (ASDs) of pSOGRO, SOGRO, and aSOGRO are overlaid with the expected signals from BBHs with different masses. The inclinations of BBHs are assumed to be zero (face-on). GW150914 signal is based on its observed masses and distance given in the literature\cite{GWTC1}. GW190426\_190642-like source is a BBH whose masses are adopted from GW190426\_190642 (105.5 and 76.0 M$_{\odot}$) but located at 500 Mpc which is closer than its actual distance (4.58 Gpc)\cite{GWTC2-1}. For the BBHs with IMBH, the masses and distances are assumed to be as indicated in the figure.
Horizon distances versus the total mass of BBHs based on the sensitivities of pSOGRO (green), SOGRO (orange), and aSOGRO (blue), respectively. We consider the cases where the mass ratios are $m_{1}/m_{2} = 1$ and 10, and additionally when the secondary mass is fixed to be 30M$_{\odot}$. All BBHs are assumed to be face-on and $\rho=8$.
Left: Expected GW signal from an equal-mass (1 M$_{\odot}$) BBH coalescence and the sensitivity curves of aLIGO, eLISA, and aSOGRO. Right: Horizon distance with respect to the total mass of BBHs when the mass ratio is one. The curve is based on the fixed SNR $\rho=8$.
Power-law integrated (PI) sensitivity curves for different detectors for SGWB. In addition, theoretical predictions and constraints are shown. The two-detector configurations with SOGRO (blue dotted line) and aSOGRO (orange dotted line) are presented in a frequency range of $0.1\,\mathrm{Hz}\leq f\leq10\,\mathrm{Hz}$.
We compare expected sensitivities for SGWB observation considering network of N detectors. We present results for networks consisting of N SOGRO's or N aSOGRO's. We assume that SGWB follows the power-law model with $\alpha=0$.
Platform thermal strain noises of pSOGRO for the first six lowest XX-modes (solid) and first two lowest XY-modes (dashed). $T_{\rm pl}=0.1$ K and $Q_{\rm pl}=10^6$. The upper-most curve is the sum.
Sketch of the pSOGRO's cooling system. All system is in a vacuum isolated in the cryostat. Radiation heat load from room temperature (R.T., 300 K) is shielded by 80 K liquid nitrogen shield plate. The platform is in the 4 K chamber and cooled by 4 K surface through helium heat exchange gas.
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