School of Engineering, Computer and Mathematical Sciences - Te Kura Mātai Pūhanga, Rorohiko, Pāngarau

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AUT is home to a number of renowned research institutes in engineering, and computer and mathematical sciences. The School of Engineering, Computer and Mathematical Sciences strong industry partnerships and the unique combination of engineering, computer and mathematical sciences within one school stimulates interdisciplinary research beyond traditional boundaries. Current research interests include:
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Browsing School of Engineering, Computer and Mathematical Sciences - Te Kura Mātai Pūhanga, Rorohiko, Pāngarau by Subject "0201 Astronomical and Space Sciences"

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    A Linear Relation between the Color Stretch sBV and the Rising Color Slope s0*(B−V) of Type Ia Supernovae
    (American Astronomical Society, 2023-04-05) Chen, Ping; Dong, Subo; Ashall, Chris; Benetti, S; Bersier, D; Bose, S; Brimacombe, Joseph; Brink, Thomas G; Buckley, David AH; Cappellaro, Enrico; Christie, Grant W; Elias-Rosa, N; Filippenko, Alexei V; Gromadzki, Mariusz; Holoien, Thomas W-S; Hu, Shaoming; Kochanek, CS; Koff, Robert; Kollmeier, Juna A; Lundqvist, P; Mattila, S; Milne, Peter A; Muñoz, JA; Mutel, Robert; Natusch, Tim; Nicolas, Joel; Pastorello, A; Prentice, Simon; Prieto, JL; Roth, Tyler; Shappee, BJ; Stone, Geoffrey; Stanek, KZ; Stritzinger, MD; Thompson, Todd A; Tomasella, Lina; Villanueva, Steven
    Using data from the Complete Nearby (redshift zhost < 0.02) sample of Type Ia Supernovae (CNIa0.02), we find a linear relation between two parameters derived from the B − V color curves of Type Ia supernovae: the color stretch sBV and the rising color slope ${s}_{0}^{* }(B-V)$ after the peak, and this relation applies to the full range of sBV. The sBV parameter is known to be tightly correlated with the peak luminosity, especially for fast decliners (dim Type Ia supernovae), and the luminosity correlation with sBV is markedly better than with the classic light-curve width parameters such as Δm15(B). Thus, our new linear relation can be used to infer peak luminosity from ${s}_{0}^{* }$. Unlike sBV (or Δm15(B)), the measurement of ${s}_{0}^{* }(B-V)$ does not rely on a well-determined time of light-curve peak or color maximum, making it less demanding on the light-curve coverage than past approaches.
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    A Monitoring Campaign (2013–2020) of ESA’s Mars Express to Study Interplanetary Plasma Scintillation
    (Cambridge University Press (CUP), 2023-04-12) Kummamuru, P; Molera Calvés, G; Cimò, G; Pogrebenko, SV; Bocanegra-Bahamón, TM; Duev, DA; Md Said, MD; Edwards, J; Ma, M; Quick, J; Neidhardt, A; De Vicente, P; Haas, R; Kallunki, J; MacCaferri, G; Colucci, G; Yang, WJ; Hao, LF; Weston, S; Kharinov, MA; Mikhailov, AG; Jung, T
    The radio signal transmitted by the Mars Express (MEX) spacecraft was observed regularly between the years 2013-2020 at X-band (8.42 GHz) using the European Very Long Baseline Interferometry (EVN) network and University of Tasmania's telescopes. We present a method to describe the solar wind parameters by quantifying the effects of plasma on our radio signal. In doing so, we identify all the uncompensated effects on the radio signal and see which coronal processes drive them. From a technical standpoint, quantifying the effect of the plasma on the radio signal helps phase referencing for precision spacecraft tracking. The phase fluctuation of the signal was determined for Mars' orbit for solar elongation angles from 0 to 180 deg. The calculated phase residuals allow determination of the phase power spectrum. The total electron content of the solar plasma along the line of sight is calculated by removing effects from mechanical and ionospheric noises. The spectral index was determined as which is in agreement with Kolmogorov's turbulence. The theoretical models are consistent with observations at lower solar elongations however at higher solar elongation ($ ]]>160 deg) we see the observed values to be higher. This can be caused when the uplink and downlink signals are positively correlated as a result of passing through identical plasma sheets.
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    Gaia22dkvLb: A Microlensing Planet Potentially Accessible to Radial-velocity Characterization
    (American Astronomical Society, 2024-07-09) Wu, Z; Dong, S; Yi, T; Liu, Z; El-Badry, K; Gould, A; Wyrzykowski, L; Rybicki, KA; Bachelet, E; Christie, GW; de Almeida, L; Monard, LAG; McCormick, J; Natusch, T; Zieliński, P; Chen, H; Huang, Y; Liu, C; Mérand, A; Mróz, P; Shangguan, J; Udalski, A; Woillez, J; Zhang, H; Hambsch, FJ; Mikołajczyk, PJ; Gromadzki, M; Ratajczak, M; Kruszyńska, K; Ihanec, N; Pylypenko, U; Sitek, M; Howil, K; Zola, S; Michniewicz, O; Zejmo, M; Lewis, F; Bronikowski, M; Potter, S; Andrzejewski, J; Merc, J; Street, R; Fukui, A; Figuera Jaimes, R; Bozza, V; Rota, P; Cassan, A; Dominik, M; Tsapras, Y; Hundertmark, M; Wambsganss, J; Bąkowska, K; Słowikowska, A
    We report discovering an exoplanet from following up a microlensing event alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the traditional bulge microlensing fields. Our primary analysis yields a Jovian planet with M p = 0.59 − 0.05 + 0.15 M J at a projected orbital separation r ⊥ = 1.4 − 0.3 + 0.8 au, and the host is a ∼1.1 M ⊙ turnoff star at ∼1.3 kpc. At r ′ ≈ 14 , the host is far brighter than any previously discovered microlensing planet host, opening up the opportunity to test the microlensing model with radial velocity (RV) observations. RV data can be used to measure the planet’s orbital period and eccentricity, and they also enable searching for inner planets of the microlensing cold Jupiter, as expected from the “inner-outer correlation” inferred from Kepler and RV discoveries. Furthermore, we show that Gaia astrometric microlensing will not only allow precise measurements of its angular Einstein radius θ E but also directly measure the microlens parallax vector and unambiguously break a geometric light-curve degeneracy, leading to the definitive characterization of the lens system.
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    Inverse MultiView. II. Microarcsecond Trigonometric Parallaxes for Southern Hemisphere 6.7GHz Methanol Masers G232.62+00.99 and G323.74–00.26
    (American Astronomical Society, 2023-07-28) Hyland, LJ; Reid, MJ; Orosz, G; Ellingsen, SP; Weston, SD; Kumar, J; Dodson, R; Rioja, MJ; Hankey, WJ; Yates-Jones, PM; Natusch, T; Gulyaev, S; Menten, KM; Brunthaler, A
    We present the first results from the Southern Hemisphere Parallax Interferometric Radio Astrometry Legacy Survey: 10 μas accurate parallaxes and proper motions for two Southern Hemisphere 6.7 GHz methanol masers obtained using the inverse MultiView calibration method. Using an array of radio telescopes in Australia and New Zealand, we measured trigonometric parallaxes and proper motions for the masers associated with the star formation region G232.62+00.99 of π = 0.610 ± 0.011 mas, μx = −2.266 ± 0.021 mas yr−1, and μy = 2.249 ± 0.049 mas yr−1, which implies its distance to be d = 1.637 ± 0.029 kpc. These measurements represent an improvement in accuracy by more than a factor of 3 over the previous measurements obtained through Very Long Baseline Array observations of the 12 GHz methanol masers associated with this region. We also measure the trigonometric parallax and proper motion for G323.74–00.26 as π = 0.364 ± 0.009 mas, μx = −3.239 ± 0.025 mas yr−1, and μy = − 3.976 ± 0.039 mas yr−1, which implies a distance of d = 2.747 ± 0.068 kpc. These are the most accurate measurements of trigonometric parallax obtained for 6.7 GHz class II methanol masers to date. We confirm that G232.62+00.99 is in the Local Arm and find that G323.74–00.26 is in the Scutum–Centaurus arm. We also investigate the structure and internal dynamics of both masers.
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    KMT-2021-BLG-2010Lb, KMT-2022-BLG-0371Lb, and KMT-2022-BLG-1013Lb: Three Microlensing Planets Detected via Partially Covered Signals
    (EDP Sciences, 2023-06-07) Han, Cheongho; Lee, Chung-Uk; Zang, Weicheng; Jung, Youn Kil; Christie, Grant W; Zhang, Jiyuan; Albrow, Michael D; Chung, Sun-Ju; Gould, Andrew; Hwang, Kyu-Ha; Kim, Doeon; Ryu, Yoon-Hyun; Shin, In-Gu; Shvartzvald, Yossi; Yang, Hongjing; Yee, Jennifer C; Cha, Sang-Mok; Kim, Dong-Jin; Kim, Seung-Lee; Lee, Dong-Joo; Lee, Yongseok; Park, Byeong-Gon; Pogge, Richard W; Natusch, Tim; Mao, Shude; Maoz, Dan; Penny, Matthew T; Zhu, Wei
    Aims. We inspect the four microlensing events KMT-2021-BLG-1968, KMT-2021-BLG-2010, KMT-2022-BLG-0371, and KMT-2022-BLG-1013, for which the light curves exhibit partially covered short-term central anomalies. We conduct detailed analyses of the events with the aim of revealing the nature of the anomalies. Methods. We tested various models that can explain the anomalies of the individual events, including the binary-lens (2L1S) and binary-source (1L2S) interpretations. Under the 2L1S interpretation, we thoroughly inspected the parameter space to determine the existence of degenerate solutions, and if they existed, we tested whether the degeneracy could be resolved. Results. We find that the anomalies in KMT-2021-BLG-2010 and KMT-2022-BLG-1013 are uniquely defined by planetary-lens interpretations with planet-to-host mass ratios of q ~ 2.8 × 10−3 and ~1.6 × 10−3, respectively. For KMT-2022-BLG-0371, a planetary solution with a mass ratio q ~ 4 × 10−4 is strongly favored over the other three degenerate 2L1S solutions with different mass ratios based on the χ2 and relative proper motion arguments, and a 1L2S solution is clearly ruled out. For KMT-2021-BLG-1968, on the other hand, we find that the anomaly can be explained either by a planetary or a binary-source interpretation, making it difficult to firmly identify the nature of the anomaly. From the Bayesian analyses of the identified planetary events, we estimate that the masses of the planet and host are (Mp/MJ, Mh/M⊙) = (1.07−0.68+1.15, 0.37−0.23+0.40), (0.26−0.11+0.13, 0.63−0.28+0.32), and (0.31−0.16+0.46, 0.18−0.10+0.28) for KMT-2021-BLG-2010L, KMT-2022-BLG-0371L, and KMT-2022-BLG-1013L, respectively.
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    MOA-2020-BLG-208Lb: Cool Sub-Saturn-Mass Planet Within Predicted Desert
    (American Astronomical Society, 2023-03-24) Olmschenk, G; Bennett, DP; Bond, IA; Zang, W; Jung, YK; Yee, JC; Bachelet, E; Abe, F; Barry, RK; Bhattacharya, A; Fujii, H; Fukui, A; Hirao, Y; Silva, SI; Itow, Y; Kirikawa, R; Kondo, I; Koshimoto, N; Matsubara, Y; Matsumoto, S; Miyazaki, S; Munford, B; Muraki, Y; Okamura, A; Ranc, C; Rattenbury, NJ; Satoh, Y; Sumi, T; Suzuki, D; Toda, T; Tristram, PJ; Vandorou, A; Yama, H; Albrow, MD; Cha, SM; Chung, SJ; Gould, A; Han, C; Hwang, KH; Kim, DJ; Kim, HW; Kim, SL; Lee, CU; Lee, DJ; Lee, Y; Park, BG; Pogge, RW; Ryu, YH; Shin, IG; Shvartzvald, Y; Christie, G; Cooper, T; Drummond, J; Green, J; Hennerley, S; McCormick, J; Monard, LAG; Natusch, T; Porritt, I; Tan, TG; Mao, S; Maoz, D; Penny, MT; Zhu, W; Bozza, V; Cassan, A; Dominik, M; Hundertmark, M; Jaimes, RF; Kruszyńska, K; Rybicki, KA; Street, RA; Tsapras, Y; Wambsganss, J; Wyrzykowski; Zieliński, P; Rau, G
    We analyze the MOA-2020-BLG-208 gravitational microlensing event and present the discovery and characterization of a new planet, MOA-2020-BLG-208Lb, with an estimated sub-Saturn mass. With a mass ratio q=3.17-0.26+0.28×10-4, the planet lies near the peak of the mass-ratio function derived by the MOA collaboration and near the edge of expected sample sensitivity. For these estimates we provide results using two mass-law priors: one assuming that all stars have an equal planet-hosting probability, and the other assuming that planets are more likely to orbit around more massive stars. In the first scenario, we estimate that the lens system is likely to be a planet of mass mplanet=46-24+42M⊕ and a host star of mass Mhost=0.43-0.23+0.39M⊙, located at a distance DL=7.49-1.13+0.99kpc . For the second scenario, we estimate mplanet=69-34+37M⊕, Mhost=0.66-0.32+0.35M⊙, and DL=7.81-0.93+0.93kpc . The planet has a projected separation as a fraction of the Einstein ring radius s=1.3807-0.0018+0.0018 . As a cool sub-Saturn-mass planet, this planet adds to a growing collection of evidence for revised planetary formation models.
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    Reducing Instrumental Errors in Parkes Pulsar Timing Array Data
    (American Astronomical Society, 2024-09-23) Rogers, Axl F; van Straten, Willem; Gulyaev, Sergei; Parthasarathy, Aditya; Hobbs, George; Chen, Zu-Cheng; Feng, Yi; Goncharov, Boris; Kapur, Agastya; Liu, Xiaojin; Reardon, Daniel; Russell, Christopher J; Zic, Andrew
    This paper demonstrates the impact of state-of-the-art instrumental calibration techniques on the precision of arrival times obtained from 9.6 yr of observations of millisecond pulsars using the Murriyang 64 m CSIRO Parkes Radio Telescope. Our study focuses on 21 cm observations of 25 high-priority pulsars that are regularly observed as part of the Parkes Pulsar Timing Array project, including those predicted to be the most susceptible to calibration errors. We employ measurement equation template matching (METM) for instrumental calibration and matrix template matching (MTM) for arrival time estimation, resulting in significantly improved timing residuals with up to a sixfold reduction in white noise compared to arrival times estimated using scalar template matching and conventional calibration based on the ideal feed assumption. The median relative reduction in white noise is 33%, and the maximum absolute reduction is 4.5 μs. For PSR J0437−4715, METM and MTM reduce the best-fit power-law amplitude (2.7σ) and spectral index (1.7σ) of the red noise in the arrival time residuals, which can be tentatively interpreted as mitigation of 1/f noise due to otherwise unmodeled steps in polarimetric response. These findings demonstrate the potential to directly enhance the sensitivity of pulsar timing array experiments through more accurate methods of instrumental calibration and arrival time estimation.
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    Systematic KMTNet Planetary Anomaly Search. VIII. Complete Sample of 2019 Subprime Field Planets
    (American Astronomical Society, 2023-05-04) Jung, YK; Zang, W; Wang, H; Han, C; Gould, A; Udalski, A; Zhu, W; Albrow, MD; Chung, SJ; Hwang, KH; Ryu, YH; Shin, IG; Shvartzvald, Y; Yang, H; Yee, JC; Cha, SM; Kim, DJ; Kim, SL; Lee, CU; Lee, DJ; Lee, Y; Park, BG; Pogge, RW; Maoz, D; Szymański, MK; Skowron, J; Poleski, R; Soszyński, I; Pietrukowicz, P; Kozłowski, S; Ulaczyk, K; Rybicki, KA; Iwanek, P; Wrona, M; Porritt, I; Green, J; Hennerley, S; Marmont, A; Mao, S; Natusch, T; Penny, MT; Natusch, T
    We complete the publication of all microlensing planets (and “possible planets”) identified by the uniform approach of the KMT AnomalyFinder system in the 21 KMT subprime fields during the 2019 observing season, namely, KMT-2019-BLG-0298, KMT-2019-BLG-1216, KMT-2019-BLG-2783, OGLE-2019-BLG-0249, and OGLE-2019-BLG-0679 (planets), as well as OGLE-2019-BLG-0344 and KMT-2019-BLG-0304 (possible planets). The five planets have mean log mass ratio measurements of (−2.6, −3.6, −2.5, −2.2, −2.3), median mass estimates of (1.81, 0.094, 1.16, 7.12, 3.34) M Jup, and median distance estimates of (6.7, 2.7, 5.9, 6.4, 5.6) kpc, respectively. The main scientific interest of these planets is that they complete the AnomalyFinder sample for 2019, which has a total of 25 planets that are likely to enter the statistical sample. We find statistical consistency with the previously published 33 planets from the 2018 AnomalyFinder analysis according to an ensemble of five tests. Of the 58 planets from 2018-2019, 23 were newly discovered by AnomalyFinder. Within statistical precision, half of the planets have caustic crossings, while half do not; an equal number of detected planets result from major- and minor-image light-curve perturbations; and an equal number come from KMT prime fields versus subprime fields.
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    VLBI Astrometry on the White Dwarf Pulsar AR Scorpii
    (Oxford University Press (OUP), 2023-01-30) Jiang, Pengfei; Cui, Lang; Yang, Jun; Zhang, Bo; Xu, Shuangjing; Shu, Fengchun; Jiang, Wu; Chen, Wen; Li, Guanghui; Xia, Bo; Weston, Stuart; Gulyaev, Sergei; Cao, Hongmin; Liu, Xiang; An, Tao
    Abstract AR Scorpii (AR Sco), the only-known radio-pulsing white dwarf binary, shows unusual pulsating emission at the radio, infrared, optical, and ultraviolet bands. To determine its astrometric parameters at the radio band independently, we conducted multi-epoch Very Long Baseline Interferometry (VLBI) phase-referencing observations with the European VLBI Network at 5 GHz and the Chinese VLBI Network plus the Warkworth 30-m telescope (New Zealand) at 8.6 GHz. By using the differential VLBI astrometry, we provide high-precision astrometric measurements on the parallax ($\pi =8.52_{-0.07}^{+0.04}$ mas) and proper motion ($\mu _{\alpha }=9.48_{-0.07}^{+0.04}$ mas yr−1, $\mu _{\delta }=-51.32_{-0.38}^{+0.22}$ mas yr−1). The new VLBI results agree with the optical Gaia astrometry. Our kinematic analysis reveals that the Galactic space velocities of AR Sco are quite consistent with that of both intermediate polars and polars. Combined with the previous tightest VLBI constraint on the size, our parallax distance suggests that the radio emission of AR Sco should be located within the light cylinder of its white dwarf.
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    γ-ray Emission in Radio Galaxies Under the VLBI Scope
    (EDP Sciences, 2020-09-23) Angioni, R; Ros, E; Kadler, M; Ojha, R; Müller, C; Edwards, PG; Burd, PR; Carpenter, B; Dutka, MS; Gulyaev, S; Hase, H; Horiuchi, S; Krauß, F; Lovell, JEJ; Natusch, T; Phillips, C; Plötz, C; Quick, JFH; Rösch, F; Schulz, R; Stevens, J; Tzioumis, AK; Weston, S; Wilms, J; Zensus, JA
    Aims. This is the second paper in our series studying the evolution of parsec-scale radio emission in radio galaxies in the Southern Hemisphere. Following our study of the radio and high-energy properties of γ-ray-emitting sources, here we investigate the kinematic and spectral properties of the parsec-scale jets of radio galaxies that have not yet been detected by the Fermi Large Area Telescope (Fermi-LAT) instrument on board NASA’s Fermi Gamma-ray Space Telescope. For many sources, these results represent the first milliarcsecond resolution information in the literature. These studies were conducted within the framework of the Tracking Active Nuclei with Austral Milliarcsecond Interferometry (TANAMI) monitoring program and in the context of high-energy γ-ray observations from Fermi-LAT. Methods. We took advantage of the regular 8.4 GHz and 22.3 GHz Very Long Baseline Interferometry (VLBI) observations provided by the TANAMI monitoring program, and explored the kinematic properties of six γ-ray-faint radio galaxies. We complemented this with ∼8.5 years of Fermi-LAT data, deriving updated upper limits on the γ-ray emission from this subsample of TANAMI radio galaxies. We included publicly available VLBI kinematics of γ-ray-quiet radio galaxies monitored by the MOJAVE program and performed a consistent Fermi-LAT analysis. We combined these results with those from our previous paper to construct the largest sample of radio galaxies with combined VLBI and γ-ray measurements to date. The connection between parsec-scale jet emission and high-energy properties in the misaligned jets of radio galaxies was explored. Results. For the first time, we report evidence of superluminal motion up to βapp = 3.6 in the jet of the γ-ray-faint radio galaxy PKS 2153−69. We find a clear trend of higher apparent speed as a function of distance from the jet core, which indicates that the jet is still being accelerated on scales of tens of parsecs, or ∼105 Rs, corresponding to the end of the collimation and acceleration zone in nearby radio galaxies. We find evidence of subluminal apparent motion in the jets of PKS 1258−321 and IC 4296, and no measurable apparent motion for PKS 1549−79, PKS 1733−565, and PKS 2027−308. For all these sources, TANAMI provides the first multi-epoch kinematic analysis on parsec scales. We then compare the VLBI properties of γ-ray-detected and undetected radio galaxies, and find that the two populations show a significantly different distribution of median core flux density, and, possibly, of median core brightness temperature. In terms of correlation between VLBI and γ-ray properties, we find a significant correlation between median core flux density and γ-ray flux, but no correlation with typical Doppler boosting indicators such as median core brightness temperature and core dominance. Conclusions. Our study suggests that high-energy emission from radio galaxies is related to parsec-scale radio emission from the inner jet, but is not driven by Doppler boosting effects, in contrast to the situation in their blazar counterparts. This implies that γ-ray loudness does not necessarily reflect a higher prevalence of boosting effects.
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