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Designing trajectories in the Earth-Moon system: a Levenberg-Marquardt approach
Authors:
António Nunes,
Sérgio Brás,
Pedro Batista,
João Xavier
Abstract:
Trajectory design in cislunar space under a High-Fidelity Ephemeris Model (HFEM) is pursued through a nonlinear optimization perspective anchored on the transition of solutions from lower fidelity models, namely the Circular Restricted Three-Body Problem (CR3BP). The optimization problem is posed in the likeness of a multiple-shooting approach, aiming for segment-to-segment continuity while tracki…
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Trajectory design in cislunar space under a High-Fidelity Ephemeris Model (HFEM) is pursued through a nonlinear optimization perspective anchored on the transition of solutions from lower fidelity models, namely the Circular Restricted Three-Body Problem (CR3BP). The optimization problem is posed in the likeness of a multiple-shooting approach, aiming for segment-to-segment continuity while tracking proximity to the original CR3BP structures. The analysis of various formulations leads to the selection of an unconstrained least-squares problem for further investigation. The nonlinear optimization problem is convexified and the use of the Levenberg-Marquardt algorithm, as an alternative to the minimum-norm update equation found in most literature, is investigated for its control over the update step and inherent robustness. Additional techniques such as adaptive weighting are employed to further consolidate the behavior of the proposed algorithm in challenging scenarios. Numerical trials evaluate the adequacy of the methodology presented and compare it to the minimum-norm baseline over various application cases, including the generation of quasi-periodic trajectories and orbital transfers between them. The proposed approach is found to outperform the baseline in applications where the initial guess is poor and the ease of including proximity constraints provides benefits in control over the shape of the converged solution.
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Submitted 21 October, 2025;
originally announced October 2025.
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Combined dark matter search towards dwarf spheroidal galaxies with Fermi-LAT, HAWC, H.E.S.S., MAGIC, and VERITAS
Authors:
Fermi-LAT Collaboration,
:,
S. Abdollahi,
L. Baldini,
R. Bellazzini,
B. Berenji,
E. Bissaldi,
R. Bonino,
P. Bruel,
S. Buson,
E. Charles,
A. W. Chen,
S. Ciprini,
M. Crnogorcevic,
A. Cuoco,
F. D'Ammando,
A. de Angelis,
M. Di Mauro,
N. Di Lalla,
L. Di Venere,
A. Domínguez,
S. J. Fegan,
A. Fiori,
P. Fusco,
V. Gammaldi
, et al. (582 additional authors not shown)
Abstract:
Dwarf spheroidal galaxies (dSphs) are excellent targets for indirect dark matter (DM) searches using gamma-ray telescopes because they are thought to have high DM content and a low astrophysical background. The sensitivity of these searches is improved by combining the observations of dSphs made by different gamma-ray telescopes. We present the results of a combined search by the most sensitive cu…
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Dwarf spheroidal galaxies (dSphs) are excellent targets for indirect dark matter (DM) searches using gamma-ray telescopes because they are thought to have high DM content and a low astrophysical background. The sensitivity of these searches is improved by combining the observations of dSphs made by different gamma-ray telescopes. We present the results of a combined search by the most sensitive currently operating gamma-ray telescopes, namely: the satellite-borne Fermi-LAT telescope; the ground-based imaging atmospheric Cherenkov telescope arrays H.E.S.S., MAGIC, and VERITAS; and the HAWC water Cherenkov detector. Individual datasets were analyzed using a common statistical approach. Results were subsequently combined via a global joint likelihood analysis. We obtain constraints on the velocity-weighted cross section $\langle σ\mathit{v} \rangle$ for DM self-annihilation as a function of the DM particle mass. This five-instrument combination allows the derivation of up to 2-3 times more constraining upper limits on $\langle σ\mathit{v} \rangle$ than the individual results over a wide mass range spanning from 5 GeV to 100 TeV. Depending on the DM content modeling, the 95% confidence level observed limits reach $1.5\times$10$^{-24}$ cm$^3$s$^{-1}$ and $3.2\times$10$^{-25}$ cm$^3$s$^{-1}$, respectively, in the $τ^+τ^-$ annihilation channel for a DM mass of 2 TeV.
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Submitted 27 August, 2025;
originally announced August 2025.
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Prospects for dark matter observations in dwarf spheroidal galaxies with the Cherenkov Telescope Array Observatory
Authors:
K. Abe,
S. Abe,
J. Abhir,
A. Abhishek,
F. Acero,
A. Acharyya,
R. Adam,
A. Aguasca-Cabot,
I. Agudo,
A. Aguirre-Santaella,
J. Alfaro,
R. Alfaro,
C. Alispach,
R. Alves Batista,
J. -P. Amans,
E. Amato,
G. Ambrosi,
D. Ambrosino,
F. Ambrosino,
L. Angel,
L. A. Antonelli,
C. Aramo,
C. Arcaro,
K. Asano,
Y. Ascasibar
, et al. (469 additional authors not shown)
Abstract:
The dwarf spheroidal galaxies (dSphs) orbiting the Milky Way are widely regarded as systems supported by velocity dispersion against self-gravity, and as prime targets for the search for indirect dark matter (DM) signatures in the GeV-to-TeV $γ$-ray range owing to their lack of astrophysical $γ$-ray background. We present forecasts of the sensitivity of the forthcoming Cherenkov Telescope Array Ob…
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The dwarf spheroidal galaxies (dSphs) orbiting the Milky Way are widely regarded as systems supported by velocity dispersion against self-gravity, and as prime targets for the search for indirect dark matter (DM) signatures in the GeV-to-TeV $γ$-ray range owing to their lack of astrophysical $γ$-ray background. We present forecasts of the sensitivity of the forthcoming Cherenkov Telescope Array Observatory (CTAO) to annihilating or decaying DM signals in these targets. An original selection of candidates is performed from the current catalogue of known objects, including both classical and ultra-faint dSphs. For each, the expected DM content is derived using the most comprehensive photometric and spectroscopic data available, within a consistent framework of analysis. This approach enables the derivation of novel astrophysical factor profiles for indirect DM searches, which are compared with results from the literature. From an initial sample of 64 dSphs, eight promising targets are identified -- Draco I, Coma Berenices, Ursa Major II, Ursa Minor and Willman 1 in the North, Reticulum II, Sculptor and Sagittarius II in the South -- for which different DM density models yield consistent expectations, leading to robust predictions. CTAO is expected to provide the strongest limits above $\sim$10 TeV, reaching velocity-averaged annihilation cross sections of $\sim$5$\times$10$^{-25}$ cm$^3$ s$^{-1}$ and decay lifetimes up to $\sim$10$^{26}$ s for combined limits. The dominant uncertainties arise from the imprecise determination of the DM content, particularly for ultra-faint dSphs. Observation strategies are proposed that optimise either deep exposures of the best candidates or diversified target selections.
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Submitted 13 October, 2025; v1 submitted 26 August, 2025;
originally announced August 2025.
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Science Prospects for the Southern Wide-field Gamma-ray Observatory: SWGO
Authors:
SWGO Collaboration,
P. Abreu,
R. Alfaro,
A. Alfonso,
M. Andrade,
E. O. Angüner,
E. A. Anita-Rangel,
O. Aquines-Gutiérrez,
C. Arcaro,
R. Arceo,
J. C. Arteaga-Velázquez,
P. Assis,
H. A. Ayala Solares,
A. Bakalova,
E. M. Bandeira,
P. Bangale,
U. Barres de Almeida,
P. Batista,
I. Batković,
J. Bazo,
E. Belmont,
J. Bennemann,
S. Y. BenZvi,
A. Bernal,
W. Bian
, et al. (295 additional authors not shown)
Abstract:
Ground-based gamma-ray astronomy is now well established as a key observational approach to address critical topics at the frontiers of astroparticle physics and high-energy astrophysics. Whilst the field of TeV astronomy was once dominated by arrays of atmospheric Cherenkov Telescopes, ground-level particle detection has now been demonstrated to be an equally viable and strongly complementary app…
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Ground-based gamma-ray astronomy is now well established as a key observational approach to address critical topics at the frontiers of astroparticle physics and high-energy astrophysics. Whilst the field of TeV astronomy was once dominated by arrays of atmospheric Cherenkov Telescopes, ground-level particle detection has now been demonstrated to be an equally viable and strongly complementary approach. Ground-level particle detection provides continuous monitoring of the overhead sky, critical for the mapping of extended structures and capturing transient phenomena. As demonstrated by HAWC and LHAASO, the technique provides the best available sensitivity above a few tens of TeV, and for the first time access to the PeV energy range. Despite the success of this approach, there is so far no major ground-level particle-based observatory with access to the Southern sky. HESS, located in Namibia, is the only major gamma-ray instrument in the Southern Hemisphere, and has shown the extraordinary richness of the inner galaxy in the TeV band, but is limited in terms of field of view and energy reach.
SWGO is an international effort to construct the first wide-field instrument in the south with deep sensitivity from 100s of GeV into the PeV domain. The project is now close to the end of its development phase and planning for construction of the array in Chile has begun. Here we describe the baseline design, expected sensitivity and resolution, and describe in detail the main scientific topics that will be addressed by this new facility and its initial phase SWGO-A. We show that SWGO will have a transformational impact on a wide range of topics from cosmic-ray acceleration and transport to the nature of dark matter. SWGO represents a key piece of infrastructure for multi-messenger astronomy in the next decade, with strong scientific synergies with the nearby CTA Observatory.
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Submitted 25 June, 2025; v1 submitted 2 June, 2025;
originally announced June 2025.
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On gamma rays as predictors of UHECR flux in AGNs
Authors:
Cainã de Oliveira,
Rodrigo Guedes Lang,
Pedro Batista
Abstract:
Active galactic nuclei (AGN) are among the main candidates for ultra-high-energy cosmic ray (UHECR) sources. However, while some theoretical and phenomenological works favor AGNs as the main sources, recent works have shown that using the very-high-energy (VHE) $γ$-ray flux as a proxy for the UHECR flux leads to a bad agreement with data. In this context, the energy spectrum and composition data a…
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Active galactic nuclei (AGN) are among the main candidates for ultra-high-energy cosmic ray (UHECR) sources. However, while some theoretical and phenomenological works favor AGNs as the main sources, recent works have shown that using the very-high-energy (VHE) $γ$-ray flux as a proxy for the UHECR flux leads to a bad agreement with data. In this context, the energy spectrum and composition data are hardly fitted. At the same time, the arrival directions map is badly described and a spurious dipole direction is produced. In this work, we propose a possible solution to these contradictions. Using the observed $γ$-ray flux as a proxy may carry the implicit assumption of beamed UHECR emission and, consequently, its beam will remain collimated up to its detection on Earth. We show that assuming an isotropic UHECR emission and correcting the $γ$-ray emission proxy by Doppler boosting can overcome the problem. The combined fit of the spectrum and composition is improved, with a change of reduced $χ^2$ from 4.6 to 3.1. In particular, the tension between the observed and modeled dipole directions can be reduced from $5.9 \ (2.1)σ$ away from the data to $3.5 \ (1.1)σ$ for $E > 8$ EeV ($E > 32$ EeV). We also show that this effect is particularly important when including AGNs of different classes in the same analysis, such as radio galaxies and blazars.
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Submitted 29 January, 2025; v1 submitted 21 August, 2024;
originally announced August 2024.
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An indirect search for dark matter with a combined analysis of dwarf spheroidal galaxies from VERITAS
Authors:
A. Acharyya,
C. B. Adams,
P. Bangale,
J. T. Bartkoske,
P. Batista,
W. Benbow,
J. L. Christiansen,
A. J. Chromey,
A. Duerr,
M. Errando,
A. Falcone,
Q. Feng,
G. M. Foote,
L. Fortson,
A. Furniss,
W. Hanlon,
D. Hanna,
O. Hervet,
C. E. Hinrichs,
J. Holder,
T. B. Humensky,
W. Jin,
M. N. Johnson,
P. Kaaret,
M. Kertzman
, et al. (37 additional authors not shown)
Abstract:
Understanding the nature and identity of dark matter is a key goal in the physics community. In the case that TeV-scale dark matter particles decay or annihilate into standard model particles, very-high-energy (VHE) gamma rays (greater than 100 GeV) will be present in the final state. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an imaging atmospheric Cherenkov telescop…
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Understanding the nature and identity of dark matter is a key goal in the physics community. In the case that TeV-scale dark matter particles decay or annihilate into standard model particles, very-high-energy (VHE) gamma rays (greater than 100 GeV) will be present in the final state. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an imaging atmospheric Cherenkov telescope array that can indirectly detect VHE gamma rays in an energy range of 100 GeV to > 30 TeV. Dwarf spheroidal galaxies (dSphs) are ideal candidates in the search for dark matter due to their high dark matter content, high mass-to-light ratios, and their low gamma-ray fluxes from astrophysical processes. This study uses a legacy data set of 638 hours collected on 17 dSphs, built over 11 years with an observing strategy optimized according to the dark matter content of the targets. The study addresses a broad dark matter particle mass range, extending from 200 GeV to 30 PeV. In the absence of a detection, we set the upper limits on the dark matter velocity-weighted annihilation cross section.
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Submitted 6 August, 2024; v1 submitted 23 July, 2024;
originally announced July 2024.
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A multi-wavelength study to decipher the 2017 flare of the blazar OJ 287
Authors:
A. Acharyya,
C. B. Adams,
A. Archer,
P. Bangale,
J. T. Bartkoske,
P. Batista,
W. Benbow,
A. Brill,
J. P. Caldwell,
M. Carini,
J. L. Christiansen,
A. J. Chromey,
M. Errando,
A. Falcone,
Q. Feng,
J. P. Finley,
J. Foote,
L. Fortson,
A. Furniss,
G. Gallagher,
W. Hanlon,
D. Hanna,
O. Hervet,
C. E. Hinrichs,
J. Hoang
, et al. (49 additional authors not shown)
Abstract:
In February 2017, the blazar OJ~287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3-10 keV) band, as measured by Swift-XRT. This event coincides with a very-high-energy (VHE) $γ$-ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of $10σ$ (from 2016 December 9 to 2017 March 31). The time-averag…
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In February 2017, the blazar OJ~287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3-10 keV) band, as measured by Swift-XRT. This event coincides with a very-high-energy (VHE) $γ$-ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of $10σ$ (from 2016 December 9 to 2017 March 31). The time-averaged VHE $γ$-ray spectrum was consistent with a soft power law ($Γ= -3.81 \pm 0.26$) and an integral flux corresponding to $\sim2.4\%$ that of the Crab Nebula above the same energy. Contemporaneous data from multiple instruments across the electromagnetic spectrum reveal complex flaring behavior, primarily in the soft X-ray and VHE bands. To investigate the possible origin of such an event, our study focuses on three distinct activity states: before, during, and after the February 2017 peak. The spectral energy distributions during these periods suggest the presence of at least two non-thermal emission zones, with the more compact one responsible for the observed flare. Broadband modeling results and observations of a new radio knot in the jet of OJ~287 in 2017 are consistent with a flare originating from a strong recollimation shock outside the radio core.
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Submitted 26 August, 2024; v1 submitted 16 July, 2024;
originally announced July 2024.
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An Angular Diameter Measurement of $β$ UMa via Stellar Intensity Interferometry with the VERITAS Observatory
Authors:
A. Acharyya,
J. P. Aufdenberg,
P. Bangale,
J. T. Bartkoske,
P. Batista,
W. Benbow,
A. J. Chromey,
J. D. Davis,
Q. Feng,
G. M. Foote,
A. Furniss,
W. Hanlon,
C. E. Hinrichs,
J. Holder,
W. Jin,
P. Kaaret,
M. Kertzman,
D. Kieda,
T. K. Kleiner,
N. Korzoun,
T. LeBohec,
M. A. Lisa,
M. Lundy,
N. Matthews,
C. E McGrath
, et al. (22 additional authors not shown)
Abstract:
We use the VERITAS imaging air Cherenkov Telescope (IACT) array to obtain the first measured angular diameter of $β$ UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak ($β$ UMa), an A1-type subgiant…
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We use the VERITAS imaging air Cherenkov Telescope (IACT) array to obtain the first measured angular diameter of $β$ UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak ($β$ UMa), an A1-type subgiant, by comparing effective temperature and luminosity constraints to model stellar evolution tracks. Previous interferometric limb-darkened angular-diameter measurements of $β$ UMa in the near-infrared (CHARA Array, $1.149 \pm 0.014$ mas) and mid-infrared (Keck Nuller, $1.08 \pm 0.07$ mas), together with the measured parallax and bolometric flux, have constrained the effective temperature. This paper presents current VERITAS-SII observation and analysis procedures to derive squared visibilities from correlation functions. We fit the resulting squared visibilities to find a limb-darkened angular diameter of $1.07 \pm 0.04 {\rm (stat)} \pm 0.05$ (sys) mas, using synthetic visibilities from a stellar atmosphere model that provides a good match to the spectrum of $β$ UMa in the optical wave band. The VERITAS-SII limb-darkened angular diameter yields an effective temperature of $9700\pm200\pm 200$ K, consistent with ultraviolet spectrophotometry, and an age of $390\pm 29 \pm 32 $ Myr, using MESA Isochrones and Stellar Tracks (MIST). This age is consistent with $408 \pm 6$ Myr from the CHARA Array angular diameter.
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Submitted 3 January, 2024;
originally announced January 2024.
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VERITAS contributions to the 38th International Cosmic Ray Conference
Authors:
A. Acharyya,
C. B. Adams,
A. Archer,
P. Bangale,
J. T. Bartkoske,
P. Batista,
W. Benbow,
J. L. Christiansen,
A. J. Chromey,
A. Duerr,
M. Errando,
Q. Feng,
G. M. Foote,
L. Fortson,
A. Furniss,
W. Hanlon,
O. Hervet,
C. E. Hinrichs,
J. Hoang,
J. Holder,
Z. Hughes,
T. B. Humensky,
W. Jin,
M. N. Johnson,
M. Kertzman
, et al. (39 additional authors not shown)
Abstract:
Compilation of papers presented by the VERITAS Collaboration at the 38th International Cosmic Ray Conference (ICRC), held July 26 through August 3, 2023 in Nagoya, Japan.
Compilation of papers presented by the VERITAS Collaboration at the 38th International Cosmic Ray Conference (ICRC), held July 26 through August 3, 2023 in Nagoya, Japan.
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Submitted 12 December, 2023;
originally announced December 2023.
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Chasing Gravitational Waves with the Cherenkov Telescope Array
Authors:
Jarred Gershon Green,
Alessandro Carosi,
Lara Nava,
Barbara Patricelli,
Fabian Schüssler,
Monica Seglar-Arroyo,
Cta Consortium,
:,
Kazuki Abe,
Shotaro Abe,
Atreya Acharyya,
Remi Adam,
Arnau Aguasca-Cabot,
Ivan Agudo,
Jorge Alfaro,
Nuria Alvarez-Crespo,
Rafael Alves Batista,
Jean-Philippe Amans,
Elena Amato,
Filippo Ambrosino,
Ekrem Oguzhan Angüner,
Lucio Angelo Antonelli,
Carla Aramo,
Cornelia Arcaro,
Luisa Arrabito
, et al. (545 additional authors not shown)
Abstract:
The detection of gravitational waves from a binary neutron star merger by Advanced LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts of this gravitational wave event, ushered in a new era of multimessenger astronomy, providing the first direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events may also produce very…
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The detection of gravitational waves from a binary neutron star merger by Advanced LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts of this gravitational wave event, ushered in a new era of multimessenger astronomy, providing the first direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events may also produce very-high-energy (VHE, > 100GeV) photons which have yet to be detected in coincidence with a gravitational wave signal. The Cherenkov Telescope Array (CTA) is a next-generation VHE observatory which aims to be indispensable in this search, with an unparalleled sensitivity and ability to slew anywhere on the sky within a few tens of seconds. New observing modes and follow-up strategies are being developed for CTA to rapidly cover localization areas of gravitational wave events that are typically larger than the CTA field of view. This work will evaluate and provide estimations on the expected number of of gravitational wave events that will be observable with CTA, considering both on- and off-axis emission. In addition, we will present and discuss the prospects of potential follow-up strategies with CTA.
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Submitted 5 February, 2024; v1 submitted 11 October, 2023;
originally announced October 2023.
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A multi-wavelength investigation of PSR J2229+6114 and its pulsar wind nebula in the radio, X-ray, and gamma-ray bands
Authors:
I. Pope,
K. Mori,
M. Abdelmaguid,
J. D. Gelfand,
S. P. Reynolds,
S. Safi-Harb,
C. J. Hailey,
H. An,
VERITAS Collaboration,
:,
P. Bangale,
P. Batista,
W. Benbow,
J. H. Buckley,
M. Capasso,
J. L. Christiansen,
A. J. Chromey,
A. Falcone,
Q. Feng,
J. P. Finley,
G. M Foote,
G. Gallagher,
W. F Hanlon,
D. Hanna,
O. Hervet
, et al. (35 additional authors not shown)
Abstract:
G106.3$+$2.7, commonly considered a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct ("head" & "tail") regions in the radio band. A discovery of very-high-energy (VHE) gamma-ray emission ($E_γ> 100$ GeV) followed by the recent detection of ultra-high-energy (UHE) gamma-ray emission ($E_γ> 100$ TeV) from the tail region suggests tha…
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G106.3$+$2.7, commonly considered a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct ("head" & "tail") regions in the radio band. A discovery of very-high-energy (VHE) gamma-ray emission ($E_γ> 100$ GeV) followed by the recent detection of ultra-high-energy (UHE) gamma-ray emission ($E_γ> 100$ TeV) from the tail region suggests that G106.3$+$2.7 is a PeVatron candidate. We present a comprehensive multi-wavelength study of the Boomerang PWN (100" around PSR J2229+6114) using archival radio and Chandra data obtained from two decades ago, a new NuSTAR X-ray observation from 2020, and upper limits on gamma-ray fluxes obtained by Fermi and VERITAS observatories. The NuSTAR observation allowed us to detect a 51.67 ms spin period from the pulsar PSR J2229+6114 and the PWN emission characterized by a power-law model with $Γ= 1.52\pm0.06$ up to 20 keV. Contrary to the previous radio study by Kothes et al. 2006, we prefer a much lower PWN B-field ($B\sim3$ $μ$G) and larger distance ($d \sim 8$ kpc) based on (1) the non-varying X-ray flux over the last two decades, (2) the energy-dependent X-ray PWN size resulting from synchrotron burn-off and (3) the multi-wavelength spectral energy distribution (SED) data. Our SED model suggests that the PWN is currently re-expanding after being compressed by the SNR reverse shock $\sim 1000$ years ago. In this case, the head region should be formed by GeV--TeV electrons injected earlier by the pulsar propagating into the low density environment.
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Submitted 6 October, 2023;
originally announced October 2023.
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Long-term monitoring of the radio-galaxy M87 in gamma-rays: joint analysis of MAGIC, VERITAS and Fermi-LAT data
Authors:
M. Molero,
P. Batista,
L. Fortson,
M. Nievas Rosillo,
E. Pueschel,
D. Ribeiro,
M. Vázquez Acosta
Abstract:
M87 was discovered in the very-high-energy band (VHE, E > 100 GeV) with HEGRA in 2003, long before its emission was detected in the high-energy band (HE, E > 100 MeV) with Fermi-LAT in 2009, opening the window to a new family of extragalactic sources with tilted jets. After a series of major VHE flares in 2005, 2008, and 2010, which were detected in multiple bands, the source has been found in a l…
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M87 was discovered in the very-high-energy band (VHE, E > 100 GeV) with HEGRA in 2003, long before its emission was detected in the high-energy band (HE, E > 100 MeV) with Fermi-LAT in 2009, opening the window to a new family of extragalactic sources with tilted jets. After a series of major VHE flares in 2005, 2008, and 2010, which were detected in multiple bands, the source has been found in a low activity state, interrupted only by comparatively smaller-scale flares. MAGIC and VERITAS, two stereoscopic Cherenkov telescope arrays located at Roque de los Muchachos Observatory (Canary Islands, Spain) and the Fred Lawrence Whipple Observatory (Arizona, US), have monitored M87 continuously and in coordination for more than 10 years. In this work, we present the data for 4 years of MAGIC and VERITAS observations corresponding to 2019, 2020, 2021 and 2022. The resulting light curves are shown in daily and monthly scales where no significant variability is observed. In addition, we show the first joint analysis using combined event data from the two VHE instruments and Fermi-LAT to compute the spectral energy distribution.
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Submitted 25 September, 2023;
originally announced September 2023.
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Prospects for $γ$-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array
Authors:
The Cherenkov Telescope Array Consortium,
:,
K. Abe,
S. Abe,
F. Acero,
A. Acharyya,
R. Adam,
A. Aguasca-Cabot,
I. Agudo,
A. Aguirre-Santaella,
J. Alfaro,
R. Alfaro,
N. Alvarez-Crespo,
R. Alves Batista,
J. -P. Amans,
E. Amato,
E. O. Angüner,
L. A. Antonelli,
C. Aramo,
M. Araya,
C. Arcaro,
L. Arrabito,
K. Asano,
Y. Ascasíbar,
J. Aschersleben
, et al. (542 additional authors not shown)
Abstract:
Galaxy clusters are expected to be dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at gamma-ray energies and are predicted to be sources of large-scale gamma-ray emission due to hadronic interactions in the intracluster med…
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Galaxy clusters are expected to be dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at gamma-ray energies and are predicted to be sources of large-scale gamma-ray emission due to hadronic interactions in the intracluster medium. We estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. We perform a detailed spatial and spectral modelling of the expected signal for the DM and the CRp components. For each, we compute the expected CTA sensitivity. The observing strategy of Perseus is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio within the radius $R_{500}$ down to about $X_{500}<3\times 10^{-3}$, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index $α_{\rm CRp}=2.3$. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure $α_{\rm CRp}$ down to about $Δα_{\rm CRp}\simeq 0.1$ and the CRp spatial distribution with 10% precision. Regarding DM, CTA should improve the current ground-based gamma-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to $\sim 5$, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with $τ_χ>10^{27}$s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario.
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Submitted 7 September, 2023;
originally announced September 2023.
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Multiwavelength Observations of the Blazar PKS 0735+178 in Spatial and Temporal Coincidence with an Astrophysical Neutrino Candidate IceCube-211208A
Authors:
A. Acharyya,
C. B. Adams,
A. Archer,
P. Bangale,
J. T. Bartkoske,
P. Batista,
W. Benbow,
A. Brill,
J. H. Buckley,
J. L. Christiansen,
A. J. Chromey,
M. Errando,
A. Falcone,
Q. Feng,
G. M. Foote,
L. Fortson,
A. Furniss,
G. Gallagher,
W. Hanlon,
D. Hanna,
O. Hervet,
C. E. Hinrichs,
J. Hoang,
J. Holder,
T. B. Humensky
, et al. (185 additional authors not shown)
Abstract:
We report on multiwavelength target-of-opportunity observations of the blazar PKS 0735+178, located 2.2$^\circ$ away from the best-fit position of the IceCube neutrino event IceCube-211208A detected on December 8, 2021. The source was in a high-flux state in the optical, ultraviolet, X-ray, and GeV gamma-ray bands around the time of the neutrino event, exhibiting daily variability in the soft X-ra…
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We report on multiwavelength target-of-opportunity observations of the blazar PKS 0735+178, located 2.2$^\circ$ away from the best-fit position of the IceCube neutrino event IceCube-211208A detected on December 8, 2021. The source was in a high-flux state in the optical, ultraviolet, X-ray, and GeV gamma-ray bands around the time of the neutrino event, exhibiting daily variability in the soft X-ray flux. The X-ray data from Swift-XRT and NuSTAR characterize the transition between the low-energy and high-energy components of the broadband spectral energy distribution (SED), and the gamma-ray data from Fermi -LAT, VERITAS, and H.E.S.S. require a spectral cut-off near 100 GeV. Both X-ray and gamma-ray measurements provide strong constraints on the leptonic and hadronic models. We analytically explore a synchrotron self-Compton model, an external Compton model, and a lepto-hadronic model. Models that are entirely based on internal photon fields face serious difficulties in matching the observed SED. The existence of an external photon field in the source would instead explain the observed gamma-ray spectral cut-off in both leptonic and lepto-hadronic models and allow a proton jet power that marginally agrees with the Eddington limit in the lepto-hadronic model. We show a numerical lepto-hadronic model with external target photons that reproduces the observed SED and is reasonably consistent with the neutrino event despite requiring a high jet power.
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Submitted 30 June, 2023;
originally announced June 2023.
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A VERITAS/Breakthrough Listen Search for Optical Technosignatures
Authors:
Atreya Acharyya,
Colin Adams,
Avery Archer,
Priyadarshini Bangale,
Pedro Batista,
Wystan Benbow,
Aryeh Brill,
M Capasso,
Manel Errando,
Abraham Falcone,
Qi Feng,
John Finley,
Gregory Foote,
Lucy Fortson,
Amy Furniss,
Sean Griffin,
William Hanlon,
David Hanna,
Olivier Hervet,
Claire Hinrichs,
John Hoang,
Jamie Holder,
T. Humensky,
Weidong Jin,
Philip Kaaret
, et al. (43 additional authors not shown)
Abstract:
The Breakthrough Listen Initiative is conducting a program using multiple telescopes around the world to search for "technosignatures": artificial transmitters of extraterrestrial origin from beyond our solar system. The VERITAS Collaboration joined this program in 2018, and provides the capability to search for one particular technosignature: optical pulses of a few nanoseconds duration detectabl…
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The Breakthrough Listen Initiative is conducting a program using multiple telescopes around the world to search for "technosignatures": artificial transmitters of extraterrestrial origin from beyond our solar system. The VERITAS Collaboration joined this program in 2018, and provides the capability to search for one particular technosignature: optical pulses of a few nanoseconds duration detectable over interstellar distances. We report here on the analysis and results of dedicated VERITAS observations of Breakthrough Listen targets conducted in 2019 and 2020 and of archival VERITAS data collected since 2012. Thirty hours of dedicated observations of 136 targets and 249 archival observations of 140 targets were analyzed and did not reveal any signals consistent with a technosignature. The results are used to place limits on the fraction of stars hosting transmitting civilizations. We also discuss the minimum-pulse sensitivity of our observations and present VERITAS observations of CALIOP: a space-based pulsed laser onboard the CALIPSO satellite. The detection of these pulses with VERITAS, using the analysis techniques developed for our technosignature search, allows a test of our analysis efficiency and serves as an important proof-of-principle.
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Submitted 30 June, 2023;
originally announced June 2023.
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Search for Ultraheavy Dark Matter from Observations of Dwarf Spheroidal Galaxies with VERITAS
Authors:
A. Acharyya,
A. Archer,
P. Bangale,
J. T. Bartkoske,
P. Batista,
M. Baumgart,
W. Benbow,
J. H. Buckley,
A. Falcone,
Q. Feng,
J. P. Finley,
G. M. Foote,
L. Fortson,
A. Furniss,
G. Gallagher,
W. F. Hanlon,
O. Hervet,
J. Hoang,
J. Holder,
T. B. Humensky,
W. Jin,
P. Kaaret,
M. Kertzman,
M. Kherlakian,
D. Kieda
, et al. (29 additional authors not shown)
Abstract:
Dark matter is a key piece of the current cosmological scenario, with weakly interacting massive particles (WIMPs) a leading dark matter candidate. WIMPs have not been detected in their conventional parameter space (100 GeV $\lesssim M_χ \lesssim$ 100 TeV), a mass range accessible with current Imaging Atmospheric Cherenkov Telescopes. As ultraheavy dark matter (UHDM; $M_χ \gtrsim$ 100 TeV) has bee…
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Dark matter is a key piece of the current cosmological scenario, with weakly interacting massive particles (WIMPs) a leading dark matter candidate. WIMPs have not been detected in their conventional parameter space (100 GeV $\lesssim M_χ \lesssim$ 100 TeV), a mass range accessible with current Imaging Atmospheric Cherenkov Telescopes. As ultraheavy dark matter (UHDM; $M_χ \gtrsim$ 100 TeV) has been suggested as an under-explored alternative to the WIMP paradigm, we search for an indirect dark matter annihilation signal in a higher mass range (up to 30 PeV) with the VERITAS gamma-ray observatory. With 216 hours of observations of four dwarf spheroidal galaxies, we perform an unbinned likelihood analysis. We find no evidence of a $γ$-ray signal from UHDM annihilation above the background fluctuation for any individual dwarf galaxy nor for a joint-fit analysis, and consequently constrain the velocity-weighted annihilation cross section of UHDM for dark matter particle masses between 1 TeV and 30 PeV. We additionally set constraints on the allowed radius of a composite UHDM particle.
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Submitted 24 February, 2023; v1 submitted 17 February, 2023;
originally announced February 2023.
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VTSCat: The VERITAS Catalog of Gamma-Ray Observations
Authors:
A. Acharyya,
C. B. Adams,
A. Archer,
P. Bangale,
J. T. Bartkoske,
P. Batista,
W. Benbow,
J. H. Buckley,
A. Brill,
M. Capasso,
J. L. Christiansen,
A. J. Chromey,
M. K. Daniel,
M. Errando,
A. Falcone,
K. A Farrell,
Q. Feng,
J. P. Finley,
G. M Foote,
L. Fortson,
A. Furniss,
G. Gallagher,
A. Gent,
C. Giuri,
O. Gueta
, et al. (64 additional authors not shown)
Abstract:
The ground-based gamma-ray observatory VERITAS (Very Energetic Radiation Imaging Telescope Array System) is sensitive to photons of astrophysical origin with energies in the range between $\approx 85$ GeV to $\approx 30$ TeV. The instrument consists of four 12-m diameter imaging Cherenkov telescopes operating at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona. VERITAS started four…
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The ground-based gamma-ray observatory VERITAS (Very Energetic Radiation Imaging Telescope Array System) is sensitive to photons of astrophysical origin with energies in the range between $\approx 85$ GeV to $\approx 30$ TeV. The instrument consists of four 12-m diameter imaging Cherenkov telescopes operating at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona. VERITAS started four-telescope operations in 2007 and collects about 1100 hours of good-weather data per year. The VERITAS collaboration has published over 100 journal articles since 2008 reporting on gamma-ray observations of a large variety of objects: Galactic sources like supernova remnants, pulsar wind nebulae, and binary systems; extragalactic sources like star forming galaxies, dwarf-spheroidal galaxies, and highly-variable active galactic nuclei. This note presents VTSCat: the catalog of high-level data products from all VERITAS publications.
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Submitted 13 January, 2023; v1 submitted 11 January, 2023;
originally announced January 2023.
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Gamma-ray observations of MAXI J1820+070 during the 2018 outburst
Authors:
H. Abe,
S. Abe,
V. A. Acciari,
T. Aniello,
S. Ansoldi,
L. A. Antonelli,
A. Arbet Engels,
C. Arcaro,
M. Artero,
K. Asano,
D. Baack,
A. Babić,
A. Baquero,
U. Barres de Almeida,
J. A. Barrio,
I. Batković,
J. Baxter,
J. Becerra González,
W. Bednarek,
E. Bernardini,
M. Bernardos,
A. Berti,
J. Besenrieder,
W. Bhattacharyya,
C. Bigongiari
, et al. (418 additional authors not shown)
Abstract:
MAXI J1820+070 is a low-mass X-ray binary with a black hole as a compact object. This binary underwent an exceptionally bright X-ray outburst from March to October 2018, showing evidence of a non-thermal particle population through its radio emission during this whole period. The combined results of 59.5 hours of observations of the MAXI J1820+070 outburst with the H.E.S.S., MAGIC and VERITAS expe…
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MAXI J1820+070 is a low-mass X-ray binary with a black hole as a compact object. This binary underwent an exceptionally bright X-ray outburst from March to October 2018, showing evidence of a non-thermal particle population through its radio emission during this whole period. The combined results of 59.5 hours of observations of the MAXI J1820+070 outburst with the H.E.S.S., MAGIC and VERITAS experiments at energies above 200 GeV are presented, together with Fermi-LAT data between 0.1 and 500 GeV, and multiwavelength observations from radio to X-rays. Gamma-ray emission is not detected from MAXI J1820+070, but the obtained upper limits and the multiwavelength data allow us to put meaningful constraints on the source properties under reasonable assumptions regarding the non-thermal particle population and the jet synchrotron spectrum. In particular, it is possible to show that, if a high-energy gamma-ray emitting region is present during the hard state of the source, its predicted flux should be at most a factor of 20 below the obtained Fermi-LAT upper limits, and closer to them for magnetic fields significantly below equipartition. During the state transitions, under the plausible assumption that electrons are accelerated up to ~ 500 GeV, the multiwavelength data and the gamma-ray upper limits lead consistently to the conclusion that a potential high-energy and very-high-energy gamma-ray emitting region should be located at a distance from the black hole ranging between 10^11 and 10^13 cm. Similar outbursts from low-mass X-ray binaries might be detectable in the near future with upcoming instruments such as CTA.
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Submitted 6 October, 2022; v1 submitted 20 September, 2022;
originally announced September 2022.
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The rigidity dependence of galactic cosmic-ray fluxes and its connection with the diffusion coefficient
Authors:
M. Vecchi,
P. -I. Batista,
E. F. Bueno,
L. Derome,
Y. Génolini,
D. Maurin
Abstract:
Thanks to tremendous experimental efforts, galactic cosmic-ray fluxes are being measured up to the unprecedented per cent precision level. The logarithmic slope of these fluxes is a crucial quantity that promises us information on the diffusion properties and the primary or secondary nature of the different species. However, these measured slopes are sometimes interpreted in the pure diffusive reg…
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Thanks to tremendous experimental efforts, galactic cosmic-ray fluxes are being measured up to the unprecedented per cent precision level. The logarithmic slope of these fluxes is a crucial quantity that promises us information on the diffusion properties and the primary or secondary nature of the different species. However, these measured slopes are sometimes interpreted in the pure diffusive regime, guiding to misleading conclusions. In this paper, we have studied the propagation of galactic cosmic rays by computing the fluxes of species between H and Fe using the USINE code and considering all the relevant physical processes and an updated set of cross-section data. We show that the slope of the well-studied secondary-to-primary B/C ratio is distinctly different from the diffusion coefficient slope, by an offset of about 0.2 in the rigidity range in which the AMS-02 data reach their best precision (several tens of GV).
Furthermore, we have demonstrated that none of the species from H to Fe follows the expectations of the pure-diffusive regime. We argue that these differences arise from propagation processes such as fragmentation, convection, and reacceleration, which cannot be neglected. On this basis, we also provide predictions for the spectral slope of elemental fluxes not yet analysed by the AMS collaboration.
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Submitted 12 March, 2022;
originally announced March 2022.
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Prototype Schwarzschild-Couder Telescope for the Cherenkov Telescope Array: Commissioning the Optical System
Authors:
C. B. Adams,
G. Ambrosi,
M. Ambrosio,
C. Aramo,
P. I. Batista,
W. Benbow,
B. Bertucci,
E. Bissaldi,
M. Bitossi,
A. Boiano,
C. Bonavolontà,
R. Bose,
A. Brill,
J. H. Buckley,
R. A. Cameron,
R. Canestrari,
M. Capasso,
M. Caprai,
C. E. Covault,
D. Depaoli,
L. Di Venere,
M. Errando,
S. Fegan,
Q. Feng,
E. Fiandrini
, et al. (47 additional authors not shown)
Abstract:
A prototype Schwarzschild-Couder Telescope (pSCT) has been constructed at the Fred Lawrence Whipple Observatory as a candidate for the medium-sized telescopes of the Cherenkov Telescope Array Observatory (CTAO). CTAO is currently entering early construction phase of the project and once completed it will vastly improve very high energy gamma-ray detection component in multi-wavelength and multi-me…
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A prototype Schwarzschild-Couder Telescope (pSCT) has been constructed at the Fred Lawrence Whipple Observatory as a candidate for the medium-sized telescopes of the Cherenkov Telescope Array Observatory (CTAO). CTAO is currently entering early construction phase of the project and once completed it will vastly improve very high energy gamma-ray detection component in multi-wavelength and multi-messenger observations due to significantly improved sensitivity, angular resolution and field of view comparing to the current generation of the ground-based gamma-ray observatories H.E.S.S., MAGIC and VERITAS. The pSCT uses a dual aspheric mirror design with a $9.7$ m primary mirror and $5.4$ m secondary mirror, both of which are segmented. The Schwarzschild-Couder (SC) optical system (OS) selected for the prototype telescope achieves wide field of view of $8$ degrees and simultaneously reduces the focal plane plate scale allowing an unprecedented compact ($0.78$m diameter) implementation of the high-resolution camera ($6$mm/ $0.067$deg per imaging pixel with $11,328$ pixels) based on the silicon photo-multipliers (SiPMs). The OS of the telescope is designed to eliminate spherical and comatic aberrations and minimize astigmatism to radically improve off-axis imaging and consequently angular resolution across all the field of view with respect to the conventional single-mirror telescopes. Fast and high imaging resolution OS of the pSCT comes with the challenging submillimeter-precision custom alignment system, which was successfully demonstrated with an on-axis point spread function (PSF) of $2.9$ arcmin prior to the first-light detection of the Crab Nebula in 2020. Ongoing and future commissioning activities are reported.
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Submitted 14 October, 2021;
originally announced October 2021.
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Detection of the Crab Nebula by the prototype Schwarzschild-Couder Telescope
Authors:
C. B. Adams,
G. Ambrosi,
M. Ambrosio,
C. Aramo,
P. I. Batista,
W. Benbow,
B. Bertucci,
E. Bissaldi,
M. Bitossi,
A. Boiano,
C. Bonavolontà,
R. Bose,
A. Brill,
A. M. Brown,
J. H. Buckley,
R. A. Cameron,
R. Canestrari,
M. Capasso,
M. Caprai,
C. E. Covault,
D. Depaoli,
L. Di Venere,
M. Errando,
S. Fegan,
Q. Feng
, et al. (49 additional authors not shown)
Abstract:
The Schwarzschild-Couder Telescope (SCT) is a medium-sized telescope technology proposed for the Cherenkov Telescope Array. It uses a novel dual-mirror optical design that removes comatic aberrations across its entire field of view. The SCT camera employs high-resolution silicon photomultiplier (SiPM) sensors with a pixel size of 4 arcminutes. A prototype SCT (pSCT) has been constructed at the Fre…
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The Schwarzschild-Couder Telescope (SCT) is a medium-sized telescope technology proposed for the Cherenkov Telescope Array. It uses a novel dual-mirror optical design that removes comatic aberrations across its entire field of view. The SCT camera employs high-resolution silicon photomultiplier (SiPM) sensors with a pixel size of 4 arcminutes. A prototype SCT (pSCT) has been constructed at the Fred Lawrence Whipple Observatory in Arizona, USA. An observing campaign in 2020, with a partial camera of 1600 pixels (2.7 degrees by 2.7 degrees field of view) resulted in detection of the Crab Nebula at 8.6 sigma statistical significance. Work on the pSCT camera and optical system is ongoing to improve performance and prepare for an upcoming camera upgrade. The pSCT camera upgrade will replace the current camera modules with improved SiPMs and readout electronics and will expand the camera to its full design field of view of 8 degrees in diameter (11,328 pixels). The fully upgraded pSCT will enable next-generation very-high-energy gamma-ray astrophysics through excellent background rejection and angular resolution. In this presentation we describe first results from the successful operation of the pSCT and future plans.
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Submitted 13 September, 2021;
originally announced September 2021.
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Design and performance of the prototype Schwarzschild-Couder Telescope camera
Authors:
C. B. Adams,
G. Ambrosi,
M. Ambrosio,
C. Aramo,
P. I. Batista,
W. Benbow,
B. Bertucci,
E. Bissaldi,
M. Bitossi,
A. Boiano,
C. Bonavolonta,
R. Bose,
A. Brill,
A. M. Brown,
J. H. Buckley,
R. A. Cameron,
M. Capasso,
M. Caprai,
C. E. Covault,
D. Depaoli,
L. Di Venere,
M. Errando,
S. Fegan,
Q. Feng,
E. Fiandrini
, et al. (49 additional authors not shown)
Abstract:
The Cherenkov Telescope Array (CTA) is the next-generation ground-based observatory for very-high-energy gamma-ray astronomy. An innovative 9.7 m aperture, dual-mirror Schwarzschild-Couder Telescope (SCT) design is a candidate design for CTA Medium-Sized Telescopes. A prototype SCT (pSCT) has been constructed at the Fred Lawrence Whipple Observatory in Arizona, USA. Its camera is currently partial…
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The Cherenkov Telescope Array (CTA) is the next-generation ground-based observatory for very-high-energy gamma-ray astronomy. An innovative 9.7 m aperture, dual-mirror Schwarzschild-Couder Telescope (SCT) design is a candidate design for CTA Medium-Sized Telescopes. A prototype SCT (pSCT) has been constructed at the Fred Lawrence Whipple Observatory in Arizona, USA. Its camera is currently partially instrumented with 1600 pixels covering a field of view of 2.7 degrees square. The small plate scale of the optical system allows densely packed silicon photomultipliers to be used, which combined with high-density trigger and waveform readout electronics enable the high-resolution camera. The camera's electronics are capable of imaging air shower development at a rate of one billion samples per second. We describe the commissioning and performance of the pSCT camera, including trigger and waveform readout performance, calibration, and absolute GPS time stamping. We also present the upgrade to the camera, which is currently underway. The upgrade will fully populate the focal plane, increasing the field of view to 8 degree diameter, and lower the front-end electronics noise, enabling a lower trigger threshold and improved reconstruction and background rejection.
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Submitted 10 September, 2021;
originally announced September 2021.
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Detection of the Crab Nebula with the 9.7 m Prototype Schwarzschild-Couder Telescope
Authors:
C. B. Adams,
R. Alfaro,
G. Ambrosi,
M. Ambrosio,
C. Aramo,
T. Arlen,
P. I. Batista,
W. Benbow,
B. Bertucci,
E. Bissaldi,
J. Biteau,
M. Bitossi,
A. Boiano,
C. Bonavolontà,
R. Bose,
A. Bouvier,
A. Brill,
A. M. Brown,
J. H. Buckley,
K. Byrum,
R. A. Cameron,
R. Canestrari,
M. Capasso,
M. Caprai,
C. E. Covault
, et al. (83 additional authors not shown)
Abstract:
The Schwarzschild-Couder Telescope (SCT) is a telescope concept proposed for the Cherenkov Telescope Array. It employs a dual-mirror optical design to remove comatic aberrations over an $8^{\circ}$ field of view, and a high-density silicon photomultiplier camera (with a pixel resolution of 4 arcmin) to record Cherenkov emission from cosmic ray and gamma-ray initiated particle cascades in the atmos…
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The Schwarzschild-Couder Telescope (SCT) is a telescope concept proposed for the Cherenkov Telescope Array. It employs a dual-mirror optical design to remove comatic aberrations over an $8^{\circ}$ field of view, and a high-density silicon photomultiplier camera (with a pixel resolution of 4 arcmin) to record Cherenkov emission from cosmic ray and gamma-ray initiated particle cascades in the atmosphere. The prototype SCT (pSCT), comprising a 9.7 m diameter primary mirror and a partially instrumented camera with 1536 pixels, has been constructed at the Fred Lawrence Whipple Observatory. The telescope was inaugurated in January 2019, with commissioning continuing throughout 2019. We describe the first campaign of observations with the pSCT, conducted in January and February of 2020, and demonstrate the detection of gamma-ray emission from the Crab Nebula with a statistical significance of $8.6σ$.
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Submitted 15 December, 2020;
originally announced December 2020.
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Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation
Authors:
The Cherenkov Telescope Array Consortium,
:,
H. Abdalla,
H. Abe,
F. Acero,
A. Acharyya,
R. Adam,
I. Agudo,
A. Aguirre-Santaella,
R. Alfaro,
J. Alfaro,
C. Alispach,
R. Aloisio,
R. Alves B,
L. Amati,
E. Amato,
G. Ambrosi,
E. O. Angüner,
A. Araudo,
T. Armstrong,
F. Arqueros,
L. Arrabito,
K. Asano,
Y. Ascasíbar,
M. Ashley
, et al. (474 additional authors not shown)
Abstract:
The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for $γ$-ray astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of $γ$-ray cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nucle…
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The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for $γ$-ray astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of $γ$-ray cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of $γ$-ray absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift $z=2$ and to constrain or detect $γ$-ray halos up to intergalactic-magnetic-field strengths of at least 0.3pG. Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from $γ$-ray astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of $γ$-ray cosmology.
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Submitted 26 February, 2021; v1 submitted 3 October, 2020;
originally announced October 2020.
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Cosmic-ray transport from AMS-02 B/C data: benchmark models and interpretation
Authors:
Yoann Genolini,
Mathieu Boudaud,
Pedro Ivo Batista,
Sami Caroff,
Laurent Derome,
Julien Lavalle,
Alexandre Marcowith,
David Maurin,
Vincent Poireau,
Vivian Poulin,
Sylvie Rosier,
Pierre Salati,
Pasquale Dario Serpico,
Manuela Vecchi
Abstract:
This article aims at establishing new benchmark scenarios for Galactic cosmic-ray propagation in the GV-TV rigidity range, based on fits to the AMS-02 B/C data with the USINE v3.5 propagation code. We employ a new fitting procedure, cautiously taking into account data systematic error correlations in different rigidity bins and considering Solar modulation potential and leading nuclear cross-secti…
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This article aims at establishing new benchmark scenarios for Galactic cosmic-ray propagation in the GV-TV rigidity range, based on fits to the AMS-02 B/C data with the USINE v3.5 propagation code. We employ a new fitting procedure, cautiously taking into account data systematic error correlations in different rigidity bins and considering Solar modulation potential and leading nuclear cross-section as nuisance parameters. We delineate specific low, intermediate, and high-rigidity ranges that can be related to both features in the data and peculiar microphysics mechanisms resulting in spectral breaks. We single out a scenario which yields excellent fits to the data and includes all the presumably relevant complexity, the BIG model. This model has two limiting regimes: (i) the SLIM model, a minimal diffusion-only setup, and (ii) the QUAINT model, a convection-reacceleration model where transport is tuned by non-relativistic effects. All models lead to robust predictions in the high-energy regime ($\gtrsim10$GV), i.e. independent of the propagation scenario: at $1σ$, the diffusion slope $δ$ is $[0.43-0.53]$, whereas $K_{10}$, the diffusion coefficient at 10GV, is $[0.26-0.36]$kpc$^2$Myr$^{-1}$; we confirm the robustness of the high-energy break, with a typical value $Δ_h\sim 0.2$. We also find a hint for a similar (reversed) feature at low rigidity around the B/C peak ($\sim 4$GV) which might be related to some effective damping scale in the magnetic turbulence.
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Submitted 25 April, 2019; v1 submitted 18 April, 2019;
originally announced April 2019.