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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
  1. XMM-Newton observation of EP240426a
  2. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  4. LIGO/Virgo/KAGRA S240422ed: EP-FXT Detection of the Potential Opitcal Electromagnetic Counterpart AT 2024hfq Reported by DECam
  5. GRB 240414A: NOEMA detection
  6. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  7. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  8. EP240426a: GMG optical upper limit
  9. LVK S240422ed: Further Swift-XRT followup of three sources
  10. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  11. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  12. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  13. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  14. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  15. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
  16. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  17. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  18. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  19. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  20. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  21. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  22. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  23. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  24. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  25. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  26. LIGO/Virgo/KAGRA S240422ed: ANU 2.3m followup of candidate counterparts
  27. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  28. GRB 240425A: Fermi GBM Final Real-time Localization
  29. Fermi trigger No 735697285: Global MASTER-Net observations report
  30. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  31. GRB 240419B: Swift-BAT refined analysis
  32. GRB 240421B: Swift-BAT refined analysis
  33. GRB 240422A: Glowbug gamma-ray detection
  34. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  35. LIGO/Virgo/KAGRA S240413p: DESGW DECam Follow-Up
  36. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  37. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  38. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  39. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  40. IceCube-240424A - IceCube observation of a high-energy neutrino candidate track-like event
  41. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  42. LIGO/Virgo/KAGRA S240422ed: MOSFIRE spectroscopy of the DECam GW-MMADS candidate AT 2024hdn
  43. LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
  44. LIGO/Virgo/KAGRA S240422ed: MOSFIRE imaging of the DECam GW-MMADS candidate AT 2024hdm
  45. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  46. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  47. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  48. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  49. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  50. LIGO/Virgo/KAGRA S240422ed: DECam GW-MMADS Candidates
  51. LIGO/Virgo/KAGRA S240422ed: Potential Magellan candidates from GCN 36263 are unrelated.
  52. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  53. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  54. GRB 240421B: GRBAlpha detection
  55. IceCube Alert 240424.08: Global MASTER-Net observations report
  56. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
  57. LIGO/Virgo/KAGRA S240422ed: SAGUARO upper limits from CSS
  58. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  59. LIGO/Virgo/KAGRA S240422ed: LAST optical observations
  60. LIGO/Virgo/KAGRA S240422ed: Potential Candidates from Magellan galaxy-based search
  61. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  62. IceCube-240419A: Upper limits from a search for additional neutrino events in IceCube
  63. LIGO/Virgo/KAGRA S240421ar: Updated Sky localization
  64. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  65. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  66. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
  67. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  68. GRB 240419A: Swift-BAT refined analysis
  69. GRB 240418A: Swift-BAT refined analysis
  70. LXT240402A/GRB240402B: Chandra X-ray detection
  71. LIGO/Virgo/KAGRA S240423br: Retraction of GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  73. GRB 240419A: Possible ATCA radio detection
  74. GRB 240421B: ATCA radio observations
  75. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  76. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  77. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility observations and candidates
  78. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  79. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  80. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  81. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  82. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  83. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  84. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  85. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  86. LIGO/Virgo/KAGRA S240422ed: MeerLICHT and BlackGEM observations report
  87. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  88. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  89. LIGO/Virgo/KAGRA S240422ed: Global MASTER-Net observations report
  90. Fermi trigger No 735470374: Global MASTER-Net observations report
  91. GRB 240421A: Glowbug gamma-ray detection
  92. GRB 240414A: radio detection with the VLA
  93. Fermi-LAT gamma-ray observations of IceCube-240419A
  94. GRB 240414A: AMI-LA radio observations
  95. GRB 240414A: LBT optical detection
  96. GRB 240419B : MITSuME Akeno optical upper limits
  97. GRB 240415B: Swift-XRT observations
  98. GRB 240415A: Swift-XRT refined Analysis
  99. Fermi GRB 240422A: Global MASTER-Net observations report
  100. GRB 240421B: AstroSat CZTI detection

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