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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 260924A: Upper limits from a neutrino search with IceCube
  2. Fermi GRB 260926C: Global MASTER-Net observations report
  3. GRB 260926C: Fermi GBM Final Real-time Localization
  4. GRB260914A: MAO/AZT-22 optical observations
  5. GRB 260926B: Fermi GBM Final Real-time Localization
  6. Fermi GRB 260926A: Global MASTER-Net observations report
  7. GRB 260924A: Near-infrared detection with MDM/MIRAGE
  8. GRB 260926A: Fermi GBM Final Real-time Localization
  9. The EP-WXT trigger 01709320726 is likely a flaring star
  10. GRB 260924A: COLIBRÍ optical observations
  11. GRB 260924A: Second-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  12. EP260924a: J-band upper limit by SYSU 80cm infrared telescope
  13. GRB 260925A: J-band upper limit by SYSU 80cm infrared telescope
  14. GRB 260925A: Swift-XRT refined Analysis
  15. EP260924a: EP-FXT follow-up observation
  16. Swift Trigger 1513439 is probably not a GRB
  17. GRB 260925A: Swift/UVOT Upper Limits
  18. Konus-Wind detection of GRB 260924A
  19. GRB 260924A: Extreme Isotropic-equivalent Gamma-ray Energy and encouragement for multiwavelength follow-up observations
  20. GRB 260923A: Glowbug gamma-ray detection
  21. GRB 260924A: Optical follow-up observations with Kinder
  22. GRB 260922A: Glowbug gamma-ray detection
  23. GRB 260925A: Enhanced Swift-XRT position
  24. GRB 260925A: COLIBRÍ optical upper limits
  25. GRB 260925A: FRAM-Auger optical limit
  26. GRB 260924A: Ondrejov D50 optical afterglow detection
  27. EP260924a: J-band upper limit with WINTER
  28. GRB 260924A: SVOM/GRM observation
  29. GRB 260924A: 2.2m CAHA spectroscopic redshift z = 3.51
  30. GRB 260925A: Swift detection of a burst
  31. GRB 260923A: Insight-HXMT/HE detection
  32. EP260924a: EP-WXT detection of an X-ray transient
  33. GRB 260924A: J-band observations by the SYSU 80 cm infrared telescope
  34. GRB 260924A: Swift/UVOT Detection
  35. GRB 260924A: GROWTH-India Telescope optical observations
  36. GRB 260924A: Swift-BAT refined analysis
  37. GRB 260924A: NuSTAR detection of prompt emission
  38. GRB 260924A: Swift/UVOT Upper Limits
  39. GRB 260924A: Swift-XRT refined Analysis
  40. Konus-Wind detection of GRB 260922A
  41. GRB 260922A: NuSTAR detection of prompt emission
  42. GRB 260921A: NuSTAR detection of prompt emission
  43. Konus-Wind detection of GRB 260921A (correction to GCN 45722)
  44. GRB 260921A: SVOM/GRM observation
  45. GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
  46. GRB 260924A: Fermi GRB Observation
  47. Konus-Wind detection of GRB 260921A (possible merger-origin)
  48. GRB 260924A: Fermi-LAT detection of a bright burst
  49. GRB 260924A: AstroSat CZTI detection
  50. GRB 260920A: SVOM/GRM observation
  51. GRB 260924A: NOT optical counterpart confirmation
  52. GRB 260924A: detection of a bright optical afterglow by the 1.5m OSN telescope
  53. GRB 260922A: CALET Gamma-Ray Burst Monitor detection
  54. GRB 260924A: Enhanced Swift-XRT position
  55. The EP-WXT trigger 01709319842 is likely a flaring star
  56. GRB 260924A: Swift detection of a burst
  57. GRB 260924A: Fermi GBM Final Real-time Localization
  58. Fermi GRB 260923A: Global MASTER-Net observations report
  59. GRB 260923A: Fermi GBM Final Real-time Localization
  60. Trigger_21914: Swift ToO observations
  61. EP260806a: e-MERLIN detection at 5 GHz
  62. GRB 260922A: Ondrejov D50 optical limit
  63. Fermi-LAT Gamma-ray Observations of IceCube-260919A
  64. Fermi-LAT Gamma-ray Observations of IceCube-260916A
  65. ATCA observations of GRB 260909A
  66. GRB 260922A: Swift-BAT refined analysis
  67. EP260920a: VLT/HAWK-I near-infrared counterpart confirmation
  68. GRB 260922A: J-band upper limit with WINTER
  69. GRB 260922A: Swift/UVOT Upper Limits
  70. GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
  71. GRB 260922A: COLIBRÍ optical upper limits
  72. GRB 260922A: Swift-XRT refined Analysis
  73. GRB 260922A: Enhanced Swift-XRT position
  74. Fermi-LAT Gamma-ray Observations of IceCube-260805A
  75. Konus-Wind detection of GRB 260810A
  76. GRB 260920A: Glowbug gamma-ray detection
  77. GRB 260918A: SVOM/ECLAIRs refined analysis
  78. GRB 260922A: SVOM/C-GFT optical upper limit
  79. GRB 260922A: Swift detection of a burst
  80. GRB 260917C: AstroSat CZTI detection
  81. GRB 260920B/EP260920b: GECAM-B detection of a burst
  82. GRB 260921A: AstroSat CZTI detection
  83. GRB 260921A: Swift-BAT refined analysis
  84. GRB 260921B: Fermi GBM Final Localization
  85. GRB 260921A: Fermi GBM Observation
  86. EP260920b: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  87. EP Alert 260921.58: Global MASTER-Net observations report
  88. GRB 260917B:: SVOM/ECLAIRs refined analysis
  89. The EP-WXT trigger 01709319528 is likely a flaring star
  90. EP260920a: VLT/HAWK-I near-infrared candidate
  91. Swift GRB 260921A: MASTER OT J094129.58+025052.5 possible optical counterpart detection with host galaxy (z=1.3)
  92. Swift GRB 260921A: Global MASTER-Net observations report
  93. GRB 260921A: Swift detection of a burst
  94. EP260920b: VLT/X-shooter spectroscopic redshift z = 3.582
  95. GRB 260921A: Fermi GBM Final Real-time Localization
  96. EP260920b: LCO observations
  97. GRB 260920A: AstroSat CZTI detection
  98. EP260920b: SVOM/VT optical observation
  99. EP260920b: refined analysis of the EP-WXT and EP-FXT observations
  100. EP260920b: COLIBRÍ optical observations

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