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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. GRB260914A: MAO/AZT-22 optical observations
  2. GRB 260926B: Fermi GBM Final Real-time Localization
  3. Fermi GRB 260926A: Global MASTER-Net observations report
  4. GRB 260924A: Near-infrared detection with MDM/MIRAGE
  5. GRB 260926A: Fermi GBM Final Real-time Localization
  6. The EP-WXT trigger 01709320726 is likely a flaring star
  7. GRB 260924A: COLIBRÍ optical observations
  8. GRB 260924A: Second-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  9. EP260924a: J-band upper limit by SYSU 80cm infrared telescope
  10. GRB 260925A: J-band upper limit by SYSU 80cm infrared telescope
  11. GRB 260925A: Swift-XRT refined Analysis
  12. EP260924a: EP-FXT follow-up observation
  13. Swift Trigger 1513439 is probably not a GRB
  14. GRB 260925A: Swift/UVOT Upper Limits
  15. Konus-Wind detection of GRB 260924A
  16. GRB 260924A: Extreme Isotropic-equivalent Gamma-ray Energy and encouragement for multiwavelength follow-up observations
  17. GRB 260923A: Glowbug gamma-ray detection
  18. GRB 260924A: Optical follow-up observations with Kinder
  19. GRB 260922A: Glowbug gamma-ray detection
  20. GRB 260925A: Enhanced Swift-XRT position
  21. GRB 260925A: COLIBRÍ optical upper limits
  22. GRB 260925A: FRAM-Auger optical limit
  23. GRB 260924A: Ondrejov D50 optical afterglow detection
  24. EP260924a: J-band upper limit with WINTER
  25. GRB 260924A: SVOM/GRM observation
  26. GRB 260924A: 2.2m CAHA spectroscopic redshift z = 3.51
  27. GRB 260925A: Swift detection of a burst
  28. GRB 260923A: Insight-HXMT/HE detection
  29. EP260924a: EP-WXT detection of an X-ray transient
  30. GRB 260924A: J-band observations by the SYSU 80 cm infrared telescope
  31. GRB 260924A: Swift/UVOT Detection
  32. GRB 260924A: GROWTH-India Telescope optical observations
  33. GRB 260924A: Swift-BAT refined analysis
  34. GRB 260924A: NuSTAR detection of prompt emission
  35. GRB 260924A: Swift/UVOT Upper Limits
  36. GRB 260924A: Swift-XRT refined Analysis
  37. Konus-Wind detection of GRB 260922A
  38. GRB 260922A: NuSTAR detection of prompt emission
  39. GRB 260921A: NuSTAR detection of prompt emission
  40. Konus-Wind detection of GRB 260921A (correction to GCN 45722)
  41. GRB 260921A: SVOM/GRM observation
  42. GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
  43. GRB 260924A: Fermi GRB Observation
  44. Konus-Wind detection of GRB 260921A (possible merger-origin)
  45. GRB 260924A: Fermi-LAT detection of a bright burst
  46. GRB 260924A: AstroSat CZTI detection
  47. GRB 260920A: SVOM/GRM observation
  48. GRB 260924A: NOT optical counterpart confirmation
  49. GRB 260924A: detection of a bright optical afterglow by the 1.5m OSN telescope
  50. GRB 260922A: CALET Gamma-Ray Burst Monitor detection
  51. GRB 260924A: Enhanced Swift-XRT position
  52. The EP-WXT trigger 01709319842 is likely a flaring star
  53. GRB 260924A: Swift detection of a burst
  54. GRB 260924A: Fermi GBM Final Real-time Localization
  55. Fermi GRB 260923A: Global MASTER-Net observations report
  56. GRB 260923A: Fermi GBM Final Real-time Localization
  57. Trigger_21914: Swift ToO observations
  58. EP260806a: e-MERLIN detection at 5 GHz
  59. GRB 260922A: Ondrejov D50 optical limit
  60. Fermi-LAT Gamma-ray Observations of IceCube-260919A
  61. Fermi-LAT Gamma-ray Observations of IceCube-260916A
  62. ATCA observations of GRB 260909A
  63. GRB 260922A: Swift-BAT refined analysis
  64. EP260920a: VLT/HAWK-I near-infrared counterpart confirmation
  65. GRB 260922A: J-band upper limit with WINTER
  66. GRB 260922A: Swift/UVOT Upper Limits
  67. GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
  68. GRB 260922A: COLIBRÍ optical upper limits
  69. GRB 260922A: Swift-XRT refined Analysis
  70. GRB 260922A: Enhanced Swift-XRT position
  71. Fermi-LAT Gamma-ray Observations of IceCube-260805A
  72. Konus-Wind detection of GRB 260810A
  73. GRB 260920A: Glowbug gamma-ray detection
  74. GRB 260918A: SVOM/ECLAIRs refined analysis
  75. GRB 260922A: SVOM/C-GFT optical upper limit
  76. GRB 260922A: Swift detection of a burst
  77. GRB 260917C: AstroSat CZTI detection
  78. GRB 260920B/EP260920b: GECAM-B detection of a burst
  79. GRB 260921A: AstroSat CZTI detection
  80. GRB 260921A: Swift-BAT refined analysis
  81. GRB 260921B: Fermi GBM Final Localization
  82. GRB 260921A: Fermi GBM Observation
  83. EP260920b: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  84. EP Alert 260921.58: Global MASTER-Net observations report
  85. GRB 260917B:: SVOM/ECLAIRs refined analysis
  86. The EP-WXT trigger 01709319528 is likely a flaring star
  87. EP260920a: VLT/HAWK-I near-infrared candidate
  88. Swift GRB 260921A: MASTER OT J094129.58+025052.5 possible optical counterpart detection with host galaxy (z=1.3)
  89. Swift GRB 260921A: Global MASTER-Net observations report
  90. GRB 260921A: Swift detection of a burst
  91. EP260920b: VLT/X-shooter spectroscopic redshift z = 3.582
  92. GRB 260921A: Fermi GBM Final Real-time Localization
  93. EP260920b: LCO observations
  94. GRB 260920A: AstroSat CZTI detection
  95. EP260920b: SVOM/VT optical observation
  96. EP260920b: refined analysis of the EP-WXT and EP-FXT observations
  97. EP260920b: COLIBRÍ optical observations
  98. EP260920b: LCO optical counterpart detection
  99. The EP-WXT trigger 01709318601 is likely a flaring star
  100. EP Alert 260921.01: Global MASTER-Net observations report

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