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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. EP260924a: EP-FXT follow-up observation
  2. Swift Trigger 1513439 is probably not a GRB
  3. GRB 260925A: Swift/UVOT Upper Limits
  4. Konus-Wind detection of GRB 260924A
  5. GRB 260924A: Extreme Isotropic-equivalent Gamma-ray Energy and encouragement for multiwavelength follow-up observations
  6. GRB 260923A: Glowbug gamma-ray detection
  7. GRB 260924A: Optical follow-up observations with Kinder
  8. GRB 260922A: Glowbug gamma-ray detection
  9. GRB 260925A: Enhanced Swift-XRT position
  10. GRB 260925A: COLIBRÍ optical upper limits
  11. GRB 260925A: FRAM-Auger optical limit
  12. GRB 260924A: Ondrejov D50 optical afterglow detection
  13. EP260924a: J-band upper limit with WINTER
  14. GRB 260924A: SVOM/GRM observation
  15. GRB 260924A: 2.2m CAHA spectroscopic redshift z = 3.51
  16. GRB 260925A: Swift detection of a burst
  17. GRB 260923A: Insight-HXMT/HE detection
  18. EP260924a: EP-WXT detection of an X-ray transient
  19. GRB 260924A: J-band observations by the SYSU 80 cm infrared telescope
  20. GRB 260924A: Swift/UVOT Detection
  21. GRB 260924A: GROWTH-India Telescope optical observations
  22. GRB 260924A: Swift-BAT refined analysis
  23. GRB 260924A: NuSTAR detection of prompt emission
  24. GRB 260924A: Swift/UVOT Upper Limits
  25. GRB 260924A: Swift-XRT refined Analysis
  26. Konus-Wind detection of GRB 260922A
  27. GRB 260922A: NuSTAR detection of prompt emission
  28. GRB 260921A: NuSTAR detection of prompt emission
  29. Konus-Wind detection of GRB 260921A (correction to GCN 45722)
  30. GRB 260921A: SVOM/GRM observation
  31. GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
  32. GRB 260924A: Fermi GRB Observation
  33. Konus-Wind detection of GRB 260921A (possible merger-origin)
  34. GRB 260924A: Fermi-LAT detection of a bright burst
  35. GRB 260924A: AstroSat CZTI detection
  36. GRB 260920A: SVOM/GRM observation
  37. GRB 260924A: NOT optical counterpart confirmation
  38. GRB 260924A: detection of a bright optical afterglow by the 1.5m OSN telescope
  39. GRB 260922A: CALET Gamma-Ray Burst Monitor detection
  40. GRB 260924A: Enhanced Swift-XRT position
  41. The EP-WXT trigger 01709319842 is likely a flaring star
  42. GRB 260924A: Swift detection of a burst
  43. GRB 260924A: Fermi GBM Final Real-time Localization
  44. Fermi GRB 260923A: Global MASTER-Net observations report
  45. GRB 260923A: Fermi GBM Final Real-time Localization
  46. Trigger_21914: Swift ToO observations
  47. EP260806a: e-MERLIN detection at 5 GHz
  48. GRB 260922A: Ondrejov D50 optical limit
  49. Fermi-LAT Gamma-ray Observations of IceCube-260919A
  50. Fermi-LAT Gamma-ray Observations of IceCube-260916A
  51. ATCA observations of GRB 260909A
  52. GRB 260922A: Swift-BAT refined analysis
  53. EP260920a: VLT/HAWK-I near-infrared counterpart confirmation
  54. GRB 260922A: J-band upper limit with WINTER
  55. GRB 260922A: Swift/UVOT Upper Limits
  56. GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
  57. GRB 260922A: COLIBRÍ optical upper limits
  58. GRB 260922A: Swift-XRT refined Analysis
  59. GRB 260922A: Enhanced Swift-XRT position
  60. Fermi-LAT Gamma-ray Observations of IceCube-260805A
  61. Konus-Wind detection of GRB 260810A
  62. GRB 260920A: Glowbug gamma-ray detection
  63. GRB 260918A: SVOM/ECLAIRs refined analysis
  64. GRB 260922A: SVOM/C-GFT optical upper limit
  65. GRB 260922A: Swift detection of a burst
  66. GRB 260917C: AstroSat CZTI detection
  67. GRB 260920B/EP260920b: GECAM-B detection of a burst
  68. GRB 260921A: AstroSat CZTI detection
  69. GRB 260921A: Swift-BAT refined analysis
  70. GRB 260921B: Fermi GBM Final Localization
  71. GRB 260921A: Fermi GBM Observation
  72. EP260920b: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  73. EP Alert 260921.58: Global MASTER-Net observations report
  74. GRB 260917B:: SVOM/ECLAIRs refined analysis
  75. The EP-WXT trigger 01709319528 is likely a flaring star
  76. EP260920a: VLT/HAWK-I near-infrared candidate
  77. Swift GRB 260921A: MASTER OT J094129.58+025052.5 possible optical counterpart detection with host galaxy (z=1.3)
  78. Swift GRB 260921A: Global MASTER-Net observations report
  79. GRB 260921A: Swift detection of a burst
  80. EP260920b: VLT/X-shooter spectroscopic redshift z = 3.582
  81. GRB 260921A: Fermi GBM Final Real-time Localization
  82. EP260920b: LCO observations
  83. GRB 260920A: AstroSat CZTI detection
  84. EP260920b: SVOM/VT optical observation
  85. EP260920b: refined analysis of the EP-WXT and EP-FXT observations
  86. EP260920b: COLIBRÍ optical observations
  87. EP260920b: LCO optical counterpart detection
  88. The EP-WXT trigger 01709318601 is likely a flaring star
  89. EP Alert 260921.01: Global MASTER-Net observations report
  90. EP260920b: Global MASTER-Net observations report
  91. EP260920b: Einstein Probe detection of an X-ray transient
  92. IceCube-260919A: Upper limits from a search for additional neutrino events in IceCube
  93. EP Alert 260920.66: Global MASTER-Net observations report
  94. EP-WXT detected a brightening of HMXB LS V +44 17
  95. EP260920a: NOT early time optical upper limits
  96. EP260920a: NOT optical upper limits
  97. GRB 260920A: Fermi GBM Final Real-time Localization
  98. EP260920a: SVOM/VT optical upper limits
  99. EP260917a: Global MASTER-Net observations report
  100. EP260920a: refined analysis of the EP-WXT and autonomous EP-FXT observations

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