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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"

12321 results found.

  1. Fermi GRB 250406A: Global MASTER-Net observations report
  2. Fermi trigger No 765619921: Global MASTER-Net observations report
  3. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  4. Konus-Wind detection of GRB 250404A / EP250404a
  5. GRB 250404A / EP250404a: Mondy optical observations
  6. EP250402a: Optical upper limit with PD 1.3m observations
  7. Fermi GRB 250404A: Global MASTER-Net observations report
  8. EP250404a: Global MASTER-Net observations report
  9. GRB 250327B: VIRT Optical Upper Limit
  10. EP250321A: J band upper limit by SYSU 80cm telescope
  11. GRB 250403A: Swift/UVOT Detection
  12. GRB 250402A: Swift/UVOT Upper Limits
  13. EP250402a: Optical upper limit with Kinder observations
  14. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  15. GRB 250403A: Swift-XRT observations
  16. GRB 250322A: 10 GHz VLA radio upper limits
  17. Fermi GRB 250403A: Global MASTER-Net observations report
  18. GRB 250402A: NUTTelA-TAO Early Optical Limits
  19. GRB 250402A: Swift-XRT observations
  20. GRB 250402A: REM optical/NIR upper limits
  21. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  22. GRB 250329B: Swift/UVOT Upper Limit
  23. GRB 250329A: Swift/UVOT Upper Limit
  24. GRB 250327B: Swift/UVOT Detection
  25. GRB 250327A: Swift/UVOT Upper Limits
  26. GRB 250327B: Kilonova-Catcher Observations
  27. GRB 250331C: Swift/UVOT Upper Limits
  28. GRB 250331B: Swift/UVOT Upper Limits
  29. GRB 250331D: Swift-XRT observations
  30. Fermi GRB 250331E: Global MASTER-Net observations report
  31. Fermi GRB 250331D: Global MASTER-Net observations report
  32. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  33. Fermi trigger No 765078057: Global MASTER-Net observations report
  34. Swift GRB 250331C: Global MASTER-Net observations report
  35. Swift GRB 250331B: Global MASTER-Net observations report
  36. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  37. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  38. GRB20250327B: 45th Parallel Observatory upper limit
  39. GRB 250328A: Swift/UVOT Detection
  40. Fermi-LAT gamma-ray observations of IceCube-250330A
  41. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  42. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  43. GRB 250331B: Swift detection of a burst
  44. GRB 250330A: SVOM/VT optical upper limit
  45. GRB 250331A: MAXI/GSC detection
  46. Fermi GRB 250330B: Global MASTER-Net observations report
  47. Fermi GRB 250330A: Global MASTER-Net observations report
  48. GRB 250330A: BOOTES-7 early optical upper limit
  49. GRB 250330A: Swift/UVOT Upper Limits
  50. GRB 250330A: Swift-XRT afterglow detection
  51. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  52. IceCube Alert 250330.35: Global MASTER-Net observations report
  53. GRB 250329B: Swift-XRT afterglow detection
  54. Swift GRB250330.26: Global MASTER-Net observations report
  55. GRB 250329B: SVOM/C-GFT optical upper limit
  56. GRB 250329B: SVOM/VT optical upper limit
  57. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  58. GRB 250329B: GWAC-F50A optical upper limit
  59. GRB 250328A: SVOM/C-GFT optical upper limit
  60. GRB 250327B: J-band observations with WINTER
  61. GRB 250328A: GWAC-F50A optical upper limit
  62. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  63. GRB 250322A: GRANDMA/TNOT optical upper limits
  64. GRB 250327A: SVOM/VT upper limits on the XRT position
  65. GRB 250327A: J-band observations with WINTER
  66. GRB 250327A: SVOM/VT optical candidate
  67. Fermi GRB 250327A: Global MASTER-Net observations report
  68. Swift GRB 250327A: Global MASTER-Net observations report
  69. GRB 250327A: COLIBRÍ optical upper limit
  70. Fermi trigger No 764700395: Global MASTER-Net observations report
  71. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  72. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  73. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  74. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  75. GRB 250322A: Swift/UVOT Upper Limits
  76. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  77. GRB 250321B: Swift-XRT observations
  78. GRB 250322A: NOT optical upper limits
  79. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  80. GRB 250322A: MASTER optical observation
  81. GRB 250321A: Swift/UVOT Upper Limits
  82. Fermi GRB 250320B: Global MASTER-Net observations report
  83. EP250321a: Global MASTER-Net observations report
  84. Swift GRB 250321A: Global MASTER-Net observations report
  85. Fermi GRB 250321A: Global MASTER-Net observations report
  86. GRB 250321A: GOTO optical upper limits
  87. GRB 250314A: Keck/NIRC2 J-band upper limit
  88. Fermi GRB 250319B: Global MASTER-Net observations report
  89. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  90. GRB 250314A: ATCA radio upper limits
  91. GRB 250317B: Leavitt Observatory optical upper limit
  92. Fermi trigger No 763933627: Global MASTER-Net observations report
  93. GRB250312A: Swift/UVOT Upper Limits
  94. GRB 250317B: Swift-XRT observations
  95. GRB 250316A: Swift/UVOT Upper Limits
  96. GRB 250314A: REM optical/NIR upper limits
  97. GRB 250316A: AbAO AS-32 Optical Upper Limit
  98. GRB 250316A: Swift-XRT observations
  99. Fermi trigger No 763862734: Global MASTER-Net observations report
  100. Fermi GRB 250316A: Global MASTER-Net observations report

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