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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"

12028 results found.

  1. Fermi GRB 250407A: Global MASTER-Net observations report
  2. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  3. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  4. Konus-Wind detection of GRB 250406B (short/hard)
  5. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  6. IceCube Alert 250406.95: Global MASTER-Net observations report
  7. Fermi trigger No 765663719: Global MASTER-Net observations report
  8. Fermi GRB 250406A: Global MASTER-Net observations report
  9. Fermi trigger No 765619921: Global MASTER-Net observations report
  10. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  11. Konus-Wind detection of GRB 250404A / EP250404a
  12. GRB 250404A / EP250404a: Mondy optical observations
  13. EP250402a: Optical upper limit with PD 1.3m observations
  14. Fermi GRB 250404A: Global MASTER-Net observations report
  15. EP250404a: Global MASTER-Net observations report
  16. GRB 250327B: VIRT Optical Upper Limit
  17. EP250321A: J band upper limit by SYSU 80cm telescope
  18. GRB 250403A: Swift/UVOT Detection
  19. GRB 250402A: Swift/UVOT Upper Limits
  20. EP250402a: Optical upper limit with Kinder observations
  21. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  22. GRB 250403A: Swift-XRT observations
  23. GRB 250322A: 10 GHz VLA radio upper limits
  24. Fermi GRB 250403A: Global MASTER-Net observations report
  25. GRB 250402A: NUTTelA-TAO Early Optical Limits
  26. GRB 250402A: Swift-XRT observations
  27. GRB 250402A: REM optical/NIR upper limits
  28. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  29. GRB 250329B: Swift/UVOT Upper Limit
  30. GRB 250329A: Swift/UVOT Upper Limit
  31. GRB 250327B: Swift/UVOT Detection
  32. GRB 250327A: Swift/UVOT Upper Limits
  33. GRB 250327B: Kilonova-Catcher Observations
  34. GRB 250331C: Swift/UVOT Upper Limits
  35. GRB 250331B: Swift/UVOT Upper Limits
  36. GRB 250331D: Swift-XRT observations
  37. Fermi GRB 250331E: Global MASTER-Net observations report
  38. Fermi GRB 250331D: Global MASTER-Net observations report
  39. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  40. Fermi trigger No 765078057: Global MASTER-Net observations report
  41. Swift GRB 250331C: Global MASTER-Net observations report
  42. Swift GRB 250331B: Global MASTER-Net observations report
  43. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  44. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  45. GRB20250327B: 45th Parallel Observatory upper limit
  46. GRB 250328A: Swift/UVOT Detection
  47. Fermi-LAT gamma-ray observations of IceCube-250330A
  48. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  49. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  50. GRB 250331B: Swift detection of a burst
  51. GRB 250330A: SVOM/VT optical upper limit
  52. GRB 250331A: MAXI/GSC detection
  53. Fermi GRB 250330B: Global MASTER-Net observations report
  54. Fermi GRB 250330A: Global MASTER-Net observations report
  55. GRB 250330A: BOOTES-7 early optical upper limit
  56. GRB 250330A: Swift/UVOT Upper Limits
  57. GRB 250330A: Swift-XRT afterglow detection
  58. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  59. IceCube Alert 250330.35: Global MASTER-Net observations report
  60. GRB 250329B: Swift-XRT afterglow detection
  61. Swift GRB250330.26: Global MASTER-Net observations report
  62. GRB 250329B: SVOM/C-GFT optical upper limit
  63. GRB 250329B: SVOM/VT optical upper limit
  64. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  65. GRB 250329B: GWAC-F50A optical upper limit
  66. GRB 250328A: SVOM/C-GFT optical upper limit
  67. GRB 250327B: J-band observations with WINTER
  68. GRB 250328A: GWAC-F50A optical upper limit
  69. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  70. GRB 250322A: GRANDMA/TNOT optical upper limits
  71. GRB 250327A: SVOM/VT upper limits on the XRT position
  72. GRB 250327A: J-band observations with WINTER
  73. GRB 250327A: SVOM/VT optical candidate
  74. Fermi GRB 250327A: Global MASTER-Net observations report
  75. Swift GRB 250327A: Global MASTER-Net observations report
  76. GRB 250327A: COLIBRÍ optical upper limit
  77. Fermi trigger No 764700395: Global MASTER-Net observations report
  78. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  79. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  80. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  81. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  82. GRB 250322A: Swift/UVOT Upper Limits
  83. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  84. GRB 250321B: Swift-XRT observations
  85. GRB 250322A: NOT optical upper limits
  86. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  87. GRB 250322A: MASTER optical observation
  88. GRB 250321A: Swift/UVOT Upper Limits
  89. Fermi GRB 250320B: Global MASTER-Net observations report
  90. EP250321a: Global MASTER-Net observations report
  91. Swift GRB 250321A: Global MASTER-Net observations report
  92. Fermi GRB 250321A: Global MASTER-Net observations report
  93. GRB 250321A: GOTO optical upper limits
  94. GRB 250314A: Keck/NIRC2 J-band upper limit
  95. Fermi GRB 250319B: Global MASTER-Net observations report
  96. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  97. GRB 250314A: ATCA radio upper limits
  98. GRB 250317B: Leavitt Observatory optical upper limit
  99. Fermi trigger No 763933627: Global MASTER-Net observations report
  100. GRB250312A: Swift/UVOT Upper Limits

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