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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"

12316 results found.

  1. EP250402a: Optical upper limit with PD 1.3m observations
  2. Fermi GRB 250404A: Global MASTER-Net observations report
  3. EP250404a: Global MASTER-Net observations report
  4. GRB 250327B: VIRT Optical Upper Limit
  5. EP250321A: J band upper limit by SYSU 80cm telescope
  6. GRB 250403A: Swift/UVOT Detection
  7. GRB 250402A: Swift/UVOT Upper Limits
  8. EP250402a: Optical upper limit with Kinder observations
  9. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  10. GRB 250403A: Swift-XRT observations
  11. GRB 250322A: 10 GHz VLA radio upper limits
  12. Fermi GRB 250403A: Global MASTER-Net observations report
  13. GRB 250402A: NUTTelA-TAO Early Optical Limits
  14. GRB 250402A: Swift-XRT observations
  15. GRB 250402A: REM optical/NIR upper limits
  16. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  17. GRB 250329B: Swift/UVOT Upper Limit
  18. GRB 250329A: Swift/UVOT Upper Limit
  19. GRB 250327B: Swift/UVOT Detection
  20. GRB 250327A: Swift/UVOT Upper Limits
  21. GRB 250327B: Kilonova-Catcher Observations
  22. GRB 250331C: Swift/UVOT Upper Limits
  23. GRB 250331B: Swift/UVOT Upper Limits
  24. GRB 250331D: Swift-XRT observations
  25. Fermi GRB 250331E: Global MASTER-Net observations report
  26. Fermi GRB 250331D: Global MASTER-Net observations report
  27. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  28. Fermi trigger No 765078057: Global MASTER-Net observations report
  29. Swift GRB 250331C: Global MASTER-Net observations report
  30. Swift GRB 250331B: Global MASTER-Net observations report
  31. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  32. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  33. GRB20250327B: 45th Parallel Observatory upper limit
  34. GRB 250328A: Swift/UVOT Detection
  35. Fermi-LAT gamma-ray observations of IceCube-250330A
  36. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  37. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  38. GRB 250331B: Swift detection of a burst
  39. GRB 250330A: SVOM/VT optical upper limit
  40. GRB 250331A: MAXI/GSC detection
  41. Fermi GRB 250330B: Global MASTER-Net observations report
  42. Fermi GRB 250330A: Global MASTER-Net observations report
  43. GRB 250330A: BOOTES-7 early optical upper limit
  44. GRB 250330A: Swift/UVOT Upper Limits
  45. GRB 250330A: Swift-XRT afterglow detection
  46. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  47. IceCube Alert 250330.35: Global MASTER-Net observations report
  48. GRB 250329B: Swift-XRT afterglow detection
  49. Swift GRB250330.26: Global MASTER-Net observations report
  50. GRB 250329B: SVOM/C-GFT optical upper limit
  51. GRB 250329B: SVOM/VT optical upper limit
  52. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  53. GRB 250329B: GWAC-F50A optical upper limit
  54. GRB 250328A: SVOM/C-GFT optical upper limit
  55. GRB 250327B: J-band observations with WINTER
  56. GRB 250328A: GWAC-F50A optical upper limit
  57. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  58. GRB 250322A: GRANDMA/TNOT optical upper limits
  59. GRB 250327A: SVOM/VT upper limits on the XRT position
  60. GRB 250327A: J-band observations with WINTER
  61. GRB 250327A: SVOM/VT optical candidate
  62. Fermi GRB 250327A: Global MASTER-Net observations report
  63. Swift GRB 250327A: Global MASTER-Net observations report
  64. GRB 250327A: COLIBRÍ optical upper limit
  65. Fermi trigger No 764700395: Global MASTER-Net observations report
  66. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  67. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  68. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  69. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  70. GRB 250322A: Swift/UVOT Upper Limits
  71. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  72. GRB 250321B: Swift-XRT observations
  73. GRB 250322A: NOT optical upper limits
  74. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  75. GRB 250322A: MASTER optical observation
  76. GRB 250321A: Swift/UVOT Upper Limits
  77. Fermi GRB 250320B: Global MASTER-Net observations report
  78. EP250321a: Global MASTER-Net observations report
  79. Swift GRB 250321A: Global MASTER-Net observations report
  80. Fermi GRB 250321A: Global MASTER-Net observations report
  81. GRB 250321A: GOTO optical upper limits
  82. GRB 250314A: Keck/NIRC2 J-band upper limit
  83. Fermi GRB 250319B: Global MASTER-Net observations report
  84. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  85. GRB 250314A: ATCA radio upper limits
  86. GRB 250317B: Leavitt Observatory optical upper limit
  87. Fermi trigger No 763933627: Global MASTER-Net observations report
  88. GRB250312A: Swift/UVOT Upper Limits
  89. GRB 250317B: Swift-XRT observations
  90. GRB 250316A: Swift/UVOT Upper Limits
  91. GRB 250314A: REM optical/NIR upper limits
  92. GRB 250316A: AbAO AS-32 Optical Upper Limit
  93. GRB 250316A: Swift-XRT observations
  94. Fermi trigger No 763862734: Global MASTER-Net observations report
  95. Fermi GRB 250316A: Global MASTER-Net observations report
  96. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  97. GRB 250314A: Swift/UVOT Upper Limits
  98. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  99. SVOM/MXT upper limit on GRB 250314A
  100. GRB 250314A: SVOM/VT upper limit

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