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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"

12334 results found.

  1. GRB 251208D: Swift-XRT observations
  2. GRB 251129A: e-MERLIN C-band observations
  3. LAT GRB251208.43: Global MASTER-Net observations report
  4. GRB 251208D: LCO optical upper limits
  5. SVOM GRB251208D: Global MASTER-Net observations report
  6. SVOM GRB251206.86: Global MASTER-Net observations report
  7. GRB 251203C: Swift/UVOT Upper Limit
  8. Konus-Wind detection of GRB 251118A
  9. Swift GRB251205A: Global MASTER-Net observations report
  10. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  11. GRB 251201B: SALT spectroscopic redshift z = 1.599
  12. GRB 251203C: J-band observations with WINTER
  13. GRB 251203C: LCO optical afterglow confirmation
  14. GRB 251203B: Swift-XRT observations
  15. GRB 251203C: LCO optical upper limits
  16. GRB 251203B: LCO optical upper limits
  17. SVOM GRB251203.77: Global MASTER-Net observations report
  18. SVOM GRB251203B: Global MASTER-Net observations report
  19. Fermi GRB 251202B: Global MASTER-Net observations report
  20. GRB251129A/EP251129a: Swift UVOT detection
  21. GRB 251202A: Swift/UVOT Detection
  22. GRB 251201B: Swift/UVOT Detection
  23. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  24. Fermi GRB 251202A: Global MASTER-Net observations report
  25. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  26. Swift GRB 251201B: Global MASTER-Net observations report
  27. SVOM GRB251201.19: Global MASTER-Net observations report
  28. Fermi GRB 251130B: Global MASTER-Net observations report
  29. IceCube Alert 251130.75: Global MASTER-Net observations report
  30. EP251130a: Swift-XRT counterpart detection
  31. EP251130a: Global MASTER-Net observations report
  32. GRB 251129A: Swift-XRT afterglow detection
  33. EP251129a: Global MASTER-Net observations report
  34. SVOM GRB251129A: Global MASTER-Net observations report
  35. Fermi GRB 251128A: Global MASTER-Net observations report
  36. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  37. GRB 251126A: Swift/UVOT Detection
  38. EP251124a: Pan-STARRS ri-band imaging and photometry
  39. Fermi GRB 251127A: Global MASTER-Net observations report
  40. Swift GRB 251126A: Global MASTER-Net observations report
  41. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  42. EP251124b: NOT r- and z-band optical upper limits
  43. Fermi GRB 251125B: Global MASTER-Net observations report
  44. EP251124b: Global MASTER-Net observations report
  45. EP251124a: Xinglong GWAC-F60A optical observation
  46. Fermi GRB 251125A: Global MASTER-Net observations report
  47. EP251124a: NOT r- and z-band optical upper limits
  48. EP251124a: Global MASTER-Net observations report
  49. EP251124a: Swift-XRT observations
  50. EP251124a: Optical upper limit with Kinder observations
  51. Fermi GRB 251124a: Global MASTER-Net observations report
  52. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  53. EP251124a: GROWTH-India Telescope optical upper limits
  54. GRB 251122A / EP251122a: EP-FXT counterpart detection
  55. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  56. GRB 251122A / EP251122a: LCO optical upper limits
  57. EP251122a: Global MASTER-Net observations report
  58. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  59. Fermi trigger No 785388351: Global MASTER-Net observations report
  60. GRB 251118A: Swift/UVOT Detection
  61. GRB 251118A: Swift-XRT afterglow detection
  62. GRB 251117A: Swift-XRT observations
  63. EP251118a: Global MASTER-Net observations report
  64. LAT GRB251118.86: Global MASTER-Net observations report
  65. Fermi GRB 251118B: Global MASTER-Net observations report
  66. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  67. GRB 251115A: Swift-XRT observations
  68. LAT GRB251117.51: Global MASTER-Net observations report
  69. GRB 251116B: SVOM/VT optical upper limit
  70. GRB 251116C: Swift-XRT observations
  71. GRB 251116C: SVOM/VT optical upper limit
  72. GRB 251111A: Mondy optical upper limit
  73. GRB 251116B: LCO optical upper limits
  74. GRB 251116C: LCO optical upper limits
  75. SVOM GRB251116C: Global MASTER-Net observations report
  76. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  77. Fermi GRB 251115A: Global MASTER-Net observations report
  78. Konus-Wind detection of GRB 251108C
  79. Fermi trigger No 784717756: Global MASTER-Net observations report
  80. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  81. Fermi GRB 251114A: Global MASTER-Net observations report
  82. Fermi GRB 251113A: Global MASTER-Net observations report
  83. GRB 251112A: Swift/UVOT Upper Limits
  84. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  85. GRB 251112B: MAXI/GSC detection
  86. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  87. Swift Trigger 1413695: a possible GRB 251112A
  88. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  89. Fermi trigger No 784621743: Global MASTER-Net observations report
  90. GRB251111A: 1.3m DFOT optical upper limit
  91. SVOM GRB251111.42: Global MASTER-Net observations report
  92. GRB 251111A: Swift-XRT observations
  93. SVOM GRB251111.22: Global MASTER-Net observations report
  94. GRB 251111A: KAIT optical upper limit
  95. GRB 251106A: Swift/UVOT Upper Limits
  96. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  97. Fermi trigger No 784329591: Global MASTER-Net observations report
  98. Fermi trigger No 784279167: Global MASTER-Net observations report
  99. SVOM GRB251108.54: Global MASTER-Net observations report
  100. SVOM GRB251106.83: Global MASTER-Net observations report

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