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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"

26507 results found.

  1. GRB 251201B: Swift detection of a burst with an optical counterpart
  2. GRB 251201B: Fermi GBM Final Real-time Localization
  3. EP251130a: Mondy optical observations
  4. EP251130a: Optical detections with Kinder observations
  5. SVOM GRB251201.19: Global MASTER-Net observations report
  6. EP251130a: SAO RAS optical observations
  7. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  8. EP251130A: Optical observation from 1.3m DFOT
  9. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  10. EP251130a: JinShan optical observations
  11. GRB 251201A: MAXI/GSC detection
  12. Fermi GRB 251130B: Global MASTER-Net observations report
  13. GRB 251127A: SVOM/GRM observation
  14. IceCube Alert 251130.75: Global MASTER-Net observations report
  15. EP251130a: Swift-XRT counterpart detection
  16. EP251130a: Global MASTER-Net observations report
  17. EP251130a: COLIBRÍ optical counterpart candidate
  18. EP251130a: Einstein Probe detection of an X-ray transient
  19. GRB 251129A / EP251129a: SAO RAS optical observations
  20. GRB 251126A: SAO RAS optical observations
  21. GRB 251128A: SVOM/GRM observation of a long burst
  22. SVOM GRB 251129A : MASTER optical counterpart detection
  23. GRB 251129A: Swift-XRT afterglow detection
  24. EP251129a: Global MASTER-Net observations report
  25. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  26. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  27. GRB 251128A: Fermi GBM Observation
  28. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  29. GRB 251129A: SVOM detection of a burst
  30. SVOM GRB251129A: Global MASTER-Net observations report
  31. GRB 251129A: SVOM detection of a burst
  32. GRB 251126A: Swift-BAT refined analysis
  33. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  34. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  35. Fermi GRB 251128A: Global MASTER-Net observations report
  36. GRB 251127A: Glowbug gamma-ray detection
  37. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  38. GRB 251126A: further SAO RAS optical observations
  39. GRB 251126A NUTTelA-TAO Early Measurements
  40. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  41. GRB251126A: MAO/AZT-22 optical observations
  42. GRB251126A: Continued optical observation from 1.3m DFOT
  43. GRB 251126A: Swift/UVOT Detection
  44. GRB 251126A: Mondy and SAO RAS optical observations
  45. GRB 251126A: Swift-XRT refined Analysis
  46. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  47. GRB 251126A: NOT optical observations
  48. GRB 251126A: 1.3m DFOT optical afterglow detection
  49. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  50. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  51. Fermi GRB 251127A: Global MASTER-Net observations report
  52. GRB 251126A: Enhanced Swift-XRT position
  53. GRB 251126A: Kilonova-Catcher optical afterglow detection
  54. GRB 251126A: Nanshan/HMT optical afterglow detection
  55. Swift GRB 251126A: Global MASTER-Net observations report
  56. GRB 251121A: Fermi GBM Observation
  57. GRB 251126A: GIT discovery of the likely optical afterglow
  58. GRB 251126A: Swift detection of a burst
  59. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  60. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  61. EP251124b: NOT r- and z-band optical upper limits
  62. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  63. Fermi GRB 251125B: Global MASTER-Net observations report
  64. EP251124b: Global MASTER-Net observations report
  65. EP251124b: EP-WXT detection of a fast X-ray transient
  66. EP251124a: Xinglong GWAC-F60A optical observation
  67. Fermi GRB 251125A: Global MASTER-Net observations report
  68. EP251124a: NOT r- and z-band optical upper limits
  69. EP251124a: Global MASTER-Net observations report
  70. EP251124a: Swift-XRT observations
  71. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  72. EP251124a: Optical upper limit with Kinder observations
  73. Fermi GRB 251124a: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  75. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  76. EP251124a: GROWTH-India Telescope optical upper limits
  77. EP251124a: Einstein Probe detection of an X-ray transient
  78. GRB 251116C: Swift-XRT confirmation of fading
  79. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  80. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  81. EP251118A: 3.6m DOT optical afterglow detection
  82. GRB 251122A / EP251122a: EP-FXT counterpart detection
  83. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  84. GRB 251122A / EP251122a: WFST optical observations
  85. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  86. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  87. GRB 251122A / EP251122a: LCO optical upper limits
  88. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  89. EP251122a: Global MASTER-Net observations report
  90. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  91. GRB 251122A / EP251122a: SVOM detection of a long burst
  92. EP251122a: Einstein Probe detection of an X-ray transient
  93. EP251118a: Continued Optical Detection with Kinder observations
  94. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  95. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  96. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  97. EP251118a: Xinglong-2.16m optical observation
  98. GRB 251115A: Fermi GBM Observation
  99. Fermi trigger No 785388351: Global MASTER-Net observations report
  100. EP251118A: 1.3m DFOT optical afterglow detection

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