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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"

28086 results found.

  1. GRB 251128A: SVOM/GRM observation of a long burst
  2. SVOM GRB 251129A : MASTER optical counterpart detection
  3. GRB 251129A: Swift-XRT afterglow detection
  4. EP251129a: Global MASTER-Net observations report
  5. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  6. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  7. GRB 251128A: Fermi GBM Observation
  8. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  9. GRB 251129A: SVOM detection of a burst
  10. SVOM GRB251129A: Global MASTER-Net observations report
  11. GRB 251129A: SVOM detection of a burst
  12. GRB 251126A: Swift-BAT refined analysis
  13. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  14. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  15. Fermi GRB 251128A: Global MASTER-Net observations report
  16. GRB 251127A: Glowbug gamma-ray detection
  17. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  18. GRB 251126A: further SAO RAS optical observations
  19. GRB 251126A NUTTelA-TAO Early Measurements
  20. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  21. GRB251126A: MAO/AZT-22 optical observations
  22. GRB251126A: Continued optical observation from 1.3m DFOT
  23. GRB 251126A: Swift/UVOT Detection
  24. GRB 251126A: Mondy and SAO RAS optical observations
  25. GRB 251126A: Swift-XRT refined Analysis
  26. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  27. GRB 251126A: NOT optical observations
  28. GRB 251126A: 1.3m DFOT optical afterglow detection
  29. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  30. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  31. Fermi GRB 251127A: Global MASTER-Net observations report
  32. GRB 251126A: Enhanced Swift-XRT position
  33. GRB 251126A: Kilonova-Catcher optical afterglow detection
  34. GRB 251126A: Nanshan/HMT optical afterglow detection
  35. Swift GRB 251126A: Global MASTER-Net observations report
  36. GRB 251121A: Fermi GBM Observation
  37. GRB 251126A: GIT discovery of the likely optical afterglow
  38. GRB 251126A: Swift detection of a burst
  39. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  40. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  41. EP251124b: NOT r- and z-band optical upper limits
  42. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  43. Fermi GRB 251125B: Global MASTER-Net observations report
  44. EP251124b: Global MASTER-Net observations report
  45. EP251124b: EP-WXT detection of a fast X-ray transient
  46. EP251124a: Xinglong GWAC-F60A optical observation
  47. Fermi GRB 251125A: Global MASTER-Net observations report
  48. EP251124a: NOT r- and z-band optical upper limits
  49. EP251124a: Global MASTER-Net observations report
  50. EP251124a: Swift-XRT observations
  51. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  52. EP251124a: Optical upper limit with Kinder observations
  53. Fermi GRB 251124a: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  55. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  56. EP251124a: GROWTH-India Telescope optical upper limits
  57. EP251124a: Einstein Probe detection of an X-ray transient
  58. GRB 251116C: Swift-XRT confirmation of fading
  59. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  60. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  61. EP251118A: 3.6m DOT optical afterglow detection
  62. GRB 251122A / EP251122a: EP-FXT counterpart detection
  63. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  64. GRB 251122A / EP251122a: WFST optical observations
  65. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  66. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  67. GRB 251122A / EP251122a: LCO optical upper limits
  68. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  69. EP251122a: Global MASTER-Net observations report
  70. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  71. GRB 251122A / EP251122a: SVOM detection of a long burst
  72. EP251122a: Einstein Probe detection of an X-ray transient
  73. EP251118a: Continued Optical Detection with Kinder observations
  74. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  75. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  76. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  77. EP251118a: Xinglong-2.16m optical observation
  78. GRB 251115A: Fermi GBM Observation
  79. Fermi trigger No 785388351: Global MASTER-Net observations report
  80. EP251118A: 1.3m DFOT optical afterglow detection
  81. GRB 251118A: Swift/UVOT Detection
  82. EP251118a / GRB 251118C: SAO RAS optical observations
  83. GRB 251118A: Glowbug gamma-ray detection
  84. GRB 251118A: Fermi GBM Observation
  85. GRB 251118A: Swift-XRT afterglow detection
  86. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  87. EP251118a: Optical detection with Kinder observations
  88. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  89. GRB 251118A: NuSTAR detection of bright prompt emission
  90. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  91. GRB 251116C: NOT optical observations
  92. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  93. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  94. GRB 251117A: Swift-XRT observations
  95. EP251118A / GRB 251118C : MASTER optical counterpart observations
  96. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  97. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  98. EP251118a: VLT near-infrared observation
  99. GRB 251116D: SVOM/GRM observation of a long GRB
  100. GRB 251119A: SVOM detection of a possible burst

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