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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"
  1. Swift GRB 251126A: Global MASTER-Net observations report
  2. GRB 251121A: Fermi GBM Observation
  3. GRB 251126A: Prompt enhanced Swift-XRT position
  4. GRB 251126A: GIT discovery of the likely optical afterglow
  5. GRB 251126A: Swift detection of a burst
  6. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  7. EP251124b follow-up observation by EP-FXT
  8. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  9. EP251124b: NOT r- and z-band optical upper limits
  10. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  11. Fermi GRB 251125B: Global MASTER-Net observations report
  12. GRB 251125B: Fermi GBM Final Real-time Localization
  13. EP251124b: Global MASTER-Net observations report
  14. EP251124b: EP-WXT detection of a fast X-ray transient
  15. EP251124a: Xinglong GWAC-F60A optical observation
  16. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  17. Fermi GRB 251125A: Global MASTER-Net observations report
  18. GRB 251125A: Fermi GBM Final Real-time Localization
  19. EP251124a: NOT r- and z-band optical upper limits
  20. EP251124a: Global MASTER-Net observations report
  21. EP251124a: Swift-XRT observations
  22. GRB 251124A: Fermi GBM Localization by automated pipeline
  23. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  24. EP251124a: Optical upper limit with Kinder observations
  25. GRB 251122B: Fermi GBM Final Localization
  26. EP251118A: 6 GHz VLA Detection
  27. Fermi GRB 251124a: Global MASTER-Net observations report
  28. GRB 251124a: Fermi GBM Final Localization
  29. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  30. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  31. EP251124a: GROWTH-India Telescope optical upper limits
  32. EP251124a: Einstein Probe detection of an X-ray transient
  33. GRB 251116C: Swift-XRT confirmation of fading
  34. GRB 251122A/EP251122a: FTW optical and NIR observations
  35. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  36. The EP-WXT trigger 01709248783 is likely a flaring star
  37. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  38. EP251118A: 3.6m DOT optical afterglow detection
  39. GRB 251122A / EP251122a: EP-FXT counterpart detection
  40. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  41. GRB 251122A / EP251122a: WFST optical observations
  42. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  43. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  44. GRB 251122A / EP251122a: LCO optical upper limits
  45. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  46. EP251122a: Global MASTER-Net observations report
  47. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  48. GRB 251122A / EP251122a: SVOM detection of a long burst
  49. EP251122a: Einstein Probe detection of an X-ray transient
  50. EP251118a: Continued Optical Detection with Kinder observations
  51. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  52. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  53. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  54. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  55. EP251118a: Xinglong-2.16m optical observation
  56. GRB 251115A: Fermi GBM Observation
  57. The EP-WXT trigger 01709248635 is likely a flaring star
  58. GRB 251121A: Fermi GBM Final Real-time Localization
  59. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  60. Fermi trigger No 785388351: Global MASTER-Net observations report
  61. EP251118A: 1.3m DFOT optical afterglow detection
  62. GRB 251118A: Swift/UVOT Detection
  63. EP251118a / GRB 251118C: SAO RAS optical observations
  64. GRB 251118A: Glowbug gamma-ray detection
  65. GRB 251118A: Fermi GBM Observation
  66. GRB 251118A: Swift-XRT afterglow detection
  67. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  68. EP251118a: Optical detection with Kinder observations
  69. GRB 251118A: GECAM-B detection
  70. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  71. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  72. EP251118a / GRB 251118C: SVOM/VT optical observation
  73. The EP-WXT trigger 01709248403 is likely a flaring star
  74. GRB 251118A: NuSTAR detection of bright prompt emission
  75. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  76. GRB 251116C: NOT optical observations
  77. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  78. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  79. GRB 251018A: FRAM-Auger optical detection
  80. GRB 251117A: Swift-XRT observations
  81. EP251118A / GRB 251118C : MASTER optical counterpart observations
  82. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  83. Konus-Wind detection of GRB 251118C (EP251118a)
  84. The EP-WXT trigger 01709248388 is likely a flaring star
  85. EP251118a: FTW optical and NIR observations
  86. GRB 251117A: Insight-HXMT/HE detection
  87. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  88. EP251118a: VLT near-infrared observation
  89. GRB 251116D: SVOM/GRM observation of a long GRB
  90. EP251118a: GOTO optical afterglow detection
  91. GRB 251119A: SVOM detection of a possible burst
  92. EP251118a: NOT spectroscopic redshift of z = 1.216
  93. EP251118a: Global MASTER-Net observations report
  94. EP251118a: preliminary result of EP-FXT follow-up observation
  95. LAT GRB251118.86: Global MASTER-Net observations report
  96. GRB 251118A: Fermi-LAT detection
  97. EP251118a: NOT candidate optical counterpart
  98. GRB 251118A: Swift ToO observations
  99. EP251118a: Einstein Probe detected of a fast X-ray transient
  100. Fermi GRB 251118B: Global MASTER-Net observations report

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