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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. Fermi GRB 251127A: Global MASTER-Net observations report
  2. GRB 251127A: Fermi GBM Final Real-time Localization
  3. GRB 251126A: Enhanced Swift-XRT position
  4. GRB 251126A: Kilonova-Catcher optical afterglow detection
  5. GRB 251126A: Asiago i-band detection
  6. GRB 251126A: Nanshan/HMT optical afterglow detection
  7. Swift GRB 251126A: Global MASTER-Net observations report
  8. GRB 251121A: Fermi GBM Observation
  9. GRB 251126A: Prompt enhanced Swift-XRT position
  10. GRB 251126A: GIT discovery of the likely optical afterglow
  11. GRB 251126A: Swift detection of a burst
  12. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  13. EP251124b follow-up observation by EP-FXT
  14. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  15. EP251124b: NOT r- and z-band optical upper limits
  16. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  17. Fermi GRB 251125B: Global MASTER-Net observations report
  18. GRB 251125B: Fermi GBM Final Real-time Localization
  19. EP251124b: Global MASTER-Net observations report
  20. EP251124b: EP-WXT detection of a fast X-ray transient
  21. EP251124a: Xinglong GWAC-F60A optical observation
  22. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  23. Fermi GRB 251125A: Global MASTER-Net observations report
  24. GRB 251125A: Fermi GBM Final Real-time Localization
  25. EP251124a: NOT r- and z-band optical upper limits
  26. EP251124a: Global MASTER-Net observations report
  27. EP251124a: Swift-XRT observations
  28. GRB 251124A: Fermi GBM Localization by automated pipeline
  29. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  30. EP251124a: Optical upper limit with Kinder observations
  31. GRB 251122B: Fermi GBM Final Localization
  32. EP251118A: 6 GHz VLA Detection
  33. Fermi GRB 251124a: Global MASTER-Net observations report
  34. GRB 251124a: Fermi GBM Final Localization
  35. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  36. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  37. EP251124a: GROWTH-India Telescope optical upper limits
  38. EP251124a: Einstein Probe detection of an X-ray transient
  39. GRB 251116C: Swift-XRT confirmation of fading
  40. GRB 251122A/EP251122a: FTW optical and NIR observations
  41. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  42. The EP-WXT trigger 01709248783 is likely a flaring star
  43. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  44. EP251118A: 3.6m DOT optical afterglow detection
  45. GRB 251122A / EP251122a: EP-FXT counterpart detection
  46. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  47. GRB 251122A / EP251122a: WFST optical observations
  48. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  49. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  50. GRB 251122A / EP251122a: LCO optical upper limits
  51. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  52. EP251122a: Global MASTER-Net observations report
  53. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  54. GRB 251122A / EP251122a: SVOM detection of a long burst
  55. EP251122a: Einstein Probe detection of an X-ray transient
  56. EP251118a: Continued Optical Detection with Kinder observations
  57. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  58. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  59. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  60. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  61. EP251118a: Xinglong-2.16m optical observation
  62. GRB 251115A: Fermi GBM Observation
  63. The EP-WXT trigger 01709248635 is likely a flaring star
  64. GRB 251121A: Fermi GBM Final Real-time Localization
  65. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  66. Fermi trigger No 785388351: Global MASTER-Net observations report
  67. EP251118A: 1.3m DFOT optical afterglow detection
  68. GRB 251118A: Swift/UVOT Detection
  69. EP251118a / GRB 251118C: SAO RAS optical observations
  70. GRB 251118A: Glowbug gamma-ray detection
  71. GRB 251118A: Fermi GBM Observation
  72. GRB 251118A: Swift-XRT afterglow detection
  73. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  74. EP251118a: Optical detection with Kinder observations
  75. GRB 251118A: GECAM-B detection
  76. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  77. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  78. EP251118a / GRB 251118C: SVOM/VT optical observation
  79. The EP-WXT trigger 01709248403 is likely a flaring star
  80. GRB 251118A: NuSTAR detection of bright prompt emission
  81. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  82. GRB 251116C: NOT optical observations
  83. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  84. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  85. GRB 251018A: FRAM-Auger optical detection
  86. GRB 251117A: Swift-XRT observations
  87. EP251118A / GRB 251118C : MASTER optical counterpart observations
  88. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  89. Konus-Wind detection of GRB 251118C (EP251118a)
  90. The EP-WXT trigger 01709248388 is likely a flaring star
  91. EP251118a: FTW optical and NIR observations
  92. GRB 251117A: Insight-HXMT/HE detection
  93. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  94. EP251118a: VLT near-infrared observation
  95. GRB 251116D: SVOM/GRM observation of a long GRB
  96. EP251118a: GOTO optical afterglow detection
  97. GRB 251119A: SVOM detection of a possible burst
  98. EP251118a: NOT spectroscopic redshift of z = 1.216
  99. EP251118a: Global MASTER-Net observations report
  100. EP251118a: preliminary result of EP-FXT follow-up observation

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