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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. GRB 251126A: 1.3m DFOT optical afterglow detection
  2. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  3. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  4. GRB 251125B: GECAM-B detection
  5. Fermi GRB 251127A: Global MASTER-Net observations report
  6. GRB 251127A: Fermi GBM Final Real-time Localization
  7. GRB 251126A: Enhanced Swift-XRT position
  8. GRB 251126A: Kilonova-Catcher optical afterglow detection
  9. GRB 251126A: Asiago i-band detection
  10. GRB 251126A: Nanshan/HMT optical afterglow detection
  11. Swift GRB 251126A: Global MASTER-Net observations report
  12. GRB 251121A: Fermi GBM Observation
  13. GRB 251126A: Prompt enhanced Swift-XRT position
  14. GRB 251126A: GIT discovery of the likely optical afterglow
  15. GRB 251126A: Swift detection of a burst
  16. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  17. EP251124b follow-up observation by EP-FXT
  18. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  19. EP251124b: NOT r- and z-band optical upper limits
  20. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  21. Fermi GRB 251125B: Global MASTER-Net observations report
  22. GRB 251125B: Fermi GBM Final Real-time Localization
  23. EP251124b: Global MASTER-Net observations report
  24. EP251124b: EP-WXT detection of a fast X-ray transient
  25. EP251124a: Xinglong GWAC-F60A optical observation
  26. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  27. Fermi GRB 251125A: Global MASTER-Net observations report
  28. GRB 251125A: Fermi GBM Final Real-time Localization
  29. EP251124a: NOT r- and z-band optical upper limits
  30. EP251124a: Global MASTER-Net observations report
  31. EP251124a: Swift-XRT observations
  32. GRB 251124A: Fermi GBM Localization by automated pipeline
  33. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  34. EP251124a: Optical upper limit with Kinder observations
  35. GRB 251122B: Fermi GBM Final Localization
  36. EP251118A: 6 GHz VLA Detection
  37. Fermi GRB 251124a: Global MASTER-Net observations report
  38. GRB 251124a: Fermi GBM Final Localization
  39. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  40. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  41. EP251124a: GROWTH-India Telescope optical upper limits
  42. EP251124a: Einstein Probe detection of an X-ray transient
  43. GRB 251116C: Swift-XRT confirmation of fading
  44. GRB 251122A/EP251122a: FTW optical and NIR observations
  45. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  46. The EP-WXT trigger 01709248783 is likely a flaring star
  47. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  48. EP251118A: 3.6m DOT optical afterglow detection
  49. GRB 251122A / EP251122a: EP-FXT counterpart detection
  50. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  51. GRB 251122A / EP251122a: WFST optical observations
  52. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  53. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  54. GRB 251122A / EP251122a: LCO optical upper limits
  55. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  56. EP251122a: Global MASTER-Net observations report
  57. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  58. GRB 251122A / EP251122a: SVOM detection of a long burst
  59. EP251122a: Einstein Probe detection of an X-ray transient
  60. EP251118a: Continued Optical Detection with Kinder observations
  61. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  62. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  63. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  64. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  65. EP251118a: Xinglong-2.16m optical observation
  66. GRB 251115A: Fermi GBM Observation
  67. The EP-WXT trigger 01709248635 is likely a flaring star
  68. GRB 251121A: Fermi GBM Final Real-time Localization
  69. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  70. Fermi trigger No 785388351: Global MASTER-Net observations report
  71. EP251118A: 1.3m DFOT optical afterglow detection
  72. GRB 251118A: Swift/UVOT Detection
  73. EP251118a / GRB 251118C: SAO RAS optical observations
  74. GRB 251118A: Glowbug gamma-ray detection
  75. GRB 251118A: Fermi GBM Observation
  76. GRB 251118A: Swift-XRT afterglow detection
  77. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  78. EP251118a: Optical detection with Kinder observations
  79. GRB 251118A: GECAM-B detection
  80. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  81. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  82. EP251118a / GRB 251118C: SVOM/VT optical observation
  83. The EP-WXT trigger 01709248403 is likely a flaring star
  84. GRB 251118A: NuSTAR detection of bright prompt emission
  85. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  86. GRB 251116C: NOT optical observations
  87. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  88. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  89. GRB 251018A: FRAM-Auger optical detection
  90. GRB 251117A: Swift-XRT observations
  91. EP251118A / GRB 251118C : MASTER optical counterpart observations
  92. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  93. Konus-Wind detection of GRB 251118C (EP251118a)
  94. The EP-WXT trigger 01709248388 is likely a flaring star
  95. EP251118a: FTW optical and NIR observations
  96. GRB 251117A: Insight-HXMT/HE detection
  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. EP251118a: GOTO optical afterglow detection

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