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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"

26203 results found.

  1. Fermi GRB 251127A: Global MASTER-Net observations report
  2. GRB 251127A: Fermi GBM Final Real-time Localization
  3. GRB 251126A: Kilonova-Catcher optical afterglow detection
  4. GRB 251126A: Asiago i-band detection
  5. GRB 251126A: Nanshan/HMT optical afterglow detection
  6. Swift GRB 251126A: Global MASTER-Net observations report
  7. GRB 251121A: Fermi GBM Observation
  8. GRB 251126A: GIT discovery of the likely optical afterglow
  9. GRB 251126A: Swift detection of a burst
  10. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  11. EP251124b follow-up observation by EP-FXT
  12. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  13. EP251124b: NOT r- and z-band optical upper limits
  14. Fermi GRB 251125B: Global MASTER-Net observations report
  15. GRB 251125B: Fermi GBM Final Real-time Localization
  16. EP251124b: Global MASTER-Net observations report
  17. EP251124b: EP-WXT detection of a fast X-ray transient
  18. EP251124a: Xinglong GWAC-F60A optical observation
  19. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  20. Fermi GRB 251125A: Global MASTER-Net observations report
  21. GRB 251125A: Fermi GBM Final Real-time Localization
  22. EP251124a: NOT r- and z-band optical upper limits
  23. EP251124a: Global MASTER-Net observations report
  24. EP251124a: Swift-XRT observations
  25. GRB 251124A: Fermi GBM Localization by automated pipeline
  26. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  27. EP251124a: Optical upper limit with Kinder observations
  28. GRB 251122B: Fermi GBM Final Localization
  29. EP251118A: 6 GHz VLA Detection
  30. Fermi GRB 251124a: Global MASTER-Net observations report
  31. GRB 251124a: Fermi GBM Final Localization
  32. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  33. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  34. EP251124a: GROWTH-India Telescope optical upper limits
  35. EP251124a: Einstein Probe detection of an X-ray transient
  36. GRB 251122A/EP251122a: FTW optical and NIR observations
  37. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  38. The EP-WXT trigger 01709248783 is likely a flaring star
  39. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  40. EP251118A: 3.6m DOT optical afterglow detection
  41. GRB 251122A / EP251122a: EP-FXT counterpart detection
  42. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  43. GRB 251122A / EP251122a: WFST optical observations
  44. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  45. GRB 251122A / EP251122a: LCO optical upper limits
  46. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  47. EP251122a: Global MASTER-Net observations report
  48. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  49. GRB 251122A / EP251122a: SVOM detection of a long burst
  50. EP251122a: Einstein Probe detection of an X-ray transient
  51. EP251118a: Continued Optical Detection with Kinder observations
  52. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  53. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  54. EP251118a: Xinglong-2.16m optical observation
  55. GRB 251115A: Fermi GBM Observation
  56. The EP-WXT trigger 01709248635 is likely a flaring star
  57. GRB 251121A: Fermi GBM Final Real-time Localization
  58. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  59. Fermi trigger No 785388351: Global MASTER-Net observations report
  60. EP251118A: 1.3m DFOT optical afterglow detection
  61. GRB 251118A: Swift/UVOT Detection
  62. GRB 251118A: Glowbug gamma-ray detection
  63. GRB 251118A: Fermi GBM Observation
  64. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  65. EP251118a: Optical detection with Kinder observations
  66. GRB 251118A: GECAM-B detection
  67. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  68. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  69. EP251118a / GRB 251118C: SVOM/VT optical observation
  70. The EP-WXT trigger 01709248403 is likely a flaring star
  71. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  72. GRB 251116C: NOT optical observations
  73. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  74. GRB 251018A: FRAM-Auger optical detection
  75. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  76. The EP-WXT trigger 01709248388 is likely a flaring star
  77. EP251118a: FTW optical and NIR observations
  78. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  79. EP251118a: VLT near-infrared observation
  80. GRB 251116D: SVOM/GRM observation of a long GRB
  81. EP251118a: GOTO optical afterglow detection
  82. GRB 251119A: SVOM detection of a possible burst
  83. EP251118a: Global MASTER-Net observations report
  84. EP251118a: preliminary result of EP-FXT follow-up observation
  85. LAT GRB251118.86: Global MASTER-Net observations report
  86. GRB 251118A: Fermi-LAT detection
  87. EP251118a: NOT candidate optical counterpart
  88. EP251118a: Einstein Probe detected of a fast X-ray transient
  89. Fermi GRB 251118B: Global MASTER-Net observations report
  90. GRB 251118B: Fermi GBM Final Real-time Localization
  91. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  92. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  93. GRB 251118A: Fermi GBM Final Real-time Localization
  94. GRB 251116C: SVOM/ECLAIRs refined analysis
  95. GRB 251116B: SVOM/ECLAIRs refined analysis
  96. GRB 251114B: GECAM-B detection of a short burst
  97. GRB 251117A: Fermi GBM observation
  98. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  99. GRB 251117A: SVOM/GRM observation of a short burst
  100. GRB 251117A: Fermi-LAT detection

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