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

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