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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. EP251124b follow-up observation by EP-FXT
  2. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  3. EP251124b: NOT r- and z-band optical upper limits
  4. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  5. Fermi GRB 251125B: Global MASTER-Net observations report
  6. GRB 251125B: Fermi GBM Final Real-time Localization
  7. EP251124b: Global MASTER-Net observations report
  8. EP251124b: EP-WXT detection of a fast X-ray transient
  9. EP251124a: Xinglong GWAC-F60A optical observation
  10. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  11. Fermi GRB 251125A: Global MASTER-Net observations report
  12. GRB 251125A: Fermi GBM Final Real-time Localization
  13. EP251124a: NOT r- and z-band optical upper limits
  14. EP251124a: Global MASTER-Net observations report
  15. EP251124a: Swift-XRT observations
  16. GRB 251124A: Fermi GBM Localization by automated pipeline
  17. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  18. EP251124a: Optical upper limit with Kinder observations
  19. GRB 251122B: Fermi GBM Final Localization
  20. EP251118A: 6 GHz VLA Detection
  21. Fermi GRB 251124a: Global MASTER-Net observations report
  22. GRB 251124a: Fermi GBM Final Localization
  23. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  24. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  25. EP251124a: GROWTH-India Telescope optical upper limits
  26. EP251124a: Einstein Probe detection of an X-ray transient
  27. GRB 251116C: Swift-XRT confirmation of fading
  28. GRB 251122A/EP251122a: FTW optical and NIR observations
  29. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  30. The EP-WXT trigger 01709248783 is likely a flaring star
  31. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  32. EP251118A: 3.6m DOT optical afterglow detection
  33. GRB 251122A / EP251122a: EP-FXT counterpart detection
  34. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 251122A / EP251122a: WFST optical observations
  36. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  37. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  38. GRB 251122A / EP251122a: LCO optical upper limits
  39. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  40. EP251122a: Global MASTER-Net observations report
  41. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  42. GRB 251122A / EP251122a: SVOM detection of a long burst
  43. EP251122a: Einstein Probe detection of an X-ray transient
  44. EP251118a: Continued Optical Detection with Kinder observations
  45. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  46. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  47. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  48. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  49. EP251118a: Xinglong-2.16m optical observation
  50. GRB 251115A: Fermi GBM Observation
  51. The EP-WXT trigger 01709248635 is likely a flaring star
  52. GRB 251121A: Fermi GBM Final Real-time Localization
  53. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  54. Fermi trigger No 785388351: Global MASTER-Net observations report
  55. EP251118A: 1.3m DFOT optical afterglow detection
  56. GRB 251118A: Swift/UVOT Detection
  57. EP251118a / GRB 251118C: SAO RAS optical observations
  58. GRB 251118A: Glowbug gamma-ray detection
  59. GRB 251118A: Fermi GBM Observation
  60. GRB 251118A: Swift-XRT afterglow detection
  61. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  62. EP251118a: Optical detection with Kinder observations
  63. GRB 251118A: GECAM-B detection
  64. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  65. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  66. EP251118a / GRB 251118C: SVOM/VT optical observation
  67. The EP-WXT trigger 01709248403 is likely a flaring star
  68. GRB 251118A: NuSTAR detection of bright prompt emission
  69. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  70. GRB 251116C: NOT optical observations
  71. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  72. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  73. GRB 251018A: FRAM-Auger optical detection
  74. GRB 251117A: Swift-XRT observations
  75. EP251118A / GRB 251118C : MASTER optical counterpart observations
  76. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  77. Konus-Wind detection of GRB 251118C (EP251118a)
  78. The EP-WXT trigger 01709248388 is likely a flaring star
  79. EP251118a: FTW optical and NIR observations
  80. GRB 251117A: Insight-HXMT/HE detection
  81. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  82. EP251118a: VLT near-infrared observation
  83. GRB 251116D: SVOM/GRM observation of a long GRB
  84. EP251118a: GOTO optical afterglow detection
  85. GRB 251119A: SVOM detection of a possible burst
  86. EP251118a: NOT spectroscopic redshift of z = 1.216
  87. EP251118a: Global MASTER-Net observations report
  88. EP251118a: preliminary result of EP-FXT follow-up observation
  89. LAT GRB251118.86: Global MASTER-Net observations report
  90. GRB 251118A: Fermi-LAT detection
  91. EP251118a: NOT candidate optical counterpart
  92. GRB 251118A: Swift ToO observations
  93. EP251118a: Einstein Probe detected of a fast X-ray transient
  94. Fermi GRB 251118B: Global MASTER-Net observations report
  95. GRB 251118B: Fermi GBM Final Real-time Localization
  96. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  97. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  98. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  99. GRB 251118A: Fermi GBM Final Real-time Localization
  100. GRB 251116C: SVOM/ECLAIRs refined analysis

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