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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. EP251124a: Xinglong GWAC-F60A optical observation
  2. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  3. Fermi GRB 251125A: Global MASTER-Net observations report
  4. GRB 251125A: Fermi GBM Final Real-time Localization
  5. EP251124a: NOT r- and z-band optical upper limits
  6. EP251124a: Global MASTER-Net observations report
  7. EP251124a: Swift-XRT observations
  8. GRB 251124A: Fermi GBM Localization by automated pipeline
  9. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  10. EP251124a: Optical upper limit with Kinder observations
  11. GRB 251122B: Fermi GBM Final Localization
  12. EP251118A: 6 GHz VLA Detection
  13. Fermi GRB 251124a: Global MASTER-Net observations report
  14. GRB 251124a: Fermi GBM Final Localization
  15. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  16. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  17. EP251124a: GROWTH-India Telescope optical upper limits
  18. EP251124a: Einstein Probe detection of an X-ray transient
  19. GRB 251116C: Swift-XRT confirmation of fading
  20. GRB 251122A/EP251122a: FTW optical and NIR observations
  21. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  22. The EP-WXT trigger 01709248783 is likely a flaring star
  23. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  24. EP251118A: 3.6m DOT optical afterglow detection
  25. GRB 251122A / EP251122a: EP-FXT counterpart detection
  26. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  27. GRB 251122A / EP251122a: WFST optical observations
  28. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  29. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  30. GRB 251122A / EP251122a: LCO optical upper limits
  31. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  32. EP251122a: Global MASTER-Net observations report
  33. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  34. GRB 251122A / EP251122a: SVOM detection of a long burst
  35. EP251122a: Einstein Probe detection of an X-ray transient
  36. EP251118a: Continued Optical Detection with Kinder observations
  37. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  38. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  39. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  40. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  41. EP251118a: Xinglong-2.16m optical observation
  42. GRB 251115A: Fermi GBM Observation
  43. The EP-WXT trigger 01709248635 is likely a flaring star
  44. GRB 251121A: Fermi GBM Final Real-time Localization
  45. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  46. Fermi trigger No 785388351: Global MASTER-Net observations report
  47. EP251118A: 1.3m DFOT optical afterglow detection
  48. GRB 251118A: Swift/UVOT Detection
  49. EP251118a / GRB 251118C: SAO RAS optical observations
  50. GRB 251118A: Glowbug gamma-ray detection
  51. GRB 251118A: Fermi GBM Observation
  52. GRB 251118A: Swift-XRT afterglow detection
  53. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  54. EP251118a: Optical detection with Kinder observations
  55. GRB 251118A: GECAM-B detection
  56. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  57. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  58. EP251118a / GRB 251118C: SVOM/VT optical observation
  59. The EP-WXT trigger 01709248403 is likely a flaring star
  60. GRB 251118A: NuSTAR detection of bright prompt emission
  61. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  62. GRB 251116C: NOT optical observations
  63. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  64. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  65. GRB 251018A: FRAM-Auger optical detection
  66. GRB 251117A: Swift-XRT observations
  67. EP251118A / GRB 251118C : MASTER optical counterpart observations
  68. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  69. Konus-Wind detection of GRB 251118C (EP251118a)
  70. The EP-WXT trigger 01709248388 is likely a flaring star
  71. EP251118a: FTW optical and NIR observations
  72. GRB 251117A: Insight-HXMT/HE detection
  73. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  74. EP251118a: VLT near-infrared observation
  75. GRB 251116D: SVOM/GRM observation of a long GRB
  76. EP251118a: GOTO optical afterglow detection
  77. GRB 251119A: SVOM detection of a possible burst
  78. EP251118a: NOT spectroscopic redshift of z = 1.216
  79. EP251118a: Global MASTER-Net observations report
  80. EP251118a: preliminary result of EP-FXT follow-up observation
  81. LAT GRB251118.86: Global MASTER-Net observations report
  82. GRB 251118A: Fermi-LAT detection
  83. EP251118a: NOT candidate optical counterpart
  84. GRB 251118A: Swift ToO observations
  85. EP251118a: Einstein Probe detected of a fast X-ray transient
  86. Fermi GRB 251118B: Global MASTER-Net observations report
  87. GRB 251118B: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  89. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  90. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  91. GRB 251118A: Fermi GBM Final Real-time Localization
  92. GRB 251116C: SVOM/ECLAIRs refined analysis
  93. GRB 251116B: SVOM/ECLAIRs refined analysis
  94. GRB 251117A: AstroSat CZTI detection
  95. GRB 251114B: Insight-HXMT/HE detection
  96. GRB 251114B: GECAM-B detection of a short burst
  97. GRB 251117A: Fermi GBM observation
  98. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  99. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  100. GRB 251116D: Insight-HXMT/HE detection

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