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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: Global MASTER-Net observations report
  2. EP251124b: EP-WXT detection of a fast X-ray transient
  3. EP251124a: Xinglong GWAC-F60A optical observation
  4. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  5. Fermi GRB 251125A: Global MASTER-Net observations report
  6. GRB 251125A: Fermi GBM Final Real-time Localization
  7. EP251124a: NOT r- and z-band optical upper limits
  8. EP251124a: Global MASTER-Net observations report
  9. EP251124a: Swift-XRT observations
  10. GRB 251124A: Fermi GBM Localization by automated pipeline
  11. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  12. EP251124a: Optical upper limit with Kinder observations
  13. GRB 251122B: Fermi GBM Final Localization
  14. EP251118A: 6 GHz VLA Detection
  15. Fermi GRB 251124a: Global MASTER-Net observations report
  16. GRB 251124a: Fermi GBM Final Localization
  17. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  18. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  19. EP251124a: GROWTH-India Telescope optical upper limits
  20. EP251124a: Einstein Probe detection of an X-ray transient
  21. GRB 251116C: Swift-XRT confirmation of fading
  22. GRB 251122A/EP251122a: FTW optical and NIR observations
  23. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  24. The EP-WXT trigger 01709248783 is likely a flaring star
  25. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  26. EP251118A: 3.6m DOT optical afterglow detection
  27. GRB 251122A / EP251122a: EP-FXT counterpart detection
  28. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 251122A / EP251122a: WFST optical observations
  30. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  31. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  32. GRB 251122A / EP251122a: LCO optical upper limits
  33. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  34. EP251122a: Global MASTER-Net observations report
  35. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  36. GRB 251122A / EP251122a: SVOM detection of a long burst
  37. EP251122a: Einstein Probe detection of an X-ray transient
  38. EP251118a: Continued Optical Detection with Kinder observations
  39. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  40. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  41. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  42. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  43. EP251118a: Xinglong-2.16m optical observation
  44. GRB 251115A: Fermi GBM Observation
  45. The EP-WXT trigger 01709248635 is likely a flaring star
  46. GRB 251121A: Fermi GBM Final Real-time Localization
  47. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  48. Fermi trigger No 785388351: Global MASTER-Net observations report
  49. EP251118A: 1.3m DFOT optical afterglow detection
  50. GRB 251118A: Swift/UVOT Detection
  51. EP251118a / GRB 251118C: SAO RAS optical observations
  52. GRB 251118A: Glowbug gamma-ray detection
  53. GRB 251118A: Fermi GBM Observation
  54. GRB 251118A: Swift-XRT afterglow detection
  55. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  56. EP251118a: Optical detection with Kinder observations
  57. GRB 251118A: GECAM-B detection
  58. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  59. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  60. EP251118a / GRB 251118C: SVOM/VT optical observation
  61. The EP-WXT trigger 01709248403 is likely a flaring star
  62. GRB 251118A: NuSTAR detection of bright prompt emission
  63. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  64. GRB 251116C: NOT optical observations
  65. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  66. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  67. GRB 251018A: FRAM-Auger optical detection
  68. GRB 251117A: Swift-XRT observations
  69. EP251118A / GRB 251118C : MASTER optical counterpart observations
  70. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  71. Konus-Wind detection of GRB 251118C (EP251118a)
  72. The EP-WXT trigger 01709248388 is likely a flaring star
  73. EP251118a: FTW optical and NIR observations
  74. GRB 251117A: Insight-HXMT/HE detection
  75. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  76. EP251118a: VLT near-infrared observation
  77. GRB 251116D: SVOM/GRM observation of a long GRB
  78. EP251118a: GOTO optical afterglow detection
  79. GRB 251119A: SVOM detection of a possible burst
  80. EP251118a: NOT spectroscopic redshift of z = 1.216
  81. EP251118a: Global MASTER-Net observations report
  82. EP251118a: preliminary result of EP-FXT follow-up observation
  83. LAT GRB251118.86: Global MASTER-Net observations report
  84. GRB 251118A: Fermi-LAT detection
  85. EP251118a: NOT candidate optical counterpart
  86. GRB 251118A: Swift ToO observations
  87. EP251118a: Einstein Probe detected of a fast X-ray transient
  88. Fermi GRB 251118B: Global MASTER-Net observations report
  89. GRB 251118B: Fermi GBM Final Real-time Localization
  90. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  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 251117A: AstroSat CZTI detection
  97. GRB 251114B: Insight-HXMT/HE detection
  98. GRB 251114B: GECAM-B detection of a short burst
  99. GRB 251117A: Fermi GBM observation
  100. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection

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