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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"

25656 results found.

  1. EP251124a: NOT r- and z-band optical upper limits
  2. EP251124a: Global MASTER-Net observations report
  3. EP251124a: Swift-XRT observations
  4. GRB 251124A: Fermi GBM Localization by automated pipeline
  5. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  6. EP251124a: Optical upper limit with Kinder observations
  7. GRB 251122B: Fermi GBM Final Localization
  8. EP251118A: 6 GHz VLA Detection
  9. Fermi GRB 251124a: Global MASTER-Net observations report
  10. GRB 251124a: Fermi GBM Final Localization
  11. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  12. EP251124a: GROWTH-India Telescope optical upper limits
  13. GRB 251122A/EP251122a: FTW optical and NIR observations
  14. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  15. The EP-WXT trigger 01709248783 is likely a flaring star
  16. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  17. EP251118A: 3.6m DOT optical afterglow detection
  18. GRB 251122A / EP251122a: EP-FXT counterpart detection
  19. GRB 251122A / EP251122a: WFST optical observations
  20. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  21. GRB 251122A / EP251122a: LCO optical upper limits
  22. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  23. EP251122a: Global MASTER-Net observations report
  24. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  25. GRB 251122A / EP251122a: SVOM detection of a long burst
  26. EP251118a: Continued Optical Detection with Kinder observations
  27. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  28. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  29. EP251118a: Xinglong-2.16m optical observation
  30. GRB 251115A: Fermi GBM Observation
  31. The EP-WXT trigger 01709248635 is likely a flaring star
  32. GRB 251121A: Fermi GBM Final Real-time Localization
  33. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  34. Fermi trigger No 785388351: Global MASTER-Net observations report
  35. EP251118A: 1.3m DFOT optical afterglow detection
  36. GRB 251118A: Swift/UVOT Detection
  37. GRB 251118A: Glowbug gamma-ray detection
  38. GRB 251118A: Fermi GBM Observation
  39. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  40. EP251118a: Optical detection with Kinder observations
  41. EP-WXT trigger 01709248403: confirmation of a stellar flare by SVOM/VT
  42. The EP-WXT trigger 01709248403 is likely a flaring star
  43. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  44. GRB 251116C: NOT optical observations
  45. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  46. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  47. GRB 251018A: FRAM-Auger optical detection
  48. The EP-WXT trigger 01709248388 is likely a flaring star
  49. EP251118a: FTW optical and NIR observations
  50. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  51. EP251118a: VLT near-infrared observation
  52. GRB 251116D: SVOM/GRM observation of a long GRB
  53. EP251118a: GOTO optical afterglow detection
  54. GRB 251119A: SVOM detection of a possible burst
  55. EP251118a: Global MASTER-Net observations report
  56. LAT GRB251118.86: Global MASTER-Net observations report
  57. GRB 251118A: Fermi-LAT detection
  58. EP251118a: NOT candidate optical counterpart
  59. EP251118a: Einstein Probe detected of a fast X-ray transient
  60. Fermi GRB 251118B: Global MASTER-Net observations report
  61. GRB 251118B: Fermi GBM Final Real-time Localization
  62. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  63. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  64. GRB 251118A: Fermi GBM Final Real-time Localization
  65. GRB 251116C: SVOM/ECLAIRs refined analysis
  66. GRB 251117A: AstroSat CZTI detection
  67. GRB 251117A: Fermi GBM observation
  68. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  69. GRB 251117A: SVOM/GRM observation of a short burst
  70. GRB 251117A: Fermi-LAT detection
  71. LAT GRB251117.51: Global MASTER-Net observations report
  72. GRB 251116C: Swift/BAT arcminute localization of a burst
  73. GRB 251116B: SVOM/VT optical upper limit
  74. GRB 251116C: Swift-XRT observations
  75. GRB 251117A: Fermi GBM Final Localization Correction
  76. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  77. GRB 251116C: SVOM/VT optical upper limit
  78. GRB 251116B: EP-FXT follow-up observation
  79. GRB 251116B: LCO optical upper limits
  80. GRB 251116C: LCO optical upper limits
  81. SVOM GRB251116C: Global MASTER-Net observations report
  82. GRB 251116C: SVOM detection of a burst
  83. GRB 251116B: SVOM detection of a burst
  84. GRB 251116A: Fermi GBM Final Real-time Localization
  85. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  86. GRB 251115A: Fermi-LAT detection
  87. Fermi GRB 251115A: Global MASTER-Net observations report
  88. GRB 251115A: Fermi GBM Final Real-time Localization
  89. GRB 251114B: Fermi GBM Final Real-time Localization
  90. GRB 251112A: Swift-BAT refined analysis
  91. Fermi trigger No 784717756: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  93. The EP-WXT trigger 01709248221 is likely a flaring star
  94. Fermi GRB 251114A: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  96. GRB 251114A: Fermi GBM Final Real-time Localization
  97. Fermi GRB 251113A: Global MASTER-Net observations report
  98. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  99. GRB 251113A: Fermi GBM Final Real-time Localization
  100. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB

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