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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 251119A: SVOM trigger sb25111901 is not a GRB
  2. EP251118a: VLT near-infrared observation
  3. GRB 251116D: SVOM/GRM observation of a long GRB
  4. EP251118a: GOTO optical afterglow detection
  5. GRB 251119A: SVOM detection of a possible burst
  6. EP251118a: NOT spectroscopic redshift of z = 1.216
  7. EP251118a: Global MASTER-Net observations report
  8. EP251118a: preliminary result of EP-FXT follow-up observation
  9. LAT GRB251118.86: Global MASTER-Net observations report
  10. GRB 251118A: Fermi-LAT detection
  11. EP251118a: NOT candidate optical counterpart
  12. GRB 251118A: Swift ToO observations
  13. EP251118a: Einstein Probe detected of a fast X-ray transient
  14. Fermi GRB 251118B: Global MASTER-Net observations report
  15. GRB 251118B: Fermi GBM Final Real-time Localization
  16. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  17. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  18. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  19. GRB 251118A: Fermi GBM Final Real-time Localization
  20. GRB 251116C: SVOM/ECLAIRs refined analysis
  21. GRB 251116B: SVOM/ECLAIRs refined analysis
  22. GRB 251117A: AstroSat CZTI detection
  23. GRB 251114B: Insight-HXMT/HE detection
  24. GRB 251114B: GECAM-B detection of a short burst
  25. GRB 251117A: Fermi GBM observation
  26. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  27. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  28. GRB 251116D: Insight-HXMT/HE detection
  29. GRB 251115A: Swift-XRT observations
  30. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  31. GRB 251117A: SVOM/GRM observation of a short burst
  32. GRB 251117A: Tiled Swift observations
  33. GRB 251117A: Fermi-LAT detection
  34. LAT GRB251117.51: Global MASTER-Net observations report
  35. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  36. GRB 251116C: Swift/BAT arcminute localization of a burst
  37. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  38. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  39. GRB 251116B: SVOM/VT optical upper limit
  40. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  41. GRB 251116C: Swift-XRT observations
  42. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  43. GRB 251117A: Fermi GBM Final Localization Correction
  44. GRB 251116D: Glowbug gamma-ray detection
  45. EP251023a: Assy AZT-20 optical observations
  46. EP251023a: UAFO and AbAO optical observations
  47. GRB 251116D: AstroSat CZTI detection
  48. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  49. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  50. GRB 251116C: SVOM/VT optical upper limit
  51. GRB 251025B: further Mondy optical observations
  52. GRB 251111A: Mondy optical upper limit
  53. GRB 251116B: EP-FXT follow-up observation
  54. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  55. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  56. GRB 251116B: LCO optical upper limits
  57. GRB 251116C: LCO optical upper limits
  58. SVOM GRB251116C: Global MASTER-Net observations report
  59. GRB 251116C: SVOM detection of a burst
  60. GRB 251116B: SVOM detection of a burst
  61. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  62. GRB 251116A: Fermi GBM Final Real-time Localization
  63. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  64. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  65. GRB 251115A: Tiled Swift observations
  66. GRB 251115A: Fermi-LAT detection
  67. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  68. Fermi GRB 251115A: Global MASTER-Net observations report
  69. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  70. GRB 251115A: Fermi GBM Final Real-time Localization
  71. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  72. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  73. GRB 251113A: Glowbug gamma-ray detection
  74. GRB 251113A: AstroSat CZTI detection
  75. GRB 251114B: Fermi GBM Final Real-time Localization
  76. GRB 251112A: Swift-BAT refined analysis
  77. Konus-Wind detection of GRB 251108C
  78. Fermi trigger No 784717756: Global MASTER-Net observations report
  79. Konus-Wind detection of GRB 251103A
  80. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  81. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  82. IPN triangulation of GRB 251108C
  83. The EP-WXT trigger 01709248221 is likely a flaring star
  84. Fermi GRB 251114A: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  86. GRB 251114A: Fermi GBM Final Real-time Localization
  87. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  88. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  89. Fermi GRB 251113A: Global MASTER-Net observations report
  90. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  91. GRB 251113A: Fermi GBM Final Real-time Localization
  92. GRB 251111A: SVOM/ECLAIRs refined analysis
  93. GRB 251025B: SVOM/ECLAIRs refined analysis
  94. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  95. GRB 251112A: Swift/UVOT Upper Limits
  96. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  97. GRB 251112A: Swift-XRT refined Analysis
  98. GRB 251108C: AstroSat CZTI detection
  99. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  100. GRB 251112B: MAXI/GSC detection

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