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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. EP251118a: NOT spectroscopic redshift of z = 1.216
  2. EP251118a: Global MASTER-Net observations report
  3. EP251118a: preliminary result of EP-FXT follow-up observation
  4. LAT GRB251118.86: Global MASTER-Net observations report
  5. GRB 251118A: Fermi-LAT detection
  6. EP251118a: NOT candidate optical counterpart
  7. GRB 251118A: Swift ToO observations
  8. EP251118a: Einstein Probe detected of a fast X-ray transient
  9. Fermi GRB 251118B: Global MASTER-Net observations report
  10. GRB 251118B: Fermi GBM Final Real-time Localization
  11. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  12. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  13. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  14. GRB 251118A: Fermi GBM Final Real-time Localization
  15. GRB 251116C: SVOM/ECLAIRs refined analysis
  16. GRB 251116B: SVOM/ECLAIRs refined analysis
  17. GRB 251117A: AstroSat CZTI detection
  18. GRB 251114B: Insight-HXMT/HE detection
  19. GRB 251114B: GECAM-B detection of a short burst
  20. GRB 251117A: Fermi GBM observation
  21. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  22. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  23. GRB 251116D: Insight-HXMT/HE detection
  24. GRB 251115A: Swift-XRT observations
  25. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  26. GRB 251117A: SVOM/GRM observation of a short burst
  27. GRB 251117A: Tiled Swift observations
  28. GRB 251117A: Fermi-LAT detection
  29. LAT GRB251117.51: Global MASTER-Net observations report
  30. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  31. GRB 251116C: Swift/BAT arcminute localization of a burst
  32. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  33. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  34. GRB 251116B: SVOM/VT optical upper limit
  35. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  36. GRB 251116C: Swift-XRT observations
  37. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  38. GRB 251117A: Fermi GBM Final Localization Correction
  39. GRB 251116D: Glowbug gamma-ray detection
  40. EP251023a: Assy AZT-20 optical observations
  41. EP251023a: UAFO and AbAO optical observations
  42. GRB 251116D: AstroSat CZTI detection
  43. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  44. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  45. GRB 251116C: SVOM/VT optical upper limit
  46. GRB 251025B: further Mondy optical observations
  47. GRB 251111A: Mondy optical upper limit
  48. GRB 251116B: EP-FXT follow-up observation
  49. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  50. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  51. GRB 251116B: LCO optical upper limits
  52. GRB 251116C: LCO optical upper limits
  53. SVOM GRB251116C: Global MASTER-Net observations report
  54. GRB 251116C: SVOM detection of a burst
  55. GRB 251116B: SVOM detection of a burst
  56. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 251116A: Fermi GBM Final Real-time Localization
  58. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  59. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  60. GRB 251115A: Tiled Swift observations
  61. GRB 251115A: Fermi-LAT detection
  62. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  63. Fermi GRB 251115A: Global MASTER-Net observations report
  64. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  65. GRB 251115A: Fermi GBM Final Real-time Localization
  66. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  67. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  68. GRB 251113A: Glowbug gamma-ray detection
  69. GRB 251113A: AstroSat CZTI detection
  70. GRB 251114B: Fermi GBM Final Real-time Localization
  71. GRB 251112A: Swift-BAT refined analysis
  72. Konus-Wind detection of GRB 251108C
  73. Fermi trigger No 784717756: Global MASTER-Net observations report
  74. Konus-Wind detection of GRB 251103A
  75. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  76. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  77. IPN triangulation of GRB 251108C
  78. The EP-WXT trigger 01709248221 is likely a flaring star
  79. Fermi GRB 251114A: Global MASTER-Net observations report
  80. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  81. GRB 251114A: Fermi GBM Final Real-time Localization
  82. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  83. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  84. Fermi GRB 251113A: Global MASTER-Net observations report
  85. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  86. GRB 251113A: Fermi GBM Final Real-time Localization
  87. GRB 251111A: SVOM/ECLAIRs refined analysis
  88. GRB 251025B: SVOM/ECLAIRs refined analysis
  89. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  90. GRB 251112A: Swift/UVOT Upper Limits
  91. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  92. GRB 251112A: Swift-XRT refined Analysis
  93. GRB 251108C: AstroSat CZTI detection
  94. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  95. GRB 251112B: MAXI/GSC detection
  96. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  97. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  98. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  99. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  100. GRB 251108B: Glowbug gamma-ray detection

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