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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 251116D: SVOM/GRM observation of a long GRB
  2. EP251118a: GOTO optical afterglow detection
  3. GRB 251119A: SVOM detection of a possible burst
  4. EP251118a: NOT spectroscopic redshift of z = 1.216
  5. EP251118a: Global MASTER-Net observations report
  6. EP251118a: preliminary result of EP-FXT follow-up observation
  7. LAT GRB251118.86: Global MASTER-Net observations report
  8. GRB 251118A: Fermi-LAT detection
  9. EP251118a: NOT candidate optical counterpart
  10. GRB 251118A: Swift ToO observations
  11. EP251118a: Einstein Probe detected of a fast X-ray transient
  12. Fermi GRB 251118B: Global MASTER-Net observations report
  13. GRB 251118B: Fermi GBM Final Real-time Localization
  14. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  15. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  16. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  17. GRB 251118A: Fermi GBM Final Real-time Localization
  18. GRB 251116C: SVOM/ECLAIRs refined analysis
  19. GRB 251116B: SVOM/ECLAIRs refined analysis
  20. GRB 251117A: AstroSat CZTI detection
  21. GRB 251114B: Insight-HXMT/HE detection
  22. GRB 251114B: GECAM-B detection of a short burst
  23. GRB 251117A: Fermi GBM observation
  24. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  25. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  26. GRB 251116D: Insight-HXMT/HE detection
  27. GRB 251115A: Swift-XRT observations
  28. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  29. GRB 251117A: SVOM/GRM observation of a short burst
  30. GRB 251117A: Tiled Swift observations
  31. GRB 251117A: Fermi-LAT detection
  32. LAT GRB251117.51: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  34. GRB 251116C: Swift/BAT arcminute localization of a burst
  35. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  36. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  37. GRB 251116B: SVOM/VT optical upper limit
  38. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  39. GRB 251116C: Swift-XRT observations
  40. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  41. GRB 251117A: Fermi GBM Final Localization Correction
  42. GRB 251116D: Glowbug gamma-ray detection
  43. EP251023a: Assy AZT-20 optical observations
  44. EP251023a: UAFO and AbAO optical observations
  45. GRB 251116D: AstroSat CZTI detection
  46. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  47. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  48. GRB 251116C: SVOM/VT optical upper limit
  49. GRB 251025B: further Mondy optical observations
  50. GRB 251111A: Mondy optical upper limit
  51. GRB 251116B: EP-FXT follow-up observation
  52. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  54. GRB 251116B: LCO optical upper limits
  55. GRB 251116C: LCO optical upper limits
  56. SVOM GRB251116C: Global MASTER-Net observations report
  57. GRB 251116C: SVOM detection of a burst
  58. GRB 251116B: SVOM detection of a burst
  59. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  60. GRB 251116A: Fermi GBM Final Real-time Localization
  61. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  62. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  63. GRB 251115A: Tiled Swift observations
  64. GRB 251115A: Fermi-LAT detection
  65. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  66. Fermi GRB 251115A: Global MASTER-Net observations report
  67. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  68. GRB 251115A: Fermi GBM Final Real-time Localization
  69. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  70. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  71. GRB 251113A: Glowbug gamma-ray detection
  72. GRB 251113A: AstroSat CZTI detection
  73. GRB 251114B: Fermi GBM Final Real-time Localization
  74. GRB 251112A: Swift-BAT refined analysis
  75. Konus-Wind detection of GRB 251108C
  76. Fermi trigger No 784717756: Global MASTER-Net observations report
  77. Konus-Wind detection of GRB 251103A
  78. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  79. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  80. IPN triangulation of GRB 251108C
  81. The EP-WXT trigger 01709248221 is likely a flaring star
  82. Fermi GRB 251114A: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  84. GRB 251114A: Fermi GBM Final Real-time Localization
  85. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  86. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  87. Fermi GRB 251113A: Global MASTER-Net observations report
  88. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  89. GRB 251113A: Fermi GBM Final Real-time Localization
  90. GRB 251111A: SVOM/ECLAIRs refined analysis
  91. GRB 251025B: SVOM/ECLAIRs refined analysis
  92. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  93. GRB 251112A: Swift/UVOT Upper Limits
  94. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  95. GRB 251112A: Swift-XRT refined Analysis
  96. GRB 251108C: AstroSat CZTI detection
  97. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  98. GRB 251112B: MAXI/GSC detection
  99. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  100. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB

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