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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. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  3. GRB 251116B: LCO optical upper limits
  4. GRB 251116C: LCO optical upper limits
  5. SVOM GRB251116C: Global MASTER-Net observations report
  6. GRB 251116C: SVOM detection of a burst
  7. GRB 251116B: SVOM detection of a burst
  8. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 251116A: Fermi GBM Final Real-time Localization
  10. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  11. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  12. GRB 251115A: Tiled Swift observations
  13. GRB 251115A: Fermi-LAT detection
  14. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  15. Fermi GRB 251115A: Global MASTER-Net observations report
  16. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  17. GRB 251115A: Fermi GBM Final Real-time Localization
  18. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  19. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  20. GRB 251113A: Glowbug gamma-ray detection
  21. GRB 251113A: AstroSat CZTI detection
  22. GRB 251114B: Fermi GBM Final Real-time Localization
  23. GRB 251112A: Swift-BAT refined analysis
  24. Konus-Wind detection of GRB 251108C
  25. Fermi trigger No 784717756: Global MASTER-Net observations report
  26. Konus-Wind detection of GRB 251103A
  27. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  28. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  29. IPN triangulation of GRB 251108C
  30. The EP-WXT trigger 01709248221 is likely a flaring star
  31. Fermi GRB 251114A: Global MASTER-Net observations report
  32. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  33. GRB 251114A: Fermi GBM Final Real-time Localization
  34. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  35. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  36. Fermi GRB 251113A: Global MASTER-Net observations report
  37. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  38. GRB 251113A: Fermi GBM Final Real-time Localization
  39. GRB 251111A: SVOM/ECLAIRs refined analysis
  40. GRB 251025B: SVOM/ECLAIRs refined analysis
  41. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  42. GRB 251112A: Swift/UVOT Upper Limits
  43. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  44. GRB 251112A: Swift-XRT refined Analysis
  45. GRB 251108C: AstroSat CZTI detection
  46. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  47. GRB 251112B: MAXI/GSC detection
  48. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  49. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  50. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  51. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  52. GRB 251108B: Glowbug gamma-ray detection
  53. Swift Trigger 1413695: a possible GRB 251112A
  54. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  55. Fermi trigger No 784621743: Global MASTER-Net observations report
  56. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  57. Fermi Gamma-ray Burst Monitor trigger 784653403/251112637 is not a GRB
  58. GRB251111A: 1.3m DFOT optical upper limit
  59. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  60. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  61. GRB 251111A: Swift-XRT afterglow detection
  62. GRB 251111A: SVOM/VT optical observations with X-band data
  63. SVOM GRB251111.42: Global MASTER-Net observations report
  64. GRB 251111A: Swift-XRT observations
  65. SVOM GRB251111.22: Global MASTER-Net observations report
  66. GRB 251111A: EP-FXT counterpart detection
  67. GRB 251013C: Chandra X-ray observations and jet break detection
  68. GRB 251111A: SVOM/VT optical observations with VHF data
  69. GRB 251111A: KAIT optical upper limit
  70. GRB 251111A: LCO optical observation
  71. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  72. GRB 251111A: SVOM detection of a soft burst
  73. GRB 251103B: Swift-BAT refined analysis
  74. GRB 251106A: Swift/UVOT Upper Limits
  75. GRB 251105B: Insight-HXMT/HE detection
  76. GRB 251106B: Insight-HXMT detection
  77. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  78. GRB 251105A: AstroSat CZTI detection
  79. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  80. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  81. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  82. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  83. GRB 251108A: Fermi GBM Final Localization Correction
  84. Fermi trigger No 784329591: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  86. Fermi trigger No 784279167: Global MASTER-Net observations report
  87. SVOM GRB251108.54: Global MASTER-Net observations report
  88. GRB 251102B: SVOM/GRM observation
  89. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  90. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  91. The EP-WXT trigger 01709248051 is likely a flaring star
  92. SVOM GRB251106.83: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  94. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  95. IPN triangulation of GRB 251105B (possible sGRB with EE)
  96. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  97. GRB 251106B: SVOM/GRM observation of a short burst
  98. GRB 251106A: Swift-XRT afterglow detection
  99. GRB 251106A: Kilonova-Catcher optical upper limit
  100. Fermi GBM Sub-Threshold Detection of GRB 251106A

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