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

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