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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. Fermi GRB 251115A: Global MASTER-Net observations report
  2. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  3. GRB 251115A: Fermi GBM Final Real-time Localization
  4. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  5. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  6. GRB 251113A: Glowbug gamma-ray detection
  7. GRB 251113A: AstroSat CZTI detection
  8. GRB 251114B: Fermi GBM Final Real-time Localization
  9. GRB 251112A: Swift-BAT refined analysis
  10. Konus-Wind detection of GRB 251108C
  11. Fermi trigger No 784717756: Global MASTER-Net observations report
  12. Konus-Wind detection of GRB 251103A
  13. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  14. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  15. IPN triangulation of GRB 251108C
  16. The EP-WXT trigger 01709248221 is likely a flaring star
  17. Fermi GRB 251114A: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  19. GRB 251114A: Fermi GBM Final Real-time Localization
  20. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  21. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  22. Fermi GRB 251113A: Global MASTER-Net observations report
  23. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  24. GRB 251113A: Fermi GBM Final Real-time Localization
  25. GRB 251111A: SVOM/ECLAIRs refined analysis
  26. GRB 251025B: SVOM/ECLAIRs refined analysis
  27. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  28. GRB 251112A: Swift/UVOT Upper Limits
  29. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  30. GRB 251112A: Swift-XRT refined Analysis
  31. GRB 251108C: AstroSat CZTI detection
  32. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  33. GRB 251112B: MAXI/GSC detection
  34. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  35. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  36. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  37. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  38. GRB 251108B: Glowbug gamma-ray detection
  39. Swift Trigger 1413695: a possible GRB 251112A
  40. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  41. Fermi trigger No 784621743: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  43. Fermi Gamma-ray Burst Monitor trigger 784653403/251112637 is not a GRB
  44. GRB251111A: 1.3m DFOT optical upper limit
  45. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  46. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  47. GRB 251111A: Swift-XRT afterglow detection
  48. GRB 251111A: SVOM/VT optical observations with X-band data
  49. SVOM GRB251111.42: Global MASTER-Net observations report
  50. GRB 251111A: Swift-XRT observations
  51. SVOM GRB251111.22: Global MASTER-Net observations report
  52. GRB 251111A: EP-FXT counterpart detection
  53. GRB 251013C: Chandra X-ray observations and jet break detection
  54. GRB 251111A: SVOM/VT optical observations with VHF data
  55. GRB 251111A: KAIT optical upper limit
  56. GRB 251111A: LCO optical observation
  57. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  58. GRB 251111A: SVOM detection of a soft burst
  59. GRB 251103B: Swift-BAT refined analysis
  60. GRB 251106A: Swift/UVOT Upper Limits
  61. GRB 251105B: Insight-HXMT/HE detection
  62. GRB 251106B: Insight-HXMT detection
  63. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  64. GRB 251105A: AstroSat CZTI detection
  65. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  66. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  67. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  68. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  69. GRB 251108A: Fermi GBM Final Localization Correction
  70. Fermi trigger No 784329591: Global MASTER-Net observations report
  71. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  72. Fermi trigger No 784279167: Global MASTER-Net observations report
  73. SVOM GRB251108.54: Global MASTER-Net observations report
  74. GRB 251102B: SVOM/GRM observation
  75. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  76. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  77. The EP-WXT trigger 01709248051 is likely a flaring star
  78. SVOM GRB251106.83: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  80. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  81. IPN triangulation of GRB 251105B (possible sGRB with EE)
  82. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  83. GRB 251106B: SVOM/GRM observation of a short burst
  84. GRB 251106A: Swift-XRT afterglow detection
  85. GRB 251106A: Kilonova-Catcher optical upper limit
  86. Fermi GBM Sub-Threshold Detection of GRB 251106A
  87. GRB 251106A: Swift/BAT arcminute localization of a burst
  88. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  89. GRB 251106A: MASTER optical observations
  90. GRB 251106A: SVOM detection of a burst
  91. GRB 251103B: AstroSat CZTI detection
  92. GRB 251025C: TERI Gamma-ray detection
  93. GRB 251016B: TERI Gamma-ray detection
  94. GRB 251016A: TERI Gamma-ray detection of a short burst
  95. GRB 250920C: TERI Gamma-ray detection
  96. Fermi trigger No 784034269: Global MASTER-Net observations report
  97. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  98. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  99. GRB 251105A: Fermi GBM Observation
  100. GRB 251105C: Fermi GBM Final Localization Correction

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