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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 S251112cm: FTW observations of galaxies within localization region
  2. Fermi GRB 251113A: Global MASTER-Net observations report
  3. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  4. GRB 251113A: Fermi GBM Final Real-time Localization
  5. GRB 251111A: SVOM/ECLAIRs refined analysis
  6. GRB 251025B: SVOM/ECLAIRs refined analysis
  7. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  8. GRB 251112A: Swift/UVOT Upper Limits
  9. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  10. GRB 251112A: Swift-XRT refined Analysis
  11. GRB 251108C: AstroSat CZTI detection
  12. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  13. GRB 251112B: MAXI/GSC detection
  14. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  15. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  16. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  17. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  18. GRB 251108B: Glowbug gamma-ray detection
  19. Swift Trigger 1413695: a possible GRB 251112A
  20. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  21. Fermi trigger No 784621743: Global MASTER-Net observations report
  22. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  23. Fermi Gamma-ray Burst Monitor trigger 784653403/251112637 is not a GRB
  24. GRB251111A: 1.3m DFOT optical upper limit
  25. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  26. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  27. GRB 251111A: Swift-XRT afterglow detection
  28. GRB 251111A: SVOM/VT optical observations with X-band data
  29. SVOM GRB251111.42: Global MASTER-Net observations report
  30. GRB 251111A: Swift-XRT observations
  31. SVOM GRB251111.22: Global MASTER-Net observations report
  32. GRB 251111A: EP-FXT counterpart detection
  33. GRB 251013C: Chandra X-ray observations and jet break detection
  34. GRB 251111A: SVOM/VT optical observations with VHF data
  35. GRB 251111A: KAIT optical upper limit
  36. GRB 251111A: LCO optical observation
  37. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  38. GRB 251111A: SVOM detection of a soft burst
  39. GRB 251103B: Swift-BAT refined analysis
  40. GRB 251106A: Swift/UVOT Upper Limits
  41. GRB 251105B: Insight-HXMT/HE detection
  42. GRB 251106B: Insight-HXMT detection
  43. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  44. GRB 251105A: AstroSat CZTI detection
  45. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  46. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  47. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  48. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  49. GRB 251108A: Fermi GBM Final Localization Correction
  50. Fermi trigger No 784329591: Global MASTER-Net observations report
  51. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  52. Fermi trigger No 784279167: Global MASTER-Net observations report
  53. SVOM GRB251108.54: Global MASTER-Net observations report
  54. GRB 251102B: SVOM/GRM observation
  55. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  56. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  57. The EP-WXT trigger 01709248051 is likely a flaring star
  58. SVOM GRB251106.83: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  60. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  61. IPN triangulation of GRB 251105B (possible sGRB with EE)
  62. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  63. GRB 251106B: SVOM/GRM observation of a short burst
  64. GRB 251106A: Swift-XRT afterglow detection
  65. GRB 251106A: Kilonova-Catcher optical upper limit
  66. Fermi GBM Sub-Threshold Detection of GRB 251106A
  67. GRB 251106A: Swift/BAT arcminute localization of a burst
  68. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  69. GRB 251106A: MASTER optical observations
  70. GRB 251106A: SVOM detection of a burst
  71. GRB 251103B: AstroSat CZTI detection
  72. GRB 251025C: TERI Gamma-ray detection
  73. GRB 251016B: TERI Gamma-ray detection
  74. GRB 251016A: TERI Gamma-ray detection of a short burst
  75. GRB 250920C: TERI Gamma-ray detection
  76. Fermi trigger No 784034269: Global MASTER-Net observations report
  77. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  78. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  79. GRB 251105A: Fermi GBM Observation
  80. GRB 251105C: Fermi GBM Final Localization Correction
  81. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  82. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  83. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  85. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  86. Fermi GBM Sub-Threshold Detection of GRB 251105B
  87. GRB 251103B: Swift/UVOT Upper Limits
  88. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  89. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  90. Fermi GRB 251105A: Global MASTER-Net observations report
  91. GRB 251105A: Fermi GBM Final Real-time Localization
  92. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  93. GRB 251103B: Fermi GBM observation
  94. GRB 251104A: SVOM detection of a burst
  95. GRB 251028A: Insight-HXMT/HE detection
  96. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  97. EP251102a: FTW optical and NIR observations
  98. GRB 251103A: WFST optical observations
  99. EP251102a: update of EP-FXT follow-up observation
  100. EP251102a: OHP/T193 optical observations

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