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

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