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

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