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

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