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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. GRB 251013C: Leavitt Observatory optical photometry
  2. Fermi GRB 251016B: Global MASTER-Net observations report
  3. GRB 251017A: JinShan observations of the optical afterglow
  4. Swift GRB 251017A: Global MASTER-Net observations report
  5. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  6. Swift Trigger 1404295 is not a GRB
  7. GRB 251016A: AstroSat CZTI detection of a short burst
  8. GRB 251017A: Enhanced Swift-XRT position
  9. GRB 251017A: COLIBRÍ Early Afterglow Detection
  10. GRB 251016B: AstroSat CZTI detection
  11. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  12. GRB 251017A: Swift detection of a burst with an optical counterpart
  13. GRB 251016A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 251016B: CALET Gamma-Ray Burst Monitor detection
  15. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  16. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  17. GRB 251007B: Swift-BAT refined analysis
  18. GRB 251016B: Fermi GBM Final Real-time Localization
  19. GRB 251014D: Swift-BAT refined analysis
  20. GRB 251016A: BOOTES-6/DPRT optical upper limit
  21. GRB 251016A: Glowbug gamma-ray detection of a short burst
  22. GRB 251013C: VLA detection
  23. sb25101602: Swift-XRT counterpart detection
  24. Fermi GRB 251016A: Global MASTER-Net observations report
  25. GRB 251016A: Fermi GBM Final Localization
  26. GRB 251016A: SVOM detection of a short burst
  27. GRB 251014A: Swift-XRT observations
  28. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  29. GRB 251014B: PRIME J-band upper limit
  30. Upper limits from a search for additional neutrino events in IceCube
  31. IceCube Alert 251014.77: Global MASTER-Net observations report
  32. Swift GRB251015.60: Global MASTER-Net observations report
  33. GRB 251013C: Kilonova-Catcher optical afterglow detection
  34. Fermi-LAT Gamma-ray Observations of IceCube-251014A
  35. GRB 251013D: Swift/UVOT Observations
  36. GRB 251013C: Swift/UVOT Detection
  37. Konus-Wind detection of GRB 251007A
  38. Fermi Gamma-ray Burst Monitor trigger 782237334/251015673 is not a GRB
  39. GRB 251013C, GCN Circular 42267, errata corrige
  40. GRB 251013C: detection of a radio counterpart at 15.5GHz
  41. GRB 251015A: Fermi GBM Final Real-time Localization
  42. GRB 251013C: SVOM/ECLAIRs refined analysis
  43. GRB 251013D: Swift-XRT observations
  44. Swift Trigger 1404295: possible GRB 251015A
  45. GRB 251014B: Swift-XRT observations
  46. GRB 251014B: Swift/UVOT Upper Limits
  47. GRB 251014B: VLT/FORS2 Optical Observation
  48. GRB 251014D: Swift/UVOT Upper Limits
  49. GRB 251014D: BOOTES-6/DPRT optical upper limit
  50. GRB 251014D: Swift-XRT afterglow detection
  51. GRB 251013C: MAO/AZT-22 optical observations
  52. GRB 251011B: SVOM/VT optical upper limit
  53. GRB 251013C: Swift ToO observations
  54. GRB 251013D: Fermi GBM Observation
  55. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) further multi-band optical observations
  56. GRB 251014A: Swift-BAT refined analysis
  57. IceCube-251014A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 251013C: OHP/T193 further optical observations and possible color evolution
  59. GRB 251013C: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
  60. GRB 251014D: Swift detection of a burst
  61. GRB 251014A: PRIME near-infrared upper limits
  62. GRB 251014C: Fermi GBM Final Localization
  63. GRB 251014A: Glowbug gamma-ray detection of a likely short burst
  64. GRB 251014A: VLT/FORS2 Optical Observation
  65. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  66. GRB 251012A: Glowbug gamma-ray detection of a likely short burst
  67. GRB 251013C: MarSEC, optical afterglow photometry
  68. GRB 251013C: OHP/T193 optical afterglow photometry and spectroscopy
  69. GRB 251014B: Swift ToO observations
  70. GRB 251013D: LAST optical upper limit on Swift/BAT-GUANO localization
  71. GRB 251014B: Swift/BAT-GUANO arcminute localization of a short burst
  72. GRB 251013C: Bassano Bresciano Observatory optical observations
  73. GRB 251013C: Early and late-time optical counterpart detection by LCO
  74. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  75. GRB 251013C: Fermi GBM Observation
  76. GRB 251013D: Swift ToO observations
  77. GRB 251014A: DDOTI Upper Limit
  78. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  79. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  80. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  81. GRB 251013C: Asiago optical observations
  82. GRB 251013A: CALET Gamma-Ray Burst Monitor detection
  83. GRB 251013C: ABObservatory optical observations
  84. GRB 251014A: SAO RAS optical upper limit
  85. GRB 251014A: Fermi GBM Observation
  86. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  87. GRB 251013C: EP-FXT counterpart detection
  88. GRB 251013C: AstroSat CZTI detection
  89. GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst
  90. GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst
  91. GRB 251013C: ALMA detection
  92. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  93. GRB 251013C: DDOTI detection of the optical afterglow
  94. GRB 251013C: SLKT optical afterglow photometry
  95. Swift GRB 251014A: Global MASTER-Net observations report
  96. GRB 251014A: Swift detection of a possibly-short burst
  97. GRB 251014A: Fermi GBM Final Real-time Localization
  98. Fermi trigger No 782044789: Global MASTER-Net observations report
  99. Fermi GRB 251013C: Global MASTER-Net observations report
  100. Fermi GRB 251013B: Global MASTER-Net observations report

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