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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 231214A: Fermi-LAT detection
  2. GRB 231214A: Enhanced Swift-XRT position
  3. GRB 231214B: Swift/BAT-GUANO detection of a burst
  4. GRB231214A: BOOTES-6/DPRT optical upper limit
  5. Fermi trigger No 724278269: Global MASTER-Net observations report
  6. Fermi trigger No 724233240: Global MASTER-Net observations report
  7. Swift GRB231214.85: Global MASTER-Net observations report
  8. GRB 231214A: Swift detection of a burst
  9. GRB 231214A: Fermi GBM Final Real-time Localization
  10. GRB 231210B: REM optical/NIR upper limits
  11. IceCube-231211A: Upper limits from a search for additional neutrino events in IceCube
  12. LIGO/Virgo/KAGRA S231213ap: Updated Sky localization
  13. LIGO/Virgo/KAGRA S231213ap: Identification of a GW compact binary merger candidate
  14. Fermi-LAT detection of increased gamma-ray activity of blazar PKS 2047+098, located inside the IceCube-231211A error region
  15. IceCube-231211A - IceCube observation of a high-energy neutrino candidate track-like event
  16. LIGO/Virgo/KAGRA S231206cc: Upper limits from Swift/BAT-GUANO
  17. LIGO/Virgo/KAGRA S231206ca: Upper limits from Swift/BAT-GUANO
  18. GRB 231212A: GECAM-C detection of a likely short burst
  19. Fermi trigger No 724035412: Global MASTER-Net observations report
  20. GRB 231210B: MeerLICHT afterglow observations
  21. GRB 231210B: Swift-BAT refined analysis
  22. IceCube Alert 231211.03: Global MASTER-Net observations report
  23. IceCube-231202A: No candidates from the Zwicky Transient Facility
  24. GRB 231210B: Swift-XRT refined Analysis
  25. GRB 231210B: Enhanced Swift-XRT position
  26. GRB 231210B: VLT/X-shooter redshift
  27. GRB 231210B: detection of the optical counterpart with the LCOGT 40cm telescope at Sutherland Observatory
  28. Fermi trigger No 723906955: Global MASTER-Net observations report
  29. GRB 231210B: Swift detection of a burst with optical counterpart
  30. Swift GRB231210.90: Global MASTER-Net OT detection
  31. Swift GRB231210.90: Global MASTER-Net observations report
  32. IPN triangulation of GRB 231129C
  33. GRB 231210A: Fermi GBM Final Real-time Localization
  34. GRB 231208A: GRBAlpha detection
  35. GRB231205B: Swift/UVOT Upper Limits
  36. GRB 231208A: Glowbug gamma-ray detection
  37. GRB 231208A: AstroSat CZTI detection of a faint burst
  38. LIGO/Virgo/KAGRA S231206ca: Updated Sky localization
  39. IPN triangulation of GRB 231205A
  40. GRB 231205B: Swift-BAT refined analysis
  41. GRB 231205B: 1.3m DFOT Optical upper limit
  42. LIGO/Virgo/KAGRA S231206cc: Updated Sky localization and Source Classification
  43. GRB 231206A: joint location of multiple instruments by ETJASMIN
  44. GRB 231205B: optical upper limit in TSHAOand AbAO
  45. LIGO/Virgo/KAGRA S231206cc: Identification of a GW compact binary merger candidate
  46. LIGO/Virgo/KAGRA S231206ca: Identification of a GW compact binary merger candidate
  47. GRB231115A: TURBO Pre-Burst Optical Upper Limits
  48. GRB 231205B: AGILE detection
  49. Fermi trigger No 723581802: Global MASTER-Net observations report
  50. GRB 231206B: Fermi GBM Final Real-time Localization
  51. GRB 231205B: Ondrejov D50 optical upper limit
  52. GRB 231205B: Swift-XRT refined Analysis
  53. Fermi-LAT gamma-ray observations of IceCube-231202A
  54. GRB 231205B: REM optical/NIR upper limits
  55. GRB 231129C: ASIM MXGS observation and localization
  56. GRB 231205B: NUTTelA-TAO / BSTI Early Optical Limits
  57. GRB 231205B: r'-band observations from MISTRAL at Observatoire de Haute-Provence
  58. GRB 231206A: GECAM-B detection of a short burst (correction)
  59. GRB 231205B : MITSuME Akeno optical upper limits
  60. GRB 231206A: GECAM-B detection of a short burst
  61. GRB 231205B: Zadko observatory - Gingin optical observations
  62. GRB 231205B: Gaoyazi/GOT optical upper limit
  63. GRB 231205B: Nanshan/HMT optical upper limit
  64. GRB 231205B: GECAM-B detection of a long burst
  65. GRB 231205B: LCOGT Optical Upper Limits
  66. GRB 231205A: DDOTI Upper Limits on the Afterglow
  67. LIGO/Virgo/KAGRA S231205c: One counterpart neutrino candidate event from an IceCube neutrino search
  68. GRB 231205B: Enhanced Swift-XRT position
  69. GRB 231204A: Glowbug gamma-ray detection
  70. Swift GRB231205.70: Global MASTER-Net observations report
  71. GRB 231204A: CALET Gamma-Ray Burst Monitor detection
  72. Fermi-LAT daily aperture light curve of T CrB now available
  73. GRB 231205B: AKO Optical Upper Limit
  74. GRB 231205B: Swift detection of a burst
  75. GRB 231205A: joint location of multiple instruments by ETJASMIN
  76. GRB 231204A: AstroSat CZTI detection
  77. GRB 231205A: GECAM-B detection of a short burst
  78. Fermi trigger No 723435916: Global MASTER-Net observations report
  79. Fermi trigger No 723326169: Global MASTER-Net observations report
  80. GRB 231205A: Fermi GBM Final Real-time Localization
  81. LIGO/Virgo/KAGRA S231129ac: Upper limits from Swift/BAT-GUANO
  82. IceCube-231202A: Upper limits from a search for additional neutrino events in IceCube
  83. Fermi trigger No 723412808: Global MASTER-Net observations report
  84. GRB 231203A: Fermi GBM Observation
  85. GRB 231204A: Fermi GBM Final Real-time Localization
  86. GRB 231203A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  87. Konus-Wind detection of GRB 231129C
  88. IceCube-231202A - IceCube observation of a high-energy neutrino candidate track-like event
  89. Fermi trigger No 723279695: Global MASTER-Net observations report
  90. The Fermi GBM team reports the detection of a likely SHORT GRB
  91. GRB 231203A: Fermi GBM Final Real-time Localization
  92. GRB 231129C: Swift-XRT afterglow detection
  93. Fermi trigger No 723149952: Global MASTER-Net observations report
  94. GRB 231129C: PROMPT optical upper limits for the MAXI/GSC X-ray counterpart and the MASTER afterglow candidate
  95. GRB 231129A: VZLUSAT-2 detection
  96. GRB 231129B: Swift-XRT observations
  97. GRB 231128A: VZLUSAT-2 detection
  98. Optical transient in the field of Messier 31, likely a new blazar: back to bright state
  99. GRB 231129C: AGILE detection
  100. GRB 231129A : MITSuME Akeno optical upper limits

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