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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 231215A: AstroSat CZTI detection
  2. GRB 231215A : MITSuME Akeno optical afterglow candidate detection
  3. GRB 231214A: Swift-XRT refined Analysis
  4. GRB 231215A: Mondy optical bright afterglow detection
  5. GRB 231214A: AstroSat CZTI detection
  6. GRB 231215C: MASTER OT detection
  7. Swift GRB231215.41: Global MASTER-Net observations report
  8. GRB 231215A: Swift-XRT observations
  9. GRB 231215B: Fermi GBM Final Real-time Localization
  10. GRB 231215A: Swift detection of a burst
  11. GRB 231214A: Fermi-LAT detection
  12. GRB 231214A: Enhanced Swift-XRT position
  13. GRB 231214B: Swift/BAT-GUANO detection of a burst
  14. GRB231214A: BOOTES-6/DPRT optical upper limit
  15. Fermi trigger No 724278269: Global MASTER-Net observations report
  16. Fermi trigger No 724233240: Global MASTER-Net observations report
  17. Swift GRB231214.85: Global MASTER-Net observations report
  18. GRB 231214A: Swift detection of a burst
  19. GRB 231214A: Fermi GBM Final Real-time Localization
  20. GRB 231210B: REM optical/NIR upper limits
  21. IceCube-231211A: Upper limits from a search for additional neutrino events in IceCube
  22. LIGO/Virgo/KAGRA S231213ap: Updated Sky localization
  23. LIGO/Virgo/KAGRA S231213ap: Identification of a GW compact binary merger candidate
  24. Fermi-LAT detection of increased gamma-ray activity of blazar PKS 2047+098, located inside the IceCube-231211A error region
  25. IceCube-231211A - IceCube observation of a high-energy neutrino candidate track-like event
  26. LIGO/Virgo/KAGRA S231206cc: Upper limits from Swift/BAT-GUANO
  27. LIGO/Virgo/KAGRA S231206ca: Upper limits from Swift/BAT-GUANO
  28. GRB 231212A: GECAM-C detection of a likely short burst
  29. Fermi trigger No 724035412: Global MASTER-Net observations report
  30. GRB 231210B: MeerLICHT afterglow observations
  31. GRB 231210B: Swift-BAT refined analysis
  32. IceCube Alert 231211.03: Global MASTER-Net observations report
  33. IceCube-231202A: No candidates from the Zwicky Transient Facility
  34. GRB 231210B: Swift-XRT refined Analysis
  35. GRB 231210B: Enhanced Swift-XRT position
  36. GRB 231210B: VLT/X-shooter redshift
  37. GRB 231210B: detection of the optical counterpart with the LCOGT 40cm telescope at Sutherland Observatory
  38. Fermi trigger No 723906955: Global MASTER-Net observations report
  39. GRB 231210B: Swift detection of a burst with optical counterpart
  40. Swift GRB231210.90: Global MASTER-Net OT detection
  41. Swift GRB231210.90: Global MASTER-Net observations report
  42. IPN triangulation of GRB 231129C
  43. GRB 231210A: Fermi GBM Final Real-time Localization
  44. GRB 231208A: GRBAlpha detection
  45. GRB231205B: Swift/UVOT Upper Limits
  46. GRB 231208A: Glowbug gamma-ray detection
  47. GRB 231208A: AstroSat CZTI detection of a faint burst
  48. LIGO/Virgo/KAGRA S231206ca: Updated Sky localization
  49. IPN triangulation of GRB 231205A
  50. GRB 231205B: Swift-BAT refined analysis
  51. GRB 231205B: 1.3m DFOT Optical upper limit
  52. LIGO/Virgo/KAGRA S231206cc: Updated Sky localization and Source Classification
  53. GRB 231206A: joint location of multiple instruments by ETJASMIN
  54. GRB 231205B: optical upper limit in TSHAOand AbAO
  55. LIGO/Virgo/KAGRA S231206cc: Identification of a GW compact binary merger candidate
  56. LIGO/Virgo/KAGRA S231206ca: Identification of a GW compact binary merger candidate
  57. GRB231115A: TURBO Pre-Burst Optical Upper Limits
  58. GRB 231205B: AGILE detection
  59. Fermi trigger No 723581802: Global MASTER-Net observations report
  60. GRB 231206B: Fermi GBM Final Real-time Localization
  61. GRB 231205B: Ondrejov D50 optical upper limit
  62. GRB 231205B: Swift-XRT refined Analysis
  63. Fermi-LAT gamma-ray observations of IceCube-231202A
  64. GRB 231205B: REM optical/NIR upper limits
  65. GRB 231129C: ASIM MXGS observation and localization
  66. GRB 231205B: NUTTelA-TAO / BSTI Early Optical Limits
  67. GRB 231205B: r'-band observations from MISTRAL at Observatoire de Haute-Provence
  68. GRB 231206A: GECAM-B detection of a short burst (correction)
  69. GRB 231205B : MITSuME Akeno optical upper limits
  70. GRB 231206A: GECAM-B detection of a short burst
  71. GRB 231205B: Zadko observatory - Gingin optical observations
  72. GRB 231205B: Gaoyazi/GOT optical upper limit
  73. GRB 231205B: Nanshan/HMT optical upper limit
  74. GRB 231205B: GECAM-B detection of a long burst
  75. GRB 231205B: LCOGT Optical Upper Limits
  76. GRB 231205A: DDOTI Upper Limits on the Afterglow
  77. LIGO/Virgo/KAGRA S231205c: One counterpart neutrino candidate event from an IceCube neutrino search
  78. GRB 231205B: Enhanced Swift-XRT position
  79. GRB 231204A: Glowbug gamma-ray detection
  80. Swift GRB231205.70: Global MASTER-Net observations report
  81. GRB 231204A: CALET Gamma-Ray Burst Monitor detection
  82. Fermi-LAT daily aperture light curve of T CrB now available
  83. GRB 231205B: AKO Optical Upper Limit
  84. GRB 231205B: Swift detection of a burst
  85. GRB 231205A: joint location of multiple instruments by ETJASMIN
  86. GRB 231204A: AstroSat CZTI detection
  87. GRB 231205A: GECAM-B detection of a short burst
  88. Fermi trigger No 723435916: Global MASTER-Net observations report
  89. Fermi trigger No 723326169: Global MASTER-Net observations report
  90. GRB 231205A: Fermi GBM Final Real-time Localization
  91. LIGO/Virgo/KAGRA S231129ac: Upper limits from Swift/BAT-GUANO
  92. IceCube-231202A: Upper limits from a search for additional neutrino events in IceCube
  93. Fermi trigger No 723412808: Global MASTER-Net observations report
  94. GRB 231203A: Fermi GBM Observation
  95. GRB 231204A: Fermi GBM Final Real-time Localization
  96. GRB 231203A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  97. Konus-Wind detection of GRB 231129C
  98. IceCube-231202A - IceCube observation of a high-energy neutrino candidate track-like event
  99. Fermi trigger No 723279695: Global MASTER-Net observations report
  100. The Fermi GBM team reports the detection of a likely SHORT GRB

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