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

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