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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. Swift GRB210222.94: Global MASTER-Net observations report
  2. GRB 210222A: MAXI/GSC detection
  3. GRB 210218A: Swift-XRT observations
  4. uGMRT radio detection of GRB 210204A
  5. GRB 210212A: Lowell Discovery Telescope observations
  6. GRB 210217A: 1.3m DFOT optical detection
  7. GRB 210217A: Swift-XRT refined Analysis
  8. GRB 210218A: Swift-BAT refined analysis
  9. Fermi GBM Sub-Threshold Detection of GRB 210217A
  10. GRB 210217A: Liverpool Telescope First Hour Observations
  11. GRB 210217A: Swift-BAT refined analysis
  12. GRB 210217A: KAIT Optical Observations
  13. GRB 210218A: MITSuME Akeno optical upper limits
  14. GRB 210218A： GWAC-F60A optical upper limit
  15. GRB 210218A: NEXT optical upper limit
  16. GRB 210218A: Swift detection of a burst
  17. ZTF21aakruew/AT2021cwd: GROND observations
  18. GRB 210212A: REM early-time optical/NIR upper limits
  19. GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
  20. GRB 210217A: Enhanced Swift-XRT position
  21. Fermi/GBM observation of a burst from SGR 1830-0645
  22. GRB 210217A: NEXT early optical afterglow observations
  23. GRB 210212A: Mondy optical observations
  24. GRB 210217A: Swift detection of a burst with an optical counterpart
  25. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Assy and Mondy optical observations
  26. IceCube-210210A: Two Additional Optical Candidate Counterparts Found by DECam
  27. GRB 210208A: 1.3m DFOT Optical upper limit
  28. GRB 210210A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
  29. Swift Trigger 1033144: Detection of SGR 1830-0645
  30. GRB 210211A: ePESSTO+ NTT optical observations
  31. Konus-Wind detection of GRB 210212B / ZTF21aakruew
  32. GRB 210212B: Swift ToO observations
  33. GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations
  34. IPN triangulation of GRB 210212B (consistent with ZTF21aakruew/AT2021cwd)
  35. GRB 210212A: 1.3m DFOT Optical upper limit
  36. GRB 210213B: Insight-HXMT/HE detection
  37. ZTF21aakruew/AT2021cwd: ZTF and LT discovery of a hostless, red, and rapidly fading optical transient
  38. GRB 210212A: Gemini South optical observations
  39. IceCube alert 134994_1103075 retraction
  40. Fermi GRB 210213A: Global MASTER-Net observations report
  41. IceCube Alert 210213.78: Global MASTER-Net observations report
  42. GRB 210213A: Fermi GBM Final Real-time Localization
  43. GRB 210210A: CAHA 2nd epoch and jet break confirmation
  44. IceCube-210210A: Four Candidate Optical Counterparts from DECam Observations
  45. Swift Trigger 1032350: Detection of SGR 1830-0645
  46. GRB 210204A (ZTF21aagwbjr/AT2021buv): continued CrAO and AbAO optical observations
  47. GRB 210212A: Possible host galaxy counterpart with the NOT
  48. Swift GRB 210212A: Global MASTER-Net observations report
  49. GRB 210212A: MITSuME Akeno optical upper limits
  50. GRB 210212A: Swift-XRT refined Analysis
  51. GRB 210212A: BOOTES-4/MET optical upper limit
  52. IceCube-210210A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 210212A: Swift/UVOT Upper Limits
  54. GRB 210212A: Swift-BAT refined analysis
  55. GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
  56. GRB 210212A: Enhanced Swift-XRT position
  57. GRB 210210A : 1.3m DFOT optical observations
  58. GRB 210212A: Swift detection of a burst
  59. GRB 210207B: GECAM detection
  60. GRB 210211A: Swift/UVOT Detection
  61. GRB 210211A: Swift-XRT refined Analysis
  62. GRB 210211A: Swift-BAT refined analysis
  63. GRB 210211A: Fermi GBM observation
  64. GRB 210210A as a BdHN II
  65. Swift-XRT observations of IceCube-210210A
  66. GRB 210209A: Swift-BAT refined analysis
  67. GRB 210211A: Enhanced Swift-XRT position
  68. GRB 210211A: MASTER optical observation of REM OT
  69. GRB 210210A: CAHA detection and likely jet break
  70. IceCube-210210A: No neutrino counterpart in ANTARES
  71. GRB 210211A: REM optical/NIR afterglow detection
  72. Fermi-LAT Gamma-ray Observations of IceCube-210210A
  73. GRB 210211A: Swift detection of a burst
  74. Swift GRB210211.36: Global MASTER-Net observations report
  75. GRB 210211A: Fermi GBM Final Real-time Localization
  76. GRB 210210A: FRAM-ORM afterglow detection
  77. Fermi trigger No 634659312: Global MASTER-Net observations report
  78. GRB 210210A: Swift-BAT refined analysis
  79. IceCube Alert 210210.50: Global MASTER-Net observations report
  80. Fermi GRB 210210B: Global MASTER-Net observations report
  81. IceCube-210210A: Upper limits from Fermi-GBM Observations
  82. IceCube-210210A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  83. GRB 210210B: Fermi GBM Final Real-time Localization
  84. IceCube-210210A: Two Candidate Counterparts from the Zwicky Transient Facility
  85. GRB 210209A: BOOTES-4/MET optical upper limit
  86. GRB 210210A: LCO Optical Afterglow Detection
  87. Swift GRB 210209A: Global MASTER-Net observations report
  88. GRB 210210A: Swift/UVOT Detection
  89. GRB 210112A: LBT host detection and correction to GCN 29319 (CAHA observations)
  90. GRB 210209A: MITSuME Akeno optical upper limits
  91. IceCube-210210A: IceCube observation of a high-energy neutrino candidate event
  92. GRB 210209A: Swift/UVOT Upper Limits
  93. GRB 210210A: Swift-XRT refined Analysis
  94. GRB 210208A: GIT optical upper limit
  95. GRB 210210A: Redshift from OSIRIS/GTC
  96. GRB 210209A: Swift-XRT refined Analysis
  97. GRB 210210A: Enhanced Swift-XRT position
  98. GRB 210210A: MASTER afterglow observation
  99. ZTF21aahifke/AT2021clk: ZTF discovery of an optical fast transient (possible afterglow)
  100. Swift GRB 210210A: Global MASTER-Net observations report

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