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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 210123A: Fermi GBM Final Localization
  2. GECAM detection of a burst possibly from the X-ray burster 4U 0614+09 or GRB 210124A
  3. GRB 210123A: Insight-HXMT/HE detection
  4. IPN triangulation of GRB 210121A
  5. GRB 210121A: GECAM detection
  6. GRB 210121A: Insight-HXMT/HE detection
  7. GRB 210120A : 1.3m DFOT optical observations
  8. ZTF21aaeyldq: GROND and CAHA jet break confirmation
  9. ZTF20aaeyldq: VLA radio detection
  10. GRB 210116A: AstroSat CZTI detection
  11. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  12. GRB 210116: AstroSat LAXPC detection
  13. GRB 210120A: MASTER OT (possibly) discovery
  14. GECAM In-Flight Trigger of GRB 210120A
  15. GRB 210104A: 3.6m DOT optical upper limit
  16. Fermi GRB 210120A: Global MASTER-Net observations report
  17. GRB 210120A: BALROG localization (Fermi Trigger 632819449 / GRB 210120299)
  18. GRB 210120A: Fermi GBM Final Real-time Localization
  19. GRB 210112A: 3.6m DOT optical detection
  20. GRB 210119A (Swift J1851.2-6148): Swift-BAT refined analysis
  21. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  22. ZTF21aaeyldq: GROND observations
  23. GRB 210119A: Insight-HXMT/HE detection
  24. GRB 210119A: Fermi GBM observation
  25. ZTF21aaeyldq: LBT near-infrared observations
  26. GRB 210112A: Insight-HXMT/HE detection
  27. Short Fermi GRB 210119A or new SGR Swift J1851.2-6148: Possible MASTER Short OT detection
  28. Fermi GRB 210119A: Global MASTER-Net observations report
  29. Swift detection of a new SGR Swift J1851.2-6148 or a short GRB 210119A
  30. GRB 210119A: Fermi GBM Final Real-time Localization
  31. ZTF21aaeyldq CAHA 2.2m detection and power-law decay
  32. GRB 200613A: Host galaxy redshift from OSIRIS/GTC
  33. GRB 210112A: Deep CAHA 2.2m detection
  34. GRB 210104A: Late-time CAHA 2.2m detection
  35. Fermi trigger No 632573937: Global MASTER-Net observations report
  36. ZTF21aaeyldq: KPED observations
  37. Konus-Wind detection of GRB 210112A
  38. Correction to GCN 29288: NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS observation
  39. ZTF21aaeyldq (AT2021any): Detection of X-ray Emission with Swift/XRT
  40. ZTF21aaeyldq: 2.2m CAHA BVRI optical observations
  41. GRB 201221D: near-infrared observation with LBT
  42. ZTF21aaeyldq: NOT optical observations
  43. ZTF21aaeyldq: Lowell Discovery Telescope observations
  44. ZTF21aaeyldq: observations with the 3.6m Devasthal Optical Telescope
  45. ZTF21aaeyldq: GTC Redshift and GRB afterglow nature confirmation
  46. GRB 201015A: evidence of supernova in LBT spectra
  47. ZTF Discovery of ZTF21aaeyldq (AT2021any): a Hostless, Young, and Rapidly Fading Transient
  48. GRB 210104A: JCMT SCUBA-2 sub-mm observations
  49. GRB 210112A: Swift/UVOT Detection
  50. GRB 210112A: Mondy optical observations
  51. GRB 210112A: 1.3m DFOT Optical upper limit
  52. GRB 210112A: OSN second epoch, decay
  53. GRB 210104A: AstroSat CZTI detection
  54. NuEm-210111A: MAXI/GSC upper limit
  55. GRB 210112A: Swift-BAT refined analysis
  56. GRB 210112A: OSN Reddened Afterglow Detection
  57. GRB 210112A: Swift-XRT refined Analysis
  58. NuEm-210111A : No neutrino counterpart in ANTARES
  59. GRB 210112A: AGILE detection
  60. GRB 210112A: Kitab a optical upper limit
  61. GRB 210104A: AROMA-N Optical Afterglow Detection
  62. GRB 210112A: Enhanced Swift-XRT position
  63. GRB 210112A: Swift detection of a burst with an optical counterpart
  64. NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  65. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-210111A
  66. GRB 210104A: Mondy optical observations, light curve
  67. MAXI GRB210110.64: Global MASTER-Net observations report
  68. GRB 210110A: MAXI/GSC detection
  69. GRB 210104A: Assy continued optical observations, correction to GCN circ. 29265
  70. GRB 210109A: MAXI/GSC detection
  71. GRB 201227A: continued Chilescope confirmation of variability of possible optical counterpart, redshift estimating
  72. Correction to GCN 29278: GRB 201216C XRT refined analysis
  73. GRB 210108A: BALROG localization (Fermi Trigger 631793415 / GRB 210108424)
  74. GRB 201216C: Swift-XRT refined Analysis
  75. GRB 210104A: SAO RAS optical observations
  76. GRB 201227A: ASIM observation
  77. GRB 210104A: GMG observations
  78. GRB210104A: VIRT optical transient detection.
  79. GRB 210104A: SARA-KP 0.9m Optical Afterglow Detection
  80. Fermi trigger No 631602681: Global MASTER-Net observations report
  81. GRB 210102B: further Swift-XRT observations
  82. GRB 210102B: Assy optical afterglow identification
  83. GRB 210104A: iTelescope optical upper limit
  84. GRB 210104A: CALET Gamma-Ray Burst Monitor detection
  85. Fermi trigger No 631584650: Global MASTER-Net observations report
  86. GRB 210104B: Swift-BAT refined analysis
  87. GRB 210104A: Assy continued optical observations
  88. Fermi GRB 210105A: Global MASTER-Net observations report
  89. GW170817: HST observations at 3.4 years from merger
  90. GRB 210104A: early ATLAS detections of the bright afterglow
  91. GRB 210105A: Fermi GBM Final Real-time Localization
  92. GRB 210104A: Swift-XRT refined Analysis
  93. GRB 210104B: Swift/UVOT Upper Limits
  94. Konus-Wind detection of GRB 210104A
  95. GRB 210104A: 1.3m DFOT Optical Afterglow Detection
  96. GRB 210104B: Swift-XRT refined Analysis
  97. GRB 210104B: Assy optical upper limit
  98. GRB 210104A: DOAO optical afterglow observations
  99. GRB 210104B: Enhanced Swift-XRT position
  100. GRB 210104A: Nanshan/NEXT optical powerlaw decay

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