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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"

27395 results found.

  1. ZTF21aayokph (AT2021lfa): MASTER OT detection 3h befor ZTF
  2. Alert from the HAWC Burst Monitor HAWC-210507A
  3. HAWC GRB 210507.443: DDOTI Upper Limit
  4. GRB 210506A: Nanshan/NEXT optical upper limit
  5. GRB 210506A: TNG NIR upper limits
  6. ZTF21aayokph (AT2021lfa): Mondy and Koshka observatory optical observations
  7. ZTF21aayokph (AT2021lfa): X-ray Detection with Swift/XRT
  8. Lowell Discovery Telescope Observations of ZTF21aayokph (AT2021lfa)
  9. ZTF21aayokph (AT2021lfa): Assy optical observations
  10. ZTF21aayokph (AT2021lfa): Nanshan/NEXT optical upper limit
  11. GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
  12. GRB 210504A: Lowell Discovery Telescope optical observations
  13. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  14. GRB 210504A: Swift-XRT refined Analysis
  15. DDOTI Observations of ZTF21aayokph (AT2021lfa)
  16. GRB 210504A: Swift-BAT refined analysis
  17. GRB 210504A: MITSuME Akeno optical upper limits
  18. Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
  19. GRB 210504A: Swift/UVOT Detection
  20. GRB 210504A: Swift detection of a burst
  21. Swift GRB210502.74: Global MASTER-Net observations report
  22. Swift Detection of MAXI J1803-298 including an optical counterpart
  23. MAXI GRB210501.83: Global MASTER-Net observations report
  24. GRB 210430A: BOOTES-1 optical limit
  25. GRB 210424B: MITSuME Akeno optical upper limits
  26. GRB 210501A: Fermi GBM Final Real-time Localization
  27. GRB 210430A: Swift-BAT refined analysis
  28. GRB 210323B: Swift-XRT observations
  29. GRB 210427A: GECAM detection
  30. GRB 210427A: BALROG localization (Fermi Trigger / GRB 210427206)
  31. GRB 210420B: Assy optical observations
  32. Fermi trigger No 640975205: Global MASTER-Net observations report
  33. GRB 210425A: GECAM detection
  34. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  35. GRB 210422A: Swift-BAT refined analysis
  36. GRB 210420B: follow-up photometry of optical afterglow at INASAN/Simeiz
  37. GRB 210420B: Zeiss-1000 of Koshka optical observations
  38. GRB 210421A: Swift-BAT refined analysis
  39. GRB 210421B: Swift-XRT observations
  40. GRB 210420B: continued Tautenburg observations
  41. GRB 210421A: GECAM detection
  42. GRB 210421A: Swift/UVOT Upper Limits
  43. GRB 210420B: follow-up photometry of the optical afterglow at Konkoly
  44. GRB 210421A: MITSuME Akeno optical upper limits
  45. GRB 210420B: Swift-BAT refined analysis
  46. GRB 210421B: Swift/BAT-GUANO detection and arcminute localization
  47. GRB 210420B: Swift-XRT refined Analysis
  48. GRB 210421A: Swift-XRT refined Analysis
  49. Fermi GRB 210421C: Global MASTER-Net observations report
  50. GRB 210419C: Swift/UVOT Upper Limits
  51. GRB 210421A: Enhanced Swift-XRT position
  52. GRB 210420B: RATIR Optical and NIR Observations
  53. GRB 210420B: Tautenburg observations
  54. GRB 210420B: Swift/UVOT Detection
  55. GRB 210413B: MITSuME Okayama optical upper limits
  56. GRB 210419C: MITSuME Akeno optical upper limits
  57. GRB 210420B: DDOTI Detection of the Afterglow
  58. GRB 210421A: DDOTI Upper Limit
  59. GRB 210419C: Swift-BAT refined analysis
  60. GRB 210420B: Multiband photometry from NOT
  61. GRB 210420B: Montarrenti Observatory optical afterglow detection
  62. GRB 210421A: Swift detection of a burst
  63. GRB 210420B: Optical observations
  64. GRB 210420B: MASTER optical counterpart detection
  65. GRB 210419C: RATIR Optical and NIR Upper Limits
  66. GRB 210419C: Montarrenti Observatory Upper Limit
  67. GRB 210419A: Swift/UVOT Upper Limits
  68. GRB 210419C: Enhanced Swift-XRT position
  69. GRB 210419A: Swift-BAT refined analysis
  70. GRB 210419A: Swift-XRT refined Analysis
  71. GRB 210419C: Swift detection of a burst
  72. GRB 210419A: Enhanced Swift-XRT position
  73. GRB 210419A: LCO Optical Upper Limit
  74. GRB 210419A: Swift detection of a burst
  75. GRB 210413B: Swift-XRT observations
  76. GRB 210413B: LOAO optical upper limit
  77. GRB 210411C: A very significant early X-ray afterglow
  78. GRB 210413A: GECAM detection
  79. GRB 210411C: Swift/UVOT Detection
  80. GRB 210411C: Swift-BAT refined analysis
  81. GRB 210411C: Swift-XRT refined Analysis
  82. GRB 210410A: MITSuME Akeno optical upper limits
  83. Swift GRB 210411C: Global MASTER-Net observations report
  84. GRB 210411C: LCO Optical Afterglow Candidate
  85. GRB 210411C: Enhanced Swift-XRT position
  86. GRB 210411D: BALROG localization (Fermi Trigger 639851475 / GRB 210411688)
  87. GRB 210411C: Swift detection of a burst with an optical counterpart
  88. GRB 210410A: Swift-BAT refined analysis
  89. GRB 210410A: Swift-XRT refined Analysis
  90. GRB 210410A: Fermi GBM detection
  91. GRB 210410A: Swift/UVOT Upper Limits
  92. GRB 210406A: Swift-XRT observations
  93. GRB 210410A: RATIR Optical and NIR Observations
  94. GRB 210409A: GECAM detection
  95. GRB 210410A: Fermi-LAT detection
  96. Swift Triggers 1042031 and 1042032 are not astrophysical events
  97. GRB 210406A: Mondy optical afterglow candidate
  98. GRB 210406B: Fermi GBM detection
  99. Konus-Wind detection of GRB 210406A
  100. GRB 210406A: Fermi GBM detection

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