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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"

12057 results found.

  1. GRB 250327A: J-band observations with WINTER
  2. GRB 250327A: SVOM/VT optical candidate
  3. Fermi GRB 250327A: Global MASTER-Net observations report
  4. Swift GRB 250327A: Global MASTER-Net observations report
  5. GRB 250327A: COLIBRÍ optical upper limit
  6. Fermi trigger No 764700395: Global MASTER-Net observations report
  7. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  8. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  9. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  10. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  11. GRB 250322A: Swift/UVOT Upper Limits
  12. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  13. GRB 250321B: Swift-XRT observations
  14. GRB 250322A: NOT optical upper limits
  15. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  16. GRB 250322A: MASTER optical observation
  17. GRB 250321A: Swift/UVOT Upper Limits
  18. Fermi GRB 250320B: Global MASTER-Net observations report
  19. EP250321a: Global MASTER-Net observations report
  20. Swift GRB 250321A: Global MASTER-Net observations report
  21. Fermi GRB 250321A: Global MASTER-Net observations report
  22. GRB 250321A: GOTO optical upper limits
  23. GRB 250314A: Keck/NIRC2 J-band upper limit
  24. Fermi GRB 250319B: Global MASTER-Net observations report
  25. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  26. GRB 250314A: ATCA radio upper limits
  27. GRB 250317B: Leavitt Observatory optical upper limit
  28. Fermi trigger No 763933627: Global MASTER-Net observations report
  29. GRB250312A: Swift/UVOT Upper Limits
  30. GRB 250317B: Swift-XRT observations
  31. GRB 250316A: Swift/UVOT Upper Limits
  32. GRB 250314A: REM optical/NIR upper limits
  33. GRB 250316A: AbAO AS-32 Optical Upper Limit
  34. GRB 250316A: Swift-XRT observations
  35. Fermi trigger No 763862734: Global MASTER-Net observations report
  36. Fermi GRB 250316A: Global MASTER-Net observations report
  37. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  38. GRB 250314A: Swift/UVOT Upper Limits
  39. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  40. SVOM/MXT upper limit on GRB 250314A
  41. GRB 250314A: SVOM/VT upper limit
  42. GRB 250313A: Swift-XRT observations
  43. Konus-Wind detection of GRB 250308A
  44. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  45. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  46. Fermi trigger No 763581136: Global MASTER-Net observations report
  47. Fermi GRB 250313A: Global MASTER-Net observations report
  48. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  49. Fermi trigger No 763509110: Global MASTER-Net observations report
  50. Fermi GRB 250312B: Global MASTER-Net observations report
  51. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  52. Swift GRB 250312A: Global MASTER-Net observations report
  53. GRB 250312A: Swift detection of a burst
  54. GRB 241213A: VIRT Optical Upper Limit
  55. GRB 241228A: VIRT Optical Upper Limit
  56. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  57. GRB 250311A: Swift-XRT observations
  58. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  59. EP250311a: Global MASTER-Net observations report
  60. GRB 250311A/EP250311a: TRT optical upper limit
  61. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  62. IceCube-250309A: Upper limits from Fermi-GBM Observations
  63. EP250308a: 1.6m Mephisto optical upper limits
  64. Konus-Wind detection of GRB 250309B
  65. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  66. GRB 250309B / IceCube-250309A: GECAM-B observations
  67. Fermi GRB 250309B: Global MASTER-Net observations report
  68. Fermi GRB 250309A: Global MASTER-Net observations report
  69. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  70. Fermi-LAT gamma-ray observations of IceCube-250309A
  71. IceCube Alert 250309.32: Global MASTER-Net observations report
  72. EP250308a: Global MASTER-Net observations report
  73. EP250308a: GSP optical upper limit
  74. EP250308a: FTW optical and NIR upper limits
  75. EP250308a: NOT optical upper limit
  76. Fermi GRB 250307A: Global MASTER-Net observations report
  77. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  78. Fermi trigger No 762963055: Global MASTER-Net observations report
  79. Swift GRB 250306A: Global MASTER-Net observations report
  80. GRB250101A: Radio upper limits from VLA observations
  81. EP250304A: Upper limits from Fermi-GBM Observations
  82. Fermi GRB 250305A: Global MASTER-Net observations report
  83. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  84. EP250302a: Optical Observations at CrAO and SAO RAS
  85. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  86. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  87. EP250304a: REM NIR upper limits
  88. EP250304a: Swift-XRT detection of a fading X-ray source
  89. EP250304a: Global MASTER-Net observations report
  90. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  91. EP250302a: REM NIR upper limits
  92. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  93. EP250302a: Global MASTER-Net observations report
  94. Fermi GRB 250302A: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  96. EP250228a: Optical observations with Kinder and Swift/UVOT
  97. GRB 250226A: KAO Optical Upper Limit
  98. GRB 250226A: AbAO AS-32 Optical Upper Limit
  99. EP250227a: Global MASTER-Net observations report
  100. EP250223A: Upper limits from Fermi-GBM Observations

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