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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"

12321 results found.

  1. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  2. GRB 250314A: Swift/UVOT Upper Limits
  3. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  4. SVOM/MXT upper limit on GRB 250314A
  5. GRB 250314A: SVOM/VT upper limit
  6. GRB 250313A: Swift-XRT observations
  7. Konus-Wind detection of GRB 250308A
  8. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  9. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  10. Fermi trigger No 763581136: Global MASTER-Net observations report
  11. Fermi GRB 250313A: Global MASTER-Net observations report
  12. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  13. Fermi trigger No 763509110: Global MASTER-Net observations report
  14. Fermi GRB 250312B: Global MASTER-Net observations report
  15. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  16. Swift GRB 250312A: Global MASTER-Net observations report
  17. GRB 250312A: Swift detection of a burst
  18. GRB 241213A: VIRT Optical Upper Limit
  19. GRB 241228A: VIRT Optical Upper Limit
  20. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  21. GRB 250311A: Swift-XRT observations
  22. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  23. EP250311a: Global MASTER-Net observations report
  24. GRB 250311A/EP250311a: TRT optical upper limit
  25. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  26. IceCube-250309A: Upper limits from Fermi-GBM Observations
  27. EP250308a: 1.6m Mephisto optical upper limits
  28. Konus-Wind detection of GRB 250309B
  29. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  30. GRB 250309B / IceCube-250309A: GECAM-B observations
  31. Fermi GRB 250309B: Global MASTER-Net observations report
  32. Fermi GRB 250309A: Global MASTER-Net observations report
  33. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  34. Fermi-LAT gamma-ray observations of IceCube-250309A
  35. IceCube Alert 250309.32: Global MASTER-Net observations report
  36. EP250308a: Global MASTER-Net observations report
  37. EP250308a: GSP optical upper limit
  38. EP250308a: FTW optical and NIR upper limits
  39. EP250308a: NOT optical upper limit
  40. Fermi GRB 250307A: Global MASTER-Net observations report
  41. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  42. Fermi trigger No 762963055: Global MASTER-Net observations report
  43. Swift GRB 250306A: Global MASTER-Net observations report
  44. GRB250101A: Radio upper limits from VLA observations
  45. EP250304A: Upper limits from Fermi-GBM Observations
  46. Fermi GRB 250305A: Global MASTER-Net observations report
  47. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  48. EP250302a: Optical Observations at CrAO and SAO RAS
  49. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  50. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  51. EP250304a: REM NIR upper limits
  52. EP250304a: Swift-XRT detection of a fading X-ray source
  53. EP250304a: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  55. EP250302a: REM NIR upper limits
  56. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  57. EP250302a: Global MASTER-Net observations report
  58. Fermi GRB 250302A: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  60. EP250228a: Optical observations with Kinder and Swift/UVOT
  61. GRB 250226A: KAO Optical Upper Limit
  62. GRB 250226A: AbAO AS-32 Optical Upper Limit
  63. EP250227a: Global MASTER-Net observations report
  64. EP250223A: Upper limits from Fermi-GBM Observations
  65. EP250227a: TRT optical upper limit
  66. GRB 250225B: VLT/HAWKI near-infrared observations
  67. EP250227a: Optical upper limits with Kinder observations
  68. EP250225a: EP-FXT follow-up observation
  69. EP250223a: J band upper limit by SYSU 80cm telescope
  70. EP250228a: Global MASTER-Net observations report
  71. GRB 250205A / EP250205A: further radio observations with the VLA
  72. EP250225a: TRT optical upper limits
  73. EP250226a/GRB 250226A: 1.6m Mephisto observations
  74. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  75. Fermi GRB 250226B: Global MASTER-Net observations report
  76. GRB 250221A: ATCA Detections and Upper Limits
  77. GRB 250225B: REM NIR upper limits
  78. Konus-Wind detection of GRB 250225B
  79. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  80. EP250226a: Global MASTER-Net observations report
  81. Swift GRB 250225B: Global MASTER-Net observations report
  82. Fermi GRB 250226A: Global MASTER-Net observations report
  83. Fermi trigger No 762205158: Global MASTER-Net observations report
  84. EP250225a: Global MASTER-Net observations report
  85. EP250225a: GSP optical upper limit
  86. Fermi GRB 250225A: Global MASTER-Net observations report
  87. EP250215A: J band upper limit by SYSU 80cm telescope
  88. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  89. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  90. GRB 250207a: ATCA Radio Upper Limits
  91. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  92. EP250223a: REM NIR upper limit
  93. EP250223a: 1.6m Mephisto and 50cm array observations
  94. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  95. EP250223a: Global MASTER-Net observations report
  96. Fermi GRB 250223A: Global MASTER-Net observations report
  97. Fermi trigger No 762020305: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  99. EP250220a: FTW optical and NIR observations and upper limits
  100. EP250220a: EP-FXT follow-up observations

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