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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"

12319 results found.

  1. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  2. SVOM/MXT upper limit on GRB 250314A
  3. GRB 250314A: SVOM/VT upper limit
  4. GRB 250313A: Swift-XRT observations
  5. Konus-Wind detection of GRB 250308A
  6. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  7. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  8. Fermi trigger No 763581136: Global MASTER-Net observations report
  9. Fermi GRB 250313A: Global MASTER-Net observations report
  10. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  11. Fermi trigger No 763509110: Global MASTER-Net observations report
  12. Fermi GRB 250312B: Global MASTER-Net observations report
  13. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  14. Swift GRB 250312A: Global MASTER-Net observations report
  15. GRB 250312A: Swift detection of a burst
  16. GRB 241213A: VIRT Optical Upper Limit
  17. GRB 241228A: VIRT Optical Upper Limit
  18. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  19. GRB 250311A: Swift-XRT observations
  20. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  21. EP250311a: Global MASTER-Net observations report
  22. GRB 250311A/EP250311a: TRT optical upper limit
  23. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  24. IceCube-250309A: Upper limits from Fermi-GBM Observations
  25. EP250308a: 1.6m Mephisto optical upper limits
  26. Konus-Wind detection of GRB 250309B
  27. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  28. GRB 250309B / IceCube-250309A: GECAM-B observations
  29. Fermi GRB 250309B: Global MASTER-Net observations report
  30. Fermi GRB 250309A: Global MASTER-Net observations report
  31. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  32. Fermi-LAT gamma-ray observations of IceCube-250309A
  33. IceCube Alert 250309.32: Global MASTER-Net observations report
  34. EP250308a: Global MASTER-Net observations report
  35. EP250308a: GSP optical upper limit
  36. EP250308a: FTW optical and NIR upper limits
  37. EP250308a: NOT optical upper limit
  38. Fermi GRB 250307A: Global MASTER-Net observations report
  39. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  40. Fermi trigger No 762963055: Global MASTER-Net observations report
  41. Swift GRB 250306A: Global MASTER-Net observations report
  42. GRB250101A: Radio upper limits from VLA observations
  43. EP250304A: Upper limits from Fermi-GBM Observations
  44. Fermi GRB 250305A: Global MASTER-Net observations report
  45. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  46. EP250302a: Optical Observations at CrAO and SAO RAS
  47. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  48. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  49. EP250304a: REM NIR upper limits
  50. EP250304a: Swift-XRT detection of a fading X-ray source
  51. EP250304a: Global MASTER-Net observations report
  52. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  53. EP250302a: REM NIR upper limits
  54. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  55. EP250302a: Global MASTER-Net observations report
  56. Fermi GRB 250302A: Global MASTER-Net observations report
  57. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  58. EP250228a: Optical observations with Kinder and Swift/UVOT
  59. GRB 250226A: KAO Optical Upper Limit
  60. GRB 250226A: AbAO AS-32 Optical Upper Limit
  61. EP250227a: Global MASTER-Net observations report
  62. EP250223A: Upper limits from Fermi-GBM Observations
  63. EP250227a: TRT optical upper limit
  64. GRB 250225B: VLT/HAWKI near-infrared observations
  65. EP250227a: Optical upper limits with Kinder observations
  66. EP250225a: EP-FXT follow-up observation
  67. EP250223a: J band upper limit by SYSU 80cm telescope
  68. EP250228a: Global MASTER-Net observations report
  69. GRB 250205A / EP250205A: further radio observations with the VLA
  70. EP250225a: TRT optical upper limits
  71. EP250226a/GRB 250226A: 1.6m Mephisto observations
  72. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  73. Fermi GRB 250226B: Global MASTER-Net observations report
  74. GRB 250221A: ATCA Detections and Upper Limits
  75. GRB 250225B: REM NIR upper limits
  76. Konus-Wind detection of GRB 250225B
  77. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  78. EP250226a: Global MASTER-Net observations report
  79. Swift GRB 250225B: Global MASTER-Net observations report
  80. Fermi GRB 250226A: Global MASTER-Net observations report
  81. Fermi trigger No 762205158: Global MASTER-Net observations report
  82. EP250225a: Global MASTER-Net observations report
  83. EP250225a: GSP optical upper limit
  84. Fermi GRB 250225A: Global MASTER-Net observations report
  85. EP250215A: J band upper limit by SYSU 80cm telescope
  86. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  87. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  88. GRB 250207a: ATCA Radio Upper Limits
  89. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  90. EP250223a: REM NIR upper limit
  91. EP250223a: 1.6m Mephisto and 50cm array observations
  92. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  93. EP250223a: Global MASTER-Net observations report
  94. Fermi GRB 250223A: Global MASTER-Net observations report
  95. Fermi trigger No 762020305: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  97. EP250220a: FTW optical and NIR observations and upper limits
  98. EP250220a: EP-FXT follow-up observations
  99. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  100. Fermi trigger No 761805304: Global MASTER-Net observations report

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