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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"

24978 results found.

  1. GRB 250225B: VLT near-infrared afterglow confirmation
  2. EP250228a: Optical observations with Kinder and Swift/UVOT
  3. Konus-Wind detection of GRB 250226A
  4. GRB 250225B: EIRSAT-1 GMOD Detection
  5. GRB 250226A: KAO Optical Upper Limit
  6. GRB 250226A: AbAO AS-32 Optical Upper Limit
  7. EP250227a: Global MASTER-Net observations report
  8. EP250223A: Upper limits from Fermi-GBM Observations
  9. EP250227a: TRT optical upper limit
  10. GRB 250225B: VLT/HAWKI near-infrared observations
  11. EP250227a: Optical upper limits with Kinder observations
  12. EP250227a: NOT optical observations
  13. EP250227a: Einstein Probe detected of a fast X-ray transient
  14. EP250228a: updates on the EP observations
  15. GRB 250226A: Fermi GBM Observation
  16. EP250223a: J band upper limit by SYSU 80cm telescope
  17. EP250228a: Swift/XRT localisation
  18. EP250228a: Einstein Probe detection of an X-ray transient
  19. GRB 250226A / EP250226a: LCO detection of the afterglow
  20. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  21. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  22. GRB 250225B: VLT/Xshooter imaging
  23. GRB 250205A / EP250205A: further radio observations with the VLA
  24. EP250225a: NOT optical candidate counterpart
  25. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  26. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  27. EP250225a: TRT optical upper limits
  28. EP250226a/GRB 250226A: 1.6m Mephisto observations
  29. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  30. EP250226a/GRB 250226A: Kinder optical follow-up observations
  31. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  32. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  34. GRB 250225B: Fermi GBM Observation
  35. GRB 250225B: REM NIR upper limits
  36. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  37. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  38. EP250223a: CrAO ZTSH optical observation
  39. GRB 250225B: VLT optical and near-infrared candidate counterpart
  40. GRB 250225B: SVOM/GRM observation of a long burst
  41. EP250226a/GRB 250226A: GSP detects optical counterpart
  42. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  43. EP250226a / GRB 250226A: TRT optical counterpart observation
  44. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  45. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  46. EP250225a: GSP optical upper limit
  47. EP250223a: GMG Optical Observation
  48. EP250225a: Einstein Probe detected of a fast X-ray transient
  49. GRB 250225B: Swift detection of a burst
  50. EP250223a: GROWTH-India Telescope optical observations
  51. GRB 250221A: Swift-BAT refined analysis
  52. EP250215A: J band upper limit by SYSU 80cm telescope
  53. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  55. EP250223a: Kinder optical follow-up observations
  56. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  57. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  58. GRB 250119B: VZLUSAT-2 detection
  59. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  60. GRB 250202B: VZLUSAT-2 detection
  61. GRB 250222A: SVOM/GRM observation of a burst
  62. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  63. GRB 250206A: VZLUSAT-2 detection
  64. EP250223a: REM NIR upper limit
  65. EP250223a: TRT optical afterglow observation
  66. EP250223a: refined analysis of the EP-WXT and FXT observations
  67. EP250223a: 1.6m Mephisto and 50cm array observations
  68. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  69. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  70. EP250223a: OASDG optical observations
  71. EP250223a: LCO detection of the afterglow
  72. EP250223a: Swift/XRT localization
  73. EP250223a: NOT optical afterglow candidate
  74. EP250223a: Einstein Probe detection of an X-ray transient
  75. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  76. GRB 250221A: Optical counterpart detection by LCO.
  77. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  78. GRB 250221A: GRANDMA/TAROT Detection
  79. GRB 250221A: Swift-XRT refined Analysis
  80. GRB 250221A: NOT optical observations
  81. GRB 250221A: 1.6m Mephisto optical detection
  82. GRB 250221A: AKO Optical Upper Limit
  83. GRB 250221A: Swift/UVOT Detection
  84. EP250220a: Liverpool Telescope upper limits
  85. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  86. GRB 250221A: REM optical/NIR afterglow detection
  87. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  88. GRB 250221A: Enhanced Swift-XRT position
  89. EP250220a: 1.6m Mephisto observations
  90. EP250220a: Liverpool Telescope optical upper limits
  91. EP250220a: Optical upper limit with Kinder observations
  92. SVOM trigger sb25022102 is not an astrophysical event
  93. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  94. GRB 250221A: Swift detection of a burst with an optical counterpart
  95. Swift GRB250221.15: Global MASTER-Net OT detection
  96. EP250220a: Xinglong optical upper limit
  97. GRB 250219A: Swift/UVOT Upper Limits
  98. GRB 250219A: OHP/T193 optical upper limit
  99. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  100. GRB 250219A: 1.6m Mephisto optical upper limits

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