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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

24773 results found.

  1. GRB 250226A: AbAO AS-32 Optical Upper Limit
  2. EP250227a: Global MASTER-Net observations report
  3. EP250223A: Upper limits from Fermi-GBM Observations
  4. EP250227a: TRT optical upper limit
  5. GRB 250225B: VLT/HAWKI near-infrared observations
  6. EP250227a: Optical upper limits with Kinder observations
  7. EP250227a: NOT optical observations
  8. EP250227a: Einstein Probe detected of a fast X-ray transient
  9. EP250228a: updates on the EP observations
  10. GRB 250226A: Fermi GBM Observation
  11. EP250223a: J band upper limit by SYSU 80cm telescope
  12. EP250228a: Swift/XRT localisation
  13. EP250228a: Einstein Probe detection of an X-ray transient
  14. GRB 250226A / EP250226a: LCO detection of the afterglow
  15. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  16. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  17. GRB 250225B: VLT/Xshooter imaging
  18. GRB 250205A / EP250205A: further radio observations with the VLA
  19. EP250225a: NOT optical candidate counterpart
  20. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  21. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  22. EP250225a: TRT optical upper limits
  23. EP250226a/GRB 250226A: 1.6m Mephisto observations
  24. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  25. EP250226a/GRB 250226A: Kinder optical follow-up observations
  26. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  27. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  28. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  29. GRB 250225B: Fermi GBM Observation
  30. GRB 250225B: REM NIR upper limits
  31. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  32. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  33. EP250223a: CrAO ZTSH optical observation
  34. GRB 250225B: VLT optical and near-infrared candidate counterpart
  35. GRB 250225B: SVOM/GRM observation of a long burst
  36. EP250226a/GRB 250226A: GSP detects optical counterpart
  37. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  38. EP250226a / GRB 250226A: TRT optical counterpart observation
  39. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  40. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  41. EP250225a: GSP optical upper limit
  42. EP250223a: GMG Optical Observation
  43. EP250225a: Einstein Probe detected of a fast X-ray transient
  44. GRB 250225B: Swift detection of a burst
  45. EP250223a: GROWTH-India Telescope optical observations
  46. GRB 250221A: Swift-BAT refined analysis
  47. EP250215A: J band upper limit by SYSU 80cm telescope
  48. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  49. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  50. EP250223a: Kinder optical follow-up observations
  51. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  52. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  53. GRB 250119B: VZLUSAT-2 detection
  54. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  55. GRB 250202B: VZLUSAT-2 detection
  56. GRB 250222A: SVOM/GRM observation of a burst
  57. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  58. GRB 250206A: VZLUSAT-2 detection
  59. EP250223a: REM NIR upper limit
  60. EP250223a: TRT optical afterglow observation
  61. EP250223a: refined analysis of the EP-WXT and FXT observations
  62. EP250223a: 1.6m Mephisto and 50cm array observations
  63. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  64. 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
  65. EP250223a: OASDG optical observations
  66. EP250223a: LCO detection of the afterglow
  67. EP250223a: Swift/XRT localization
  68. EP250223a: NOT optical afterglow candidate
  69. EP250223a: Einstein Probe detection of an X-ray transient
  70. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  71. GRB 250221A: Optical counterpart detection by LCO.
  72. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  73. GRB 250221A: GRANDMA/TAROT Detection
  74. GRB 250221A: Swift-XRT refined Analysis
  75. GRB 250221A: NOT optical observations
  76. GRB 250221A: 1.6m Mephisto optical detection
  77. GRB 250221A: AKO Optical Upper Limit
  78. GRB 250221A: Swift/UVOT Detection
  79. EP250220a: Liverpool Telescope upper limits
  80. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  81. GRB 250221A: REM optical/NIR afterglow detection
  82. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  83. GRB 250221A: Enhanced Swift-XRT position
  84. EP250220a: 1.6m Mephisto observations
  85. EP250220a: Liverpool Telescope optical upper limits
  86. EP250220a: Optical upper limit with Kinder observations
  87. SVOM trigger sb25022102 is not an astrophysical event
  88. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  89. GRB 250221A: Swift detection of a burst with an optical counterpart
  90. Swift GRB250221.15: Global MASTER-Net OT detection
  91. EP250220a: Xinglong optical upper limit
  92. GRB 250219A: Swift/UVOT Upper Limits
  93. GRB 250219A: OHP/T193 optical upper limit
  94. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  95. GRB 250219A: 1.6m Mephisto optical upper limits
  96. GRB 250219A: Swift-XRT observations
  97. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  98. Konus-Wind detection of GRB 250215A / EP250215a
  99. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  100. GRB 250217C: Swift-XRT observations

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