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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"

24849 results found.

  1. EP250226a/GRB 250226A: Kinder optical follow-up observations
  2. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  3. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  5. GRB 250225B: Fermi GBM Observation
  6. GRB 250225B: REM NIR upper limits
  7. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  8. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  9. EP250223a: CrAO ZTSH optical observation
  10. GRB 250225B: VLT optical and near-infrared candidate counterpart
  11. GRB 250225B: SVOM/GRM observation of a long burst
  12. EP250226a/GRB 250226A: GSP detects optical counterpart
  13. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  14. EP250226a / GRB 250226A: TRT optical counterpart observation
  15. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  16. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  17. EP250225a: GSP optical upper limit
  18. EP250223a: GMG Optical Observation
  19. EP250225a: Einstein Probe detected of a fast X-ray transient
  20. GRB 250225B: Swift detection of a burst
  21. EP250223a: GROWTH-India Telescope optical observations
  22. GRB 250221A: Swift-BAT refined analysis
  23. EP250215A: J band upper limit by SYSU 80cm telescope
  24. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  25. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  26. EP250223a: Kinder optical follow-up observations
  27. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  28. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  29. GRB 250119B: VZLUSAT-2 detection
  30. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  31. GRB 250202B: VZLUSAT-2 detection
  32. GRB 250222A: SVOM/GRM observation of a burst
  33. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  34. GRB 250206A: VZLUSAT-2 detection
  35. EP250223a: REM NIR upper limit
  36. EP250223a: TRT optical afterglow observation
  37. EP250223a: refined analysis of the EP-WXT and FXT observations
  38. EP250223a: 1.6m Mephisto and 50cm array observations
  39. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  40. 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
  41. EP250223a: OASDG optical observations
  42. EP250223a: LCO detection of the afterglow
  43. EP250223a: Swift/XRT localization
  44. EP250223a: NOT optical afterglow candidate
  45. EP250223a: Einstein Probe detection of an X-ray transient
  46. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  47. GRB 250221A: Optical counterpart detection by LCO.
  48. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  49. GRB 250221A: GRANDMA/TAROT Detection
  50. GRB 250221A: Swift-XRT refined Analysis
  51. GRB 250221A: NOT optical observations
  52. GRB 250221A: 1.6m Mephisto optical detection
  53. GRB 250221A: AKO Optical Upper Limit
  54. GRB 250221A: Swift/UVOT Detection
  55. EP250220a: Liverpool Telescope upper limits
  56. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  57. GRB 250221A: REM optical/NIR afterglow detection
  58. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  59. GRB 250221A: Enhanced Swift-XRT position
  60. EP250220a: 1.6m Mephisto observations
  61. EP250220a: Liverpool Telescope optical upper limits
  62. EP250220a: Optical upper limit with Kinder observations
  63. SVOM trigger sb25022102 is not an astrophysical event
  64. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  65. GRB 250221A: Swift detection of a burst with an optical counterpart
  66. Swift GRB250221.15: Global MASTER-Net OT detection
  67. EP250220a: Xinglong optical upper limit
  68. GRB 250219A: Swift/UVOT Upper Limits
  69. GRB 250219A: OHP/T193 optical upper limit
  70. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  71. GRB 250219A: 1.6m Mephisto optical upper limits
  72. GRB 250219A: Swift-XRT observations
  73. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  74. Konus-Wind detection of GRB 250215A / EP250215a
  75. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  76. GRB 250217C: Swift-XRT observations
  77. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  78. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  79. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  80. GRB 250217C: SVOM/GRM observation
  81. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  82. SVOM/sb25021804: SVOM detection of a long X-ray transient
  83. GRB 250213A: Swift-XRT observations
  84. GRB 250216A: AstroSat CZTI detection
  85. GRB 250217C: AstroSat CZTI detection of a short burst
  86. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  87. GRANDMA/OPD observations of GRB250215A
  88. GRB 250215A / EP250215a: LCO detection of the afterglow
  89. GRB 250215A: Swift/UVOT Upper Limits
  90. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  91. GRB 250215A: Fermi GBM Observation
  92. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  93. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  94. GRB 250215A: Swift-XRT refined Analysis
  95. GRB 250215A: SVOM/GRM observation
  96. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  97. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  98. EP250207b: Xinglong optical upper limit
  99. EP250212a: Xinglong optical upper limit
  100. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates

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