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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28285 results found.

  1. EP250302a: Einstein Probe detection of an X-ray transient
  2. EP250302a: SVOM/C-GFT optical observations
  3. GRB 250226A: GRANDMA Optical Observations
  4. EP250302a: Montarrenti Observatory optical detection
  5. EP250302a: Nanshan/HMT optical counterpart detection
  6. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  7. GRB 250225B: VLT near-infrared afterglow confirmation
  8. EP250228a: Optical observations with Kinder and Swift/UVOT
  9. Konus-Wind detection of GRB 250226A
  10. GRB 250225B: EIRSAT-1 GMOD Detection
  11. GRB 250226A: KAO Optical Upper Limit
  12. GRB 250226A: AbAO AS-32 Optical Upper Limit
  13. EP250227a: Global MASTER-Net observations report
  14. EP250223A: Upper limits from Fermi-GBM Observations
  15. EP250227a: TRT optical upper limit
  16. GRB 250225B: VLT/HAWKI near-infrared observations
  17. EP250227a: Optical upper limits with Kinder observations
  18. EP250227a: NOT optical observations
  19. EP250227a: Einstein Probe detected of a fast X-ray transient
  20. EP250228a: updates on the EP observations
  21. GRB 250226A: Fermi GBM Observation
  22. EP250223a: J band upper limit by SYSU 80cm telescope
  23. EP250228a: Swift/XRT localisation
  24. EP250228a: Einstein Probe detection of an X-ray transient
  25. GRB 250226A / EP250226a: LCO detection of the afterglow
  26. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  27. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  28. GRB 250225B: VLT/Xshooter imaging
  29. GRB 250205A / EP250205A: further radio observations with the VLA
  30. EP250225a: NOT optical candidate counterpart
  31. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  32. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  33. EP250225a: TRT optical upper limits
  34. EP250226a/GRB 250226A: 1.6m Mephisto observations
  35. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  36. EP250226a/GRB 250226A: Kinder optical follow-up observations
  37. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  38. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  40. GRB 250225B: Fermi GBM Observation
  41. GRB 250225B: REM NIR upper limits
  42. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  43. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  44. EP250223a: CrAO ZTSH optical observation
  45. GRB 250225B: VLT optical and near-infrared candidate counterpart
  46. GRB 250225B: SVOM/GRM observation of a long burst
  47. EP250226a/GRB 250226A: GSP detects optical counterpart
  48. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  49. EP250226a / GRB 250226A: TRT optical counterpart observation
  50. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  51. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  52. EP250225a: GSP optical upper limit
  53. EP250223a: GMG Optical Observation
  54. EP250225a: Einstein Probe detected of a fast X-ray transient
  55. GRB 250225B: Swift detection of a burst
  56. EP250223a: GROWTH-India Telescope optical observations
  57. GRB 250221A: Swift-BAT refined analysis
  58. EP250215A: J band upper limit by SYSU 80cm telescope
  59. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  60. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  61. EP250223a: Kinder optical follow-up observations
  62. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  63. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  64. GRB 250119B: VZLUSAT-2 detection
  65. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  66. GRB 250202B: VZLUSAT-2 detection
  67. GRB 250222A: SVOM/GRM observation of a burst
  68. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  69. GRB 250206A: VZLUSAT-2 detection
  70. EP250223a: REM NIR upper limit
  71. EP250223a: TRT optical afterglow observation
  72. EP250223a: refined analysis of the EP-WXT and FXT observations
  73. EP250223a: 1.6m Mephisto and 50cm array observations
  74. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  75. 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
  76. EP250223a: OASDG optical observations
  77. EP250223a: LCO detection of the afterglow
  78. EP250223a: Swift/XRT localization
  79. EP250223a: NOT optical afterglow candidate
  80. EP250223a: Einstein Probe detection of an X-ray transient
  81. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  82. GRB 250221A: Optical counterpart detection by LCO.
  83. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  84. GRB 250221A: GRANDMA/TAROT Detection
  85. GRB 250221A: Swift-XRT refined Analysis
  86. GRB 250221A: NOT optical observations
  87. GRB 250221A: 1.6m Mephisto optical detection
  88. GRB 250221A: AKO Optical Upper Limit
  89. GRB 250221A: Swift/UVOT Detection
  90. EP250220a: Liverpool Telescope upper limits
  91. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  92. GRB 250221A: REM optical/NIR afterglow detection
  93. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  94. GRB 250221A: Enhanced Swift-XRT position
  95. EP250220a: 1.6m Mephisto observations
  96. EP250220a: Liverpool Telescope optical upper limits
  97. EP250220a: Optical upper limit with Kinder observations
  98. SVOM trigger sb25022102 is not an astrophysical event
  99. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  100. GRB 250221A: Swift detection of a burst with an optical counterpart

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