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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"

24759 results found.

  1. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  2. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  3. GRB 250225B: VLT/Xshooter imaging
  4. GRB 250205A / EP250205A: further radio observations with the VLA
  5. EP250225a: NOT optical candidate counterpart
  6. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  7. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  8. EP250225a: TRT optical upper limits
  9. EP250226a/GRB 250226A: 1.6m Mephisto observations
  10. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  11. EP250226a/GRB 250226A: Kinder optical follow-up observations
  12. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  13. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  15. GRB 250225B: Fermi GBM Observation
  16. GRB 250225B: REM NIR upper limits
  17. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  18. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  19. EP250223a: CrAO ZTSH optical observation
  20. GRB 250225B: VLT optical and near-infrared candidate counterpart
  21. GRB 250225B: SVOM/GRM observation of a long burst
  22. EP250226a/GRB 250226A: GSP detects optical counterpart
  23. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  24. EP250226a / GRB 250226A: TRT optical counterpart observation
  25. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  26. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  27. EP250225a: GSP optical upper limit
  28. EP250223a: GMG Optical Observation
  29. EP250225a: Einstein Probe detected of a fast X-ray transient
  30. GRB 250225B: Swift detection of a burst
  31. EP250223a: GROWTH-India Telescope optical observations
  32. GRB 250221A: Swift-BAT refined analysis
  33. EP250215A: J band upper limit by SYSU 80cm telescope
  34. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  35. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  36. EP250223a: Kinder optical follow-up observations
  37. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  38. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  39. GRB 250119B: VZLUSAT-2 detection
  40. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  41. GRB 250202B: VZLUSAT-2 detection
  42. GRB 250222A: SVOM/GRM observation of a burst
  43. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  44. GRB 250206A: VZLUSAT-2 detection
  45. EP250223a: REM NIR upper limit
  46. EP250223a: TRT optical afterglow observation
  47. EP250223a: refined analysis of the EP-WXT and FXT observations
  48. EP250223a: 1.6m Mephisto and 50cm array observations
  49. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  50. 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
  51. EP250223a: OASDG optical observations
  52. EP250223a: LCO detection of the afterglow
  53. EP250223a: Swift/XRT localization
  54. EP250223a: NOT optical afterglow candidate
  55. EP250223a: Einstein Probe detection of an X-ray transient
  56. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  57. GRB 250221A: Optical counterpart detection by LCO.
  58. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  59. GRB 250221A: GRANDMA/TAROT Detection
  60. GRB 250221A: Swift-XRT refined Analysis
  61. GRB 250221A: NOT optical observations
  62. GRB 250221A: 1.6m Mephisto optical detection
  63. GRB 250221A: AKO Optical Upper Limit
  64. GRB 250221A: Swift/UVOT Detection
  65. EP250220a: Liverpool Telescope upper limits
  66. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  67. GRB 250221A: REM optical/NIR afterglow detection
  68. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  69. GRB 250221A: Enhanced Swift-XRT position
  70. EP250220a: 1.6m Mephisto observations
  71. EP250220a: Liverpool Telescope optical upper limits
  72. EP250220a: Optical upper limit with Kinder observations
  73. SVOM trigger sb25022102 is not an astrophysical event
  74. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  75. GRB 250221A: Swift detection of a burst with an optical counterpart
  76. Swift GRB250221.15: Global MASTER-Net OT detection
  77. EP250220a: Xinglong optical upper limit
  78. GRB 250219A: Swift/UVOT Upper Limits
  79. GRB 250219A: OHP/T193 optical upper limit
  80. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  81. GRB 250219A: 1.6m Mephisto optical upper limits
  82. GRB 250219A: Swift-XRT observations
  83. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  84. Konus-Wind detection of GRB 250215A / EP250215a
  85. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  86. GRB 250217C: Swift-XRT observations
  87. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  88. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  89. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  90. GRB 250217C: SVOM/GRM observation
  91. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  92. SVOM/sb25021804: SVOM detection of a long X-ray transient
  93. GRB 250213A: Swift-XRT observations
  94. GRB 250216A: AstroSat CZTI detection
  95. GRB 250217C: AstroSat CZTI detection of a short burst
  96. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  97. GRANDMA/OPD observations of GRB250215A
  98. GRB 250215A / EP250215a: LCO detection of the afterglow
  99. GRB 250215A: Swift/UVOT Upper Limits
  100. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow

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