Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. See news and announcements

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"

18651 results found.

  1. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  2. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  3. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  4. EP250304a: Chandra detection
  5. GRB 250225B: Swift-BAT refined analysis
  6. GRB 250311A: Tiled Swift observations
  7. IPN triangulation of GRB 250308A (short)
  8. GRB 250309B: Swift-XRT refined Analysis
  9. GRB 250309B / AT2025dws: Swift-UVOT detection
  10. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  11. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  12. GRB 230509B: Tiled Swift observations
  13. GRB 250306A: EIRSAT-1 GMOD detection
  14. Konus-Wind detection of GRB 250306A
  15. GRB 250306A: Swift-BAT refined analysis
  16. GRB 250306A: NuSTAR detection of the prompt emission
  17. GRB 250306A: AstroSat CZTI detection
  18. Swift GRB 250306A: Global MASTER-Net observations report
  19. GRB 250306A: Swift detection of a burst
  20. IPN triangulation of GRB 250222A
  21. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  22. EP250304a: Swift-XRT detection of a fading X-ray source
  23. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  24. EP250302a: Swift/UVOT detection
  25. EP250302a: Swift-XRT observations of a fading X-ray source
  26. EP250228a: Optical observations with Kinder and Swift/UVOT
  27. GRB 250225B: EIRSAT-1 GMOD Detection
  28. GRB 250225B: VLT/HAWKI near-infrared observations
  29. EP250228a: updates on the EP observations
  30. EP250228a: Swift/XRT localisation
  31. GRB 250225B: INTEGRAL SPI-ACS detection
  32. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  33. GRB 250225B: Fermi GBM Observation
  34. GRB 250221A: ATCA Detections and Upper Limits
  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. Konus-Wind detection of GRB 250225B
  38. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  39. GRB 250225B: VLT/FORS2 candidate optical afterglow
  40. GRB 250225B: SVOM/GRM observation of a long burst
  41. GRB 250221A: EP-FXT detection of the X-ray afterglow
  42. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  43. Swift GRB 250225B: Global MASTER-Net observations report
  44. GRB 250225B: Swift detection of a burst
  45. GRB 250221A: Swift-BAT refined analysis
  46. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  47. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  48. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  49. GRB 250207a: ATCA Radio Upper Limits
  50. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  51. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  52. GRB 250119B: VZLUSAT-2 detection
  53. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  54. GRB 250219A: EP-FXT afterglow detection
  55. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  56. EP250223a: REM NIR upper limit
  57. EP250223a: TRT optical afterglow observation
  58. EP250223a: refined analysis of the EP-WXT and FXT observations
  59. EP250223a: SVOM/VT optical observation
  60. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  61. 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
  62. EP250223a: OASDG optical observations
  63. EP250223a: LCO detection of the afterglow
  64. EP250223a: early optical detection by BOOTES-4
  65. EP250223a: NOT redshift z = 2.756
  66. EP250223a: Swift/XRT localization
  67. GRB 250221A: VLA radio detection
  68. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  69. GRB 250221A: continued Mondy optical observations, brightening afterglow
  70. GRB 250221A: Optical counterpart detection by LCO.
  71. GRB 250221A: Mondy optical observations
  72. Konus-Wind detection of GRB 250221A
  73. GRB 250221A: Assy optical observations
  74. GRB 250221A: GRANDMA/TAROT Detection
  75. GRB 250221A: Swift-XRT refined Analysis
  76. GRB 250221A: NOT optical observations
  77. GRB 250221A: 1.6m Mephisto optical detection
  78. GRB 250221A: AKO Optical Upper Limit
  79. GRB 250221A: Swift/UVOT Detection
  80. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  81. GRB 250221A: REM optical/NIR afterglow detection
  82. GRB 250221A: Enhanced Swift-XRT position
  83. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  84. GRB 250221A: Swift detection of a burst with an optical counterpart
  85. Swift GRB250221.15: Global MASTER-Net OT detection
  86. Swift GRB250221.15: Global MASTER-Net observations report
  87. GRB 250219A: Swift/UVOT Upper Limits
  88. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  89. GRB 250219A: 1.6m Mephisto optical upper limits
  90. GRB 250219A: SVOM/VT optical counterpart
  91. GRB 250219A: Swift-XRT observations
  92. GRB 250219A: Swift ToO observations
  93. GRB 250217C: Swift-XRT observations
  94. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  95. GRB 250217C: Tiled Swift observations
  96. IPN triangulation of GRB 250217C (short)
  97. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  98. SVOM/sb25021804: SVOM detection of a long X-ray transient
  99. GRB 250213A: Swift-XRT observations
  100. GRB 250215A / EP250215a: LCO detection of the afterglow

Advanced

Download all Circulars as a .tar.gz archive:
Looking for U.S. government information and services? Visit USA.gov