Skip to main content
Circulars over Kafka event name backfill. 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"

18694 results found.

  1. GRB 250311A: Swift-XRT observations
  2. GRB 250228A: Fermi GBM Observation
  3. GRB 230509B: 1.3m DFOT Optical observations
  4. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  5. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  6. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  7. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  8. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  9. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  10. EP250304a: Chandra detection
  11. GRB 250225B: Swift-BAT refined analysis
  12. GRB 250311A: Tiled Swift observations
  13. IPN triangulation of GRB 250308A (short)
  14. GRB 250309B: Swift-XRT refined Analysis
  15. GRB 250309B / AT2025dws: Swift-UVOT detection
  16. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  17. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  18. GRB 230509B: Tiled Swift observations
  19. GRB 250306A: EIRSAT-1 GMOD detection
  20. Konus-Wind detection of GRB 250306A
  21. GRB 250306A: Swift-BAT refined analysis
  22. GRB 250306A: NuSTAR detection of the prompt emission
  23. GRB 250306A: AstroSat CZTI detection
  24. Swift GRB 250306A: Global MASTER-Net observations report
  25. GRB 250306A: Swift detection of a burst
  26. IPN triangulation of GRB 250222A
  27. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  28. EP250304a: Swift-XRT detection of a fading X-ray source
  29. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  30. EP250302a: Swift/UVOT detection
  31. EP250302a: Swift-XRT observations of a fading X-ray source
  32. EP250228a: Optical observations with Kinder and Swift/UVOT
  33. GRB 250225B: EIRSAT-1 GMOD Detection
  34. GRB 250225B: VLT/HAWKI near-infrared observations
  35. EP250228a: updates on the EP observations
  36. EP250228a: Swift/XRT localisation
  37. GRB 250225B: INTEGRAL SPI-ACS detection
  38. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  39. GRB 250225B: Fermi GBM Observation
  40. GRB 250221A: ATCA Detections and Upper Limits
  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. Konus-Wind detection of GRB 250225B
  44. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  45. GRB 250225B: VLT/FORS2 candidate optical afterglow
  46. GRB 250225B: SVOM/GRM observation of a long burst
  47. GRB 250221A: EP-FXT detection of the X-ray afterglow
  48. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  49. Swift GRB 250225B: Global MASTER-Net observations report
  50. GRB 250225B: Swift detection of a burst
  51. GRB 250221A: Swift-BAT refined analysis
  52. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  53. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  55. GRB 250207a: ATCA Radio Upper Limits
  56. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  57. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  58. GRB 250119B: VZLUSAT-2 detection
  59. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  60. GRB 250219A: EP-FXT afterglow detection
  61. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  62. EP250223a: REM NIR upper limit
  63. EP250223a: TRT optical afterglow observation
  64. EP250223a: refined analysis of the EP-WXT and FXT observations
  65. EP250223a: SVOM/VT optical observation
  66. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  67. 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
  68. EP250223a: OASDG optical observations
  69. EP250223a: LCO detection of the afterglow
  70. EP250223a: early optical detection by BOOTES-4
  71. EP250223a: NOT redshift z = 2.756
  72. EP250223a: Swift/XRT localization
  73. GRB 250221A: VLA radio detection
  74. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  75. GRB 250221A: continued Mondy optical observations, brightening afterglow
  76. GRB 250221A: Optical counterpart detection by LCO.
  77. GRB 250221A: Mondy optical observations
  78. Konus-Wind detection of GRB 250221A
  79. GRB 250221A: Assy optical observations
  80. GRB 250221A: GRANDMA/TAROT Detection
  81. GRB 250221A: Swift-XRT refined Analysis
  82. GRB 250221A: NOT optical observations
  83. GRB 250221A: 1.6m Mephisto optical detection
  84. GRB 250221A: AKO Optical Upper Limit
  85. GRB 250221A: Swift/UVOT Detection
  86. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  87. GRB 250221A: REM optical/NIR afterglow detection
  88. GRB 250221A: Enhanced Swift-XRT position
  89. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  90. GRB 250221A: Swift detection of a burst with an optical counterpart
  91. Swift GRB250221.15: Global MASTER-Net OT detection
  92. Swift GRB250221.15: Global MASTER-Net observations report
  93. GRB 250219A: Swift/UVOT Upper Limits
  94. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  95. GRB 250219A: 1.6m Mephisto optical upper limits
  96. GRB 250219A: SVOM/VT optical counterpart
  97. GRB 250219A: Swift-XRT observations
  98. GRB 250219A: Swift ToO observations
  99. GRB 250217C: Swift-XRT observations
  100. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart

Advanced

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