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"

24598 results found.

  1. EP250225a: the candidate optical counterpart is an AGN
  2. EP250302a: Kinder optical follow-up observations
  3. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  4. EP250302a: Swift/UVOT detection
  5. EP250302a: optical observation from the INAF Asiago Observatory
  6. EP250302a: REM NIR upper limits
  7. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  8. EP250302a: Mondy Observations and Optical Light Curve
  9. EP250302a: VLT/MUSE optical redshift z = 1.131
  10. EP250302A: VLT near-infrared observations
  11. EP250302A: VLT/X-shooter tentative redshift
  12. EP250302a: OHP/T193 optical and spectroscopic observations
  13. EP250302a: Swift-XRT observations of a fading X-ray source
  14. EP250302a: Einstein Probe detection of an X-ray transient
  15. EP250302a: SVOM/C-GFT optical observations
  16. GRB 250226A: GRANDMA Optical Observations
  17. EP250302a: Montarrenti Observatory optical detection
  18. EP250302a: Nanshan/HMT optical counterpart detection
  19. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  20. GRB 250225B: VLT near-infrared afterglow confirmation
  21. EP250228a: Optical observations with Kinder and Swift/UVOT
  22. Konus-Wind detection of GRB 250226A
  23. GRB 250225B: EIRSAT-1 GMOD Detection
  24. GRB 250226A: KAO Optical Upper Limit
  25. GRB 250226A: AbAO AS-32 Optical Upper Limit
  26. EP250227a: Global MASTER-Net observations report
  27. EP250223A: Upper limits from Fermi-GBM Observations
  28. EP250227a: TRT optical upper limit
  29. GRB 250225B: VLT/HAWKI near-infrared observations
  30. EP250227a: Optical upper limits with Kinder observations
  31. EP250227a: NOT optical observations
  32. EP250227a: Einstein Probe detected of a fast X-ray transient
  33. EP250228a: updates on the EP observations
  34. GRB 250226A: Fermi GBM Observation
  35. EP250223a: J band upper limit by SYSU 80cm telescope
  36. EP250228a: Swift/XRT localisation
  37. EP250228a: Einstein Probe detection of an X-ray transient
  38. GRB 250226A / EP250226a: LCO detection of the afterglow
  39. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  40. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  41. GRB 250225B: VLT/Xshooter imaging
  42. GRB 250205A / EP250205A: further radio observations with the VLA
  43. EP250225a: NOT optical candidate counterpart
  44. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  45. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  46. EP250225a: TRT optical upper limits
  47. EP250226a/GRB 250226A: 1.6m Mephisto observations
  48. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  49. EP250226a/GRB 250226A: Kinder optical follow-up observations
  50. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  51. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  53. GRB 250225B: Fermi GBM Observation
  54. GRB 250225B: REM NIR upper limits
  55. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  56. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  57. EP250223a: CrAO ZTSH optical observation
  58. GRB 250225B: VLT optical and near-infrared candidate counterpart
  59. GRB 250225B: SVOM/GRM observation of a long burst
  60. EP250226a/GRB 250226A: GSP detects optical counterpart
  61. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  62. EP250226a / GRB 250226A: TRT optical counterpart observation
  63. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  64. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  65. EP250225a: GSP optical upper limit
  66. EP250223a: GMG Optical Observation
  67. EP250225a: Einstein Probe detected of a fast X-ray transient
  68. GRB 250225B: Swift detection of a burst
  69. EP250223a: GROWTH-India Telescope optical observations
  70. GRB 250221A: Swift-BAT refined analysis
  71. EP250215A: J band upper limit by SYSU 80cm telescope
  72. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  73. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  74. EP250223a: Kinder optical follow-up observations
  75. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  76. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  77. GRB 250119B: VZLUSAT-2 detection
  78. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  79. GRB 250202B: VZLUSAT-2 detection
  80. GRB 250222A: SVOM/GRM observation of a burst
  81. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  82. GRB 250206A: VZLUSAT-2 detection
  83. EP250223a: REM NIR upper limit
  84. EP250223a: TRT optical afterglow observation
  85. EP250223a: refined analysis of the EP-WXT and FXT observations
  86. EP250223a: 1.6m Mephisto and 50cm array observations
  87. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  88. 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
  89. EP250223a: OASDG optical observations
  90. EP250223a: LCO detection of the afterglow
  91. EP250223a: Swift/XRT localization
  92. EP250223a: NOT optical afterglow candidate
  93. EP250223a: Einstein Probe detection of an X-ray transient
  94. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  95. GRB 250221A: Optical counterpart detection by LCO.
  96. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  97. GRB 250221A: GRANDMA/TAROT Detection
  98. GRB 250221A: Swift-XRT refined Analysis
  99. GRB 250221A: NOT optical observations
  100. GRB 250221A: 1.6m Mephisto optical detection

Advanced

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