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"

24658 results found.

  1. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  2. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  3. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  4. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  5. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  6. GRB 250309B: PRIME near-infrared detection
  7. GRB 250225B: Swift-BAT refined analysis
  8. GRB 250311A/EP250311a: TRT optical upper limit
  9. EP250311a/GRB 250311A: EP-WXT detection
  10. GRB 250311B: SVOM detection of a burst
  11. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  12. GRB 250309B / AT2025dws: further SAO RAS optical observations
  13. EP250308a: 1.6m Mephisto optical upper limits
  14. Konus-Wind detection of GRB 250309B
  15. IPN triangulation of GRB 250308A (short)
  16. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  17. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  18. GRB 250309B: Swift-XRT refined Analysis
  19. GRB 250309B / IceCube-250309A: GECAM-B observations
  20. GRB 250309B / AT2025dws: SAO RAS optical observations
  21. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  22. GRB 250309B: Fermi GBM Observation
  23. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  24. IceCube-250309A: No candidates from the Zwicky Transient Facility
  25. Fermi-LAT gamma-ray observations of IceCube-250309A
  26. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  28. EP250308a: GSP optical upper limit
  29. EP250308a: Einstein Probe detection of an X-ray transient
  30. EP250308a: NOT optical upper limit
  31. GRB 250306A: EIRSAT-1 GMOD detection
  32. GRB 250306A: Swift-BAT refined analysis
  33. GRB 250306A: NuSTAR detection of the prompt emission
  34. EP250304a: MeerKAT detection of a possible radio counterpart
  35. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  36. GRB 250305A: AstroSat CZTI detection
  37. EP250302a:Xinglong optical observations
  38. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  39. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  40. GRB250101A: Radio upper limits from VLA observations
  41. GRB 250305A: SVOM/GRM observation of a burst
  42. The EP-WXT trigger 01709132323 is likely a flaring star
  43. EP250304A: Upper limits from Fermi-GBM Observations
  44. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  45. EP250302a: Optical Observations at CrAO and SAO RAS
  46. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  47. EP 250304A: Optical counterpart detection by LCO
  48. EP250302A: 1.3m DFOT optical afterglow detection
  49. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  50. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  51. EP250304a: REM NIR upper limits
  52. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  53. EP250302a: Mondy Continued Optical Observations
  54. EP250304a: Swift-XRT detection of a fading X-ray source
  55. EP250304a: TRT optical counterpart detection
  56. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  57. EP250304a: Einstein Probe detection of an X-ray transient
  58. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  59. EP250302a: SAO RAS optical observations
  60. EP250302a : GIT optical follow-up
  61. EP250225a: the candidate optical counterpart is an AGN
  62. EP250302a: Kinder optical follow-up observations
  63. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  64. EP250302a: Swift/UVOT detection
  65. EP250302a: optical observation from the INAF Asiago Observatory
  66. EP250302a: REM NIR upper limits
  67. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  68. EP250302a: Mondy Observations and Optical Light Curve
  69. EP250302a: VLT/MUSE optical redshift z = 1.131
  70. EP250302A: VLT near-infrared observations
  71. EP250302A: VLT/X-shooter tentative redshift
  72. EP250302a: OHP/T193 optical and spectroscopic observations
  73. EP250302a: Swift-XRT observations of a fading X-ray source
  74. EP250302a: Einstein Probe detection of an X-ray transient
  75. EP250302a: SVOM/C-GFT optical observations
  76. GRB 250226A: GRANDMA Optical Observations
  77. EP250302a: Montarrenti Observatory optical detection
  78. EP250302a: Nanshan/HMT optical counterpart detection
  79. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  80. GRB 250225B: VLT near-infrared afterglow confirmation
  81. EP250228a: Optical observations with Kinder and Swift/UVOT
  82. Konus-Wind detection of GRB 250226A
  83. GRB 250225B: EIRSAT-1 GMOD Detection
  84. GRB 250226A: KAO Optical Upper Limit
  85. GRB 250226A: AbAO AS-32 Optical Upper Limit
  86. EP250227a: Global MASTER-Net observations report
  87. EP250223A: Upper limits from Fermi-GBM Observations
  88. EP250227a: TRT optical upper limit
  89. GRB 250225B: VLT/HAWKI near-infrared observations
  90. EP250227a: Optical upper limits with Kinder observations
  91. EP250227a: NOT optical observations
  92. EP250227a: Einstein Probe detected of a fast X-ray transient
  93. EP250228a: updates on the EP observations
  94. GRB 250226A: Fermi GBM Observation
  95. EP250223a: J band upper limit by SYSU 80cm telescope
  96. EP250228a: Swift/XRT localisation
  97. EP250228a: Einstein Probe detection of an X-ray transient
  98. GRB 250226A / EP250226a: LCO detection of the afterglow
  99. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  100. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization

Advanced

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