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"
  1. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  2. EP250302a: Mondy Continued Optical Observations
  3. EP250304a: VLT/X-shooter redshift z = 0.200
  4. EP250304a: Swift-XRT detection of a fading X-ray source
  5. EP250304a: TRT optical counterpart detection
  6. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  7. EP250304a: Global MASTER-Net observations report
  8. EP250304a: Einstein Probe detection of an X-ray transient
  9. The EP-WXT trigger 01709132212 is not a real source
  10. EP250302a: SVOM/VT optical observation
  11. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  12. EP250302a: SAO RAS optical observations
  13. EP250302a : GIT optical follow-up
  14. EP250302a: VLT/X-shooter redshift confirmation
  15. EP250225a: the candidate optical counterpart is an AGN
  16. EP250302a: Kinder optical follow-up observations
  17. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  18. EP250302a: Swift/UVOT detection
  19. EP250302a: NUTTelA-TAO Early Measurments
  20. EP250302a: optical observation from the INAF Asiago Observatory
  21. EP250302a: REM NIR upper limits
  22. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  23. EP250302a: Mondy Observations and Optical Light Curve
  24. EP250302a: VLT/MUSE optical redshift z = 1.131
  25. INTEGRAL: end of scientific operations
  26. EP250302A: VLT near-infrared observations
  27. EP250302A: VLT/X-shooter tentative redshift
  28. EP250302a: OHP/T193 optical and spectroscopic observations
  29. EP250302a: Global MASTER-Net observations report
  30. EP250302a: Xinglong F60B optical observation
  31. EP250302a: Swift-XRT observations of a fading X-ray source
  32. EP250302a: Einstein Probe detection of an X-ray transient
  33. EP250302a: SVOM/C-GFT optical observations
  34. GRB 250226A: GRANDMA Optical Observations
  35. EP250302a: Montarrenti Observatory optical detection
  36. Fermi GRB 250302A: Global MASTER-Net observations report
  37. EP250302a: FTW optical and NIR detection
  38. EP250302a: Nanshan/HMT optical counterpart detection
  39. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  40. GRB 250302A: Fermi GBM Final Real-time Localization
  41. GRB 250228A: Fermi GBM Final Localization
  42. The EP-WXT trigger 01709132140 is likely a flaring star
  43. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  44. GRB 250225B: VLT near-infrared afterglow confirmation
  45. EP250228a: Optical observations with Kinder and Swift/UVOT
  46. Konus-Wind detection of GRB 250226A
  47. GRB 250225B: EIRSAT-1 GMOD Detection
  48. GRB 250226A: KAO Optical Upper Limit
  49. GRB 250226A: AbAO AS-32 Optical Upper Limit
  50. EP250227a: Global MASTER-Net observations report
  51. EP250223A: Upper limits from Fermi-GBM Observations
  52. EP250227a: TRT optical upper limit
  53. GRB 250225B: VLT/HAWKI near-infrared observations
  54. EP250227a: Optical upper limits with Kinder observations
  55. EP250227a: NOT optical observations
  56. EP250227a: Einstein Probe detected of a fast X-ray transient
  57. EP250228a: updates on the EP observations
  58. GRB 250226A: Fermi GBM Observation
  59. EP250225a: EP-FXT follow-up observation
  60. EP250223a: J band upper limit by SYSU 80cm telescope
  61. EP250228a: Swift/XRT localisation
  62. EP250228a: Global MASTER-Net observations report
  63. EP250228a: Einstein Probe detection of an X-ray transient
  64. GRB 250226A / EP250226a: LCO detection of the afterglow
  65. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  66. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  67. GRB 250225B: VLT/Xshooter imaging
  68. GRB 250205A / EP250205A: further radio observations with the VLA
  69. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  70. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  71. GRB 250225B: INTEGRAL SPI-ACS detection
  72. EP250225a: NOT optical candidate counterpart
  73. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  74. EP250226a / GRB 250226A: SVOM/VT optical observations
  75. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  76. EP250225a: TRT optical upper limits
  77. EP250226a/GRB 250226A: 1.6m Mephisto observations
  78. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  79. EP250226a/GRB 250226A: Kinder optical follow-up observations
  80. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  81. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  82. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  83. Fermi GRB 250226B: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  85. GRB 250226B: Fermi GBM Final Real-time Localization
  86. GRB 250225B: Fermi GBM Observation
  87. GRB 250221A: ATCA Detections and Upper Limits
  88. GRB 250225B: REM NIR upper limits
  89. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  90. Konus-Wind detection of GRB 250225B
  91. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  92. EP250223a: CrAO ZTSH optical observation
  93. GRB 250225B: VLT optical and near-infrared candidate counterpart
  94. GRB 250225B: VLT/FORS2 candidate optical afterglow
  95. GRB 250225B: SVOM/GRM observation of a long burst
  96. GRB 250226A: GECAM-B detection
  97. GRB 250221A: EP-FXT detection of the X-ray afterglow
  98. GRB 250214A: SVOM/GRM observation
  99. EP250226a/GRB 250226A: GSP detects optical counterpart
  100. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov