ALMA Special Session AAS 247

Monitoring the transient sky: the role of ALMA in the WSU era

Explosive and bright phenomena typically emit most of their radiation at short wavelengths, but monitoring at longer wavelengths is a key tool for the identification of the progenitors and emission type (synchrotron, thermal), as well as for the general characterization of the contextual environment and underlying processes at play. Transient sources tend to be faint and rapidly dampening at sub-mm wavelengths, over timescales varying from hours to months - proving to be challenging targets for detection. Recent results, especially based on ALMA data, have shown an increased interest in this technique as a complement to rapid follow-up in the optical and X-ray domain. Sub-mm transient studies can include science cases as varied as monitoring the activity of accreting and merging systems (AGNs, protostars, novae, neutron mergers) and detecting the afterglows of bright transients (GRBs, XRFs, FRBs) likely originating from explosive phenomena during stars’ end of life.

In the current emerging era of extensive transient detections – in particular from LSST and Roman - the complementarity of highly sensitive and timely sub-mm observations will prove essential for rapid and effective monitoring of a large range of sources.

ALMA is now undergoing a major upgrade - the Wideband Sensitivity Upgrade (WSU) – including an upgraded digital signal processing and transmission system, a new correlator, and four new wideband receivers, with additional receiver bands to follow. In addition to the transformational increase in instantaneous spectral grasp and correlated continuum bandwidth, the improved receiver temperatures and overall system efficiency will eventually increase continuum sensitivities by a factor of 3 or more in upgraded bands. For transients, ALMA-WSU will open sub-mm monitoring to a new regime of fainter and farther sources.

This session will feature presentations of recent impactful results on a variety of progenitors and phenomena, highlighting the specific role of sub-mm observations and the impact of ALMA-WSU to time-domain subfields. Invited speakers include Jennifer Donovan Meyer (NRAO), Abygail Waggoner (Wisconsin), Kate Alexander (Arizona), Tarraneh Eftekhari (Northwestern), Boris Georgiev (Arizona).

Presentations:

T. Eftekhari: Opening the Millimeter Transient Window: Wide-Field CMB Surveys and ALMA’s Next Generation Capabilities

J. Donovan Meyer: The Wideband Sensitivity Update

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